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The timing of moulting in wild and captive steller sea lions (eumetopias jubatus) 2003

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T H E T I M I N G O F M O U L T I N G I N W I L D A N D C A P T I V E S T E L L E R S E A L I O N S (EUMETOPIAS JUBATUS) by Raychel le G . Dan ie l B. Sc. B io logy, Un ivers i ty of A l a ska Southeast, 1999 A THESIS S U B M I T T E D I N P A R T I A L F U L F I L M E N T O F T H E R E Q U I R E M E N T S F O R T H E D E G R E E O F M A S T E R OF S C I E N C E in T H E F A C U L T Y OF G R A D U A T E STUDIES Depar tment of Zoo logy August , 2003 W e accept this thesis as conforming to the requi red standard T H E U N I V E R S I T Y OF BRIT ISH C O L U M B I A © Raychel le Danie l , 2003 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of _ The University of British Columbia Vancouver, Canada ABSTRACT I documented the t im ing and progress ion of the mou l t b y sex and age class i n a w i l d popu la t i on of Steller sea l ions (Eumetopias jubatus) on Lowr i e Island, A l a s ka (Ju l -Nov 2001) and f r om captive animals at the Vancouver A q u a r i u m Ma r i ne Science Centre (1993-2000). In the w i l d , juveni les (ages 1-2 years) were the first to mou l t fo l lowed by adul t females, bu l l s and pups. The mean date w h e n juveni les started their mou l t was 21 Jun w h i c h was s ignif icant ly different f r om the mean start date of 07 A u g for adul t females, and dif fered f rom the mean start date for pups of 01 Sep (one mon th later). M e a n complet ion dates were also about one mon th apart (19 Sept for juveni les, 26 Oct for adul t females and 17 N o v for pups). Du ra t i on of the mou l t was about 45 days for each age group (pups and adul t females). However , dura t ion of the mou l t for captive sea l ions was longer (averaging 83.5 days) and dif fered among years and w i t h i n age classes. Patterns of hair loss i n the w i l d (i.e., the progress ion of the mou l t over the body surface) di f fered among (i) pups, (ii) juveni les and ear ly mou l t i ng adul t females, and (iii) bu l l s and later mou l t i ng adul t females. Differences i n the t im ing and progress ion of the mou l t may be related to phys io log ica l changes and interactions of hormones associated w i t h body cond i t ion and the reproduct ive cycle. ii T A B L E OF C O N T E N T S A B S T R A C T '. i i T A B L E O F C O N T E N T S i i i LIST OF T A B L E S v LIST O F F I G U R E S v i A C K N O W L E D G E M E N T S v i i C H A P T E R I: S T E L L E R S E A L I O N S A N D E P I D E R M A L COVER INGS . . . , 1 P inn iped Adapta t ions i n Pelage 2 Steller Sea L i o n Pelage 3 Steller Sea L i o n B io logy & Seasonal Cyc le 4 Importance of a M o u l t i n g S tudy on Steller Sea L ions 5 C H A P T E R II: T I M I N G O F M O U L T I N G I N W I L D S T E L L E R S E A L I O N S 8 Introduct ion ; 8 Methods 10 Study Site 10 Data Var iab les 11 Mou l t Progress ion 12 T im ing of M o u l t - Popu la t i on 13 Dura t i on of M o u l t - Ind i v i dua l 15 Relat ionship to N u m b e r of Sea L ions Coun ted 16 Results 17 T im ing of M o u l t - Popu la t i on 17 Dura t i on of M o u l t - Ind i v i dua l 19 Relat ionship to N u m b e r of Sea L ions Coun ted 22 Mou l t Progress ion 23 D iscuss ion 26 T im ing of Steller Sea L i o n M o u l t 26 What Dr ives the Steller Sea L i o n Mou l t ? 27 Effects of M o u l t on Popu la t ion Counts 33 Potent ia l Biases 35 Op t ima l Instrument At tachment 36 Future Research - Is the Steller Sea L i o n M o u l t Energet ica l ly Expensive?... . 39 Summary 41 C H A P T E R III: T I M I N G O F M O U L T I N C A P T I V E A N I M A L S 43 Introduct ion 43 Methods 43 Results 44 D iscuss ion 50 Capt ive M o u l t Du ra t i on 50 W i l d and Capt i ve M o u l t Du ra t i on Compar i son 51 Summary 53 L I T E R A T U R E C I T E D 54 A P P E N D I X 62 LIST OF T A B L E S Table 2.1. M e a n dates for the start and end of mou l t i ng for juveni les, adul t females and pups est imated f r om logistic regression 17 Table 2.2 M e a n dura t ion of mou l t i ng and mean start and end dates for focal adul t females and pups 20 Table 2.3. Summary of mode l fit for mou l t stage and popu la t ion counts, i n c lud ing general ized l inear mode l regression coefficients 22 Table 3.1. Summary statistics for the mean durat ion of mou l t i ng for captive animals at the Vancouver Aqua r i um , 1993 - 2001 45 Table 3.2 M e a n dura t ion of mou l t i ng for captive an imals at the Vancouver Aqua r i um , 2000 - 2001 45 Table 3.3. M e a n date that mou l t i ng started and ended for capt ive Steller sea l ions by age class i n consecutive years, 2000 and 2001 49 L I S T O F F I G U R E S Figure 1.1. Steller sea l ion range 5 F igure 2.1. Examp le of mou l t i ng Steller sea l ions 11 F igure 2.2. Discrete body areas assigned to each Steller sea l i on 13 F igure 2.3. Loess curve f itted to propor t ion of mou l t i ng Steller sea l ions 18 F igure 2.4. Mou l t i n g probabi l i t ies of focal adul t females and pups that w o u l d have started or completed their mou l t 21 F igure 2.5. N u m b e r of Steller sea l ions counted on Lowr i e Island, July - August , 2001 23 F igure 2.6. Progress ion of mou l t for adul t females and pups of the year 25 F igure 2.7. Regress ion of number of females and pups counted 34 F igure 3.1. M o u l t dura t ion of capt ive Steller sea l ions 47 vi ACKNOWLEDGEMENTS First, I am thankfu l to m y supervisor, Dr . A n d r e w Trites for h is keen interest i n the sea l i on mou l t as we l l as for his support and expertise. To m y committee members, Drs. Dave Rosen and Lee Gass I extend immeasurab le grat i tude for contr ibut ing their t ime, thought fu l comments and guidance. Fund i ng for this project was p rov i ded b y the N o r t h Pacif ic Univers i t ies Ma r i ne M a m m a l Research Consor t ium. Add i t i o n a l f und ing and f ie ld logist ical suppor t was p rov i ded by the A l a s ka Depar tment of F i sh and Game. In part icu lar I am indebted to T o m Gelatt. K e n Pitcher and Bo yd Porter p rov ided va luable in fo rmat ion for Lowr i e f ie ld logistics. Researchers and staff at the Vancouver A q u a r i u m Ma r i ne Science Centre mainta ined careful documentat ion on the mou l t of the capt ive sea lions, for wh i c h I am grateful. I appreciate the "stel lar" f ie ld assistance f r om Jamie Womb l e and especia l ly Nad i ne P inne l l for her camarader ie and for hang ing in unt i l the end. W i thou t Pamela Rosenbaum we st i l l m igh t be on Lowr ie - I 'm thankfu l for a l l y ou r help! The Mar i ne M a m m a l Research Un i t lab, students and staff are great fr iends and colleagues that p rov i ded mora l support, we l l - t imed coffee runs and romps i n the hal l , a long w i t h ins ight fu l suggestions and ideas. In part icular I va lue the eclectic genius and assistance of Ru t h Joy and Ar l i s s W insh ip . To K r i s t i n for organis ing F T D D suppor t group. To Anna , And i e and E m m a for su rv i v i ng the first year. To Kate W i l l i s for her thought on the moul t and its correlat ion w i t h her s tudy on heat f lux. I 'm thankfu l for suppor t f r om m y Juneau fami ly , Brendan, John, Ne i l , Laur i , O r i and Jeffie, and especial ly La ra for her f r iendship. Quyana caknek to m y parents for tolerat ing the choices a long m y life pathway. A n d special thanks to K e v i n for a lways be ing there, offering encouragement, care and compass ion when I needed it most. vii CHAPTER I: STELLER SEA LIONS A N D EPIDERMAL COVERINGS The epidermis helps to reduce desiccation and assists wi th respiration and osmoregulation among amphibious (and lower aquatic) vertebrates. In warm blooded vertebrates, the epidermis may provide cryptic colouration, mating advertisement or thermoregulation, and extensions of it may serve in specialised functions such as flying or swimming (Ebling and Hale 1970; Ling 1970). Epidermal glands can also aid in moisture maintenance and thermoregulation (Ebling and Hale 1970; Ling 1965). The function of the epidermis is more seasonally related to life-history events in birds (to attract mates) and mammals (to serve as camouflage) than in amphibians (Ling 1972). Seasonal renewal of the epidermis in birds and many mammals is coordinated with other energy- expensive life cycle events such as reproduction and migration (Ling 1972). Hair is a mammalian characteristic that is thought to have evolved after the establishment of internal thermoregulation from keratinised, spiny sensory thickenings anchored in an amphibian-like epidermis (Ling 1970; Smith 1958). In mammals, one function of an epidermal covering is to provide a partition between the fluctuating environment and internal homeostatic environment (Young 1957). Hair may also play a role in thermoregulation, defence (e.g. porcupine, hedgehog) and sensory perception. The plasticity in the form and function of hair can be observed between species of closely derived ancestry (Ling 1972). Periodic regeneration of the mammalian integument (hair, and in some cases, the entire epidermis) is important given the overall functionality of hair. The generalized mammalian hair cycle begins below the surface of the skin with mitotic activity near the anchoring base of the follicle. The mitotic activity leads to an expansion of the bulb down into the dermis and a darkening in l pigmentat ion (Bu l lough and Laurence 1958). A s the new hair g rows upwa rd , the o ld hair becomes loose and eventual ly falls out of the shared fol l ic le. Once the new hair is fu l l y -g rown, the bu lb migrates up to the ep idermis and becomes dormant unt i l the next cycle begins. The mamma l i a n ha i r replacement cycle varies b y species. In some, there may be a s lough ing of the entire