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Age determination, reproduction, growth and population analysis of the harbor seal, Phoca vitulina richardi… Bigg, Michael Andrew 1966

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AGE DETERMINATION, AND P O P U L A T I O N PHOCA  REPRODUCTION,  ANALYSIS  VTTULINA  GROWTH  "OF T H E HARBOUR  RICHARDI  SEAL.,  GRAY  by MICHAEL B.Sc.,  ANDREW  University  A THESIS  of  SUBMITTED  British  IN  THE REQUIREMENTS  BIGG Columbia,  PARTIAL  OF  in  Department  the  FULFILMENT  FOR T H E D E G R E E  MASTER  1962  OF  SCIENCE  of Zoblogy  We  accept  required  this  thesis  as  conforming to  standard  T H E U N I V E R S I T Y OF B R I T I S H September,  1966  COLUMBIA  the  OF  In presenting  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s  f o r an advanced degree a t t h e U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e study„  I f u r t h e r agree t h a t permission..for  and  extensive copying of t h i s  t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by t h e Head o f my Department o r by h i s r e p r e s e n t a t i v e s .  I t i s understood t h a t  or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n w i t h o u t my w r i t t e n  permission^  The U n i v e r s i t y o f B r i t i s h Vancouver 8 Canada S  Columbia  copying  s h a l l not be a l l o w e d  I  ABSTRACT  Studies  have  reproduction, harbour  seal  upon gross tracts, teeth  In the  and  criterion a  organic"  and  seals  and  spring  band d u r i n g  f o r m a t i o n may  result  southeastern  Columbia)  parturition  lactation  then  thereafter 2  to  2.\  in  months  lasts  of  postnatal  the  are  based  reproductive  and a s s o c i a t e d  Two "dense, an  canine  specimens  annulations  "less  summer a n d  fall.  internal  Vancouver occurs  Island  September.  about  band  during  dense,  more  Their  during  ovulation  230  deposited  (southern  Implantation is  used  rhythm.  primarily  6 weeks w i t h  were  are  inorganic"  opaque  from an  and b i r t h  They  cementum a n n u l a t i o n s  and the  in  1965.  age.  translucent  structure  examinations  319  and  1964  of  determination,  richardi).  measurements,  postnatal  winter  In  vitulina  histological  between  annually, the  (Phoca  on age  and p o p u l a t i o n  42 p r e n a t a l  collected  as  growth  growth  of  b e e n made  is  days  British  July,  shortly delayed later.  for  i l  The  male's  months  in  main breeding advance  of  season begins  the  female's  but  at  least  ends  4  shortly  after. Extensive cycle  of  both  Atlantic  clines sexes  in  are  the  timing  found i n  ovulations  occur  2 to  at  all  produce young  adult  females  at  5 and 6 y e a r s  Prenatal Postnatal  asymptotic  males rate  reproductive  Pacific  and  about  ratios  then  sexual  of  10$  of  age '  A b o u t 88.9$  each  year.  grow  at  of  Males  age.  and females grow  longer  about  than  slightly and  36$  similar faster  heavier  rates. and  at  : 1 from implantation at  resulting  live 30  1  maturity  females  do n o t  s e l d o m more a  are  increases  percentage generally  3 years.  of  however,  5 years  sizes.  reach  In  males  males,  being  Sex  2 and  at  with peak p e r i o d s  larger  the  the  Oceans.  First  mature  of  in  in  older  longer  5 years,  a gradually  age  than  their  groups. 20  years  until  mortality increasing Males  and  females  years.  random k i l l  sample  the  average  annual  sex  i i i  ratio  is  46.9$ males,  3 3 . 7 $ o f males  and 4 9 . 6 $ o f a l l  females  and  are mature.  From b o u n t y r e t u r n r e c o r d s and r e p r o d u c t i v e and p o p u l a t i o n d a t a a minimum p o p u l a t i o n e s t i m a t e 75,000 seals density  of  is  made f o r B r i t i s h C o l u m b i a .  about 4 . 4  seals  per mile of  of  This is  coastline.  a  iv  ACKNOWLEDGEMENTS  This the  research  Fisheries  Nanaimo,  I in  this  Fisher carried the  of  Zoology,  under  whose  out.  His and  been g r e a t l y  also  go to  the  particular  Mr. many G.  McNaughton, been  this  helpful  Hansen  hunters E.  Lockhart  their  of  Dr.  Dentistry,  University  of  authorized  the  their  sectioning  machine  of for  assistance  go  to  Dr.  H.D.  research  has  been  of  the  supply  during  manuscript thanks Co.,  him,  in  and  Lindstrom.  It  that  the  much o f  British  Gillings-Hamco tooth  B.  Faculty  Columbia,  must  Ltd.,  D.  Middaugh,  cutting  Fisher,  their  Southerland,  D.  H.D.  at  Columbia.  Special  who  cooperation  have been c o l l e c t e d .  Dr.  Hansen Fur  a n d R.  Station  suggestions  appreciated.  seal  use  thanks  from  British  for  preparation  Anttila,  L.  through  the  H.G.  of  many p e o p l e  direction  in  Biological  University  many  a contract'  Canada w i t h  Particular  have  and  to  project.  to  Board's  Columbia,  am i n d e b t e d  project  supported by  Research  British  Department  was  has data of  kindly thin  sections.  Mr.  V  G.  Pike  Board ting  at the  would McT.  and  I.  MacAskie  Nanaimo, use  also Cowan,  of  have  the  very  helpful  Research in  express  my a p p r e c i a t i o n  Dr.  H.  Nordan,  and  Zoology,  Agriculture  manuscript.  and D r . for  permit-  facilities.  to  Faculty the  Fisheries  like  of  of  been  the  Station's  Department of  of  Dr. W.D.  their  I to  A.M. Perks Kitts  critical  of  Dr. of  I. the  the  examination  vi  TABLE OF CONTENTS  Page ABSTRACT  i  ACKNOWLEDGEMENTS  iv  TABLE OF CONTENTS  vi  LIST OF TABLES  viii  LIST OF FIGURES  x  INTRODUCTION  1  GENERAL METHODS AND MATERIALS  5  AGE DETERMINATION Introduction Method Cementum d e p o s i t i o n Discussion  8 8 9 16  REPRODUCTION Introduction Female r e p r o d u c t i o n Method Annual a d u l t c y c l e 1. P a r t u r i t i o n 2. L a c t a t i o n 3. O v u l a t i o n 4. Delay o f i m p l a n t a t i o n 5. G e s t a t i o n p e r i o d Age at sexual m a t u r i t y Fertility Causes o f i n f e r t i l i t y  19 20 21 25 26 28 28 29 35 38  vii Page Male  reproduction «  Method Annual  Age a t  40 adult  cycle  42  sexual maturity  50  Discussion  57  GROWTH Introduction  ,  64  Method  65  Prenatal  67  Postnatal  74  Discussion  POPULATION  79  ANALYSIS  Introduction Population composition 1. 2. 3.  Sex r a t i o Percent mature A sampling test  Population  82 „, 84 86 88  dynamics  1. N a t a l i t y 2. M o r t a l i t y Population estimate Discussion  89 90 97 101  SUMMARY  103  LITERATURE CITED  109  APPENDICES  117  MANAGEMENT  RECOMMENDATIONS  120  v l i i  LIST  OF  TABLES  Table I II  Page Age  at  sexual  Number both  III  Age  of  and IV  corpora  ovaries specific  females  maturity  of  for  albicantia  found  ...  fertility  In  34 mature  66  between  implantation  ovulation  Fertility  in  36 a  random sample  of  72  adult  •  females V  Age a t  38 sexual  maturity  for  46  males  c o l l e c t e d from southeastern Vancouver I s l a n d and the a d j a c e n t m a i n l a n d d u r i n g t h e m a i n m a l e b r e e d i n g s e a s o n (May t o September) VI  Calculations of  the  for  estimating  gestation  period  the  and  51  duration  implantation  dates VII  VTII  71  Comparison of  and  and w e i g h t s  Weights  of  eastern  8 pups  Vancouver  v.  Annual a  female  for  P.  v.  collected Island  at  birth richardi  from the  ...  73  south-  end  of  74  Maximum l e n g t h s P.  X  male  lengths  weaning IX  32  in  females  58  collected  females  138  and weights  recorded  for  richardi average  random sample  78 percent of  of  males  mature  males  in 87  ix  Table  XI  Page  Life  table  males XII  Life  table  females XIII  The  in  1963  for  of  114 r a n d o m l y  of  1 year  number  seals and  for  1 year  age 131 of  and  randomly age  bounty  British  collected  older  and  92  collected  older  claims  for  93 harbour  Columbia between  1914  99  X  LIST  OF  FIGURES  Figure 1.  Page Canine  tooth  19 m o n t h s 2.  Closure  of  10 the  canine  percentage  depositing  no  of  4.  5.  6.  7.  0 to  11  years  cavity-  parturition  Diameter relation events  teeth  translucent  cementum i n  months  and  12  age  months  to 15  Distribution of Scheffer, 1958, in  pulp  canine  cementum,  cementum and opaque 29  to  12  Monthly  groups  from b i r t h  age  rate  opening  3.  development  of  Phoca v i t u l i n a p . 89) a n d t h e  times  (from variation 23  changes of the corpus luteum to the annual reproductive  in 30  Annual change i n t e s t i s weight, seminif e r o u s t u b u l e d i a m e t e r and degree o f spermatogenesis  43  Annual change i n epididymus weight, d i a m e t e r and o c c u r r e n c e o f sperm i n tubules  46  tubule the  8.  Baculum  growth  by  weight  for  98  males  ..  54  9.  Baculum  growth  by  volume  for  98  males  ..  55  10.  Prenatal  body growth  implantation  to  birth  by  length  from 68  xi  Figure 11.  12.  "13.  14.  Page P r e n a t a l body growth by weight from i m p l a n t a t i o n to b i r t h  69  Body growth by l e n g t h f o r 165 s e a l s (79 males and 86 females)  76  Body growth by weight f o r 117 s e a l s ( 6 0 males and 57 females)  77  S u r v i v a l curve f o r males and females.  95  INTRODUCTION  The is  the  most  Except  for  harbour widely  most  polar  between  1958)  (Pig.  favored seals any  than  that  or  the  known  5 miles  of  the  northern  described  the  its  is  from  (Fisher,  fur  seal  (Kenyon  harbour  1949)  (Van  (Fisher,  Scheffer of  which  are  tentatively  respective  seal  are 200  found i n  almost  seldom comparable  Sergeant,  1965) has  1953)  although  associated  Bemmel,  (Scheffer,  to  100  and W i l k e ,  with tides  it  is seasons  and  the  subspecies,  all  I956),  1952).  (1958) r e c o g n i z e s  delineated They  to  1955,  morphologically very  distribution.  North  No m i g r a t i o n  seal  (Bartholemew,  circum-  environment,  harp  the  up  pinnipeds.  and r e e f s  may b e  shore.  movements  day  of  freshwater  local  of  estuaries  Individuals or  range  and 80°  25°  have  time  to  arctic,  where g r o u p s  for  Linnaeus, the  latitudes  marine  vitulina  member o f  Mud f l a t s ,  4).  of  Phoca  distributed  may g a t h e r .  to  been  the  habitats,  type  more  of  seal,  5  similar.  them u p o n t h e i r  are  distributions:  listed  as  He  has  geographical  follows  with  their  -2-  Phoca  1. North  Atlantic;  Zemla,  British P_.  2. Atlantic; North  vitullna  vitulina  Portugal  to  Isles, v.  Sea,  Novaya  Delay;  Ellesmere  western  North  Island,  and  to  Carolina.  Lakes,  P_.  Hudson P.  4. Herschel  Strait  v.  mellonae  P_.  v.  richardi eastern  v.  largha  to  Shantung  In  Canada,  recognition  for The  commercial  fishing  (Scheffer nuisance  to  namatodes (Scott  the  Sea  species  involves  to  North Baja,  eastern  has  Seal  America; Mexico.  Asia;  1944)  upon f i s h to  some  Bering  1958).  economic  features  its  of  with  instances Sarber,  it  trapped  has in  the  1947)  nets,  life  the  are  become  fishermen. in  its  association  and  where  host  Phocanema  gained  Many  (Imler  terminal  and F i s h e r ,  Bering  industry.  loss  s u c h as  western  Pallas;  1952)  predator  be  and Lower  Gray;  conflicting  Slipp,  financial  known  the  first  (Fisher, and  Upper  Peninsula.  two  biology.  recorded  Doutt;  Bay.  Islands,  5.  a  to  Baltic  eastern  Iceland.  concolor  Greenland  3.  in  and  the  Linnaeus;  It  Porrocaecum)  As  this  parasite  local  resulting is  cycle  (  a  also of  decipiens forms  an  -3-  obvious the  cyst  value  of  For has  in  the  the  years. for  In  the  while was  jaw  in  In  of  harbour  prizes boots  each  Canada,  every  contrast  in  the  British hides  f r o m $5  for  when t h e  of  b e e n made  In  This  1952.  this  and  to  ment  program f o r  cooperative  of  project  a  of  given  age,  bounty  $5  Its  pelt  is  recently  fur  garments,  this  skin  (1963)  industry  as  feature  a n d up  status  of  the  Columbia since was  new  undertaken  fishery.  between  Board's  Biological  Station  ment  Zoology at  the  of  been  Department.  to  $50  the at  of  a  has  Fisheries  University  1964  for  It  Nanaimo  harbour  Fisher's in  a biological basis  this  venture  has  of  the  hunter  a prime  Fisheries  number  1 year  only The  seal  the  British  provide  aspects,  of  high.  No a s s e s s m e n t has  the  a  1964,  into  status  for  $30  demand i s  over  such commodities To  to  a  for  lowers  species.  payment  seal  turned  it  Department  $10  Columbia.  and c u r i o s .  brings  the  a  these  important,  important  up u n t i l  nose to  fishes,  bounties  Canada  economically attained  of  eastern  for  many  measures,  system  western  given  of  commercially  control  sponsored a  flesh  and  seal work  to  do  managebeen  a  Research the  British  DepartColumbia.  _ 4 -  Although a carried the  world,  (I965), as  on i t s none,  have  except  an  annulations.  this  seal's  by  latter  canine  population  of  general  related  determined  tooth of  out  number  investigations biology  for  their  the  aging  The p r e s e n t to  development,  c o m p o s i t i o n and  various  recent  findings  accurate  technique  in  to  work the  method  research  describe  been  parts  by  such makes of  growth  of  Bishop  seals  aspects  reproduction, dynamics.  have  age,  as use the and  GENERAL  on  319  Between F e b r u a r y  1964  postnatal  prenatal  from B r i t i s h came the  adjacent from  Strait, and  a n d 42  Columbia.  from the  taken  METHODS AND M A T E R I A L S  southeastern mainland.  southern  half  of  were  specimens  of  specimens  Queen C h a r l o t t e  collected  Vancouver  Vancouver  data  1965,  Island  were  Island,  Islands,  and  also  Johnstone Skeena  River  Kitimat.  large  been  quantity  largely  value  as  a  due  "fur"  opportunity  information  to  its  material  spring  to  early  months  of  the  Hansen  Fur  possible  Ltd.,  supplied  with  a wooden  keg and  filled specimen  for of  with  collect  labels.  Mr.  reliable samples  hunter  10$  late other  selected,  Each  times.  from  cooperation  these  during  bags  Co.,  has  economic  personally  not  gather  substantial  to  kill  sample  was  to  seal  were c o n t a c t e d  their  formalin,  this  Although a  it  able  acquired  Through the  Hansen  hunters  on  collected  autumn,  year.  of  professional  was  being  recently  bearer.  of  H.G.  of  of  amount  of  seals  majority  A few  south western  The u n i q u e a  The  and December  was  buffered For  every  -6-  set  of  associated  collected, very  $ 2 . 5 0 was  reproductive  paid.  This  tract  and  kill  arrangement  data  worked  satisfactorily. From each  and  jaw,  reproductive  formalin.  From  carcass organs the  body,  possible, spring  niped material Biological the  be  technique  rifle,  at  the  Nanalmo  is  preserved and the  using  in  the female,  ovaries. a  the  Where  Chatillon  and measured  collection  Research  have  also  Spalding  solitary  either to  for  by  done  .222 o r  one  The  waiting  is  from .243,  or  pin-  Boards' been  included  the most  effective  ambush  by  cruising close  with  w i t h 4 to  a  Pike.  harbour  in  spotted shore  of  and Gordon  habits,  frequent,  until  generally the  the  Individually.  known  a boat  s u c h as  David  their  been  are in  of  from  Fisheries  at  hunted  has  they  Shooting  3 0 0 lb),  permission of  s e a l s must  coastline  from  associated  specimens  Station  Because  areas  and  jaw  length.  Several  with  routinely  were w e i g h e d ,  (capacity  examined the  both gonads  removed and  specimens  scale  standard  horns  were  male,  b a c u l u m were u s u a l l y uterine  personally  in the  to  high  8 power  shore. velocity .  -7-  telescopic As head  the  above  select is  sights. seal  water  for  its  presents  as  sex  a relatively  a  stated,  birthday.  Thus,  months  are  of  extensively Scheffer  used  be  in  southeastern is  variations  It of  cycle  from a l l  processes  have  seal  all  result  the  unless  seal's  closest  from 6 months  0 and  5.9  months  definition  has  been  For  1954).  to  group,  investigations  pups  Island  analyses Specific in  shown  that  1 month  in  in  areas  British to  certain been  Vancouver  discussed  be  about  Thus,  be  fur  between  its  population.  year to  c a n be  This  Vancouver  will  events.  other  pups.  unable The  the  refer  old  Those  in  of  of  aging  are  (Kenyon,  convenience  born  even  to  on J u l y  though  15  •thei/ibirth  weeks.  