ep iderma l layer. In others, hairs may be replaced one at a t ime. M i to t i c act iv i ty of the ep idermis is l i ke ly control led by photoper iod and the endocr ine system, and inf luenced b y temperature and reproduct ive hormones (Ebl ing and Ha le 1970; L i n g 1984). In mice, h i gh energy produc t ion (glucose and oxygen) is required to suppor t h i gh mitot ic act ivity (Bu l lough and Laurence 1958). Thus mou l t i ng is an energet ical ly expensive act ivity that must be coordinated w i t h other energetical ly demand ing activities, such as reproduct ion. Pinniped Adaptations in Pelage The potent ia l for heat loss i n water is approx imate ly 27 t imes greater than in air. In p inn ipeds, this thermoregulatory difference is par t ia l ly a l leviated by the presence of hair on the sk in (L ing 1970). No r the rn fur seals (Callorhinus ursinus), for example, have dense coats of under hairs that trap air and a id i n thermoregulat ion wh i l e i n water; wh i l e nor thern elephant seals (Mirounga angustirostris) appear to sit at the other end w i t h a sparse pelage. Cetaceans have adapted a hairless sk in w i t h a substantial insu lat ing b lubber layer. P inn ipeds a l l lack erector muscles that cause ha i r to stand erect i n response to env i ronmenta l changes such as decreasing temperature (which w o u l d a id i n thermoregulat ion on land). Howeve r , the absence of erector muscles enables the hairs to l ie flat over one another w h e n wet, creating a smooth surface (L ing 1970). The smooth surface may then increase 2 hydrodynamic fluidity and assist with propulsion in the water. Another function of hair in pinnipeds may be to act as mechanical protection from abrasion on rocks and hard surfaces when they haul out on land or ice (Ling 1970; Ling 1984). All pinnipeds are constrained on land when pups are born, and most are constrained to breed on land. The time spent on land may lead to increased wear on the pelage leading to the need to periodically renew their hair. The pelage may further function to provide an abrasive surface while hauled out on ice and slippery land surfaces. Steller Sea Lion Pelage Steller sea lions (Eumetopias jubatus) belong to the family Otariidae and regenerate their hair coat annually. Adult pelage consists of hollow guard hairs with as many as three under hairs in a shared follicle/shaft, which is typical of most mammals (Scheffer 1964; Vania 1972). The chocolate-brown pelage of pups lacks under hairs (Scheffer 1964) and is darker in colour than the tawny adult pelage. Steller sea lions do not undergo a catastrophic moult, with a sloughing of the entire epidermal layer, similar to elephant seals. Instead, each new hair replaces and pushes out the old hair from the shared follicle. The replacement of the pelage is believed, from captive observation at the Vancouver Aquarium Marine Science Centre, to start at one end of the body and spread progressively towards the other. Therefore, the moulting period is defined as the time when new hair is first visible on the surface until all old hair has been shed. A major function of hair for Steller sea lions may be to act as mechanical protection from abrasion on rocks and hard surfaces when they haul out. Unlike some pinnipeds that migrate for up to 10 months of the year, Steller sea lions regularly haul out every one to two days year round (Calkins and Pitcher 1982; Milette and Trites 2003; Trites and Porter 2002). The regular hauling out might 3 increase the wear and damage to the pelage. Therefore pelage requires per iod ic replacement of w o r n and damaged hairs. Steller Sea Lion Biology & Seasonal Cycle Steller sea l ions are po lygynous and sexual ly d imorph i c . Ma les become sexual ly mature between 5 to 7 years of age, but may not become successful breed ing bu l l s un t i l 9 to 10 years of age (Pitcher and Ca lk ins 1981; Thorste inson and Lens ink 1962). Bu l l s have a thick neck, t r iangular-shaped head, and may be more than double the size of females. Terr i tor ia l bu l l s hau l out on rookeries (sites t rad i t ional ly used to give b i r th and mate) f r om approx imate ly m i d - M a y through mid-Ju ly i n their A l a s kan range (Gis iner 1985). Pregnant females beg in hau l ing out on rooker ies i n ear ly June, g i v ing b i r th w i t h i n days to a single pup . Females constant ly attend to their pups for the first ten days on average, thereafter alternat ing between about one day at sea and one day on shore du r i ng early lactation. Howeve r , du r i ng later lactation they increase the amounts of t ime at sea, to an average of two days wh i l e spend ing less than a day onshore (Milette and Trites 2003; Sandegren 1970; Trites and Porter 2002). Lactat ion may last u p to three, years, but wean ing usua l l y occurs du r i ng the first year (Calk ins and Pitcher 1982). Breed ing occurs on land approx imate ly ten days after females g ive b i r th (Gentry 1970), but the embryo does not imp lant i n the uterus unt i l October (Calk ins and Pitcher 1982), co inc id ing w i t h the presumed start of the mou l t ing per iod. Mou l t i n g occurs after the pupp i ng per iod between Ju ly and December but the exact t im ing is not we l l def ined (Vania 1972). 4 Figure 1.1. Range of Steller sea lions. Squares indicate rookery locations. Lowrie Island is the largest rookery in their range. Steller sea lions range throughout the Pacific R i m from California to Alaska and Japan (Figure 1.1). From the 1970's to the 1990's their range-wide population size decreased by about 80%. As a result the U.S. population was declared endangered in 1997 west of 144° Longitude - the line that separates two genetically distinct populations (Bickham et al. 1996; Loughlin et al. 1992; National Marine Fisheries Service 1992; Trites and Larkin 1996). A number of studies are underway to determine possible reasons for their continued decline. Importance of a Moulting Study on Steller Sea Lions The regeneration of hair can be energetically expensive (Bullough and Laurence 1958). Phocid females and beluga whales (Delphinapterus leucas) may conserve energy during the moult by either hauling out onto land or moving into warmer water (Boily 1995) since optimal conditions for mitosis includes higher temperatures (Feltz and Fay 1966). Furthermore, it might be beneficial to conserve energy by minimising thermal conductance during the moult, by 5 mov ing to wa rmer temperatures. Some phocids, such as the harbour seal, hau l out i n greater numbers du r i ng their mou l t than other t imes du r i ng the year and it is at this t ime that popu la t i on surveys are conducted (Ca lambok id i s et al. 1987; Stewart and Yochem 1984; Thompson et al. 1989). Howeve r , it is not k n o w n whether greater numbers of Steller sea l ions and other otar i ids hau l out dur ing the moult , nor if the Steller sea l i on mou l t is energetical ly expensive. The t im ing and progress ion of the mou l t for Steller sea l ions probably varies by sex and age class (Calk ins and Pitcher 1982; Van i a 1972) g iven the differences i n mou l t i ng pheno logy that have been documented i n other species of p inn ipeds. In nor thern fur seals, the in i t iat ion of the mou l t becomes progress ive ly later as males and females age (Scheffer and Johnson 1963). In harbour seals (Phoca vitulina), year l ings are the first to moul t , fo l l owed by subadults (males and females), adul t females, and lastly adu l t males (Danie l et al. 2003; Thompson and Rothery 1987). Furthermore, larger numbers of a l l sex and age classes of harbour seals hau l out du r i ng the earl ier stages of their moult, a behav iour that m igh t be due to the higher energetic cost associated w i t h hair growth. If the max ima l numbers of animals i n each sex and age class occurs at different times, it confounds popu la t ion based surveys. Interpretat ion of studies us ing popu la t ion based surveys need to understand and incorporate under l y ing assumptions. A goal of m y study was to document the t im ing of the moult , a little k n o w n phase of the Steller sea l i on seasonal cycle. Documen t i ng the discrete t im ing of the mou l t w o u l d he lp to complete our unders tand ing of their life history. M a n y of the studies that investigate causes su r round ing the decl ine of Steller sea l ions use electronic instruments g lued to the hai r on the back of sea l ions to collect transmitter data. K n o w i n g when the different sex and age classes 6 moul t and h o w it relates to max ima l numbers of an imals hau led out may help to opt imise the dep loyment of these instruments. M y thesis documents the progress ion of mou l t i ng for Steller sea l ions in the w i l d (Chapter 2) and i n capt iv i ty (Chapter 3). Emphas i s is p laced on determin ing and document ing when mou l t i ng starts and ends for different sex and age classes of w i l d Steller sea l ions. I predict that differences exist i n the t im ing of the Steller sea l i on moul t . Based on the t im ing of the mou l t by sex and age class f ound in other p inn iped species, I hypothesise that juveni les w i l l mou l t pr ior to the adults. I further predict that mou l t stage m igh t inf luence numbers of ind iv idua l s hau led out on land. Based on the hau l out behav iour of other p innipeds, and assuming that the mou l t is also energetical ly expensive for Steller sea l ions, I hypothes ise that more animals w o u l d hau l out onto l and du r i ng the earlier stages of the moul t . 7 C H A P T E R II: T I M I N G OF M O U L T I N G IN W I L D S T E L L E R S E A LIONS Introduction Steller sea l ions, l ike other p innipeds, shed their ha i r annual ly . However , relat ively l itt le is k n o w n about the t im ing and progress ion of their mou l t ing . They are k n o w n to regular ly hau l out onto land throughout the breed ing and non-breeding seasons, and are bel ieved to mou l t after the June-July pupp i ng per iod i n their A l a s kan range (Vania 1972). Whether or not they hau l out i n greater numbers wh i l e mou l t ing , as has been shown for phoc ids, is not k n o w n (Ca lambok id is et al. 1987; Stewart and Yochem 1984; Thompson et al . 1989). Regenerat ing hair can be energetical ly expensive. Eu ropean badgers, Meles meles (Stewart and Macdona l d 1997) consume greater amounts of food wh i l e they mou l t due to the cost associated w i t h p roduc ing prote in at the cel lular level (Bu l lough and Laurence 1958). Ma l e harp seals (Phoca groenlandica) lose mass and expend litt le act iv i ty du r i ng the mou l t i ng per iod , ind icat ive of h igh energy expendi ture (Chabot and Stenson 2002). The energetic costs for mou l t i ng Steller sea l ions are not k n o w n but are presumed to be h igh . Temperature and thermal conductance are impor tant factors in f luenc ing both the t im ing and the costs associated w i t h the mou l t whereby some species alter behav iours to offset the costs of these molecu lar processes. The speed of one of the basic unde r l y i ng molecular processes of mou l t ing , mitosis, is temperature dependent. E levated temperatures app l ied to cu l tured p inn iped ep idermal cells increases their mitot ic rates (Feltz and Fay 1966) and may act to expedite the mou l t i ng per iod. Another factor that affects aquatic animals du r i ng their mou l t is thermal conductance (heat f low) to the env i ronment f r om the body. The nor thern elephant seal (Mirounga angustirostris) and harbour seal, (Phoca vitulina) hau l out for extended per iods wh i l e they moul t , presumably 8 because air temperatures are h igher on land relative to water (L ing 1970). The temperature difference reduces energy expenditure associated w i t h mainta in ing h igh ep iderma l temperatures for mitosis and min imises thermal conductance. A m o n g cetaceans, studies have indicated that be luga whales (Delphinapterus leucas) may also conserve energy wh i l e they mou l t their ep idermis b y mov i ng into warmer water (Boi ly 1995; Watts et al. 1991). Furthermore, thermal conductance of nor thern fur seal pups decreased after their first mou l t presumably compensated b y for their new pelage and thicker b lubber layer (Donohue et al. 2000). Some species of p inn ipeds, such as elephant seals undergo a catastrophic, rap id shedd ing of the entire ep idermal layer. Others shed i nd i v i dua l hairs, whereby new hai r pushes out its shared fol l ic le (Sokolov 1960). For these species, the pattern of hair replacement general ly progresses over the body, usua l ly beg inn ing at one or both ends and then spread ing across the remain ing surface. The mou l t for the Steller sea l ion is progress ive (Van ia 1972), but the topography of the progress ion has not been documented. The t im ing of the mou l t for Steller sea l ions probab ly varies by sex and age class (Ca lk ins and Pitcher 1982; Van i a 1972). Differences i n mou l t i ng pheno logy have been documented i n other p inn ipeds, i n c l ud ing harbour seals (Daniel et al. 2003; Thompson and Rothery 1987) and nor thern fur seals (Scheffer and Johnson 1963). Dif ferent mou l t t imings by sex and age class may have impl icat ions for popu la t i on mon i to r ing (Danie l et al . 2003; Ha r konen et al. 1999). Popu la t ion surveys for p inn ipeds are conducted, usua l l y f r om the air, du r ing per iods w h e n they are v is ib ly hau led out on land or f r om numbers of pups counted direct ly on the rookeries. The estimated abundance of one or more classes of sea l ions based on surveys cou ld be over- or under-est imated if animals preferential ly hau l out du r i ng specif ic or crit ical mou l t t imes. 9 A foremost goa l of m y study was to document the t im ing of the mou l t for Steller sea l ions, to establ ish a t imeframe for a l itt le k n o w n but cr it ical event of their annua l cycle. A better unders tand ing of sea l i on behav iour du r i ng this t ime per iod might p rov ide some ins ight into behav ioura l aspects su r round ing their decline, because we k n o w very little du r i ng the fa l l and w in te r months about Steller sea l ions. Ano the r purpose of m y study was to establ ish the progress ion over the body i n order to determine opt ima l t im ing to glue electronic devices to the hair of Steller sea l ions. Electronic instruments he lp to collect scientif ic data on behaviour, ecology and phys io logy that contr ibute to so lv ing the puzz le of their decl ine. In this study, I documented the t im ing of mou l t i ng i n a popu la t i on of w i l d Steller sea l ions i n the eastern Gu l f of A l a ska to determine (i) progress ion of mou l t over the body, (ii) t im ing of mou l t for the populat ion, by sex and age classes, (iii) durat ion of mou l t for i nd iv idua l s and (iv) the inf luence of mou l t stage on popu la t ion counts. Methods Study Site Steller sea l ions were observed on Lowr i e Island, A l a s k a (54.86° latitude, 133.54° longitude, F igure 1.1) f rom July - November , 2001 b y mysel f and a f ie ld assistant. L ow r i e Is land is part of the Forrester Is land complex of rookeries, wh i ch is current ly the largest breed ing aggregat ion i n the w o r l d for Steller sea l ions w i t h near ly 3000 pups bo rn annual ly i n recent years (Ca lk ins et al. 1999). It consists of a rocky outc ropp ing and cobble hau lout substrate. Sites were surveyed on or w i t h i n 30m f rom the ma in is land and d i v i ded the is land into nor th and south halves. 10 Data Variables M o u l t stage was v i sua l l y determined by d iscern ing o l d and n ew hair w i t h 10x40 binoculars. M o u l t stages inc luded (i) not yet mou l t ing , (ii) mou l t i ng and (iii) complete ly mou l t ed . I def ined the moul t as the t ime w h e n animals were v is ib ly shedd ing their o l d hair and the presence of n ew hair was evident. O l d and new hair was easi ly differentiated since new hai r was l ighter i n colour than o ld hair (Figure 2.1). Ha i r co lour of older animals was genera l ly l ighter than that of younger ind i v idua l s . For example, pups bo rn w i t h a da r k -b rown coat mou l t into a l ighter, in termed iary coat du r i ng their first year. Year l ings i n turn mou l t into the adul t coat, w h i c h is l ight tan or beige. Figure 2.1. Example of moulting Steller sea lions. Pups have dark chocolate coloured coats (far right). Yearling (middle) with darker old hair and lighter new hair. Adult female (far left) with a patch of lighter new hair on foreflipper. i I We documented mou l t stage direct ly i n the f ie ld, and later i n the lab f rom dig i ta l photographs us ing a N i k o n D l camera w i t h 300mm z o o m lens and doubler. An ima l s were d i v i ded into the fo l l ow ing sex and age classes: adult females, pups of the year, juveni les, terr itor ial males and subadu l t males (as def ined by Trites and Porter, 2002). Lowr i e Is land is p redominant l y popu lated by adul t females and pups w i t h some juveni les (juveniles and pups might be attended by their mother, or alone wh i l e their mother feeds). The few observed terr itorial bu l l s were easi ly identi f iable because of their d ist inct mane w i t h thick and coarse hair, l ighter co lour and dist inct ive head shape. Subadu l t males were also easi ly dif ferent iated f r om adult females. H o w e v e r we cou ld not use phys ica l characteristics to differentiate juveni les by sex at the distances observed. Moult Progression I d i v i ded the body into six regions to achieve easy and consistent mou l t stage descr ipt ions (Figure 2.2). The head was def ined as the area anterior to the ears (A), wh i l e the neck extended f rom the ears to the anterior insert ion of the forefUppers (B). Foreflippers consisted of the upper ha i red por t ion to the insert ion point w i t h the torso (C), and hindflippers started at the tai l back towards the end of the ha i red reg ion on the appendages (D). The torso was the reg ion between the foref l ippers and the h indf l ippers (E). F inal ly, the ventrum (not shown i n Figure 2.2) was the be l ly region, d is t ingu ished by the imag inary l ine between the posterior insert ion po in t of the foref l ipper and h ind f l i ppe r appendages. These body regions were used both i n the f ie ld and later i n the lab f r om photographs. We determined mou l t stage for each discrete area of the body and used four categories i n the f ie ld, based on the dec imal va lue of the p ropor t i on of new 12 HEAD NECK FOREFLIPPERS TORSO HINDFLIPPERS Figure 2.2. Discrete body areas assigned to each individual Steller sea lion. to o ld hair. Categor ies were broad ly encompass ing and inc luded: x = 0.0, 0.0 < x < 0.5, 0.5 < x <1.0, and x = 1.0. The progress ion of mou l t was qual i tat ively descr ibed i n the pattern of the spread of the new hai r across these body regions over t ime for each sex and age class. Timing of Moult - Population Scan surveys were used to quant i fy the mou l t process for the popu la t ion as a who le . A complete survey consisted of a v is i t to a l l areas on the is land where sea l ions were hau led out. T w o sequential days were requ i red to survey the entire i s land at the start of the f ie ld season, due to the number of animals present. Howeve r , later i n the season when overa l l sea l i on numbers decreased, we surveyed the entire is land i n a single day. W e conducted 52 complete surveys between Ju ly and November 2001. Data were not inc luded for incomplete surveys. The start and end survey points on the is land were 13 alternated each day relative to the north-south i s land or ientat ion. G r oup locat ion on the is land was s imi lar day to day, but