reproductive  eastern  will  is  half  size.  a particular  age  assumed t h a t  1  As  to  one  hunter  sampling  1 year  and Chapman,  will  lumped  a  as  it  range  the  age.  classified  a  about  and t i t t l e : . fOK  When r e f e r r i n g  17.9  target,  unbiased  otherwise  only  determined  have  and been of  are  timing  Columbia,  seasonal  treatment the  the  accurately  Island  data  there  of  data  describe  the  appropriate  specimens sections.  and  dental  south-  mainland.  lumped from a l l the  be  annual  area,  adjacent  annual  cannot  reproductive  f r o m one  the  regional  and  For  areas. data  will  -8-  AGE  DETERMINATION  Introduction For widely age  many p i n n i p e d s  accepted  as  determination.  canine  teeth  opaque  and  zones  are  have  hispida  show  urslnus  bands  while  (Hewer,  1964),  (Laws,  are  Fisher,  and  changes  in  observed  in  1954b),  Pusa  (  al.,  Phoca)  leonina  clearest  Eumatoplas  et  Pagophllus  1958)  i960),  of  These  (Kubota,  and M l r o u n g a  cementum bands and  best  1950),  (Fisher,  1958a),  (Mansfield  are  (Scheffer,  groenlandicus  seasonal  of  bands  dentine.  been  for  sections  alternating  with  have  criterion  ground  cementum o r  Dentine  (McLaren,  vitulina grypus  to  Lobodon carclnophagus  Phoca)  1953),  used  annulations  accurate  Generally,  been c o r r e l a t e d  Callorhinus  I96I),  most  translucent  odontogenesis.  (  the  dental  in  (Laws,  Phoca  Halichoerus  jubata  (Spalding,  1964b).  Method Cementum a n n u l a t i o n s examined u s i n g observed  with  thin  in  untreated  reflected  light  the  harbour  sections under  a  of  seal  were  canine  15 p o w e r  teeth  binocular  _ 9  microscope,  a principle  Mandibular used. in  Each  water  was  for  connective present,  canines,  tissue  calculated Each  and a l l o w e d  canine  saw  thick,  was  ment,  had been days  first  At possesses cylinder cementum, diameter  to  its  to  thin were  readily  cleared  in  boiling  opening  was  depth.  Wards  Bioplastic 100  centre  to  using  200 a  diamond  machine).  without  Although  further  treat-  d i s t i n g u i s h e d when  benzyl  of  Whenever  and  sectioning visible  were  scraped clean  slices,  the  (1953).  right,  cavity  width  Laws  after  dry.  pulp  from  the jaw  then  embedded i n  cut  were most  prior  Cementum  in  were  annulations they  the  the  Longitudinal  (Gillings-Hamco  dental  of  averaging  Mounting Medium. microns  from  minutes,  45  diameter  by  suggested by  generally  extracted  about  the  first  benzoate  for  sections  several  examination.  deposition birth,  the  newly  a completely of  prenatal  and  a pulp  (Fig.  IA).  Hallchoerus  erupting  formed  dentine cavity  grypus,  A s was  permanent  enamel about  cap,  15  opening of found by  subsequent  a  thin  mm l o n g , 5  to  Hewer  dentine  canine  no  6 mm i n (1964)  deposition  -10begins  at  a  resulting readily  Fig.  slightly  in  1.  age.  A .  large  dentine  pulp  shell.  the  an  tooth  cap,  a  as  Canine  of  at  formation  observable  months  Note  the  reduced pulp  visible  1 9 months  external  Neonatal  with  ridge  and  Tooth development  only  a  small  (Fig.  showing  (t),  dentine  dentine  at  ridge  pulp  a  ridge,  IB).  from b i r t h  tooth  opening  neonatal  diameter,  a neonatal  development  cavity B.  of  cavity  to  an  1 9  enamel  thin  9 months.  (—).  cavity  C.  Tooth  opening  remaining. Cementum f o r m a t i o n after  6  to  7 mm o f  dentine  begins have  at been  2  to  3 months  deposited.  of It  age  -Il-  ls  laid  the a  down f r o m  pulp  opening.  clear,  narrow,  By mately to  by  of  the  shows  this is  birth. group  thus  this  not  dentine  the  the  the  to  be  line.  grown  has  approxi-  been  reduced  appears  to  exceed  remaining  pulp  opening  is  sealed  years,  except  4  during of  first  pulp  that  seals  small which  2,  the  months  12  opening  confused with  a  Figure  suggests  the  for  closure after  size  no  other  under  12  months,  serves  as  to  of  cementum d e p o s i t i o n  12 m o n t h s  begins  ridge.  first  opening  Each  is  sections  on  the  age  are  annulations  side  subsequent  used  side are  of  an  in the  of  year's  distal  therefore  root  a useful  crown  progressively  This  is  now  sequence,  basis  neonatal  has  and b l o o d v e s s e l s .  ridge.  taken  pulp  the  to  dentine  relationship  when c r o s s be  dentine  the  ridge  cementum and  age  e x t e n d over> t o t h e  however,  the  neonatal  line,  the 2  rapid  can  Up does  and  closure  On t h e  the  Cementum g r o w t h  nerves  most  of  defined  and  cementum i n for  age  of  nim.  dentine  canal  rate  well  7 months  3.5  level  Between  mm l o n g e r  4  about  that  the  aging  the  index. often  neonatal  addition,  (crown  important  side)  to  consideration  aging,  as  slices  must  ridge  to  insure  that  represented.  8  E E  6-1  O)  c 'c o> a o  ir>  4-  •  D u  _a a  ro  i  S.  2-  3  E o  Q  t « — f t . mm  o"I  r  2  Age Fig.  2,  ( years)  C l o s u r e r a t e o f the c a n i n e p u l p c a v i t y c o l l e c t e d from south e a s t e r n Vancouver mainland.  1—[—i—i—i—|—i—i—r~ 3  4  5  opening. F r o m 115 seals I s l a n d and the adjacent  -13The  alternating  (dark)  cementum bands  to  neonatal  the  opaque run  line.  (light)  and  longitudinally  Where  areas  cleared  with benzyl  benzoate,  appears  contain  many m i n u t e  parallel  which  to  pass  across  direction.  the  These  band  canals  reflecting  quality.  section  in  acetone  for  the  canals  seem t o  f i l l  are  no  longer  coloured which  f o r m one  remain  distinct  groups  are  may b e  difficulty  may  explain  tions has  are  no  almost  air  more  why  in  in  canals  or  appear  densely  to  condition. differ  calcified  Support  for  this  and  each  The  design,  from  and  several  or  adjacent  and  there  group. some  dark  cream of  anastomose  preparations  detect.  fibrous  clearing,  agent  another  distinguishing  to  to  the  longitudinal  may  one  canals  light-  Occasionally,  to  band  filled  soaking  fibres,  These  light  its  prior  are  in-  -lateral  clearing  collagen  uncleared  impossible  by  days  Revealed  close  the air  band  or  the  and p a r a l l e l .  transparent  therefore  with  zone.  found very  the  parallel  been  antero  time,  several  perhaps  light  an  give  With  visible.  strands,  in  and  have  completely  translucent  This ambula-  band,  and c l e a r s  however, to  an  Its  composition  would  the  light  being  having  contention  less  band,  organic  comes  matter.  from the  work  -14-  of  Irle  on the  (I960),,  teleost  fish  analagous  otoliths.  and a u t o r a d i o g r a p h i c  slices  the opaque  smaller lucent  calcium  deposited  band  type,  this  0 to  first  are is  November.  a  July.  and  trans-  July,  laterally  line, is  laid  and one h a l f In  annually,  subsequent the  opaque  a  29  from  line  years  from June  sequence  Fig.  11 m o n t h s ,  line to  line.  September down  laid  only  of  years.  laid is  3  f o r age  the neonatal  line,  translucent  line  to  down  a dark  time  is  a  the percentage  the end o f to  band  this,  years.  0-29  a  annual  deposition  against  until  from  when e a c h  the annual  type  is  To e s t a b l i s h  a n d 12 m o n t h s  In  light  April  May a n d t h e  of  one band  The s e c o n d  April  deposited  however,  age g r o u p s  deposited  to  to  time,  in  11 m o n t h s  December  to  the  formation  comparison p l o t t i n g  depositing  2.\ b a n d s  the band  h a s b e e n made  From b i r t h ,  The  otolith,  protein  (i960) e s t a b l i s h e d  was n o t d e t e r m i n e d .  summarizes  groups  that  The e x a c t  comparison each  and F i s h e r  specimen  nature.  teeth  than  of  zone.  known-age  for  crystals  more  in  electron-  examinations  zone c o n t a i n s  carbonate  Mansfield  in  found  He s h o w e d b y X - r a y ,  microscopic that  annulations  from  from  down  2 lines  to  from are  December  November.  Fig.  3.  Monthly  percentage  of  translucent  cementum  groups  11 m o n t h s  seals  0 to  collected  adjacent  canine (•) and  teeth  12 m o n t h s  from southeastern  mainland.  depositing  and opaque cementum to  no cementum (o)  in  29 y e a r s .  Vancouver  Island  age  From  225  and  the  (A),  -16There tion the  of  the  the  to  dark  light  12 m o n t h  Apparently change  to  line  month age  0-11  dark  appears  be  phase  group,  lengthening with  the  cementum o c c u r s to  year  29  in  transition  group  it  is  shift  In  times  no  light  to  dark  early  dura-  age.  time  mid-April,  or  the  increasing  in  little  from  a  In  from  the  v/hereas  in  June.  occurs  in  the  cementum.  Discussion The phenomenon o f activity as  the  is  exhibited  rodents  ungulates  (Van  (Low  (Nishiwaki  et  al.,  Involved it  record  one  of  Is  somehow  effect  quality  or  could sing  be  several  physiological  in  former  mule  that  of  most  annulations  the  metabolism tooth  1964),  1963), cetaceans The of  causative  them.  represent  events to  groups  which  alter  deposition.  a  the  The  change  either  of  some o b v i o u s l y  stres-  circumstance  or  of  rhythm.  is  deer.  I966),  physiological  animal's  a manifestation  The found  believed  quantity  (McEwan,  for  dental  mammalian  and p i n n i p e d s .  unclear  in  Stephenson,  1963),  1958)*  the  and  and J o n k e l ,  remain  or  differences  such diverse  and Cowan,  (Stoneberg  Generally  in  Nostrand  carnivores  factors  annual  proposed for One  is  laid  two  an  Internal  cementum  down d u r i n g  annulations the  rut,  -17-  and  the  (Low  other  during  and Cowan,  relationship their  the  suggested fasting,  has  tooth  bands,  (see  line  in  are  well  gen  a n d many  possible  and  large  probably The  ments  at  neonatal  line  of  laid  which  has  been  or  all  arises  in  weaning,  pregnancy. on  the  bear).  internal  for  reproduction,  processes  (Aschoff,  on o d o n t o g e n e s i s  their  involvement  for  rhythms glyco-  their  1965), be  their  the  activity,  cannot Is  possessing  explaining  the  As  other  species  1966,  black  dentine  are  been p o s s i b l e , In  seal  this in  bands  birth,  breeding  of  (1962a)  and J o n k e l ,  disregarded.  difficult  to  assess  animals.  involves  birth  each  either  difficulty  presence  stressing  with  to 9  shortage  example  elephant  and up  4  best  Stoneberg  effects  The  and Ingham  associations  other  wild  food  Carrick  annually,  established  Unfortunately,  winter  the  southern  always  such  of  Perhaps  molting,  not  find  existence  of  coincide  feeding,  to  by  least  dentine  hand,  winter  At  to  It  in  given  interpretation  in  period  1963).  is  annulations. down  the  of  both  effects are and  harbour  seal  stressing of  almost dentine  an  bands  and r h y t h m i c  abrupt  certainly ridge.  canine  change  of  factors. environ-  represented The  reasons  by  the  for  the  -18-  subsequent  formation  clear.  They  the  or  molt  before the  the  first  variation definite winter  is  after  and  fall, is  fact  ability constant the  is  no  the  however,  as  light  they  are  (Imler  and  food source why in  a a  number o f  seal zoo  Also  transition  to  be  date  to  for  down during^  annual  there  thin  is  a In  fat  and  During  and  change under  19 y e a r s  (personal hunters); hand,  in  dark  to  relatively should  Further,  gradual light  the  avail-  a prolonged  the  the  usually  and dark b a n d s ,  suggest  tend  (poorly  19^7)  other  (i960).  the  (densely  local  the  explained is from the  an  cementum  kept  light  to  laid  water.  on is  M a n s f i e l d and F i s h e r available  to  less  either  occurs  are  Sarber,  reconcile,  conditions  evidence  period.  seals  the  quality,  are  cementum  in  to  the  appropriate  found by  dark  shot  shot  to  is  body c o n d i t i o n .  and c o r r e s p o n d e n c e w i t h  if  or  in  deposited,  difficult that  lines  related  deposited,  being  related  Certainly  when t h e  being  on b e i n g  is  change  spring,  lines  a n d no b r e e d i n g  intake.  food  and d a r k  2.\  in  experience, It  as  T h e y may b e  calcified) sink  directly  year.  and  summer  be  molt,  seasonal  float  light  reproduction, first  calcified) to  cannot  of  have as  was  there fasting  shift  cementum  in  -19-  with  increasing  age.  An a l t e r n a t i v e expression perhaps  of  related  progressively This  is  I962  III),  1963),  some  late-running  to  the  later  found i n  explanation  same  molt  Callorhlnus  and Phoca  although  this  vitulina  was  not  leonlna  dental  rhythm,  increasing (Carrick  (Scheffer  (personal  found by  the  responsible  with  urslnus  in  internal  factor  time  Mirounga  lies  a  age.  et  and  for  al., Johnson,  observations,  Stutz,  1966).  REPRODUCTION  Introduction No c o m p r e h e n s i v e on r e p r o d u c t i o n (Amoroso, (Harrison,  et  al.,  i960)  the  microscopic  and  accessory  and Bishop cycle  for  exception tions  in  the  harbour  1951* have  investigation seal.  a  general  and macroscopic  organs.  Fisher  (1954a),  the of  female. Bishop  have been  For  (1965),  reported  in  the only the  a  et  of  authors  al.,  1952), of  the  gonads  Harrison  (i960)  suggested  male  made  description  structure  (1965) h a v e p r e s e n t e d  been  Several  (Harrison,  1965),  given  has  cycle,  incidental literature  annual with  the  observa(Fisher,  -20-  1952,  (Harrison,  1954a),  1944).  Venables  Venables  (1959) h a v e  events,  Few  data  age  at  efficiency. with  now.  and V e n a b l e s  available  sexual is  these has  reproductive  for  determining  organs, the  annual  and  behavior.  annual  that  b e e n made  gonad  be  dealt  describe  occurring  where  cycle,  will  to  changes  except  Slipp,  reproductive  factors  and c y t o l o g i c a l  the  or  and  1957),  on the  maturity  No a t t e m p t  histological  (1955,  described .breeding  are  It  (Scheffer  i960),  it  is  such as  the  in  essential  spermato-  genesis .  Female  Reproduction Method Data  from both  have been used female's were  lactation.  razor and  for In  cut  blade.  size  Diameters greatest  of  the  the  into  width  each  laboratory,  and  of  depth.  aspects  ovary  with a  and c o r p o r a by  for  of  the  carcasses  foetuses  were c h e c k e d  estimated  laboratory  Fresh  each  2 mm t h i c k  lutea were  the  certain  presence  slices  corpora  and  physiology.  Sections  for  field  determining  reproductive  examined  versely  in  the  and  for  was  trans-  hand the  held  presence  albicantia. averaging  the  -21-  Annual 1.  adult  Parturition In  adjacent  Twinning local  is  presence  who  August  The  Is  on June 1965*  therefore 7 weeks  during  the  period  will  range  Venables, and  seals  4  in  to be  was  or  Mr.  skin  or  that  of  July. as  Mohr  In  The  Bay  is  the  mother birth,  range  of  pups  The peak  mid-July.  near on  Bay. approxi-  being  Estimates  3 weeks  (Venables  about  5 weeks  (Fisher, 1965).  born  pupping  are  1963*, B i s h o p ,  21,  that  from Boundary  of  Co.,  on June  its  latest  the  earliest  Hansen Fur  a birth  w i t h most  areas  (Harrison,  The  recorded  considered  1957),  of  by  Females  observation  1964.  5 weeks  by  water;  swimming w i t h  also  exists,  reported  the  from Boundary  seen  August.  (1944).  in  the  pup  early  solitarily.  personal  30,  and  1964,  Slipp  and  single  been  in  Hansen  suggested  other  1955*  7 weeks  by  earliest  mately  the  land  on  a  has  (Linstrom)  young  a pup  of  Island  June  it  and  b o r n pup  Grey 7,  although  reported  a newly  Point  It  was  late  Scheffer  other  received  1963. of  of  parturition  hunter  their  Vancouver  between  rare,  and by  have  birth  occurs  seal  (1952), may  southeastern  mainland,  generally  a  cycle  and 1952)  for  -22-  Fisher that  the  (personal  pupping  time  communication)  of  later  as  one g o e s  north  while  on  the  coast,  explored pupping the  west  this time  on  using  mammals.  findings,  interesting  Firstly, they  they  suggest  parturition March, for  pattern  earliest  times  for  the  Hokkaido  (Japan),  (Mexico), also  Vancouver  and n o r t h between  St.  and Booth  represented  eastern  exist  found i n  western  these  f r o m one  distribution.  