changed seasonally. If we started at the south end on D a y 1, we began surveys f rom the nor th end of the i s land on Day 2. It was not possible to survey al l animals present i n a g roup w h e n there were large numbers of an imals present. Later i n the season, w h e n fewer animals and fewer groups were present, effort was made to ascertain a sample size of at least 30 ind iv idua l s . Surveys systematical ly started on the r ight s ide of a group of animals, and moved left. W e obtained mou l t stage for as many sides of an ind iv idua l ' s body as possible, spend ing a m a x i m u m t ime per iod of 15-30 minutes per i nd i v i dua l . In the f ie ld, we categorised each an imal for sex, age, and mou l t stage by body region. The stages of mou l t for each body reg ion w e obta ined i n the f ie ld were summed to calculate a single stage of mou l t for each an ima l for the analyses. In order to assign an i nd i v i dua l to a single mou l t stage we had to v i ew al l the body areas for one side (except the vent rum, F igure 2.2). I assumed that the pattern of mou l t on the left and r ight sides of each an ima l was symmetr ica l . Thus mou l t stages were extrapolated for an an ima l that presented either its left or r ight side. Da ta cou ld not be collected f rom the ventra l surface because it was rare to ever observe the be l ly of a Steller sea l ion i n the w i l d . Howeve r captive studies indicate (Chapter 3) that the ven t rum reg ion moul ts after other areas. In the laboratory, I entered data into an Exce l spreadsheet and double checked each entry per i nd i v i dua l against photographs for correct mou l t stage to m in im i ze error f r om data transcr ipt ion. A l l mou l t stages were summed to prov ide a single va lue per i nd i v i dua l per day. An ima l s were considered to be mou l t ing if n ew hai r was noted on any single area (e.g. head only). Sea l ions were categorised as complete ly mou l ted if a l l o l d hair was gone. I determined the propor t ion of an imals i n each mou l t stage for each survey date and fit a 14 weighted b i nom ia l mode l w i t h a logit funct ion. I conducted a l l statistical analyses i n SP LUS . A l l dates were set i n days f r om the first date that mou l t i ng was observed i n the study popu lat ion, 27 Ju ly 2001. I est imated the start date of mou l t ing for each sex and age class f r om the b i nom ia l mode l where the probabi l i ty of an imals not mou l t i ng was 0.99. S imi lar ly , I f ound the mean date when mou l t i ng ended f r om a we ighted b inomia l mode l where the probabi l i ty of the propor t ion of an imals f in ished mou l t i ng was 0.99. Sma l l sample sizes for bul ls and sub-adult males meant that I used on ly juveni les, adu l t females and pups i n the analysis. Duration of Moult - Individual I used focal samp l ing for i nd i v i dua l l y recognisable sea l ions that consisted of b randed an imals or repeatedly recognisable animals (i.e. those w i t h dist inct ive scars and funga l patches). Funga l patches have been used re l iab ly i n prev ious studies and do not change w i t h i n a single season (Mi lette 1999), mak i ng it possible to re l iab ly track a single i nd i v i dua l throughout its moul t . W e ident i f ied focal an imals i n the f ie ld f r om dig i ta l photographs taken du r i ng the scan surveys. Res ight ing of focal animals was conducted pr io r to each scan survey. M o u l t dura t ion was the t ime between w h e n new hai r was first observed on an an ima l un t i l a l l o l d hair had been shed. I determined durat ions for a l l focal adult females and pups . M o u l t durat ion and start and end dates between pups and adul t females were statistical ly compared us ing standard two sample t-tests. I used data f r om ind i v i dua l s where both start and end times were observed. I also compared the t im ing of mou l t i ng between pups and adu l t females us ing a Kap lan-Me ie r su rv i va l probabi l i ty . Surv i va l analysis a l l owed for inc lus ion (using censoring) of those animals whose end times may not have been direct ly observed since probabi l i t ies are estimated day to day based on the number of 15 i nd iv idua l s i n a mou l t stage for that part icular day. I calculated the probabi l i t ies that pups or adu l t females w o u l d be mou l t i ng for each day fo l l ow ing the date when the first an ima l of either age class was observed mou l t i ng . S imi lar ly , I calculated the probab i l i ty of animals mou l t i ng and mov i n g into the next mou l t stage (completely moul ted) by date fo l l ow ing the day w h e n the mou l t was first observed. Relationship to Number of Sea Lions Counted I fit a b i nom ia l regression to determine whether mou l t stage had any effect on the overa l l counts of Steller sea l ions on shore. I used data on ly for the days w h e n a total count was avai lable. I used a number of h ierarcha l mode ls and compared us ing a general l inear mode l of the form: stage ~ age + date + count, l ink=logit. 16 Results Timing of Moult - Population Juveni les were the first to start to moult , f o l l owed by adul t females, then pups and bu l l s (Figure 2.3). A total of 52 complete da i l y surveys were conducted. The mean mou l t start date was 21 Jun (20 - 24 Jun, 95% CI) for juveniles, 07 A u g (26 Ju l - 10 Aug,) for adul t females, and was 01 Sep (26 A u g - 2 Sep) for pups (Table 2.1). M e a n mou l t complet ion dates were 19 Sep (15-19 Sep) for juveni les, 26 Oct (19 - 29 Oct) for adul t females and 17 N o v (12 - 18 Nov ) for pups. Table 2.1. Mean dates for the start and end of moulting for juveniles, adult females (AF) and pups estimated from a logistic regression. Start End Juvs Mean 21-Jun-01 19-Sep-01 95% Cl 20 - 24 Jun 15-19 Sep A F Mean 7-Aug-01 26-Oct-01 95% Cl 26 Jul-10 Aug 19 - 29 Oct Pups Mean 1-Sep-01 17-Nov-01 95% Cl 26 Aug - 2 Sep 12 - 18 Nov 17 Aug Sep Oct Nov Dec Figure 2.3. Loess curve fitted to proportion of (a) moulting juveniles, (b) adult females, and (c) pups showing (d) comparative difference in timing of moult. The error bars represent S E . Tick marks on the x-axis show the first day of each month. 18 Duration of Moult - Individual The dura t ion of the mou l t averaged 45.7 days (± 3.7 days, 95% CI, n=29) for focal adul t females and 45.0 days (± 4.4 days, n=30) for focal pups. They d i d not differ s igni f icant ly f r om each other (Table 2.2). Howeve r , the start of the mou l t of the two focal groups d i d differ s igni f icant ly as i l lustrated by the separate l ines based o n a Kap l an Me ie r surv iva l probabi l i ty analysis (Figure 2.4). The Kap l an Me ie r probabi l i ty analysis, conducted f r om the focal observations, shows the probabi l i ty of the popu la t ion mov i ng f r om one mou l t stage to another. The steepest por t ion of the l ine i n F igure 2.4 indicates the greatest rate of change in the popu la t ion f r om one mou l t stage to another. For adu l t females a large shift f r om not mou l t i ng to mou l t ing occurred about 30 days f o l l ow ing the start of their mou l t (25 August ) . In contrast, the propor t ion of pups swi tch ing to mou l t ing was more constant. Comp le t i on of the mou l t was re lat ive ly rap id for both pups and adu l t females, as ind ic ted by the steep rate of decl ines shown in the probabi l i ty of f in i sh ing the mou l t i n F igure 2.4. A d u l t females experienced the greatest change a round day 80 (15 October), wh i l e the transi t ion for pups was relat ively qu ick overa l l . 19 Table 2.2 Mean duration of moulting (in days) and mean start and end dates for focal adult females (AF) and pups. Comparisons between pups and adult female mean dates were made with standard two sample t-tests. A F Pup t P df Mean Days S E 45.7 1.83 45.0 2.14 -0.22 0.828 57 Mean Start S E 27-Aug-01 2.29 26-Sep-01 2.27 9.4 <0.001 57 Mean End S E n 12-Oct-01 2.00 29 10-Nov-01 1.51 30 11.9 <0.001 52 20 0 25 50 75 100 125 Days since first animal moulted Figure 2.4. The probabilities (with SE) that the adult female and pup populations would a . start the moult or b . have completed their moult following the date that the first moulting animal was noted (which was an adult female observed on 27 July 2001). Probabilities are based on a Kaplan Meier Survival probability analyses. Loess fitted curves. 21 Relationship to Number of Sea Lions Counted In general, there was an overa l l decl ine i n the number of Steller sea l ions counted on Lowr i e Is land du r i ng the study per iod (Figure 2.5). The greatest rate of decl ine appeared to occur immediate ly after the adu l t females started mou l t ing (between the not mou l t i ng stage and the mou l t i ng stage) we l l before the end of their mou l t . Date was the most rel iable pred ictor for the stages of mou l t (Table 2.3). Cont ra ry to predict ions, count d i d not contr ibute s ignif icant ly to mou l t stage, nor were sex and age rel iable predictors. Table 2.3. Summary of model fit for moult stage (not moulting or completely moulted) and population counts, including generalized linear model regression coefficients. sequential terms glm regression coefficients (first to last) Stage coefficient S E t df dev. resid. Pr (Chi) Not moulting intercept 21.35 26.50 0.81 sex/age -6.15 5.13 -1.20 9 0.92 0.34 date -0.42 0.43 -0.97 8 6.29 0.01 count -0.002 0.01 -0.41 7 0.18 0.67 Completely moulted intercept -11.39 10.72 -1.06 sex/age 2.92 1.47 1.99 23 0.39 0.53 date 0.10 0.09 1.22 22 8.89 0.003 count 0.00 0.00 0.03 21 0.00 0.98 Note deviance in null model for not moulting sequential ANOVA: 8.048 and for done moulting ANOVA: 10.6607. Model: glm (stage~age+date+count, link=logit) 22 Figure 2.5. Number of Steller sea lions (in all sex and age classes) counted on Lowrie Island, July - August, 2001. The two grey scale bars above the graph represent the proportion of adult females (Adults) and pups moulting (white = none moulting, black = all moulting). The white diamond represents a peak in the proportion moulting. T h e proportion moulting beyond the end of observation (November 24) were extrapolated from Figure 2.3. Moult Progression F o r a l l sex a n d age classes, the general m o u l t started o n one or two areas of the b o d y a n d spread over the rest of the b o d y i n a regular fashion. Scarred areas of the b o d y , i f present, were a m o n g the first regions to m o u l t . A d u l t females appeared to have two dist inct patterns of m o u l t i n g that were d i s t i n g u i s h e d b y whether they were early or late moulters . Females that 23 were late to start mou l t i ng tended to beg in los ing ha i r o n their shoulders, cont inu ing d o w n towards their foref l ippers and ventra l reg ion (Figure 2.6). N e w hair then appeared on their h indf l ippers and progressed over the dorsa l m id l ine and up f r om the ven t rum and sides. The last places to mou l t were the neck, fo l lowed by the head. The second pattern of mou l t (for those w h o started early) was s imi lar to the late mou l t i ng females except that n ew hai r in i t ia l ly appeared concurrent ly near the eyes and on the snout and foref l ippers. Bu l l s appeared to mou l t i n a s imi lar fashion to later mou l t i ng adul t females, a l though too few sightings were made to d r aw f i rm conclusions. However , juveni le mou l t patterns appeared to resemble that of earl ier mou l t ing females, w i t h new hai r appear ing near the eyes and snout. The last areas to mou l t were their necks and the sides of their torsos. Pups began mou l t i ng on their h indf l ippers w i t h new hair short ly appear ing on the tops of their heads (Figure 2.6). Pups that had been branded also appeared to experience ear ly hair loss, w i t h new hai r f irst observed on the h indf l ipper reg ion near the tai l . M o u l t on the h ind f l ippers moved up the sides and dorsa l m id l i ne towards the head. The mou l t also progressed up across the ventra l reg ion wh i l e it moved s imul taneous ly d o w n the side of the head. It then progressed across the neck towards the dorsa l m id l ine . The last regions to mou l t were on the sides immed ia te ly above the foref l ippers. A characteristic " s haw l " often connected the two sides, just pr ior to this stage (Figures 2.1 and 2.6). 24 Figure 2.6. Progression of moult for (a) adult females and (b) pups of the year. Numbers indicate the progression of moult over time. 25 Discussion Timing of Steller Sea Lion Moult The timing of the Steller sea l ion mou l t di f fered b y sex and age class. Juveni les were the first to mou l t i n early July, fo l l owed b y adu l t females at the end of July, and by pups and bul l s i n early September. The dura t ion of vis ib le mou l t for i nd i v i dua l s w i t h i n a l l age classes was about 6.5 weeks, a l though the durat ion of the staggered mou l t for the popu la t ion as a who l e was about 21 weeks (Jul - Nov ) . A m o n g p inn ipeds i n general, the time f rom the first mitot ic event unt i l the o ld hair is pushed out ranges f r om 6 weeks for harbour seals to 14 weeks for northern fur seals. It takes about two weeks of this time for a hair to be fu l l y v is ib le once it reaches the surface of the epidermis unt i l it forces the o ld fol l ic le out of the shared shaft (L ing 1984). Thus the durat ion of the phys io log ica l mou l t of Steller sea l i on is at about 8.5 weeks. Shedd ing is the f ina l stage of the hair cycle (L ing 1970; L i n g 1984). A m o n g Steller sea l ions, I observed three dist inct patterns of progress ion of hair loss: ear ly-moul t ing adul t females (and juveniles), later-moul t ing adu l t females (and bulls), and pups of the year. The progress ion of the mou l t over the body surface of Steller sea l ions appears to have three dist inct patterns that are specif ic to age and sex class (i.e., pups, juveni les, bu l l s and adul t females). In the case of adu l t females, there appear to be two dist inct patterns depend ing on whether the female moul ts early or late i n the season. M o u l t patterns have been documented i n on ly one other p inn iped species, the N e w Zea land sea l ion (McConkey et a l . 2002), where the pattern resembled that of the early mou l t ing adul t females i n this study. A s w i t h 26 the Steller sea l ion, male N e w Zea land sea l ions started mou l t i ng on the face and fl ippers, fo l l owed b y the mane (neck), the ventra l m id l i ne and the sides. The t im ing of the mou l t has been documented i n a diverse range of species, revea l ing a general tendency for juveni les to mou l t before o lder animals. Examples where juveni les mou l t pr ior to other age classes have been documented i n p ied f lycatchers (Ficedula hypoleuca) (S i ikamak i et al. 1994), European badgers (Stewart and Macdona l d 1997), and harbour seals (Danie l et al. 2003; Thompson and Rothery 1987). A m o n g otari ids, juveni le N e w Zea land sea l ions (Phocarctos hookeri) mou l ted pr io r to subadults and adults (McConkey et al. 2002), and year l ing nor thern fur seals mou l ted first, f o l l owed by adult males then females (Scheffer and Johnson 1963). The Steller sea l i on mou l t fo l lowed these general patterns. What Drives the Steller Sea Lion Moult? The prox imate mechan i sm for the mamma l i an mou l t is thought to be control led by env i ronmenta l s t imu l i - photoper iod and temperature - wh i c h trigger a ho rmona l response that results i n hair g rowth . Other factors such as body cond i t ion and reproduct ive hormones probab ly also inf luence when different sex and age classes moult . Poor nutr i t ion, that m ight lead to poor body condit ion, has been documented to affect the qual i ty of pelage and delay the t im ing of hair regenerat ion i n a number of mamma l s and b i rds (L ing 1970; S i i kamak i et al. 1994; Stewart and Macdona l d 1997). There are four major categories w i t h i n wh i c h the costs associated w i t h the Steller sea l i on moul t , for a l l sex and age classes cou ld be classif ied. They are direct, indirect, potent ia l confl ict ions, and med ia t ing effects. D i rect energetic costs inc lude those that direct ly sequester energy f r om an an imal ' s budget, such as g rowth of the hair and ho rmona l action. Indirect costs inc lude those events 27 that require direct energy input but that m ight d ivert energy al located towards the moult , such as thermoregulat ion. L im i t i ng or potent ia l ly conf l ic t ing costs might affect the sea l i on mou l t can be behav ioura l or phys io log ica l i n nature and cou ld inf luence the mou l t such that their requirements may take precedence over expedi t ing the moult , such as fasting l imitat ions that m igh t affect hau l out t ime and elevated sk in temperatures that he lp the moul t . Med i a t i ng effects of the mou l t inc lude those occurrences that might act to suppor t or depress the moult, such as body cond i t ion and the external environment, temperature. T w o of the b iochemica l responses that m ight d irect ly affect the juveni le mou l t are a pair of antagonist ic sets of hormones: thy ro id (st imulating) and Cortisol ( inhibit ing) (Eb l ing and Ha le 1970; Ketterson and N o l a n 1992; M o h n 1958; N o l a n et al. 1992; Payne 1972; Riv iere et al. 1977). Thy ro i d hormones (such as thyrox ine - T4, t r i iodothyron ine - T 3 , and reverse T 3 - rT3) st imulate oxidat ive metabol ism and mobi l i se energy stores. Cor t i so l is a g lucocort ico id (a stress hormone) that st imulates gluconeogenisis, increasing b l ood sugar levels. In the male European badger, thy ro id hormones st imulated their moul t , part icu lar ly when testosterone was suppressed (Maure l et al. 1987). A m o n g p inn ipeds the t im ing of the mou l t for y oung (sexually immature) an imals appears to correlate w i t h antagonist ic thyroxine-Cortisol ho rmona l concentrations (John et al. 1987; Riv iere et al . 1977). Converse ly , frequent sampl ing i n capt ive harbour seals lead to no apparent correlat ion between the concentrations of thy ro id hormone and the mou l t (Renouf and Brotea 1991). Instead they hypothes ised that the changes in hormone concentrat ion were correlated to the t im ing and quant i ty of food intake. The adul t female Steller sea l i on mou l t occurs after the pupp i ng and breeding per iods. A med ia t ing effect associated w i t h the t im ing of their mou l t might inc lude lowered body condit ion, a result of energy al located to partur i t ion 28 and early lactation. Ano the r indirect cost that m igh t inf luence their timing inc ludes de layed imp lanta t ion and the oncoming w in ter season. In most p innipeds, mat ing occurs after the pupp i ng per iod and but before most females depart the rookeries w i t h their pups. Af ter mat ing, the embryo undergoes deve lopmenta l d iapause. It is not k n o w n what signals the embryo to implant, but it usua l l y occurs i n the later fal l, before winter . H o r m o n a l inf luences associated w i t h imp lanta t ion cou ld further ind i rect ly affect the adul t female moult . The mou l t of adul t female Steller sea l ions cou ld be ind i rect ly affected by reproduct ive hormones such as estrogen, progesterone and prolact in. Levels of estrogen (an inh ib i tor of hair growth) are at h i gh concentrations fo l l ow ing partur i t ion i n a number of p inn iped species (Boyd 1991). Stewart and Macdona l d (1997) suggest that lactation may reduce body cond i t ion and st imulate the p roduc t i on of prolact in. Levels of pro lact in are elevated dur ing lactation for most p inn ipeds (Boyd 1991) and might indicate increased