by  4  distinct  Europe.  extremes, area  to  Baffin  another  in  latest  Island,  over  and  months areas:  latest  are  they  the  reveal  Secondly,  (Alaska),  The  of  variability.  separated  Thirdly,  clines  4,  February  Island  the  marine  earliest  areas  into  personal  Figure  are  (Maine).  Island,  with  the  The  4 widely  Bay  in  and  species  Lawrence  I  observations.  respectively.  pupping are  Canada,  study  and  reproductive  the  of  distribution  associated  that  and J u l y  the  a  literature  confirm Fisher's  progressively  earlier. with  presented  of  coast  becomes  published  with persons  an  east  throughout  suggested  becomes  further,  correspondence The  seal  the  it  observation variation  species,  this  has  times,  for  south-  Shetland show  pupping  most  Baja  of  Islands  that times  Its  P i g . 4.  D i s t r i b u t i o n o f Phoca v i t u l i n a p a r t u r i t i o n times.  (from  S c h e f f e r , 1958,  p. 8 9 ) and the v a r i a t i o n i n  Source f o r p a r t u r i t i o n times. A l l e n , 1942. Barabash - N i k i f o r o v , 1938 3 - B e l k i n , 1964. Bigg, personal observation. 4. Bishop, 1965. 5. Burns, p e r s o n a l communication. 6. Evans, p e r s o n a l communication. 7. 8. F i s h e r , 1952. F i s h e r , 1954a. 9. 10. H a l l i n g e n , p e r s o n a l communication. 11. H a r r i s o n , I960. 12. Havinga, 1933. 1. 2.  13.  14. 15. 16. 17. 18. 19. 20. 21. 22.  23.  24.  Jensen, p e r s o n a l communication. Joensen, p e r s o n a l communication. Jonsson, p e r s o n a l communication. Kruse, p e r s o n a l communication:. M a n s f i e l d , p e r s o n a l communication.  0ynes, 1964.  S c h e f f e r and S l i p p , 1944. Templeman, 1957. Venables and V e n a b l e s , 1957. Venables and V e n a b l e s , I960. Wheeler, p e r s o n a l communication. Wilke, 1954.  1  -24-  Pupping exhibit are  during  Northward, Islands,  chain May is  it  to  the  reported  gradually  Kodiak  occurs  the to  during  to  Baja,  parturition western  Baja,  in  It  Skeena  this  during  in  June-July. occurs  the  Commander  from  across  the  the  southeast, in  is  June,  July.  now  California,  to  pupping is  later  Island,  From  earlier in  Aleutian  and  reversed  pupping is  March-  advanced  Vancouver  in  March.  later,  is  pups  Vancouver  so  rather  that than  May-June;  April-May  where  later.  in  and  in  March.  Atlantic  March and  May-June;  cline  to  and  date  River  Ocean  Hokkaido,  the  gradually  A comparable and n o r t h  become  to  Pacific  February  Islands  summer,  Washington,  is  In  southeastern  the  May-June;  in  Islands,  becomes  north  Eastward,  G o i n g now  southward  Oregon,  Kurile  April-May.  the  clines.  winter,  from the  births  to  Island  In  the  and J u n e .  still  around  marked r e g i o n a l  born  April,  times  in  situation  Ocean.  April,  Labrador,  while June  Between B a f f i n  earlier  going  In  prevails Maine, in  and  Nova in  Island  eastward,  with  in  pups  west  first  Scotia,  Baffin and  the  not  Island,  Europe,  Greenland  appear until In  pupping in  June,  -25-  and  Iceland  and  the  No b i r t h the  eastern  because a  Faeroes  pattern  Atlantic  there  are  the  regional  summary,  harbour  regional eastern  seal,  clines North  northeastern western north  the  note  most  of  It  the  probably  but  for  exists,  probably  times  on  States,  later  later  in and  southward  eastward  later  of  exhibit  northward  United  becoming  becoming  distribution  later  western  becoming  adaptive  westward  implications  discussion.  that,  timing the  May.  In in  In the  the  Atlantic. The  in  d)  in  demonstrated  variations  becoming  b)  c)  been  parturition  a)  Asia;  Pacific;  north  over  the  by  yet  here)  scale.  America,  Canada;  has  extinct  distribution.  reduced geographical In  (now  do  exist.  dates  findings  regional  of of  2.  At  present,  differences These  reproductive workers  in  must  will it  in  be  events  different  is  be  important  female  accounted are  considered to  reproductive for  when  compared w i t h  the  areas.  Lactation Lactation  lasts  about  6 weeks.  This  is  -26-  implled the  last  last was  the  birth  female on  kept are  in  September  by in  local close  Harrison  Venables  and  last that  It  is  of  last  and  period  with  the  Fisher to  2  of  6  records  weeks,  Work done their  to  by  newly  weeks.  6  difference  pregnant  female  however,  (1954a), 3  glands  Havinga  5 week  last  the  McNaughton)  a month.  from 4  only  field  figure.  females  it  time  mammary  that  weeks.  Ovulation  al.,  is  completed rather  examined  her  (1955) f o u n d a  may  et  1946)  direct  occur  least  while  19&5,  careful  this  suckling pup.  Unlike  tions  that  7,  in  lactation at  observation  (McNaughton  captive  sighting  the  The  with  a  Venables  3.  Limited  August  hunters  suggests  the  suggests  seal  (1951) o f  and  on  19^5.  suggests  between the  17,  (1963) on  born pups,  from  with milk  agreement  Sergeant  work  occurred  collected  (1933) a l s o and  present  in  the  northern  ovulation  and  occurs  than  just  indirect  September.  (4 f r o m J u l y ,  fur just  after  data Of  5 from  10  seal  (Enders,  after  lactation  parturition.  indicate  that  lactating  August,  1 from  ovula-  females September)  -27-  none  had o v u l a t e d  corpus that  luteum.  there  was  no  cows  specimen,  caught  Its  ovulated 13  less  with  a  old,  probably  several  a  yet  in  female  taken  ovaries.  10,  also  multiparous  any this  of  centre and  year  13  appeared  1965, to  from for  the  had a  on  large  year  formed c o r p o r a  12,  old  1965, to  (8  lutea  collected  invasion. time  mm c o r p u s  12  follicles  to  fluid  first  September  1 three  old  capture.  luteal  mid-September,  specimens  10.:  a 7 mm f o l l i c u l a r  formed  new  reports  in  One  a  luteum  I965.  nullihad 11  were  on October  not mm)  in  found 9  and  1965. It  same  17,  earlier,  in  had  Well  4 multiparous  Wash.  had o v u l a t e d  females  but  ovulation  the  had  edge  weeks  absence  a week p r i o r  luteum  3 mm f o l l i c u l a r  ovulated,  both  than  which  Two m u l t i p a r o u s parous  from  of  September  lacy  A 3 year  with  on  the  (i960) s i m i l a r l y ;  evidence  taken  mm c o r p u s  centre,  judged by  Harrison  lactating  have  as  time. other  appears  and n u l l i p a r o u s No new  month  study.  from  than  corpora  these females lutea  September  Harrison  results  (1963)*  in  ovulate  have the  been area  however,  that at  both the  found covered  reports  in by  that  -28-  ovulations the  Wash,  period,  have  3 months  activity  around  the  this  in  the  Islands.  normal  mating  4 months  More  near  describe  (1959)  3 to  taken  work  earlier  is  required  point.  Delay  calculated validity,  of  Implantation  28,  from October probably  in  therefore Is  text  with 28  to  implantation  a  method  to  2  Gestation  will  be  to  about  7  ovulation 2-2^-  November  28  on  weeks is is  the (1954a)  months.  defined  birth.  VI).  months  and F i s h e r 3  and  occur  (1965) s u g g e s t s  period  is  of  been  and T a b l e  of  As  delay  Gestation  to  have  estimated  2 months,  (1963) s u g g e s t  date  growth  13.  Bishop  from i m p l a n t a t i o n  data(for  is  December  under  times  iii times  mid-September,  slightly  5.  period  a range  expected.  and H a r r i s o n  growth  on P r e n a t a l  implantation  November  implantation  from p r e n a t a l see  peak  period  than  adults,  and V e n a b l e s  Blastocyst  delay  young  subadults  Shetland  4.  The  In  earlier  and V e n a b l e s  sexual  on  occurred  here As  as  the  and average  the  average parturition  -29-  date  July  Using  a  similar  times,  Bishop  period  to  be  is  unclear.  be  about  Age  at  (1965) h a s  age  seasons  the  third  indirect  more p r a c t i c a l variation  of  The  for  this  reason  discrepancy  gestation  about  (1954a),  for  an by  age  at  to  9 months.  calculating  already the  sexual  ovulation.  This  can  be  of  first  ovu-  back  the  number  experienced by  presence  means  female  only 12, was  of  the  each  corpus  one  first a  I965, taken  ovulation recently  during  the  mating  year. method has  application.  the  the  examination  On S e p t e m b e r  her  The  gestation  albicantia.  nulliparous  of  by  direct  examined.  season  implantation  the  first  indirectly  and c o r p o r a  ovulated  determining  days.  230  calculated  used  from  represented  By  thus  (1963) e s t i m a t e s  at  directly  reproductive as  is  Maturity  the  and  period  and F i s h e r  criterion  is  lations,  luteum  days.  271  Sexual  determined  was  method f o r  1 months  maturity  ovary  gestation  Harrison  The  of  the  15*  corpus  luteum  proven  Figure  to  be  5 shows  diameter  as  it  of the  far monthly  relates  ••  20-  «°  • •  ^ 1 5 -  ••  ^ ••• •  • • ••  £  •  .2 10-  • • •  »  t  •  £ £  •  •  •  *t »\\ %  O  t  \  o  o\o o*  %  %  Q  «  o  O * % ODD • = °  5 -  A  A implantation  ovulation  0-  o  = Postpartum  A parturition  I  N  Prepartum  M  A  M  A lactation completed  T J  Time ( months j Pig.  5.  Diameter changes of the corpus luteum i n r e l a t i o n to the annual reproductive events. P r o m 57 f e m a l e s c o l l e c t e d f r o m s o u t h e a s t e r n V a n c o u v e r I s l a n d and the a d j a c e n t m a i n l a n d . The c u r v e i s f i t t e d by e y e .  N  -31-  to  the  of  10  annual to  15 mm i s  January,  after  maximum o f there  is  be  used  one  20 mm a t  as  year  In  Table  were  the  time  with  the of  the  diameter corpus  the  of  less  luteum  can for  Nineteen  way.  results  tissue,  history  ovulation. this  a  parturition  reproductive  in  to  connective a  and  of  They the  first  are  direct  method  I.  with  third  ovulations occurring  36$ and  17$  in  bined.  Small  lump  percentages  the  because  increases  of  with  Thus  detected  along  First years  albicans  diameter  September  Following  invasion  index of  from the  summarized,  term.  A  between  gradually  2 months.  an  ovulations  it  rapid  a corpus  10 mm l n  events.  maintained  which  a very  producing than  reproductive  no  year  olds  year  old.  immatures  sample  immatures yet  a  first  This at  had o v u l a t e d  in  size for  has  the  were  between  and made  fourth  ovulation  once.  that All  ages  2 to  second year,  recorded  years.  least  the  fourth  indicates  four at  the  occur  fifth it  years  com-  necessary  from the  occurred  females  in  47$  and f i f t h  there  5  in  must  5  years four  one be  6 years  to  five  some or  older  TABLE  Age  I.  Age a t  sexual maturity  (years)  at last mating season  for  138  females.  No Sample size  previous ovulation  0  35  35  0  0  0.0  1  14  14  0 *  0  0.0  2  11  7  4  0  36.4  3  18  3  12  3  83.3  4  5  0  3  2  100.0  5  7  0  1  6  100.0  48  0  0  48  100.0  6-28  First ovulation  Previous ovulations  % mature  -33-  In (Fisher, the  can  be  over  seals,  s u c h as  1954b) a n d P u s a  corpus  visible  some  albicans  structure usefully  several  is  for  hlspida  retained  in  estimating  maturation  Unfortunately  regression rates  in  both  Table or  ovaries  II  shows  harbour  when are  that  only  seal  the  1 or  number o f  related  even  absence  is  (see  "Fertility").  present  up  to  because  As  there  in  a multiparous  retained  for  no  4 years.  structure  in  less  the the in  corpora  and  these  more latter  corpora  very  old  always  at  estimating  would  1 corpus  albicans  structure  1 year  but  may b e  the  the age  predictive at  sexual  not  efficiency  the  Therefore  3  females;  female,  than  age.  contain  reproductive  least  seals.  albicantia  individual's ovaries  ages  not  Missed pregnancies  2.  their  is  to  s e l d o m do  explain high  in  is  the  greater  than  therefore  this  because  are  Individuals  4 corpora albicantia,  generally  macroscopically  applied  the  apparent  a  It  albicantia  is  as  1958a),  5 years.  to  This  (McLaren,  to  years.  between  groenlandlcus  4  applicable  variable  Pagophilus  Is  retained  value  of  this  maturity  must  - 43  TABLE  Age at  II.  Number  both  of  corpora  ovaries  (years)  of  Number  albicantia  of corpora  last  found  females.  58  in  albicantia  0  1  2  3  4  2  4  0  0  0  0  3  0  3  0  0  0  4  0  1  0  0  0  5-8  0  11  12  0  0  9-14  0  3  10  3  3  15-28  0  1  5  2  0  ovulation  be  limited,  for  applied  to  corpora  albicantia  of  3 and 4 y e a r  1 in  the same  the  most  earliest  earliest were  luteum  Estimates  was  age  age  derived  to  one  group  found  olds,  ovulating  conclusion  corpus  purposes,  in  and  2  must from  to  year,  be  olds,  5 to at  the  being  ovulate.  2 year in  this  8  As a  maximum  year  olds,  2 years. analysis  no  The of  the  counts. for  the  age  at  maturity  made  by  other  -35-  workers  are  years. 2  Scheffer  years, for  50$  Havinga the  (1956a, Bishop  within  and  Slipp  an  to  for  it  is  accurate  establish  range  of  the  his  at  5  least  Bishop  (1965)  fourth  year,  5 years. aging  to  2  (1944) s u g g e s t  3 years,  a n d 50$  suggests  used  annulations)  calculated  (1933),  third  1959) has  the  Of  suggests and  these,  technique  Laws only  (tooth  estimates.  Fertility Fertility 66  adult  corpora tive so  female  that  of  if  the  it  assuming  that  were  all  of  varies  those  tracts  from  was  in  taken  for  They  corpora are  implantation progress  easily  examination  or  during  the  lutea,  representato  had  detected.  of  ovulation recently  This  delayed  avoids Implantation  pregnant. III  for  each  were  which  from an  embryos.  period  c o u l d be  Table  failures  and  pregnancy  occurred,  results  determined  reproductive  albicantia  only  period  was  presents age  group  recorded  in  were between  f r o m 0$  to  a  100$  summary from 2  to  7 females,  of 28  these  6  fertility  years.  out  2 and 7 y e a r s  over  the  of of  years  66  Reproductive females,  age. with  As no  success  pattern  -36-  TABLE  Age  at  III.  (  Y  last  ovulation.  r  fertility  collected  s  A  )  v  Number  size  pregnant  in  between  %  e  mature  66  implantation  r  a  g  $  fertility  e  fertility  2  2  0  0.0  )  3  13  11  84.6  )  4  4  4  100.0  )  5  5  4  80.0  )  6  5  5  100.0  )  7  6  4  66.7  )  8-28  31  31  100.0  100.0  the  percent  Increased  efficiency  has  resulting  from  35  each of  and  Sample  fertility  of  specific  females  ovulation  of  Age  age,  no  age,  been c a l c u l a t e d  females, year.  with  Of  small 80$ the  sample  would 31  reproductive  be  to  reduce  size.  Thus  expected  specimens failures  average  to  between were  the  80.0  variation  from  the  produce 8  and  recorded;  sample  pups 28  years the  -37percent  of  is  100$.  thus  reproductive These  greater  than  females  examined were  to  the  parturition,  mortality It  the  adult  fertility  and  clear  young born  in  a  age  be  is  phocids,  s u c h as  in  these of  data  slightly  many  of  months  the  prior  intrauterine  that  females  at  least  keeping for  with  age  the  will  Thus  to  number  depend  for  Table  of  once)is that  reported  (0ritsland,  is  of  98$  1964).  the that  (animals This  for  other  w i t h 86$  w i t h 84$  which  on  shows  88.9$-'..  leonina  weddelli  IV  adults  72  of  significance,  a random sample  Mirounga  Cystophora c r i s t a t a of  group  expected.  1956b), L e p t o n y c h o t e s  8 years  several  additional  a random sample  estimate  age  c o n d i t i o n because  fecund population.  ovulated  over  probably  related  that  for  are  some  sample  in  and  estimates  collected  from  fertility have  this  distribution.  must  potentially  for  actual  c o u l d be  is  success  (Laws,  (Bertram, for  194-0)  females  -38-  TABLE  Fertility  IV.  adult  72  Age at  (Yrs)  last  in  a  random sample  of  females.  %  Sample  *  Age  total  specific  size  2-7  40  55.6  80 %  44.5  8-28  32  44.4  100 %  44.4  Total:  72  *  Causes  of  The  3  of  the or  females  3  100.0  factors  and perhaps first  88.9  responsible as  The  23-27  were  infertility  have  a)  unsuccessful  mating  blastocyst  to  Implant,  embryonic  which  abortion. have  1 multiparous  nature.  