energy expenditures that cou ld suppress the moul t . Howeve r , progesterone concentrations (a ha i r g rowth st imulator) tend to be h igh later i n the season after the blastocyst implants (Boyd 1991; L i n g 1984), co inc id ing w i t h the mou l t per iod. Unfor tunate ly l itt le is k n o w n about pro lact in or progesterone i n Steller sea l ions. The t im ing of the mou l t and the two observed patterns of mou l t progress ion m igh t also be related to whether adul t females were accompanied by nurs ing pups of the year or juveniles, or had not reproduced. Nu r s i n g females have greater food requirements than those w i thout pups (Winsh ip et al. 2002) and may therefore be i n poorer body condit ion. In add i t i on to the indirect energetic cost (relative to the moult) associated w i t h a suck l i ng pup , females w i t h nurs ing pups are l i ke ly to spend more time on the rookery du r i ng the early pupp i ng per iod (May - June), w i t h less foraging opportuni t ies relat ive to females 29 w i t h nurs ing juveni les and females w i thout of fspr ing. Females both accompanied by juveni les and w i thout of fspr ing can leave the rookery for extended per iods of t ime to forage. The increased t ime spent forag ing might be beneficial to these females result ing i n re lat ively good body cond i t ion that expedites the moul t . Thus females that have either not reproduced or were suppor t ing a nurs ing juveni le may have mou l ted earl ier than those w i t h pups. Such a phenomenon appears to account for the mou l t of Co l umb i an g round squirrels (Neuhaus 2000) and ye l l ow bel l ied marmots, Marmota flaviventris (Armitage and Sa lsbury 1993), where non-breeding females mou l t ed before those that were reproduct ive ly active. Weather condit ions, a med iat ing effect, were not recorded at the Steller sea l i on study site, but the early mou l t i ng adul t females and juveni les may have been exposed to s l ight ly wa rmer ambient temperatures that may have been more conduc ive to mou l t i ng . In general, July and Augus t are wa rme r months in Southeast A l a s ka w i t h l itt le w i n d and swel l , and September f requent ly has cooler temperatures and increasing swe l l and rain. W h e n ambient temperatures are high, such as du r i ng Ju ly and Augus t when juveni les and adu l t females moult, animals may shunt excess heat towards the head and f l ippers (Hart and I rv ing 1959). These areas cou ld i n turn be the first to mou l t if increased surface temperatures speed the mitot ic process (Ebl ing and Ha l e 1970; Feltz and Fay 1966). The onset of the mou l t among the adul t female popu la t i on appears to be in i t ia l ly g radua l as ind icated by the gradua l s lope of the change in the probabi l i ty of the female popu la t ion mov i ng into the active mou l t stage (Figure 2.4). The popu la t i on then rap id l y shifts into the active mou l t i ng stage near day 25 and mainta ins a re lat ive ly constant rate of in i t iat ion of mou l t i ng through day 40. The rap id shift observed at day 25 may be due to the effect of thyroxine, 30 wh i ch is be l ieved to promote or init iate hair g rowth i n rats (Mohn 1958) and harbour seals (Riviere et al. 1977), and was shown to peak i n gray seals (Halichoerus grypus) at the po int of rap id ha i r shedd ing (Boi ly 1996). The onset and apparent synchrony of the mou l t m ight also be related to the immanent departure of mothers w i t h their pups f rom the rookery. It is not k n o w n if the ini t ia l stages of the mou l t are more energetical ly expensive, but has been hypothes ised for harbour seals (Daniel et al. 2003). If the ear ly stage of the mou l t are also more energetical ly expensive for sea lions, it m ight also be benefic ia l for adult females to qu i ck l y proceed through this stage. The mou l t of male sea l ions may be direct ly affected p r imar i l y by the reproduct ive ho rmone testosterone and also by their body condi t ion. The male European badger mou l t was inh ib i ted by the presence of testosterone wh i ch co inc ided w i t h poor b od y cond i t ion (Maure l et al. 1987; Stewart and Macdona l d 1997). It may also be the case for male harbour seals that breed aquat ical ly and lose body mass du r i ng the mat ing season due to the energy al located to f ind ing females and secur ing reproduct ive encounters (Walker and Bowen 1993), acting to potent ia l ly confl ict w i t h the moul t . The combinat ion of testosterone and poor body cond i t ion after breed ing may be w h y male harbour seals are last to moult . E levated levels of testosterone i n bu l l Steller sea l ions also co inc ide w i t h the mat ing season (Ha rmon et al. 1999) du r i ng wh i c h they defend territories and lose weight and body mass (Winsh ip et al. 2001). Thus, the poor body condi t ion of bul ls after the per iod of terr itor ial i ty may mediate a later t im ing of moul t . Pups, a long w i t h bul ls, were the last to moul t . The t im ing of the pup mou l t might be ind i rect ly affected by energy al located to g rowth and deve lopment of thermoregulat ion for an aquatic l ife. Pups also are affected by their mothers ' behaviour, because they w i l l f o l l ow her w h e n she leaves the rookery to go to another hau lout site. In this case, the mothers ' behav iour creates 31 a potent ia l ly conf l ic t ing or l im i t ing effect on the pups ' mou l t . A m o n g some p inn iped species, such as harbour seals, pups mou l t their nata l pelage in utero, emerging w i t h an adu l t coat, and can enter the water w i t h i n minutes of b i r th. Species, such as Wedde l l seals, that do not shed their p u p coat in utero do not usua l ly enter the water unt i l they have completed their mou l t about 2 to 4 weeks after b i r th (L ing 1974). Howeve r , Steller sea l i on pups undergo their postnatal mou l t 4 months after b i r th and regular ly enter the water for brief per iods after spending their f irst mon th on shore, increasing the potent ia l thermal cost associated w i t h their moul t . Metabo l i c measurements f rom northern fur seals indicate that post-moult pups had lower metabol isms when in water compared to pre-moul t pups (Donohue et al. 2000). If a s imi lar phenomenon appl ies to Steller sea l i on pups, the t im ing of their mou l t m ight reflect their transit ion f r om a re lat ive ly sedentary per iod on shore to an aquatic, thermal ly more stressful existence. It is also possible that the t im ing of mou l t reflects body cond i t ion g iven that some of the last pups to mou l t appeared to be in poorer body condi t ion. The est imated end of the mou l t for the focal an imals was earl ier than the estimated mou l t f r om the scan surveys. G i v en that the focal animals were branded it is possible that they were born earlier, on average, than the scan- sampled animals observed to mou l t last. These same scan-sampled pups were frequently observed du r i ng Novembe r begging and t ry ing to sneak suckles f rom other females, and their h ips and ribs v i s ib ly showed relat ive to other ind iv idua l s w h o had completed their mou l t and were usua l l y observed w i t h their mothers and appeared fat and healthy. 32 Effects of Moult on Population Counts There d i d not appear to be a relat ionship between overa l l numbers of animals on shore and the stage of mou l t of different sex and age classes (Figure 2.5). Howeve r , counts at the rookery may not reflect overa l l numbers of sea l ions hau led out throughout the region. The dramatic decl ine i n overa l l numbers of sea l ions counted at the rookery occurred after the adul t females began their moult, rather than after the mou l t was completed as m igh t be expected for a species restricted to l and for thermoregulatory reasons (such as harbour seals). Large numbers of females appeared to leave the rookery for other areas wh i l e they were we l l into their mou l t (when rap id shedd ing of o ld hair may occur). A further look at the re lat ionship between the presence of females w i t h pups (Figure 2.7) showed females tended to outnumber pups w h e n densit ies were h igh (i.e., ear ly i n the season) and were outnumbered later i n the season as numbers d ropped and females spent longer at sea. 33 Figure 2.7. Regression of the number of females with number of pups counted. (r=0.40, d.f.