for  either  c)  females  mm)  fertile  Infertility  resorption, are  fertility  See p o p u l a t i o n a n a l y s i s f o r t h e d e f i n i t i o n o f random sample.  been c l a s s i f i e d failure  sample  %  ovulation  the  In  the  first  ovulated  for  the  female.  uterine  horns  horn circumferences very  b)  similar  to  In were in  those  of  each of  category  first  the  time,  case a  or  of  the  juvenile  case  (range  immature  females  -39-  (range  mm)  16-23  multiparous corpora  females  lutea  were  tissue  invasion.  parous  female  to  an  from l|-  early  may  regression,  female 5.3 that  time,  corpus  was  taken  cm l o n g  It  size,  of  to  she  should  for  a  small  the  same  females  at  that  definitely  in  progress  showed was  14  a n d was  normally  pregnant  probable  cause  for  specimen c o l l e c t e d  to  the  The  mm i n  of  multi-  cause  to  say  taken  size  as  Embryonic  in  a  primiparous was  of  only cm  37  similar  in  The  to  to  was a  for  The  equivalent  failure  1964.  signs mm)  (l4  This  be  obvious  An a b o r t i o n  reproductive  which about  to  degeneration.  condition.  or  occurred.  size  diameter,  29,  this  foetus  macroscopically  o n May  the  embryo  time.  average  signs  in  was  no  respective  connective  have  showed  1964.  Their  difficult  because  about  1,  nonpregnant  failure  is  luteum  a n d was  compared and  stages  attributed  enough  on March  luteum  average  be  corpus  fertile  resorption  varying  also  than  4 8 - 7 0 mm).  Implantation  long  The  for  in  examination,  have been  those  (range  Reproductive  may  after  resorbed. of  much s m a l l e r  resorption.  a gross  months  and  the  the  the  multiparous  uterine  rugae  -40-  had of  an u n u s u a l l y orange  yellow  tinge,  discoloration,  postpartum c o n d i t i o n . two  thirds  contain  (11  visible  multiparous resorbed to  the  previous  implies  taken  foetus  mm)  to  corpus  expected  small the  long  of  was  example.  Its  that.pregnancy  some  time  before  Male  reproduction  14,  must  embryonic  to  have  not  yet  or  examination corpus  appearance at  about  Another  A small  in  presence  only  aborted  1964,  evidence.  present,similar  did  recently  tissue.  enough p r i o r  uterine  normal  size,but  on June  patches  l u t e u m was  a m o u n t s "^of c o n n e c t i v e  traces  (10  similar The  its  female,  the  remove  luteum  mm)  with  this  to  late  been maintained  date for  loss.  Method From m a l e s , weighed values an  separately being  averaged  histological  removed  from  epididymus,  to  the  the  testis  the  center  except  in  nearest  when b o t h  analysis, of  the  and  small the few  epididymus  tenth  of  a  gonads  were  slices  of  right  gram, taken.-  tissue  testis  instances  was  For  were  and  where  only  the  left  was  collected.  sectioned, and  and  eosin.  niferous  stained  The  and  Slices with  average  epididymus  random o b s e r v a t i o n s  10  each or  of  the  absence  degree  of  f r o m an  of  mature  of  E a c h b a c u l u m was first  removing  boiling remove  the the  most  bone  in  checked  the  water  remaining  tubules  flesh for  semi-  from  for  the  presence  In  the  testis,  was a  with  the  determined section.  examination  about  connective  the  Concurrently,  in  for  of  estimated  section.  1  prepared  of  haematoxylln  were  development  all  embedded,  diameters  spermatozoa.  spermatogenlc  inspection  tubules  was  wax  Harris's  outside  in  tubules  10  were  a  knife, minutes  45  tissue.  by then to  Drying  was  Q  done two  for  growth  water a  12  hours  ln  an  parameters  displacement,  oven  were  at  90  C.  On  recorded:  and weight  to  the  the  cooling, volume  nearest  by  tenth  of  gram. The  sexual because  annual  maturity of  determined  their  reproductive will  be  cycle  treated  dependence  simultaneously.  and  the  age  independently,  upon one  another  at although  they  were  -42-  Annual  adult  The from  an  eastern Sexual  annual  and  older.  suggest  a  be  will  to and  and c o n t e n t , annual  months  of  from  during  winter  months  of  reduced  spring,  to  17  weight  changes  tubule  diameters.  about  200  November, found  to  summer a n d are  microns, while  gm o r  fall  size.  seasonal The  to  of  any  is  given  6  in  30  to  3^  gm,  thirds  6, activity. the  average  weights of  their  parallelling in  diameters, March  section  while  two  approximately  February.  gonad  March,  differences  age  examination  to  Closely  of  definition.  Figure  in  whose  years  and November,  about  between  male  this  the  in  south-  mainland.  histological  largest  occur  as  who  December  25  sizes  from December  here  April-May  ranges  from  adjacent  fluctuation  weight  are  taken  support  as  testicular the  determined  be p r e s e n t e d  sections  definite  the  defined  from a gross  size  Between the  and  was  males  spermatoza or  Evidence  following  testis  Island  will  cycle  mature  3^  contains  Results of  of  Vancouver maturity  the  reproductive  analysis  epididymus or  cycle  the  seminiferous averaging  and  October-  160  microns  are  Fig.  6.  Annual change i n t e s t i s weight, s e m i n i f e r o u s t u b u l e diameter and degree o f s p e r m a t o g e n e s i s . F r o m 3^ m a t u r e m a l e s c o l l e c t e d from s o u t h e a s t e r n Vancouver I s l a n d and the a d j a c e n t m a i n l a n d . The g r a p h j o i n s a v e r a g e m o n t h l y v a l u e s .  -44-  It weight  is  significant  and  tubule  that  sizes  closely  periods  of  sperm p r o d u c t i o n  Usually  50  to  producing the only the  100 p e r c e n t  mature  winter  spermatldia 9 winter  producing The  sperm at  months  do or  of  November)  active  and  three that  are  the  peak  are  actively  Seldom  during  sperm,  of  testis  November.  generally  although  are  in  that  continuously  sizes there  2 out  their  of  tubules  phase of  are  or  during  sperm,  period  some m a l e s  of  (Marchwhich  the  and  during  which  sperm throughout  from most  A similar  9 month  a  the  semimonth  3  which  sperm p r o d u c t i o n o c c u r .  regress  continual  a  investigated  and most  producing  produce  rate,  is  phase,  large  and  pression  time.  in  with  tubules  contain  there  regression  of  to  parameters  resting  out  the  had 40 p e r c e n t  testicular  testis  tubules  reduced  March  this  (December-February)  a  peaks  coincide  spermatocytes,  of  Indicate  appears  the  sperm. results  niferous  in  tubules  samples  therefore  tubules  both  and become  other  males  to  may  the  either  winter  active give  It  slightly  the  im-  sperm p r o d u c t i o n .  analysis  done  on  the  at  epididymus  in  - 4  Figure  7 describes  behaviour. does  not  August  It and  February, The  Unlike  exhibit  weight.  an  in  average the of  both  also March  adult  males  testes  are  it  which by  most  May,  80$  peak  closely tubule  225  value of  to  microns  are  incidence  have  about  from A p r i l to  definitely  adults the  will  have  males  them.  (n=0)  epididymal tubular  vari-  between  minimum to  During  Poor  of  17$  though  all  sizes  ejaculatory  the  sample  and O c t o b e r  establish  have  occur  about  even  reflect  Maximum  the  only  sperm,  producing  the  November.  however,  between.  h a n d do  from December  to  in  weights  the  sperm i n  from March  actively  of  in in  ms  6 gms  other  while  found  epididymal  9 S  of  microns  270  epididymus  variation  diameters.  of  testicular  parallelling  and November,  and November,  of  seasonal  value  sizes  by  of  extends  impossible  the  on the  The  representation  however,  tubule  March 210  to  gradient  diameters  February. ducts  low  seminiferous  to  175  marked  parallel  a continuous  activity  months  testis,  average  average  with  testicular  the  an  -  functional  a well  has  epididymus  ation  a  5  (n=l)  months  sperm. sperm,  make in Certainly  presumably  100  Pig.  7.  Annual change i n epididymus w e i g h t , t u b u l e d i a m e t e r and o c c u r r e n c e o f sperm i n the t u b u l e s . Prom 34 m a t u r e m a l e s c o l l e c t e d from s o u t h e a s t e r n Vancouver I s l a n d and the adjacent mainland. The g r a p h j o i n s a v e r a g e m o n t h l y v a l u e s .  -47-  all  in  June  and J u l y  September. tubules  and  An a v e r a g e  are  spermic  At p r e s e n t ,  it  of  c a n be  safely  for  at  least  the  end o f  testis found  sexual  based upon the  breeding to  and not fact  almost the  tends  of  that  and  the  the  epididymus  beginning  to  of  main extends  May  to  presence  of  s p e r m may b e  for  their  this  the  the  only  or  maturity  presence  the  in  the  produced i n  year  while  a restricted  would  sperm,  the  sperm i n  contention.  male  testi-  epididymal  capability  month o f  sperm  establishing  that  support  that  and  for  spermatogenesis,  epididymus,  upon  any  for  the  only  epididymus  season  state  sterile  and  The  in  being  season  in  the  mammalian  completed within  criterion  testis.  percent  stated  in  95)  the  epididymus  May  is  of  Thus  s h o u l d be  August  period.  the  (1962, p .  sperm u s u a l l y  breeding  also  patterns  and Walton  fertile.  from  in  September.  reviewing  maturation cular  5 months,  found  all  85  this  when s p e r m c a n b e  Bishop  to  65  during  period  In  definitely  The  therefore  it  the is  period, main be  from  September.  Very  few: d a t a  .have  been p u b l i s h e d on the  extent  -48-  and  time  seal. in  of  breeding  Epididymal  the  Wash  southern to  the  October  sperm has  (Harrison,  British at  season  Kodiak  been  the  (Fisher,  Island,  male  harbour  found during  during  i960),  Columbia  of  September and  1952)  Alaska  June in  from  (Bishop,  May  personal  communication), Dr.  Fisher  has  unpublished  data  Nova  a n d New  Scotia  permitted  on male  the  of  October only  occasionally  conditions April  are  is  Thus,  months  l\  in  suggested  31,  for  keeping for  the  the with  the  half the  west  of  testis. of  Adults  is  July  the  sperm i n  taken  seasonal  coast.  on  midand  are  year,  taken the  limit  only  their  on December epididymus  season the  and  first  Although  a breeding  males  to  epididymus  months  had  the  October  for  other  there  to  1955.  and g e n e r a l l y  the  each  and  1951  in  testis  significant.  a n d May  12,  collected  from June in  his  the  in  in  some o f  both  last  found  found  seals  abundant  the  quote  between  adults  June  represent  testis.  least This  From  sperm are  specimens  and  during  July. no  of  sperm are  epididymus  half  3  that  harbour  Brunswick  A good r e p r e s e n t a t i o n suggests  me t o  of  at  east  coast.  of  months  9  7,  -49-  Two First,  t h i n g s can be Implied from these d a t a .  the l e n g t h of the breeding season and probably  the d u r a t i o n of the main b r e e d i n g p e r i o d s are the same f o r males on the east and the west c o a s t o f Canada. Second, the end of the b r e e d i n g season on the e a s t c o a s t i s about 2.\ months e a r l i e r than that In southe a s t e r n Vancouver I s l a n d .  I t i s i n t e r e s t i n g to note  t h a t females i n Nova S c o t i a and New  Brunswick  have  t h e i r pups \\ to 2 months e a r l i e r than Vancouver I s l a n d females.  Although the p a u c i t y of the data  d e s c r i b i n g the male and female r e p r o d u c t i v e events does not permit a c c u r a t e r e p r o d u c t i v e comparisons between these two areas, i t w o u l d seem probable that both sexes have made e q u i v a l e n t adjustments t i m i n g of these r e p r o d u c t i v e events.  i n the  Males would  t h e r e f o r e be expected to p a r a l l e l the c l i n a l a d j u s t ments shown by the female  ( F i g . 4 ) throughout most of  the d i s t r i b u t i o n of the s p e c i e s . D e s p i t e the apparent a b i l i t y of males to mate w e l l ahead of the female b r e e d i n g season, t h e r e i s l i t t l e dence to suggest that most a d u l t mating at  evi-  encounters occur  any o t h e r time than d u r i n g the p o s t l a c t i o n a l e s t r o u s  -50-  period  of  mating  season  have  Age  the  female. of  begun to  at  the  sexual  sexual  (n and  the  season  have  maturity  For  collected adjacent  (May  to  being  immature, whose  the  testicular  the  most  during were  the  Each  was  seminiferous  tubules  either  breeding  whose  males  mature  the  of  baculum all  Vancouver main  males  Island  breeding  to  determine  classified Immature contain  have  as males  only  maturing developed  spermatidia,  males  age  of  the  season;  germ c e l l s  spermatocytes,  spermatozoa;  in  examined  mature.  the  degree  gonads  or  those  of  the  southeastern  maturing,  males  level  of  estimate  and changes  status.  during  the  to  male:  former,  from  spermatogonia include  the  September)  reproductive  those  in  mainland  their  are  gonads  been used  development,  rate.  = 46)  the  the  maturity  spermatogenic growth  female,  a month a f t e r  regress.  Two c r i t e r i a at  Within  have  or  epididymal  sperm. Table  V  summarizes  this  classification  to  Into  the  TABLE V .  Age (Years)  A g e a t s e x u a l m a t u r i t y f o r 46 m a l e s c o l l e c t e d f r o m s o u t h e a s t e r n Vancouver I s l a n d and the a d j a c e n t m a i n l a n d d u r i n g the main male b r e e d i n g s e a s o n (May t o September).  Sample size  i  $  Immature Spermatogonia  i  Maturing  S p e r m a t o c y t es  Spermatidia  Testicular sperm  Mpa itdu irde y m a l E sperm  0  7-  100  0  0  0  0  1  6  100  0  0  0  0  2  4  100  0  0  0  0  3  '8  25  38  12  25  0  4  6  17  66  0  17  0  5  7  0  0  14  29  57  6  4  0  0  0  0  100  7  2  0  0  0  0  100  8-11  2  0  0  0  0  100  *  For  1 exception  see  text.  *  -52-  percent  of  each  Clearly,  up  to  is  in  the  found  the  third  from the  category 2 years  year  occurs  immatures; The  first  ducts  are  males  at  rest  are  years  group  the  5 year  year  age  or  sperm d u r i n g 8  are  age  age  old  the  taken  no  epididymal  as  all  other  weights  and  this.  It  breeding  to  Baculum criterion  have  are  breeding  It  for  breeding has  the  are  season.  is  with  present,  there  of  the  immature; all  the  males  exception  (testis,,  6  epididymal  sperm  considered mature,  late  few  mature.  57$  testicular  features  are  ejaculatory  possess The  seen  similar  are  exception,  diameters, in  A  where  found to  mid-May,  probably  growth  one  as  stages  none  none  during  !  An e s t i m a t e d  mature,  greater  but  activity  It begins  sperm.  year,  years.  11  activity  sperm i n  olds.  sperm.  the  tubule  fourth  With  in  is  to  0  tubules.  maturing,  are  tubule  to  spermatogenlc  testicular  reproductive  is  no  developmental  the  maturing.  of  age,  of  of  to  In  most  this  ages  there  range  from spermatogonia situation  In  seminiferous when  large  found  and  and baculum  size)  transition  from  Is  an but  however, epididymus suggest the. n o n -  condition. frequently  determining  the  age  b e e n u s e d as at  sexual  a  maturity  in  -53-  pinnipeds  (Fisher,  (Hewer,  1958a),  sigmoidal, generally  the  limited  Prior  weights  in  and  8  and by  occur to  at  at  the  its  which  represent  the  harbour  show  9  the  volume. ages  first  is  with weights  times  and volumes  values  of  by  gm a n d  16  the  about  age be  cc  13  sexual be  of  seal. curves  is  of  the  and 7  to  increasing times.  bacula  inflexion years.  8  very  Inflexions,  are  at  is  shown t o  each curve  26  distinctly begins  d o u b l i n g t o .4 gm a n d  Between  growth  will  3 years,  respectively. rapid  the  i n f l e x i o n growth  and volumes  is  growth  growth  In  to  2  1956b),(McLaren,  growth  rapid  interpretation  validity  weight  points  age  This  Figures by  As  1964).  c o n s i d e r e d to  maturity.  (Laws,  1954b),  slow, cc  .4  however,  there  by  32  about  Asymptotic  reached  after  the  second  Inflexion. Like w o u l d be  the  other  accessory  expected to  be  hormones.  From I t s  be  from ages  greatest  most those  rapid. ages  growth 3 to  Immaturity prior  to  under  the  sex  organs,  the  influence  curve  these  7 years,  would first  thus  baculum of  be  Inflexion  sex  influences  when g r o w t h  is  represented (0-2  growth  must the by  years);  Fig.  8.  Baculum growth by weight f o r j o i n s average y e a r l y values.  98  males.  The  graph  20  o  o  -56-  maturity and  by  those The  tion are  of  ages  maturing  by  4 and  with  some  a  of  testicular  growth  in  the  hormones  in  are  years,  6  a  reduced  mature the  by  rate  all  males but  is  been  of  At  its  epididymides  are  mature  as  some  of  average  this  however,  that  most  time,  that  greatest  time.  are size  the  some  continues  age at  is  of  the  first males. from  the  although  would  peak It  be  size  of  quite  mature  prior  of  baculum  the  sex  age,  determined  most males  the  of  workers.  of  and  Certainly, as  of  rapid  attainment  5 years  greatest,  of  stages  amounts the  In  intensifi-  beginning  the  reached  the  activity.  suggested by  males.  males  growth  initial  than  considera-  age,  sudden  the  the  rather  at  a  Increased  probable, and  is  baculum growth  rate.  7 years  baculum  the  is  of  baculum  and  Thus,  has  found i n  gonad a n a l y s i s , at  activity  maturing  baculum growth  At  as  from a  2 years  there  +)  ages.  comes  slow  (7 y e a r s  spermatogenic  olds  circulation,  the  sperm c a n be  of  reflect  maturity  to  with  baculum.  baculum growth  second  intermediate  Up  lack  5 year  the  situation  immature  cation  These  the  both c r i t e r i a .  definitely  sexual  after  most p r o b a b l e  associated 3,  those  to  this is  -57-  reached perhaps sexual  2 years  after  the  attainment  of  maturity.  These agree  1 to  conclusions  closely  of  Bishop  at  6 years,  Harrison Fisher  with  the  (1965) who and  on  the  aged  finds  suggests  data that  that  (i960) e s t i m a t e s  (1952) a n d  age  sexual  (by males  age  to  (1933),  maturity  tooth  annulations)  normally  some may  the  Havinga  at  do  be  mature  so  at  5.  5  to  6  at  years,  years.  3  Discussion In  basic  reproductive to  that  design, cycle  found  in  in  the  the  description given  the  harbour  other  members  investigated.  The  to  reproductive  complete  single as  it  pup is  size  this  the  to  tendency  The have  cycle,  bearded a pup  Despite  8-5  (from  of  only  the  months.  Laws the  about  Is  once  45 to  similar  a  year  which an  2  variation kg),  a  exception  every  years In  the  parturition)  (1956b) h a s  pinnipeds  the  family  during  family to  very  the  seal  implantation  throughout  is  phocid takes  pup p r o d u c e d , ( 4 . 5  period  about  female  born.  1958b). of  gestation remains  is  thought  (McLaren, the  one  seal  for  with  noted the  -58-  exception  of  period  about  takes  is  place  annual 4  the  odobenids, 1 year  over  a 6  variation.  months  of  the  (Fay,  to  are  lactation  varies  in  end o r  after  An  apparent  mates The  Pusa  about  duration  hlsplda  from  exception  of  way  this  through  delayed  depending upon the  duration  is  As w i t h males is  has  one  to  to  the  Pusa  than  take  hlspida,  lactation  the  place.  1958a).  between  time.  to  the  which  (McLaren,  varies  lactation  1^  Towards  and mating  proportional  female  a number  of  This  period  to  reproduction  fundamental  during  spermatogenlc prior  phocids,  testicular  condition  2 months  more  from  ovulation.  period of  breeding species  inversely  to  The in  1958a).  is  remaining  lactation,  days  12  implantation  species,  parturition  to  10  ovulation  to  the  implantation.  (McLaren,  lactation,  half  of  generally little  parturition,  (0ritsland, 1964)  cristata  gestation  Birth  concerned with  and d e l a y  months  the  8 week p e r i o d w i t h  ovulation,mating  Cystophora  which  1955).  Following  year  period  in  the  a year  remainder.  activity mating  is  the  similarities.  activity  the  in  believed  season  and  with  There a  non-  In  most  to  begin  in  all  it  1 is  -59known  to  notes  that  for  at  least  begins  however,  end  shortly  have  research  is  Pagophilus to  3  been  month advance  the  required  f r o m one as  a point  cycle,  It  regional also the  of  that  breeding the  to  each  in  season  cycles  Using  the  the  equivalent  each  of  other  although  be  the  of  more  a  cycle  reoriented  pupping  season  reproductive there  are  cycle.  The  adjustment  male.  sex bear  to  that  4  adjustment  the  6  reproductive  female's  from Figure  in  differences  in  rioted  Pusa  later  another.  of  the  Thus  is  the  constant  made  data in  timing  relationship  other.  A number  for:  barbatus  ability  an  None,  point.  it's  the  mating.  seal,  is  in  spermatogenesis  approach  of  shown  clines  suggest  of  to  to  harbour  this  reference  was  before  feature  seal  region  the  on  (1954b)  groenlandicus,  4 months  found i n  harbour  Fisher  demonstrated  An i n t e r e s t i n g of  thereafter.  parturition hispida  (McLaren,  1958)  also  times.  whose  exhibit Clines  (McLaren,  1958b),  going northward;  (Mansfield,  phocids  have  1958a) a n d  1940),  been  Erignathus  pupping dates  Leptonychotes  (Bertram,  regional  become  weddelll  whose  births  become  -6o-  , later  going Where  be  south between distributions  detected,  well  but  marked.  grypus  pups  in  January-February, and  the  Baltic  Pagophllus Atlantic and  the  cycle  White  of  sider  common t o  of  the  host  of  mutual  aquatic  to  seal,  patterns  not  of  it  1957);  northwest  in  March-April,  (Fisher, the  1955). reproductive  members  reproductive  the  explain  July-December,  the  all  similar  reasons  variation  be  important  exhibited  by  other  the  problems  phenomenon i n  will  of  similarities  ecological  the  are  in  (Davies,  adjust  environment,  existence  attempting harbour  if  basis  the  the  most  in  in  cannot  Halichoerus  Islands  regionally  an  the  Mayen  to  for  the  Jan  pups  clines  Lawrence  Atlantic  which  S.  7o  differences  St.  capacity  and  in  of  February-March  presented  Thus  Gulf  0  o  S and  include:  in  On t h e  likely  this  Sea  family.  in  regional  February-March  the  o  60  discontinuous  eastern  in  March,  appears  found  the  the  Sea  of  groenlandicus  in  The  are  frequently  Examples  which  latitudes  the  in  to  members  are family.  the  also of  cycle con-  the  group. In of  a  a  seasonally  species  varying  increases  environment,  when t h e  occurrence  the of  survival certain  -61-  critlcal  reproductive  ecological it  is  young been  into  a  argued  Baker,  (  Fisher,  The the 1)  to  important  (  for  conditions.  difficult  be more  for  for  a (  (  ecological  it  must  this  satisfy  occur  in  to  one  restr-lcted it  must  clines the  4)  of  must the  et  a l . ,  which  of  has  also  phocids  1962  IV  ).  suitability  reqirements  short  the  the  animals  defines  several a  birth  period  range  of  :  of  the  pupping  a  present  species  broad  timing  regional  variation;  at  in  the  be  to  over  the  maintain  whole the  season;  pupping season  least  This  ) and  1961  over  pupping  the  the  could  area;  exhibit in  than  control  limitation  distribution  3)  only  favorable  speaking,  terrestrial  quantity  so as  season  of  Carrick,  p h o c i d s must  with  combination  environment.  Bullough,  ),  1954b  which  survival  number  ),  1938  coincide  Teleologically  Imagine  suitable  time,  2)  events  of  shows  harbour  pattern its a  of  geographical  occurrence  so  that  corresponding  seal  it  must  also  govern  -62-  5)  the  breeding  season  the  regional  variations  as  each  the of  pupping phocid,  must  It the  is  onset  mammals births  the  young  in  Canada.  western Also,  mid-winter  summer  in  at  on  diet  live  the  one  to  be  species  limitation  many  north.  North  America,  is  cor-  is  one  not  obviously in  births area  of  western  reversed  latitudes, in  This  later  distribution  It  and i t  ice-flows  terrestrial  progressively  Asia.  same  latitude  and  western  may in  occur mid-  another.  adjustments  unique  Europe  female;  shown  the  For  limited  eastern  eastern  the  One p o s s i b l e  pups  a  in  present  in  for  seal,  to  the  be  least  parallel  increasing  the  goes  harbour  and  in  one  only  States,  with  as  valid  can  at  delayed.  reflected  is  United  in  the  to  shown b y  year  for  male  specific.  that  is  the  adaptation  species  known  is  the  season the  spring  this  relation  be  well of  of  month o f  of  of  in the  almost  explanation  for  the  seal  may b e  1 to  2 months  after  shrimp  Crangon  harbour  pup.  For  exclusively  on  reproductive  the  differences  related  to  the  weaning,  -63-  (=  Crago).  throughout  Representatives the  exception of are of  no  young  the  fish  It  seals Scotia  has  by  It  (Fisher, IV),  Different  data  species  found  of  that  hypothesis, closely  the  the  harbour  with  for to  are  found the  which  be  in  Columbia,  possible  there  the  New  stomachs  Brunswick  and u n p u b l i s h e d and  will bulk  In  Holland  of  their  date), by  apparently  for  eat  diet  the is  does  not  female  et  thus of  the  al.,  (Bertram,  and  a  groenlandicus  oriented  pattern  that  p u p may b e  (Carrick,  have  young,  the  the  weddelli  particular  parallels  Indicates  Pagophllus  may  the  however,  for  leonina  seals  for  phocids  diet  and L e p t o n y c h o t e s  according  in  seals  Mlrounga  diets  cycle  reported  (1951),  but  seal  mellonae  on o t h e r  been  invertebrate  This  the  genus  1964a).  1954b),  to  of  (1952  invertebrate  has  this  British  Older  (Spalding,  rule.  in  Fisher  occasionally,  transitional  been  Sergeant  (1933).  Published  1962  vitulina  taken  Wash b y  Havinga shrimp  Phoca  data.  and Nova in  distribution  of  to  different  pup  food  explain  1940).  why  adjustment,  availability. the at  male least  seal.  A second p o s s i b l e  explanation  for  the  reproductive-  -64-  ecological  association  circumstance, in  the  past,  only  such  as  The  be  cycle.  If  Evidence  for  this  in  in  as  sexes  seals.  any  combination to  that  from  zoos,  cause  for  can  comes  the  be  found  today  triggers, are  now  orienting In  this  way,  reconciled.  from  transequatorial  and female  southern  b o t h make  Just  which  controlled  cycle.  southern  is  temperature,  are  existing  reproductive  When m a l e  taken  the  (Wunschmann,  nature  differences  reproductive in  in  original  hypothesis  are  limiting  clinal  water  hemisphere  the  October  April  of  seals  northern  shift  both  regional  transplanting elephant  the  involve  phenomenon w h i c h by  photoperiod or  equivalent  to  clinal  from  some  similar  maintained  dissociated the  rather  perhaps  described. may  but  may n o t  southern  hemisphere  a 6 month  Instead  hemisphere,  of  phase  pupping  they  pup  In  1964).  GROWTH  Introduction ' Very postnatal  few  data  growth  of  have the  been p u b l i s h e d on p r e n a t a l harbour  seal.  This  has  and  resulted  -6 5  from  the  difficulty  in  all  periods  of  the  lack  an a c c u r a t e  of  associate  sampling pregnant  gestation  growth  and u n t i l aging  are  by  and  and  Slipp  Fisher  Bishop tions for  Scheffer  (1965) h a s and has  the  and  seal  in  Growth  in  this  description  of  standard  ation  with  neonatal  and  in  the  from other  augment  a  of  Prenatal  growth  growth  and  aging by  dental  his  Slipp recently, annula-  growth  findings  be  restricted  to  length  and weight  vari-  Except have  teeth.  sample  postnatal  More  will  body  ages  small  (1963)  Alaska.  sex.  authors  Harrison  (1931).  summary o f  section  specimens,  annulations ments  age  Sperry  for  to  pertinent  Scheffer  (1933),  made u s e  presented  harbour  and  (1944),  Havlnga  (1952),  (1944) a n d  growth  from  with which  most  prenatal  by  technique The  for  at  recently  measurements.  publications Scheffer  very  females  for  been  prenatal  determined  Where p o s s i b l e , have been  a  and from  measure-  incorporated  to  size.  Method  analysis  of  60  adult  has  been  female  determined  uteri  from  an  from o v u l a t i o n  to  -66-  term  pregnancy.  implantation, blastocyst Following measured case  of  During  attempts  for  size  small  An e s t i m a t e growth well  curve  of  the  none  were  have been  of  was  either  an  the  sizes  portions done  implantation  (1958a) o n p r e n a t a l in  the  Some  of  the  from  their  starvation  umbilicus during  latter mothers was  obtained s t i l l  the  of  seals  and become  suspected,  primarily  between  lost.  no w e i g h t s  Data-have been c o l l e c t e d May  for  from  165  of  of They  pups  of  with  hunting residents. separated  cases  where  recorded.  postnatal  and November.  the  Collection  been  were  and  tables.  local  In  used.  work  growth.  and  the  The  the  and  course  had p r o b a b l y  to  pattern.  from those  found by  date  data  present.  normal  pups  the  seal  text  In  l e n g t h was  times,  ringed  subsequent were  examination  adapted  found. and  implantation  growth  this  were  free  length.  crown-rump  average  the  removed  standard  human f o e t a l  Neonatal  taken  but  established for  delayed  recover  fitting  described  by  to  b e e n made b y  McLaren  or  and  embryos,  (1955) o n w a l r u s  are  embryos  of  has  procedures Pay  estimation,  body weight  very  period  w e r e made  implantation, for  the  seals  Where  -6 7  pregnant females were weighed, the weight o f the f o e t u s has been s u b t r a c t e d so as to minimize the seasonal weight v a r i a t i o n .  Prenatal F o e t a l lengths and weights are summarized i n F i g u r e s 10 and 11.  As no newly implanted  foetuses  were 'collected to e s t a b l i s h the range o f i m p l a n t a t i o n times, i t has been convenient  to c a l c u l a t e them from the  known p a t t e r n o f human f o e t a l growth. account  An accurate  o f p r e n a t a l human growth, from known c o n c e p t i o n  dates, i s g i v e n by Schour ( i 9 6 0 ) .  As the harbour s e a l  e x h i b i t s delayed i m p l a n t a t i o n ( F i s h e r , 1954a) and humans do not, Schour's data, p r e s e n t e d  i n Appendix I  has been a d j u s t e d to r e p r e s e n t growth from  Implantation  to p a r t u r i t i o n . When human g e s t a t i o n time and body l e n g t h are expressed  as a percent o f the b i r t h time and s i z e ,  a growth curve showing t h e i r r e l a t i v e r e l a t i o n s h i p can be p l o t t e d , as i n Appendix I I .  From t h i s curve an  estimate o f the percent o f the g e s t a t i o n p e r i o d comp l e t e d can be determined  f o r any f o e t a l harbour s e a l  l e n g t h which i s converted to a percent o f the neonatal size.  1000-  co  Time ( months)  Pig. 1 0 .  P r e n a t a l body growth by l e n g t h from i m p l a n t a t i o n to b i r t h . From 3 3 embryos and 1 1 n e o n a t a l pups c o l l e c t e d from southe a s t e r n Vancouver I s l a n d and the adjacent mainland. The growth curve i s d e r i v e d from human growth i n Appendix I I I .  15000  . =6 O  =Q  D — Sex unknown  S  O  N  D  J  F  M  A  M  J  J  A  S  Time ( months) Fig.  11.  Prenatal  body growth by  weight  from  implantation  to  birth.  From 27 embryos and 5 n e o n a t a l pups c o l l e c t e d from s o u t h e a s t e r n Vancouver I s l a n d and the a d j a c e n t m a i n l a n d . The g r o w t h c u r v e i s d e r i v e d f r o m human g r o w t h i n A p p e n d i x III.  -70-  Table  VI  shows  how  individual  and average  calculated  for  taken  a  as  possible  differences  after  tion  time  to  average  approximately  December  13.  November  28.  These  The  uterine  230  and e a r l y  There  gestation  days  7 weeks  average  with  are  examination  in  September  November  (n  = 2).  =» 5 ) , h o w e v e r , Is  evidence  human a n d h a r b o u r  for  (n  All  larger  time  reflect  is  females  taken  embryos.  the  assumption  growth  curves  the between  have  = 2), October those  times  is  keeping with  to  thus  to  28  date  found  the  implanta-  period  had  seal  rate'  the  this  adult  None were  the  implantation  in  for  was  and  in  implantation  times  foetuses  growth  from October  sites  (n  after  the  been  period  apparent  necessarily  The  and December.  