=22.9, p<0.001). Regression line was fit to adult counts less than 100 individuals. The broken line represents a 1:1 ratio. The departure of females pr ior to the complet ion of their mou l t might signify that the later stages of mou l t are not as energetical ly expensive as the earlier stages. Med i a t i ng effects of poor weather and less food avai lab i l i ty might outwe igh the direct costs of hair g rowth du r i ng the later mou l t result ing i n females leav ing the rookery. Energetic requirements for nurs ing increase as the pup grows and m igh t result i n females increasing the length of their foraging trips (Mi lette and Trites 2003). In the winter months the p ropor t i on of t ime spent away f r om the rookery increased (Trites and Porter 2002). It is also possible that 34 the energetic ga in of t rave l ing to protected in land locations to feed outweighs the direct energetic cost of complet ing the mou l t on the rookery. The greatest numbers of juveni les (ages 1-3 y) were observed du r i ng early Augus t just before the overa l l numbers of sea l ions dec l ined. Tradi t ional ly , counts of pups and non-pups have been made du r i ng the pupp i n g per iod (the end of June, beg inn ing of July) when highest numbers of adu l t females, pups and bul ls are be l ieved to be on shore. Mos t of these rookery surveys focus on counts of pups and reproduct ive females, but few juveni les are observed. Numbe r s of mou l t ing juveni les at the rookery appeared to increase after the peak of pupp ing . Thus Augus t m igh t be an opportune t ime to observe juveni les g i ven the central role they are be l ieved to p lay i n the decl ine of sea l i on popu la t ions i n the Gu l f of A l a ska and the A l eu t i an Islands. Cond i t i on indices m igh t be deve loped for juveni les du r i ng this t ime of year to compare among regions du r i ng this energetical ly expensive per iod of their life cycles. Potential Biases A fundamenta l assumpt ion of this mou l t i ng study was that the animals observed on shore represented the popu la t ion as a who le . Wh i l e there is no in format ion to suggest otherwise, it cou ld be argued that the focal animals were more l ike ly to hau l out and be seen because they were better fed and were i n better body cond i t ion than other animals. An ima l s that are more l ike ly to hau l out on land may have mou l ted faster than ind i v idua l s that were absent, if hau l ing out on land has some benefit that expedites the mou l t . Ano the r factor that cou ld have inf luenced the t im ing and progress ion of the mou l t was the presence of parasites such as sea l ice (e.g., Proechinophthirus fluctus, Antarctophthirus callorhni). Sea lice cou ld have confounded the estimated start date for the p u p mou l t because many of the p u p rumps (region above the 35 tail) were ba ld - l i ke ly due to lice. O n a ba ld surface new hai r is easy to recognise. Emergent new hairs may be v is ib le on a ba ld surface up to 2 weeks pr ior to the shedd ing of o l d hair, as was the case for the pups . However , this was not the case for adu l t females. A further caut ionary note is that the dates of the mou l t observed at Lowr i e Island may not be the same throughout the range of Steller sea l ions. The t im ing of the mou l t may also vary if it is ind i rect ly affected b y the t im ing of pupp ing . The t im ing of p upp i n g has been shown to vary by t ime and space w i t h the mean earliest pups bo rn 4 Jun on Forrester (Lowrie) and the latest mean pups born 21 Jun at A n o N u e v o Is land (Pitcher et al. 2001). Howeve r , reg ional differences are l ike ly to be smal l . Differences i n body condi t ion cou ld also va ry by region and might inf luence the moul t . If body condi t ion affects the t im ing of the moult , and animals i n the western range are phys io log ica l ly stressed, as has been hypothes ised to occur i n this popu la t ion (Trites and Donne l l y 2003), it cou ld result i n h igher concentrations of glucocort icoids that may also inh ib i t mou l t ing (Ebl ing and Ha le 1970; John et al. 1987; M o h n 1958). Such changes have been noted i n the t im ing of the mou l t for harbour seals i n the Gu l f of A laska , a l though reasons for this shift are not k n o w n ( A D F G , unpub l i shed data). Optimal Instrument Attachment Researchers use rad io tracking instruments aff ixed to sea l i on fur to examine movement across t ime and space (two and three d imens ional) that might p rov ide ins ight into behaviour, phys io logy and forag ing ecology. The life of an instrument g lued to the fur w i l l theoretical ly be one year f rom mou l t to moult; therefore, it is important to maximise the t ime the inst rument is attached to the fur. The max ima l use of an electronic instrument w i l l require an opt ima l t ime frame for attachment. The opt ima l t im ing to glue electronic instruments to 36 Steller sea l i on fur is a funct ion of the t im ing and progress ion of the mou l t and the t ime w h e n the greatest numbers for different sex and age classes w o u l d be present. The first factor affecting the opt imisat ion of inst rument attachment is the t iming and progress ion of the moult , wh i c h shou ld serve as the earliest t ime for attachment. Instruments have fal len off premature ly i n the past due to be ing g lued to o ld hair before it had complete ly shed. Instruments shou ld be g lued to hair that has reached its m a x i m u m length, but this po int is d i f f icu l t to ascertain i n the f ie ld. In the w i l d , instruments are typ ica l ly g lued to sea l i on fur on the do r sum beh ind the head and neck. The mou l t of this area differs for a l l sex and age classes such that the op t ima l t ime to attach electronic instruments also varies by mon th and year. A d u l t females general ly completed their mou l t by the first to second week of October. N e w hai r appeared on the dorsa l m id l i ne as ear ly as the m idd le of September. Earl iest attachment of instruments to adul t females shou ld therefore occur at the end of the first week of October to a l l ow their ha i r to reach its m a x i m u m length. Juveni les can safely be assumed to have completed their mou l t by the m i dd l e of September and this t ime w o u l d be the earliest recommended to affix devices to them, g iven that their backs mou l t pr ior to other areas of the body . Pups are the last to mou l t and have greater var iat ion in their complet ion t imes. The earliest pup mou l t was completed i n the m idd le of November . Howeve r , the presence of a " s h aw l " mou l t stage (Figure 2.1) might prec lude early attachment of instruments to pups. A t best, the end of November to early December is p robab ly the best t ime to capture and glue devices to pups that are i n good heal th and have f in ished their moul t . The second factor to consider for opt ima l inst rument attachment is the time when the greatest numbers of ind iv idua l s for each sex and age class are 37 avai lable or easi ly accessible. K n o w i n g when sea l ions congregate reduces the time spent l ook ing for more ind iv idua ls , increasing cost-effectiveness. The t ime when the largest numbers of animals are concentrated is not the same for each sex and age class and might be at a different t ime i n re lat ion to the mou l t ing per iod. The largest congregat ion of females and bu l l s occurs du r i ng the pupp i ng per iod, before the moul t . Howeve r some females rema in beyond their mou l t i n September to look after their pups. Thus a larger p ropor t i on of the remain ing females w i l l have completed their moult , and w o u l d make instrument attachment more cost efficient. Numbe r s of pups rema in relat ively h i gh on the rookery dur ing the pupp i ng and nu rs ing per iods, but numbers of i nd i v idua l s decl ine as the mou l t progresses. Pups fo l l ow their mothers to hau lout sites w i t h i n du r i ng late fal l, near the end of their moult , mak ing this an op t ima l t ime for access to many ind iv idua l s that have completed their moul t . The numbers of juveni les observed at the rookery were the greatest du r i ng the earl ier stages of the mou l t (August), wh i ch was not a good t ime for instrument attachment. Ano the r t ime per iod w i t h increased concentrations of juveni les and sub adul t sea l ions is du r i ng the fal l and winter months w h e n mou l t i ng ind iv idua l s congregate at inshore haulouts. There is no single op t ima l t ime for a l l sex and age classes for instrument attachment. Instead, the targeted sex and age class shou ld be first opt imised to when al l o l d hair is shed i n the targeted body region, then thereafter w i t h the next t ime they occur i n greater concentrations (not necessari ly the peak). By focusing on secondary peaks in abundance, there m igh t be a r isk of accessing fewer ind iv idua ls , but this cost is not as great as the probab i l i ty of hav ing fewer ind iv idua l s that have completed the moult , curta i l ing the p rob l em of instruments fa l l ing off premature ly . 38 Future Research - Is the Steller Sea Lion Moult Energetically Expensive? A n area for further s tudy is evaluat ing the energetic cost of the Steller sea l ion moult . Th is eva luat ion cou ld be done by examin ing behav ioura l adaptations and phys io log ica l compensat ions that deal w i t h the energetic costs associated w i t h the mou l t as have been observed i n other species of p inn ipeds . There is evidence of h i gh energetic costs associated w i t h the mou l t i n l and mammals (Neuhaus 2000; Perez-Barber ia and Nores 1996; Stewart and Macdona l d 1997) and poss ib ly amph ib ious mammals . Semi-aquatic mamma l s that have little fat stores, such as beaver and muskrat, p ro long their mou l t to span an entire year, un l i ke animals of s imi lar ancestry that mou l t twice a year (L ing 1970). The extended mou l t is l i ke ly due to balance of energy al located to other events w i t h i n their seasonal cycle and the direct cost of hair replacement. The t im ing of the mou l t for these species contends w i t h other costly events of their seasonal cycle, i n c lud ing mat ing, implantat ion and h ibernat ion. In an amphib ious species such as the beaver or muskrat a role of the pelage may act greatly towards thermoregulat ion in air. The role of the pelage i n water is less def ined (L ing 1970). The t im ing of the mou l t for them might be better balanced to span the entire year and ma inta in the funct ion of thermoregulat ion rather than be devoted to a brief and energetical ly costly t ime per iod. Behav ioura l adaptat ion i n response to med ia t ing effects associated w i t h the mou l t may exp la in the need for phocids to hau l out on l and and for belugas to move to wa rmer estuaries du r i ng the mou l t i ng per iod (Boi ly 1995). Ha rbour seals and belugas cou ld mou l t i n cooler water, but w o u l d require h igher energy input to ma inta in elevated ep idermal temperatures. Phys io log ica l adaptat ion may inc lude alter ing energy expenditure, as ind icated by a change i n metabol ic rate. Seasonal s tudy of the metabol i sm i n harbour seals f ound a l owered resting 39 metabol ic rate du r i ng the moult , poss ib ly due to lowered act iv i ty levels (Rosen and Renouf 1998). The gray seal, for example, can lower its metabol ic rate dur ing the mou l t to compensate for less energy input (Boi ly 1996). The nor thern and southern elephant seal share the same genus but have adapted different energy-sav ing strategies that incorporate both phys io log ica l and behav ioura l adaptat ions du r i ng the mou l t (Boyd et a l . 