implantation  Individual  and  have  seal  This  Thus,  not  implantation  of  September  natal  would  dates  sample, s i z e  become  differences.  calculated  December  of  February.  differences  results  would  period,  1 7 harbour  February.  effects  which  size  ranging  to  of  a compromise between biasing  foetuses  gestation  implantation  sample  from December  chosen  the  that are  (n  during  pre-  =  4)  TABLE VT.  Field  #  C a l c u l a t i o n s f o r e s t i m a t i n g the d u r a t i o n o f the g e s t a t i o n p e r i o d and i m p l a n t a t i o n dates.Prom 17 harbour s e a l embryos c o l l e c t e d from southeastern Vancouver I s l a n d and the adjacent mainland.  Capture Embryonic $ length date length( cm) completed (a)  G 7 B12 13 18 21  <*>  Dec.9/64  1.4  • " 13/64 " 13/64 " 13/64  1.5 6.6 1.6 1.2 2.1  " 25/64  Jan.12/65  013  14  " "  14/65 16/65  "  17/65  "  20/65  10  " "  22/64 22/64  48  Feb.  "  31/65 2/65  "  13/65  " "  26/64 26/64  16  B25 G18  D 9  B29  34 A 1 2  Term Average  J u l y 15  7.5 8.1 6.6 10.0 10.5 3.6 8.2 25.0  (c)  $ g e s t a t i o n Days to G e s t a t i o n Days s i n c e birth completed period implanta(days) tion (d) (e) (f) (g)  1.7  9.0  1.8  9.5 20.5 9.5 8.0  8.0 1.9  1.4 2.5 9.0 9.8 8.0 12.0  12.7  238  217 213 213 213 201 183 181  11.0 21.5 22.5 20.5 25.0 26.0 16.0 23.0  235 268 235 218 206 231 231  179 178  224 233 234 206  175 173 173 164 162  213 268  21 22  47 22 18 25 49 52 47 58 60  26.5  13.9 32.5 31.9  27.O 41.0 40.5  151 138 138  207 234 232  37 53 91 62 94 93  83.0  100.0  100.0  0  230  230  11.5 27.0  4.3 9.9  30.1  39.5  C a l c u l a t i o n methods f o r : * 100  (°)  ( ) f  83.0  (d) (e)  from human growth and g e s t a t i o n (Appendix I I ) u s i n g c. J u l y 15 - a.  e  x 100 - d ^ average o f f (= 230) a - g 100$  f ) ( ) g  n  x  Implantat i o n date (h)  Nov. Nov. Oct. Nov. Dec. Dec. Nov. Nov. Dec. Nov. Nov. Dec. Dec. Nov. Dec. Nov. Nov.  19 22 28 22 8 19 27 26 2  24 24 17 10 4 14 25 26  Nov. 28  -72-  approximately gestation curve raw  and growth  c a n he  data  and  duration  sizes  have  imposed upon the  curve a  10 a n d and  result  growth  of  growth  not of  the  most  probable  prenatal  prenatal  sexual  apparent  when b i r t h  male  female  between  the  for  10 a n d  and  T test, in  are  and  No  is  weight  or  data  superin  theoretical  the  Such  relative  seal  can  clear This  are  significant  of  had  serve  not as  the  seal.  which  95$ c o n f i d e n c e either  if  compared.  from those  size  apparent.  this  lengths  are  the  curve  11 i t  the  III.  harbour  predicted  sizes  of  very  from  conversion  and weight  is  growth  neonatal  values  expected  curve  weights  study  sexes,  growth  correlation  been  relative  seal  Appendix  dimorphism e x i s t s .  subspecies.  (Student's  in  length  the  From F i g u r e s  the  The  human a n d  Thus  for  gestation.  values  have  similar.  present  seal's  a close  the  harbour  the  b e e n made  been  the  using  to  A predicted  the  hypothetical  11,  would  curves  and  for  plotted  actual  reduced  completed.  constructed  When t h e  Figure  when  o n human g r o w t h  and d e r i v e d ages  equivalent  that  is  particularly  In  Table  compiled have  no  been  from published  differences  limits) length.  are  VII  found  TABLE  VII.  Comparison o f  Length  Present  93.3 87.6  It  80.7  71.8  85.I 85.O  study 1!  11  II  II  II  11  11  11  86.5 87.8  11  87.O  II  II  85.O  1!  84.5  73.7 76.2 76.2 80.5 89.2  Tl  Slipp,  and w e i g h t s  &  11  11  11  11  10.9 11.4  11  tt  1!  it  Fisher, 11  11  1952 11  it  11  11  84.0  1!  91.0  Scheffer  73.0  Imler  ti  &  P_.  Present it  9.6 11.4 11.4  Female  it  ti  Fisher,  1952  11  it  ti  11  10.9  Scheffer & Slipp, 1944  13.7  Imler  ll.O  1947  &  Stroud,  richardi.  (kg)  study  it  y_.  Present  study  12.3 12.7 11.8  Fisher,  1952  12.3 11.8 12.5 7.5  Sarber,  Author  10.4  14.5  1944 II  for  Author  Male  13.6  n  11  ti  11  it  tt  ti  it  »  Scheffer  Slipp,  Imler  1947  9.1  (mean) S.D. t  Average  birth S.D.  81.0  (mean)  published  Slipp,  .7 .0  9.4 .43 size:  & Sarber, 11.5  83.0  6.6  i  2.7  cm  11.5  1.6  t  .8  Kg  & 1944  &  Sarber  V i c t o r i a Undersea Gardens  un-  11.5 ( m e a n )  11  11  1944 1947  S5.0  lengths  study  Present  83.8  II  Scheffer  87.5  68.1  Author  84.5  1952  it  birth  Weight  Female  11  Fisher,  80.5 91.5  and female  ( cm)  Author  Male  male  (mean)  -74-  Lengths  average  8 3 . 0 - 2.7 cm w i t h  a standard  of  6.7 cm (95$ c o n f i d e n c e  limits)  and range  to  93.3 c m , w h i l e  average  11.5 t  standard range  weights  deviation  deviation  f r o m 68.1  .8 k g w i t h a  o f 1.6 k g ( 9 5 $ c o n f i d e n c e  limits) and  f r o m 7.5 t o 14.5 k g .  Postnatal During very by  t h e 6 week  f a t , doubling their  weaning  TABLE  nursing period,  weight  t o 22 k g ( T a b l e  Weights  o f 8 pups c o l l e c t e d  eastern Vancouver weaning,  Date  Aug. Aug.  I s l a n d at  Sex  22/65 22/65  Sept.12/65 Sept.14/65 Sept.17/65 Sept.17/65 Sept.20/65  Sept.20/65  VIII)  (1965) r e p o r t s  from  south-  Weight  (kg)  the end o f  i9.a  Male • Male Male Female Male Female Female Male  22.7 31.8 20.9 22.7 19.1 22.3 19.1  Average:  results  become  time.  VIII.  Bishop  pups  22.2  a similar  from the extremely  high  weight  gain.  f a t andprotein  This content  -75-  6f  the mother's  example,  milk.  h a s 52$ f a t  Matthews,  however,  modest  in  weaning seek  (Coulson  the pup i s  food by  small  sample  o f males  male  generally  assymtotic  values  length  reached  at  6  An e s t i m a t e for  t h e male  difference  seal  Following  1964).  and' must  for a l l postnatal  comparisons  average  Is  gain  pup i n 3 weeks  by the mother  are summarized i n F i g u r e s  plotted  are  deserted  t h e 350$  made b y t h e g r e y  and H i c k l i n g ,  and weights  Unfortunately, the  seal  gain,  itself.  Lengths taken  elephant  for  has 40$ f a t and  The weight  194l).  1953) a n d t h e 200$ g a i n  17 d a y s  milk,  (Amoroso and  i n comparison with  made b y t h e s o u t h e r n (Laws,  a n d 11$ p r o t e i n  (Sivertsen,  is  grypus  Cystophora o r i s t a t a  1951),  6$ p r o t e i n  Halichoerus  of  12 a n d 13  each  over  slightly  time  larger.  and weight  respectively.  sex are  1 years  up t o t h i s  seals  values  by  of age.  The  suggest  that  For the of  limited  the  female,  150 c m a n d 65 k g  years. of  t h e most p r o b a b l e  c a n b e made  assymtotic  values  from a comparison o f the  i n t h e maximum s i z e s  attained  by both  sexes.  180-  — o = -  60-  T  T 4  6  7  =0^ = §  T  8-10  11-15  A g e ( years ) F i g .  12,  Body growth by l e n g t h f o r 165 s e a l s (79 males and 86 females) The graph j o i n s average v a l u e s .  T  16-29  00  T 2  T 3  6  T  7  8-10  T  11-15  T  16-29  A g e ( years]  F i g . 13.  Body growth by weight f o r 117 s e a l s (60 males and 57 f e m a l e s ) . The graph j o i n s average v a l u e s .  -78-  Table by  a  IX  number o f  largest both the  lists  males  length latter  expected  worthy 69  same  as  TABLE  by be  tend  to  the  IX.  the  on t h i s exceed  larger  by  a n d 87  females  of  in  Thus  36$.  Bishop  the  the the  largest  former male  same  in  and  94  by  values,for  Maximum l e n g t h s P. v . r i c h a r d i .  Length  (cm)  (kg)  (cm)  174  89 106 136 116  I65  144  85 109 71 111  114  -  and  in  10$  this  or  can be . to  is  be  note-  assymtote  essentially  of the  study.  recorded  for  Author  Weight  Weight  I69 170 I65 183  208  160 160  99 90  172  128  157  94  155  in  It  and weights  Female  females  amount,  males,  taken The  assymtote  weight.  kg f o r  Length  -  seals  subspecies.  the  kg  largest  (1965) f o u n d a w e i g h t  predicted  Male  Mean:  workers  length  that  kg f o r  sizes  and weight,  to  cm i n  165  the  Present Bishop, Fisher, Scheffer Scheffer Nanaimo Station, data.  study. 1965. 1952. & Slipp,1944, & Slipp,1944, Biological unpublished  -79-  Discusslon Laws growth  (1956a,  trends  within  (1959) t h a t  there  patterns  suggest  to  specialization group  Is  the  that  is  rate,  aged  data  able  to  a and  make  now b e  tested  smallest  in  length  rapid  growth  is  slow  being  growth  the being  he p o i n t s  size,  a more  Although  available  the  the  (Mlrounga)  females,  larger  was  specialized  to  generalizations,  rapid little  Laws,  pattern  out  he  and age which  was at  can  material.  other  implies  least  specialized,  seal  with  the  these  to  this  most  maturation.  of  w i t h aged  The  growth aquatic  then  towards  vitulina  of  Monachinae,  Working  from  degree  and  postulated  seal  elephant  earlier  has  harbour  the  Relative  Laws,  the  the  the  estimates  maturity  the  is  He  phocids.  with  growth  from subfamily  increasing the  trend  on Phoca  sexual  of  next  advanced.  there  growth  evidence an  with  reviewed  Phocldae.  and f i n a l l y  Cystophorinae, most  is  Phocinae,  Lobodontinae,  the  the  within  most p r i m i t i v e ,  has  1959)  phocids,  the  harbour  and w e i g h t .  growth  represented  by  and  late  species  seal  According maturity. which  Is  one  to When  complete  most  -80-  of  their  as  Mlrounga  a  slow  growth  From  rate  the  was  at  in  the  estimates at  with  the  on r e p r o d u c t i o n . significant  states  that  growth  and  of was  pinnipeds,  production  higher  a  at  By  of that  than  the  most.  such has  was  indeed  of  average  in  seal  completed  the  seal  phocld  when a b o u t  averages  difference  between  of  87$  growth  before nutritive  in  the  Present 91$,  species  12  and m a t e r n a l  young.  a  (1956a),  From  aiding  is  pattern.  relationship  thus  he  section  presents  Laws  age  however,  completing growth  large  an  harbour  maturity.  reduced,  This  was  growth  seal  general  foetal  harbour  sexual  This,  suggested  reached  at  the  female  harbour  sexual  age  percent  fundamental  relatively the  seal  there  proposed by  almost  would be  year,  between  the  from the  competition  requirements  indicates  Is  the  5 years.  3 years  puberty  completed.  pregnancy,  at  hypothesis  age  the  For  Thus  there the  and  be  departure  Another  which  found that  year. to  first  harbour  relationship  maturity  variance  the  for  Laws  females  first  the  completed).  (36$  known, linear  during  end o f  species  approximate maturity  the  completed)  (85$  growth  maturity  by  or  could result  data slightly from  -81-  the  fact  young  that  for  her  comparison, her 1  growth  the  an  the  the  adult  phocids.  equal  (e.g.  male  Species the  in  female  breeding for  by  this  role  are  curve  of  the  sociological that  it  the  the  1  male  in  their  expressed in  maturity.  follows  the  total  is  size is  others  while  several  growth  Males,  In  times  body  size.  The  (e.g.  Phoca  than  social  this  contest aggressive  attainment  sigmoidal  increase  characteristic  others  larger  who m u s t  the  are  leonina).  to  double  larger  s t i l l  larger  adapted  in  and  among  they  an o r g a n i z e d  Growth  of  urslnus)  slightly  Mlrounga  secondary  ratio  varies  have  the  of  84$  9.  in  (e.g.  only  weight  from s l i g h t l y  harem.  the  :  barbatus),  and harem,  male,  of  large By  (Callorhinus  female  associated with  increasing is  the  much l a r g e r  system,  role  some,  anywhere  which  territory  of  difference  Erlgnathus  to  a birth  a very  weight.  completes  seal  ratio  has  : 6 by  1  schauinslandi);  may b e  vltulina)  fur  seal  c o m p l e t i n g 88$  sex  In  Monachus  seal  Alaska  in  of  and has  Intermediate  (e.g.  the  a ratio  by p u b e r t y  The  harbour  elephant  intermediate  having  female  size,  while  : 15,  is  the  growth  occurring  female  of  at  differs  mammalian p a t t e r n  in of  -82-  the  single  sigmoid,  species.  All  behaviour thus  in  males  of  harbour  latter  exhibit  is  available  the  this  as  no  found  in  evidence  the on  the  seal  suggests  category.  Hence,  secondary  growth  POPULATION  non-harem  forming  breeding  promiscuity as  expected,  and the  acceleration.  ANALYSIS  Introduction Two b a s i c population tion  requirements  c o m p o s i t i o n and  s h o u l d be  randomly  sampling.  These  former,  generally  are  Investigations. harvested ice  or  group  are  land  taken  representative the  of  exploitation  being  dependent  a  species  the  of  entire  b y man h a s upon the  assess  form  the  are  large the  random and  sample  market  the  In  the  pinniped  commercially aggregations  year.  will  demand,  is  seldom Further,  frequently  on  Usually  exploitation  k i l l  popula-  during  population. been  of  particularly  to  of  that  stable  which  seasons  not  analysis are  sampled and  difficult  certain  Thus  dynamics  when t h e y  c o m p o s i t i o n Is  selective.  the  considerations,  Most  at  in  be as  inconsistent,  changes  in  -83-  p o p u l a t i o n c o m p o s i t i o n might w e l l a f f e c t I t s s t a b i l i t y . To a l a r g e degree these problems have not been i n v o l v e d i n the c o l l e c t i o n o f harbour s e a l data. At l e a s t In B r i t i s h Columbia, no l a r g e groups are formed, data, are r e p r e s e n t e d from s e v e r a l d i f f e r e n t areas and from a l l times o f the year, and because t h i s  seal  must be hunted i n d i v i d u a l l y , commercial h a r v e s t i n g i s not s e l e c t i v e as to sex and very l i t t l e ,  i f any, to s i z e .  E x p l o i t a t i o n f o r bounty and more r e c e n t l y f o r the h i d e , has remained at about the same l e v e l f o r the past 50 y e a r s , suggesting that man's e f f e c t on the s t a b i l i t y of the p o p u l a t i o n has remained r e l a t i v e l y c o n s t a n t . The core of t h i s s e c t i o n w i l l t h e r e f o r e c e n t r e mainly upon the a n a l y s i s o f those s e a l s which are c o n s i d e r e d to have been randomly  collected.  Method Of a l l p o s t n a t a l s e a l s examined, c o n s i d e r e d as being randomly c o l l e c t e d . s e a l s which, to my knowledge, r e s p e c t to age or sex. employed,  each was  245 w i l l  be  These are  have been taken without  In cases where hunters were  asked to save the f i r s t 20 s e a l s  -84-  shot  every  possible The  month.  unconscious  sample  that  the  excludes  kill  population season. annual  will  This  for  averaging  pupping  with  following  pups be  was  their  just case  sections  of  just  values  the  bias  are  to  by  prior  parameters.  prior in  to  the  to  so  average  pupping  deriving This  average  has  exist  been  just  after  pupping.  "Growth"  treated  hunter.  the  the  necessitates  calculated  any  months) of  to  reduce  the  0-5.9  representative  certain  those  designed  (ages  limitation  done b y  As  was  sampling  composition  values  because  This  chapter,  independently,  interrelationships,  were  the but,  derived  contemporaneously.  Population  composition  1.  Sex  ratio  From to  be  males  Of  the  a  sample  or'essentially  50  pups  examined,  deviation  from  the  from 158  of  sampling pre-weaned  1:1  a  45$  embryos,  prenatal  were  found  ratio.  c o m p r i s e d 58$.  This  however,  Bishop were  49$  sex  1:1  males  ratio,  variation. pups,  35  probably  (1965) f o u n d  males.  In  other  results that  for  phocids  -8 5  for  which  the  male  50  large  ratio  the  Here  the  the  sex  an  is  From ages  but  females.  groups,  section  is  0 to  ratio from  5 years The  : of  result  very  much.  4 6 . 5 $ were  composition  over  reference  must  (Tables  estimated  that  during  the  all  pups  of  at to  ages  become  will the  differs  born  end o f  the  average  ratios,  important  for  or  later  when  curve  of  age  Figure  of  males  to  1 with  equal  survival  In  is  a gradual  the  con-  size.  individual  die  average  46.9$ males.  ratio  males  pupping  of  the  XI  the  is  the  age  in  The  sex  survival  be  be  pupping  47.2$ males.  population  5 years, 1  the  tables  changes  the  from  life  Thus,  and  of  on  32 f e m a l e  will  approximately after  all  estimate  implied  by  for  and p r e - p u p p i n g  sex  be  sex  245.  year  differ  range  245 s e a l s ,  of  age  examined,  the  average  ratio  difference  The  Is  of  whole  sidering  sample  to  been  the  it  and  does  unlikely  following  post-pupping  as  and  32 m a l e  season  This  is  random  year  random sample  for  it  the  and X I I ) . season  within  the  if  To o b t a i n  to  be  Thus,  whole  made  have  to  .In  the  pups  tends  situation,  males.  of  component  - 3$.  1:1  numbers  more  in  14.  females both  rapidly  decrease  groups  sexes,  than the  -86-  p r o p o r t i o n of males a f t e r 5 y e a r s .  Age groups  older  than 20 years w i l l be composed almost e n t i r e l y o f females.  I t i s t h e r e f o r e noteworthy  that the value o f  an average sex r a t i o c a l c u l a t i o n w i l l depend upon the degree o f sampling b i a s . the  younger age groups, the r a t i o w i l l tend to be  to the 1 : 1 r e l a t i o n s h i p , the  I f sampling i s b i a s e d towards closer  while i f i t i s b i a s e d towards  o l d e r ages, the r a t i o w i l l  suggest fewer males than  females.  2.  Percent mature The percentage o f males and females  which  have a t t a i n e d s e x u a l m a t u r i t y i n a p o p u l a t i o n can o n l y be m e a n i n g f u l l y determined from a random sample. u s i n g the l i f e  table  Again  data, the average annual p e r c e n t  mature can be determined by averaging the v a l u e s  calculated  f o r the p o p u l a t i o n j u s t p r i o r t o , and j u s t a f t e r the pupping  season. For  the female segment of the p o p u l a t i o n , 72  females were found to be mature i n the random sample of Table X I I .  Thus Just a f t e r pupping  (sample  s i z e = 163),  44.2$ of a l l females are mature, while j u s t p r i o r to  -87-  pupping  55.0$  minus  (163  are  the  mature.  number  The  of  annual  pups  born =  average  is  131)  therefore  49.6$. For percentage percent the  the of  male  males  which  These  calculations  TABLE X.  are  (Table  males  mature  0 1 2 3  %  5 6-20  : 100.0  = from  c  = a x  mature  in  XI)  by  and  each  shown  age  in  is  each  the  average derived age  group  Table  b  % mature in post  V  the  group  percentage  Table  of  of  (Table V ) .  X.  males  % mature in pre-  pupping  pupping  Annual average  sample c  sample d  mature e  0.0 0.0 0.0 0.0 0.0 5.5  24.0  37.8  29.5  T a b l e XI  = from  b  0 0 0 0 0 57 100  24.0  a  b  age  21.9 15.1 10.3 10.9 8.2 9o6  4  are  mature in each  sample a  Total  are  annual  Annual average p e r c e n t of mature a random sample o f m a l e s .  % of post pupping  (Yrs)  which  the  composition represented  random sample  Age  segment,  d =  33.7 £  c  i a - $ pups e = c + d  2  born  in  -88-  Thus  just  just  prior  average  after to  is  pupping,  pupping  therefore  3.  that  the  tion  composition  random  to  some  is  provided  and  degree  just  for  by  some  of:  in  British  shooting  weeks  in  one  would  be  expected  as  presently  is  selected between  the  excellent probably  and to  doing  sample  the  April  These  months  chosen  would  be  near  could  be  accurately  would  not  term  and  of  annual  the  of  begun u n t i l  and  sample. taken  This  by  Bill  experienced  seal  hunting  technique  remaining  for  several  our  population  as  randomly  their  files,  which from  yet or  they  1954  pregnant  their  June  season  of  seals  and  popula-  most  because  noted,  data  for  and May,  thus  the  Their  assumption  average  most  this  the  pupping  field  From  number  months were  the  usually  possible.  total  have  to  for the  randomness  ambush,  area,  the  represents  Columbia.  from  The  37.8$.  possible  prior  the  while  test now  sample  are  mature,  mature.  33.7$  is  Don M c N a u g h t o n ,  hunters  there  A sampling A test  29.5$ a r e  they had  to  females  pupping  July.  shot  1964.  reproductive the  coast,  status season  Their  records  -89-  show  that  of  the  858  randomly  pregnant.  The p r e s e n t  for  seals  of  the the  245  of  all  mature  Therefore, of  858  seals  females. sample the  females  on  this  the  Population  be  the  reproductive  pups 1  expected  to is  have only  224 3.9$  considered  and  each  McNaughton s  factors  are  and r e a l i z e d  natality  the  or  birth  capacity  rate, to  88.9$ year.  sample pregnant the  2  equivalent  eliminated,  physiological c a n be  reproductive  is  and  dependent  a d d new  Theoretically,  its  from  mature,  Natality  expressed at  seal  53.5$ were  reinforced.  population.  mortality  were  discrepancy  Natality, the  representative  produce  the  that  dynamics  1.  to  would  c o m p o s i t i o n s may b e  assumptions  upon  females  basis  would  As  (being  were  233  suggests  season composition),  55.0$ of a l l  females,  seals,  investigation  collected  prepupplng  shot  individuals  when a l l  natality  maximum.  estimated  ecological  can The  for  and p o p u l a t i o n  be maximum  the data.  harbour As  -90-  fernales of  all  just  may m a t u r e females  prior  Thus,  as  In  would  for  female  these  per  natality  mature  (72), t h e i r  the year  68$  of  Time  the  for  reproductive  sexes  format  is  figures  test",  random sample season)  and  the  from the  and  .49  Thus,  the  seal  of  life  from the  per  year.  attained. actual  number  (38.9$),  and  pups p e r  female  realizes  were  number  245  seals to  Quick  Techniques.  that  be  of  applied  been  about  (1963)  Using In  prior  to  condata  the  in same  the  pups p r o d u c e d by  (just 64.  have  random sample  p r e s e n t e d by  the  calculated  tables  1  pups  .58  seldom  XII).  maximum  female  .39  72$  (Table  is  success  58$  natality.  Investigational  "sampling  is  reproductive is  year,  pups p e r  calculated  specific  both  standard  Wildlife  after  periods  figure  age,  Mortality  2.  in  .73  this  potential  of  a random sample  respectively.  structed  just  born each  and  when  2 years  mature  random sample,  its  as  respective  year  Actual  per  be  pupping i n  reality,however,  from  early  o n e p u p may b e  natality per  to  as  the  the  pupping  Assuming that  the  -91sex  ratio  pups  at  would  birth  have  An e s t i m a t e from b i r t h  of  composition  on the  of  the  kill  d'  ,  deaths  XI  1  to  vital than  relative  specific  the  the  can  first  age  now b e  the  number  The  the  1000,  surviving  mortality  rate,  q  made  resulting first  number  Column 3 c o n v e r t s per  sample.  distribution,  second gives  deaths  male  32  year.  statistics. the  and  random  summarize  gives  the  female  32  to  from  derived  and  1,  statistics  and XII  left  the  :  added  each group.  represents age  the  and  column  in  been  rather  Table  is  d  per ,  ,  the  taken, absolute  while  1000,  is  x,  1  column  .  4  The  determined  from  the  X ratio (l_.)  of  the  number  e x p r e s s e d as  dying  (d )  to  x  a percent.  the  The  number  surviving  mean e x p e c t a t i o n  of  A.  life,  e„,  animals  is  calculated  between  age  from  groups °  the  L  *  mean number  (where L x  =1 x  v  of , 1 /  x  ,\)  (x+1)'  +  2 In  the  equation  e  = L  x  x  + L / „ -, \ (x+1) X  From the  1  values,  .  .  , + L/  v  (x+n)  x  survivorship  curves  have  X  been  constructed  general  form  they  for are  both very  sexes  in  similar,  Figure the  14.  cohort  In numbers  TABLE  XI.  Life  table  The number a starting  for  Number Age  (years) X  0 1 2  dead  collected d<  X  32  114 r a n d o m l y  Number  dead p e r 1000 d  X  2  14  i i  3  20  12 13  0  4  5 6 7 8 9 10  14  15 16 12  14 13 • 8 1  1  1  7  7 0  7  15 16  2  14  17 18  0  0  19  20  Total  0  0  Age  fic mortality rate  1000 781 630 527  413  336 240  151 96 76 ,69 55 35 28 28 21  7  146  1000  0  0  speci-  q  1  0  0  of  survivors p e r 1000  7 7 7 7 7  0  1 year  Number  X  3  3  males  e s t i m a t e d (see t e x t ) pupping season.  1  219 151 103 109 82 96 89 55 20  22  collected  o f pups b o r n has been c o h o r t j u s t a f t e r the  X  21.9  19.3 16.3 20.7 19.6 28.6 37.1 36.4 20.8 9.2 20.3 36.4 20.0 0.0 25.0 66.7 0.0 0.0 0.0 0.0 100.0  W  age to  and  older.  represent  Mean  Life  expectancy e X  4.0 4.0 3.9 3.5 3.3 3.0 3.0 3.4 4.1 4.0 3.4 3.1 ' 3.6 3.4 2.4 2.0 3.9 2.9 1.9 .9 .6  TABLE The  XII.  number  just  after  X  0 1 2 3 4 5 6 7 8 9 10 11 12 13 14  15 16 17 18 19 20  21 22 23 24  25 26 27 28 29 Total  Life of pups  table born  the pupping  d»  randomly c o l l e c t e d  season.  Symbol  d X  32 36 17 11 15 5 6 6  5 3 3 2 6 5 1 0 3 0 0 1 3 0 1 0' 0 0 0 1 0 1 163  f o r 131  has been e s t i m a t e d  meanings  are given  1 X  197 221 104  68 92 31 37 37 31 18 18 12 37 31 6 0 18 0 0 6 18 0 6 0 0 0 0 6 0 6 1000  females  1 year  (see t e x t ) to r e p r e s e n t  x-  q  X  (*)  19.7 27.5 17.9  410  22.4  318 287 250 213 182 164  9-7 12.9  134 97 66 60 60 42 42 42  36 18 18 12 12 12 12 12 6 6 0  a  i n Table  1000 803 582 478  146  o f age  14.2  14.8  14.6 9.9 11.0  8.2 27.6 32.0 9.1 0.0 30.0 0.0 0.0 14.3 50.0  0.0  33.3 0.0 0.0 0.0 0.0 50.0 0.0 100.0  and  older.  starting  cohort  XI.  e X  5.0 5.1 5.9 6.1 6.0 6.6 6.2 6.1 6.0 6.0 5.6 5-2 4.6 5.2 6.4 6.0 5.0 5.9 4.9 3.9 3.5 5.5 4.5 5.5 4.5 3.5 2.5 1.5 1.5 •5  -94-  being  reduced  slowing curves Prom the  with of  an  very  increasing  the  Pearl  analysis  female  annual  birth  29  on r e a c h i n g to  19.6$ to  the  of  sexual  maturity  data  and  Males  tend  to  years  3.4  years  has  an a d d i t i o n a l It  longer,  Is  5.3  the  the  years  interesting  reflect  relatively  change  at  a  to  is  this  life  slightly  probably during  time, the  head, or  span of  only  although  average  average  mean  to  to  note  that  can  neck, Immature  20  life for  live  female  longer  related  years  some r e a c h  male,  expected  from  the  bulls  females  The  from  17.6$  increasing  male  around  years  c a n be  while  rates,  5 years,  1965).  that  years),  a  30  (Bishop,  indicates  (0-17  have  females  diagonal  mortality  averaging  Seldom w i l l scars.  25  to  adult  scars  such  also  groups  tail.  the  at  Frequently fresh  the  mortality.differs  the  possess  to  seen  gradually  classification.  specific  The  of  are  (1935)  rate,  Male  and  They  is  years.  season.  compared as  age  curve  aggressiveness  shoulders  old  the  mortality  s e e n w i t h many  males  age.  25.0$ a n n u a l l y .  breeding be  initially  and Minor  survival  constant to  rapidly  as  expectancy most  only  (0-25  age  about years)  live. these  mortality  Age ( years Fig.  1 4 .  Survival  curve  for  males  and  females.  -96-  e s t i m a t e s are very s i m i l a r to known r a t e s i n the southern elephant s e a l (Mirounga  leonina).  In marking  (branding)  s t u d i e s i t was found that between b i r t h and 7 and 8 years of age there i s 86.0$ m o r t a l i t y i n males and 79.5$ i n females  (Carrick, et a l . ,  1962 V ) .  Over the same p e r i o d  (from F i g . 14) harbour s e a l m o r t a l i t y Is approximately 87.5$ and 77.0$ r e s p e c t i v e l y .  Annual m o r t a l i t y i n both  sexes o f C a l l o r h i n u s u r s i n u s has been estimated at 5 to 8$ (Kenyon, e t a l . , females  1954), i n H a l i c h o e r u s grypus, 6.7$ f o r  (based on Kenyon, e t a l . ,  1954) and 40$ f o r mature  males (Hewer, 1964) and In both sexes o f Lobodon carcinophagus, 25$ (Laws, I 9 5 8 ) . M o r t a l i t y i n the harbour s e a l f o r the f i r s t 12 months i s a t s t r i k i n g v a r i a n c e w i t h harem forming p i n n i peds.  When both sexes a r e averaged, m o r t a l i t y i n the  harbour s e a l f o r t h i s p e r i o d i s 20.8$, o r , w i t h e x c e p t i o n of the a d u l t males,  approximately e q u i v a l e n t to that o f  the o l d e r age groups.  C a l l o r h i n u s u r s i n u s on the other  hand i s estimated to s u f f e r a 60$ m o r t a l i t y d u r i n g the same period  (Kenyon, et a l . ,  to 50$ ( C a r r i c k , et a l . ,  1954), while Mirounga 1962 V ) .  l e o n i n a , 40  Coulson and H i c k l i n g  (1964) suggest t h a t m o r t a l i t y ranges from 9$ to 40$ In the  -97-  first  month o f  found  that  crowding highest that  a  this  at  birth,  low e a r l y  section  data  the largest rates.  s u c h as  Population  has been  Columbia  large  very  from of  size.  is  found i n a  relatively  seal.  mortality  seal  numbers  refer  like  t h e numbers  from study  the Department probably  not  many  approximations at  quote while  f o r the e n t i r e  the present  does  to  the  seasonally other  to e m p i r i c a l l y  (op. c i t . ,  may r a n g e  is  surprising  infertility".  Past  have p l a c e d  t h e number  number  not  of  the  rate  McNaughton and McNaughton),  Alaska)  having  is  difficult  1964a) a n d 20,000  that  harems  the harbour  the harbour  into  population  the degree  estimate  Because aggregate  of  with  They  it  on p r e n a t a l  on "Causes  grypus.  Thus,  mortality  breeder  For  for Halichoerus  was a s s o c i a t e d  mortality  solitary  it  life  estimate  for  (Spalding,  seal  Scheffer  subspecies  hunters,  (1958)  Data  and from  return  f a r In  the bounty suggest  excess  that  of these  suggests  (California  50,000 t o 200,000.  of Fisheries  the  British  17,000 from  pinnipeds,  to  derived records  t h e minimum  figures.  -98-  Table annual shot The  XIII  bounty  in  return  British  average  seals.  As  the  level  of  must  represent assumes  over  this  that  of  c a n be  years. the is all is  the  remained  to  present  sustain  It  was  to  4.7  of  to  I963.  years  is  2922  able  to  many y e a r s ,  withstand the  sustainable  constant  and  then  is  the  XI  random sample averaging  is the  the  bounty  includes  the  data  year.  to  mortality  on the  360  survivors  are  it  data  890,  takes  is  or  pupping,  survival  about  6 pups  to  60$  4.7  curve  from the  of and  cropping  When t h e  left  4.7  mean age  because  Thus  to  the  about  after  of  kill  equal  and X I I ) ,  immediately  cohort  the  cropping.  (Tables  determined by  starting  If  present  and  related  k i l l .  p o p u l a t i o n number w h i c h  tables  throughout  figure  sex c o m p o s i t i o n o f  annual  the  seals  1914  to  groups  years.  this  life  age  the  Fisheries  number o f  these  random sample,  estimate  annual  and  of  years  been  minimum a n n u a l  has  to  of  for  period  used  the  the  38  age  approximately average  for  the  necessary  now  kill  for  over  exploitation  samples p r i o r  age  records  p o p u l a t i o n has  From the average  Department  that  the  required  the  Columbia,  yearly  this  one  gives  years (Fig.  annual mortality  replace  of  every  14),  -99-  TABLE seals  XIII.  Figures the  The number  in British  Columbia  from F i s h e r  Federal  Year  1914-15 1915-16 1916-17 1917-18  of  of  seals  bounty  400  bounty  3546  bounty  3282 1168 1001 Annual  By  year  o l d seal  t h e same  seals  token,  a year,  population  which  whose  would  average  is  from  average  of  961 1978 1949 2740  1948-49 1949-50 1950-51 1951-52  2693 2556 2289 2791 3397 3257 4333 3987 3426 4053  3741  3431 2878 2351 2118 4962  2922  removed  to maintain  require  harbour  1944-45 1945-46 1946-47 1947.43  1952-53 1953-54 1954-55 1955-56 1956-57 1957-58 1958-59 1959-60 1960-61 1961-62 1962-63 1963-64  1933 4295 4569 No  No.  Year  567 3209 5944 6308 6084 4300 No  for  and u n p u b l i s h e d data  748  No  claims  1914 a n d 1963.  Fisheries.  2237 749 78'5  1918-27 1927-28 1928-29 1929-30 1930-31 1931-32 1932-33 1933-34 1934-36 1936-37 1937-38 1938-39 1939-40 1940-41 1941-42 1942-43 1943.44  4.7  between  (1952),  Department  No.  of bounty  from  the population.  an average  age Is  also  17,532 p u p s  kill  of  4.7 y e a r s ,  t o be b o r n  2922 the  annually.  -100-  If  adult  there  are  average must  females  19,721 a d u l t  of  adult  British  Surveys, would  personal  be a t  are  seals  4.4  objections  and the r e l i a b i l i t y true  number  cannot  of bounty than  belief  have  not been  impossible  considered,  to assess  estimate.  First,  conversations seals  that  sink  In  been  collected.  deep  accurately,  seal  are  water,  hunters  shot or i f  Most  to  they  people  the  experience  150,000 which  present  Increase  the  and from  many  personnel,  because  the bounty will  and i s  factors  and F i s h e r i e s  involved  assumptions  questioned,  are at  but would  are,  coastline.  100,000 t o  are not recovered they  density of  2 important  because  from p e r s o n a l  with  many  from  least  Hydrographic  the estimate  seals.  is  coastline  mile  returns  i n the neighbourhood of arises  of  may b e r a i s e d  be l e s s  be a t  of  there  sex r a t i o  the average  per statute  annual  49.6$,  annual  Department  more' p r o b a b l y This  is  16,900 m i l e s  (Canadian  suggests,  As t h e  number w o u l d  communication),  least  the data  females  The average  the t o t a l  Columbia  as  required.  to t o t a l  As t h e r e  Although  the  females  thus  seals.  74,878  made  females  b e 39,760 f e m a l e s .  53.1$ f e m a l e s ,  in  a r e 88.9$ e f f i c i e n t  they  has n o t  say con-  -101-  servatively not it  have is  has  that  at  least  been recorded  very  unlikely  40$ o f t h e s e a l s  i n the bounty  that  never  e x c e e d e d 7,000, s o t h a t  probably between  not be t h i s  returns.  f o r the past  b e e n e x p l o i t e d t o i t s maximum.  high,  3,000 a n d 7,000  shot  Second,  5° y e a r s ,  the  seal  The annual  take  has  the sustained  but would  would  be  kill  would  somewhere  seals.  Discussion Although factors seal, when  which  control  certain  a n d how t h e s e  potential. related  to  known  natality  is  degree  this  i n the young  f r o m 8 t o 28 y e a r s  is  which  impart  In  the harbour  study  can suggest  2/3 o f t h e  theoretical  between  seldom,  This  a greater  difference  must be  Reproductive  females  of possible physiological,  variables This  about  to the age o f t h e f e m a l e .  those  ecological  operate.  produce a pup each y e a r .  host  of the  from the present  could  To a l a r g e  found only  years;  Is  p o p u l a t i o n numbers  findings  Realized  are  little  If  failures  ages  2 to  ever,  fail  may b e a t t r i b u t e d  sociological or stress  7  to a  ecological  on the young.  n o t a n uncommon p h e n o m e n o n a n d i s  reported  for a  -102-  number of t e r r e s t r i a l  animals.  Except f o r a d u l t males, the p o s t n a t a l m o r t a l i t y r a t e i s very s i m i l a r f o r both males and females, pups and o l d e r s e a l s .  Thus the nature bf the m o r t a l i t y  f a c t o r s must be random w i t h r e s p e c t to age and  sex.  Sources o f m o r t a l i t y have been g i v e n by Wilke (1954-), S c h e f f e r and  Slipp  (1944), and Bishop  (1965) which i n c l u d e  a t t a c k s by k i l l e r whales, sharks and eagles and mothers d e s e r t i n g pups.  Man  i s p r o b a b l y one of the most  important  p r e d a t o r s , but l i k e the o t h e r e f f e c t s , h i s I n f l u e n c e i s not p r e s e n t l y p o s s i b l e to a s s e s s .  In none of the specimens  p e r s o n a l l y examined, except f o r d e s e r t e d pups, was any obvious  s i g n of s i c k n e s s or s k i n d i s e a s e .  there  Several  hunters, however, have r e p o r t e d shooting the o c c a s i o n a l s e a l w i t h a mangy appearance when normal molt would not be i n p r o g r e s s .  A number of specimens c o l l e c t e d have  been found w i t h 2 to 6 i n c h s c a r s on t h e i r b o d i e s . H a b i t a t type must be an important determining numbers of harbour  seals.  factor in  In Alaska where  a bounty system has a l s o been i n e f f e c t f o r s e v e r a l years, harbour  s e a l s have been estimated to number about 6,000  i n the Copper R i v e r mouth (Imler and Sarber,  194-7) and i n  -103-  excess  10,000  of  Island)  at  the  on T u g i d a k  height  1965).  Seldom i n  than  to  100  of  areas  of  produce  many  times  more  Columbia.  The  nutritional  effect,  than  those  have of  pupping  Hansen  comparable pelts  difference as  season  Fur  size  than  is  Co.,  those  waters  greater  Kodlak (Bishop,  herds  in  probably  Alaskan  a relatively  British  (southwest  Columbia are  reported.  200  that  to  the  British  reports  sidered  Island  of  Ltd.,  Alaska in  also  will  British  related are  more  to  a  generally  production  of  confish  Columbia.  SUMMARY  1.  This was  study made  to  harbour  assess  this  seal  (Phoca  vitullna  seal's  status  In  Columbia.  It  is  based upon a g r o s s  examination  of  42  prenatal  collected 2.  on the  Aspects  in  1964  and  and  319  and  British histological  postnatal  age  determination,  reproduction,  population  are  described  an  tracks,  teeth.  growth  specimens  1965.  of  tive  richardi)  from  measurements  Cementum a n n u l a t i o n s  in  analysis  of  growth  reproduc-  and a s s o c i a t e d the  canines  and  canine  were  used  -104-  as the c r i t e r i o n f o r age. 3.  Age  determination  Canine  t e e t h b e g i n d e p o s i t i n g cementum at 2 to 3  months of age.  The  f i r s t a n n u l a t i o n i s composed of  opaque cementum and i s l a i d down i n 2 months. second  The  zone i s t r a n s l u c e n t and d e p o s i t e d i n 5 months.  Subsequent a l t e r n a t i n g bands are d e p o s i t e d over 6 month p e r i o d s , the t r a n s l u c e n t "dense, i n o r g a n i c " zone during the winter and s p r i n g and the opaque " l e s s dense, more o r g a n i c " band d u r i n g the summer and fall. may  The reason f o r the f o r m a t i o n of a n n u l a t i o n s  r e s u l t from an i n t e r n a l rhythm.  Seals up to 12 months o f age can be a c c u r a t e l y d i s t i n g u i s h e d from o t h e r age groups on the b a s i s of canine pulp c a v i t y 4.  size.  Reproduction a)  Annual c y c l e  In southeastern Vancouver I s l a n d and the adjacent mainland, p a r t u r i t i o n of a s i n g l e pup  occurs from  late  June to e a r l y August. An examination  of b i r t h times over most of i t s  d i s t r i b u t i o n i n the P a c i f i c and A t l a n t i c Oceans r e v e a l s  -105-  extensive  clinal  gradually  later  the  Pacific  north  (July)  and  In  Atlantic  the  Maine  differences. from Japan to  earlier  earlier  eastward  No c l i n e s There  is  have also  adjustments clinal  to  from  been  the  southeastern  Vancouver  in  September,  short  period. delayed tion  dates  growth) and  for  to  approximately have  parturition) males  testis, and have  been  occur  average  Adult  of  November lasts are  28.  about  seasonal  seminiferous sperm i n  the  (March). from  (June-July) the  and  Faeroes  northwestern  (May).  Europe.  reproductive  for  this  unusual  unclear. Island after the to  2  ovulation the  (from 28  Gestation  lactation then Implanta-  human  foetal  and December  13  (implantation  to  days.  breeders.  tubules  is  2-§- m o n t h s .  October  230  occurs  6 week  blastocyst  calculated  between  to  Reasons  time  Implantation  Mexico  comparable  male.  In  Island  for  for  to  Island  going north  latter  found  phenomenon r e m a i n  a  later  around  Vancouver  latter  Baffin the  evidence  in  the  becomes  (March-April)  becomes  (February-March)  southeastern  from  it  Pupping  and  epididymus  They  have  epididymus for  at  least  enlarged  tubules 5  months  -106-  and  perhaps  breeding in  up t o  season  males  least b)  Vancouver  would  4 months  Age a t  appear  In  time)  at  years  combined.  by  in  c)  the  the  May t o  epididymus) September.  of breeding  at  females.  mature  o f a g e , 47$ a t Approximately at  (ovulate  f o r the  3 a n d 17$ a t 57$ o f  5 years  first  4 and 5  the males  and most  i f  mature not  a l l  of age.  Fertility  Females those of  of  the epididymus)  6 years  Is  in  The main  maturity  36$ o f t h e f e m a l e s 2 years  (sperm  Island  advance  sexual  the year.  t o be c a p a b l e  About  (sperm  of  f o r t h e male  southeastern  Thus  9 months  2 to 7 years  8 t o 28 y e a r s  the p o t e n t i a l l y  o f age average average  100$.  fecund population  80$ f e r t i l i t y  while  F o r a random  sample  fertility  averages  88.9$. 5.  Growth Prenatally  male  term  averaging  6  sizes  weeks  and female  of nursing males  larger  females.  rates  are similar  83.0*2.7 c m a n d 11.5^.8  pup weights  Postnatally than  growth  tend  t o grow  approximately slightly  Asymptotic  sizes  kg.  with After  double.  faster  and  are reached  at  -107-  6  years  when m a l e s  females Unlike does  65  kg and  are  about  exhibit  a  cm  165  and  cm.  150  harem f o r m i n g p i n n i p e d s  not  kg and  87  secondary  the  growth  harbour  seal  male  acceleration  at  maturity. Present that  the  members to  be  findings harbour of  the  confirm  the  s u g g e s t i o n by  seal  one  of  Phocidae.  an e x c e p t i o n  growing  pinnipeds  growing  species.  Population Specimens  is  to  This  the  Laws  slowest  seal,  growing  however,  his  (Laws)  observation  to  mature  later  tend  than  (1959)  appears  that  slow  rapid  analysis randomly  sampled from the  main components f o r  the  analysis  of  p o p u l a t i o n are  the  population composition  and dynamic s. Prom  implantation  approximately relatively 17.6$ 5  of  annually. ratio  5 years  constant  age  mortality  Males and  age  then  their  sex  females  19.6$  up  mortality  after  becomes more  the  from b i r t h  average  Consequently,  gradually  of  Postnatally  1:1.  annually.  years  to  In  5 years favour  ratio have  a  to  death  to  maturity  Increases of of  is  age  the  females.  averaging  to  at 25.0$  sex In  -.108-  a random sample of the p o p u l a t i o n , the average annual sex r a t i o was  c a l c u l a t e d to be  46.9$.  Males seldom l i v e longer than 2 0 years and seldom more than 3 0  females  years.  In a random sample of males the average annual percent of mature males i s 3 3 . 7 $ ,  and c o r r e s p o n d i n g l y i n a  random sample of females,  49.6$  are mature.  Females r e a l i z e about 6 8 $ of t h e i r p o t e n t i a l  natality.  T h i s i s a t t r i b u t e d to f a c t o r s a s s o c i a t e d w i t h the lower f e r t i l i t y r a t e of young  females.  From bounty r e c o r d s of the Department of F i s h e r i e s and from the d e r i v e d r e p r o d u c t i v e and p o p u l a t i o n data  an  estimate of the minimum number of s e a l s i n B r i t i s h Columbia i s g i v e n as 7 5 , 0 0 0 s e a l s . of at l e a s t 4 . 4  T h i s Is a d e n s i t y  s e a l s per s t a t u t e m i l e of c o a s t l i n e .  -109-  LITERATURE  CITED  A l l e n , G.M. 1942. The harbour s e a l .  New E n g l . Nat.  15:38.  Amoroso, E.C., Bourne, G.H., H a r r i s o n , R.J., Matthews, L.H., Rowlands, I.W. and Sloper, J.C. 1965. 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NR. 5, 1-14.  P e a r l , R.  and Minor, J.R. 1935. Experimental s t u d i e s on the d u r a t i o n of l i f e . 14. The comp a r a t i v e m o r t a l i t y of c e r t a i n lower organisms. Quart. Rev. B i o l . 10:60-79.  Quick, H.F.  I963. Animal p o p u l a t i o n a n a l y s i s , p. 228. In Mosby, H.S. (Ed.), W i l d l i f e I n v e s t i g a t i o n a l Techniques. Wildlife  190Society.  S c h e f f e r , T.H. and Sperry, C.G. 1931. Food h a b i t s of the P a c i f i c harbour s e a l , Phoca r l c h a r d l i . J . Mammal. 12(3):214-226. S c h e f f e r , V.B. 1950. Growth l a y e r s on the t e e t h of P i n n l p e d i a as an I n d i c a t i o n of age. Science 112:309-311.  S c h e f f e r , V.B. 1958. " S e a l s , Sea L i o n s and Walruses. A Review of the P i n n l p e d i a " . Stanford University Press. S c h e f f e r , V.B. and Johnson, A.M. 1963. Molt In the northern f u r s e a l . U.S. F i s h and W i l d l . Ser. Spec. S c i . Rep., No. 450, 34 pp. S c h e f f e r , V.B., and S l i p p , J.W. 1944. s e a l i n Washington S t a t e .  The Am.  harbour M i d i . Nat.  32:373-416.  S c h e f f e r , V.B. and Wilke, F. 1953. R e l a t i v e growth i n northern f u r s e a l . Growth 17:129-145. Schour, I. i 9 6 0 . Noyes' O r a l H i s t o l o g y and Lea and F e b i g e r , 440 pp. S c o t t , D.M.  Embryology.  and F i s h e r , H.D. 1958. Incidence of the a s c a r i s Porrocaecum d e c i p i e n s i n the stomachs o f 3 s p e c i e s of s e a l s along the southwestern A t l a n t i c mainland. J . F i s h . Res. Bd. Can. 15(4):495-5l6.  -115-  Sergeant,  D.E.  (Phoca J. Sergeant,  E.  the  Bd. D.J.  Stoneberg,  Stutz,  S.S.  Templeman,  common  East  U.K.  Migrations Atlantic.  Skr.  seal  Anglian  coast.  29:707-717.  o f harp s e a l s i n the J . F i s h . Res. Bd.  fur  seal,  British Can.  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Venables,  U.M.  and V e n a b l e s ,  survey  Proc. Wilke,  F.  of  L.S.V.  Northern  zool.  Soc.  Ireland,  Lond.  1954. Seals of northern Mammal. 35:218-224.  Wunschmann,  i960.  A  seal  1956-1957.  133(3):490-494. Hokkaido.  J.  A . 1964. Bericht uber die Totgeburt eines Sudlichen See-Elefanten im B e r l i n e r Zoo. F r e u n d e d e s K o l n e r Z o o 7:103-105.  -117-  APPENDIX I  Growth by l e n g t h and weight In the human f o e t u s from I m p l a n t a t i o n to b i r t h . Adapted from Schour, i 9 6 0 , p. 43, who r e p r e s e n t s growth from c o n c e p t i o n .  Age (days) since implantation 0 7 14 21 28 35 42 49 77 105 133 161 189 217 245 259  *  gestation completed 0.0 2.7 5.4 8.1 10.8 13.5 16.2 I8.9 29.7 40.5 51.4 62.2 73.0 83.8 94.6 100.0  C - R length (mm)  $ growth (length) completed  .1 .2 2.0 5.0 8.0 12.0 17.0 23.0 56.0 112.0 160.0 203.0 242.0 277.0 313.0 350.0  .03 .06 .6 1.4 2.3 3.4 4.9 6.6 16.0 32.0 45.7 58.0 69.I 79.1 89.4 100.0  Weight (gm)  -  .02  1.0 14.0 105.0 310.0 640.0 1080.0 1670.0 2400.0 3300.0  -118-  APPENDIX  0  20  40 % Gestation  II  60  80  completed  R e l a t i v e r e l a t i o n s h i p between growth by l e n g t h and g e s t a t i o n ( i m p l a n t a t i o n to b i r t h ) f o r the human f o e t u s . Values are taken from Appendix I .  100  -119-  APPENDIX  Predicted from the  prenatal  is  230  weight  Age  (  harbour  human g r o w t h  conversion  assumes  is  birth  1 1 , 5 0 0 gm.  d  a  y  since implantation  0 6 12 19 25 31 37 44 69 93 118 143 168 193 218 230  data  that  days,  s  Dec .  Dec .  Dec . Dec . Dec .  Jan. Jan.  Feb. Feb . Mar. Apr. May  June  July July  seal  the  of  A p p e n d i x I.  is  )  - R  C  830.O  length (mm)  28 3 9 16 22 28 3 10 4 28 25 19 14 8 3 15  lengths  seals  length  Date Nov.  III  .2 .5 4.8 12.0 19.2 28.8 40.8 55.2 134.4 268.8 384.0 487.2  58O.8  664.8 751.1 83O.O  and  gestation mm a n d  weights  The  period  birth  Weight  (1  -  .07  3.5  49.0 367.5 IO85.O 2240.0 3780.0 5845.0 8400.0 11500.0  -120-  MANAGEMENT  The p r e s e n t are  at  least  investigation  75,000 h a r b o u r  and more p r o b a b l y This  150,000. mercial and ment  exploitation  l)  of  and c o n t r o l , the s e a l ' s harvest  should be invoked than  As b o u n t y number  valuable  limit  means  further  are  of  the  o f 5000 s e a l  to .insure  have  a  under-  exceeded  the r e s t r i c t i o n the s e a l ' s  fish,  prevent  possible  exploitation  demand.  yield,  condition.  on commercial over  skins  sustained  no l i m i t rarely  not increase  Increased  the manage-  recommendations  and to  com-  considered  of  effects  of  Columbia,  100,000 t o  been  efficient  the present  returns  there  biology,  f o r 40 years,  therefore,  of  a reassessment  a more  that  in British  a f a r more  The f o l l o w i n g  An a n n u a l  rather  seals  has p r e v i o u s l y  warrants  to provide  suggests  the magnitude  than  program.  standing  in  represents  fishery  therefore  proposed  RECOMMENDATIONS  this  could,  predatory  but would in  act  to  times  -121-  The  cropping of  tinued. pups  Most  is  where  estuaries here  other  age  no  with  effects  to  the  will  fall  a  biology  of  population  status  may b e  are a  s h o u l d be for  large  often  easily  shotgun; The with  little  during  of  (Stutz, the  hide  continued  particularly  and moult frequently  the  the  the  these  in  aspects,  from  rather  During  decreasing  of  enforced  pups,  percent  s h o u l d be seal,  areas  population.  occurs  reduction  research  Its  also  moult  Further  this  is  few  only,  season.  thereby  annual In  pups  except  open  It  and  parent  season  a  hunting  however.  a greater  sink,  resulting  ivity,  boat  that  con-  s u c h as  Pups  not,  November,  efficiency. the  fast  the  present  In  aggregate,  are  hunting  summer a n d  that  a  s h o u l d be say  except  a cropping of  June u n t i l  shot  to  groups  is  A closed  than  tend  will  a n d mud f l a t s .  taken  or  sealers  unprofitable  seals  result  newborn pups  seals harvest  months  1966), value.  into  the  productso  reassessed.  that  

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