1993). The elephant seals may be affected by different geographic and env i ronmenta l factors. Nor thern elephant seals l i v i ng a long the Ca l i fo rn ia coastl ine are less active and have lower metabol ic rates wh i l e mou l t i ng compared to southern elephant seals i n the Antarct ic that have a higher metabol ic rate and may need to be more active. To explore behav ioura l and phys io log ica l adaptat ions among mou l t ing Steller sea l ions, a measure of f ie ld metabol ic rate w o u l d be requ i red i n add i t ion to determin ing act iv i ty patterns of k n o w n i nd i v i dua l sea l ions du r i ng the mou l t ing per iod. The body cond i t ion of i nd iv idua l s of different sex and age classes cou ld be fo l l owed throughout their entire seasonal cycle. For example, the effect of reproduct ion and lactation on the t im ing of the mou l t of adul t females w o u l d p rov ide further ins ight on h o w sea l ions balance energetic costs of events w i t h i n their seasonal cycle. The body cond i t ion and metabol ic rate of reproduc ing (females w i t h pups vs. juveniles) and non reproduc ing females cou ld be fo l l owed and compared to see if females nu r s ing pups de lay their mou l t relative to other females. Ano the r f ru i t fu l area for further research is to examine the progress ion of the mou l t by measur ing surface temperature or heat f lux across the Steller sea l ion body us ing thermisters and thermal cameras. If increased temperatures are necessary for mitos is and the produc t ion of hair, then the ear ly stages of the mou l t may be detected non- invas ive ly . A thermal camera m igh t detect these 40 "hot spots" and cou ld be used to examine the early mou l t (not seen by eye) i n a w i l d popu la t i on of sea l ions or other mou l t i ng p inn ipeds. Add i t i ona l l y , it w o u l d be advantageous to document "hot spots" on the body for different sex and age classes, i n part icular to see if they relate to the different patterns of mou l t progress ion observed i n Steller sea l ions. A pup 's abi l i ty to thermoregulate may differ f rom that of an adult, and an interesting study might examine both the progress ion of "hot spots" and metabol ic rate to examine if they are associated w i t h the moult . In most mamma l i a n species, the metabol ic rate i n juveni les is s ignif icant ly h igher than i n adults due to the h igh cost of body g rowth (Brody 1945). Both metabol ism and heat f lux i n northern fur seal pups decreased s igni f icant ly after their mou l t was completed, l i ke ly a result of a more efficient pelage and thicker b lubber layer (Donohue et al. 2000). Such phys io log ica l changes m igh t also exist i n Steller sea l i on pups and might inf luence their mou l t topography. Summary I determined the t im ing and progress ion of the mou l t for w i l d Steller sea l ions (Eumetopias jubatus) on Lowr i e Island, A laska . O n average, the mou l t started on 21 Jun for juveni les, 7 A u g for adul t females, and on 26 Oct for pups that were bo rn i n June. M e a n complet ion dates also di f fered s igni f icant ly (19 Sep for juveniles, 26 Oct for adul t females and 17 N o v for pups). The mean durat ion of the mou l t was s imi lar for adul t females (45.7 days) and pups (45.0 days). However , the pattern and progress ion of hair loss over the body surface differed for 1) pups, 2) juveni les and early mou l t ing adul t females, and 3) bu l l s and later mou l t ing adul t females. Differences i n the t im ing and patterns (progression) of the mou l t m ight be inf luenced by body cond i t ion and phys io log ica l changes associated w i t h age and reproduct ive state. Numbe r s of i nd i v i dua l s hau led out 41 does not appear to be inf luenced by the moult , and may be affected by other aspects of their seasonal cycle that might take precedence over the phys io log ica l cost of the moul t . The t im ing and pattern of the mou l t have impl icat ions on research study designs that re ly on attaching electronic devices to sea l i on fur. 42 C H A P T E R III: T I M I N G O F M O U L T I N C A P T I V E A N I M A L S In t roduc t ion Steller sea l ions have been raised at the Vancouve r A q u a r i u m Mar ine Science Centre (Vancouver, BC , Canada) since 1993 to s tudy their nutr i t iona l and phys io log ica l requirements. F ive pups were brought to the A q u a r i u m i n 1993, one in 1994, four i n 1997, and f ive i n 2000. A l l animals (except 1) were obtained f rom the Scott Islands rookery complex (50.12 ° N latitude, 128.06 °W longitude) at the northern end of Vancouver Island, Br i t i sh Co l umb ia . Da ta f r om captive studies can p rov ide a general baseline compar ison for wha t m igh t be observed in the w i l d and can he lp formulate questions and hypotheses for further study. The added benefit of us ing captive animals is that their phys ica l condit ions and nutr i t iona l supplements are known , un l ike most i nd i v i dua l s that might be observed i n the w i l d . The fo l l ow ing presents observations of mou l t i ng among capt ive Steller sea l ions he ld at the Vancouver Aqua r i um . The data are contrasted w i t h observations f r om the w i l d to gain further ins ight into the mechanisms that might inf luence the t im ing and durat ion of mou l t ing . Me thod s The onset and progress ion of the mou l t were documented at the Vancouver A q u a r i u m Ma r i ne Science Centre, (Vancouver, BC) since 1993. An ima l s were mon i to red for in i t ia l signs of new hair du r i ng week l y health checks. Subsequently, areas where new hair appeared were shaded on data forms conta in ing two Steller sea l i on profi les (one v i ewed f r om the side and the other f rom above - F igure 2.2 composite). Observat ions were made by researchers w h o wo r k ed w i t h the sea l ions on a da i l y basis and were able to readi ly detect the onset of mou l t ing . 43 A total of 56 complete mou l t records were made on 15 ind iv idua l s (10 females and 5 males) represent ing 9 age classes (Append i x 2). A mou l t record consisted of the mou l t progress ion for an i nd i v i dua l du r i ng one season. For this study, I sorted the 56 records to inc lude on ly data that encompassed an ind iv idua l ' s complete mou l t (wi th both start and end dates). In some cases the first date of recorded mou l t was not the actual start date and those data were omitted. The dura t ion of the mou l t was def ined as the t ime f r om when the first signs of new hai r were observed unt i l the last o ld hair was shed for each i nd i v i dua l . I calculated the mean durat ion of the mou l t for completed mou l t records across a l l ages and years. I made compar isons between age classes and years us ing standard two sample t-tests. I invest igated the progress ion of the mou l t for capt ive Steller sea l ions for the year 2001 w i t h analysis methodo logy s imi lar to that app l i ed to w i l d animals (Chapter 2). Deta i led records w i t h shorter intervals between observations were kept for animals i n 2001 compared to other years. O n l y these data were used for determin ing the progress ion of the captive moult . I ass igned mou l t stage for each body area as i n Chapter 1 (Figure 2.2). Results A total of 33 mou l t i ng records were used i n the analyses that had a complete start- and end-moul t t ime. These records represented 14 ind iv idua l s (9 females and 5 males) and 7 age classes (one i nd i v i dua l was omit ted due to incomplete records. Du ra t i on of mou l t dif fered among years and w i t h i n age classes (Table 3.1), w i t h a mean durat ion of 83.5 days (4.6, SE) for a l l combined years and ages. M e a n mou l t durat ion was 82.1 (4.9 SE) days for females (n=20) and 85.7 (9.1 SE) days for males (n=13, Table 3.1). 44 Dura t i on of the mou l t differed among years (Table 3.2). Before 2000 (n=15) the average mou l t durat ion was 64:9 (3.5 SE) days, wh i l e i n 2000 (n=9) the average mou l t dura t ion increased to 93.3 (7.8 SE) days. M o u l t dura t ion increased again i n 2001 (n=9) to 104.7 (8.2 SE) days. Dura t i on also di f fered by age class (Figure 3.1). In 2001, the mean durat ion was 85.6 (4.9 SE) days for animals under age 3 y (n=5), and was 128.5 (5.1 SE) days for those animals 3+ y (n=4, Table 3.2). Table 3.1. Summary statistics for the mean duration of moulting (in number of days) for captive animals at the Vancouver Aquarium, 1993 - 2001. Mean S E n Variance S D all animals all years 83.5 4.6 33 685.1 26.2 age 0 (all years) 79.4 5.6 11 348.1 18.7 ages 1&2 (all years) 72.7 5.5 11 330.4 18.2 ages 3+ (all years) 98.5 10.1 11 1121.3 33.5 female (all years) 82.1 4.9 20 469.9 21.7 male (all years) 85.7 9.1 13 1074.4 32.8 45 Table 3.2 Mean duration of moulting (in number of days) for captive animals at the Vancouver Aquarium, 2000 - 2001. Mean S E n Variance S D year 2001 (all ages) 104.7 8.2 9 608.8 24.7 year 2000 (all ages) 93.3 7.8 9 550.0 23.5 before 2000 (all ages) 64.9 3.5 15 184.2 13.6 ages 3+ in 2001 128.5 5.1 4 102.3 10.1 ages1&2 (year 2001) 85.6 4.9 5 118.3 10.9 46 150 1 0 1 2 3 4 5 6 7 8 A g e (y) Figure 3.1. Moult duration (in number of days) by age of captive Steller sea lions. Symbols represent 6 individual animals. Loess fitted curve. 47 An ima l s under the age of 3+ y were al l pups (n=5) i n 2000 and became yearl ings in 2001 (Table 3.3). The mean start date of mou l t i ng for this cohort was 24 A u g (4.2 SE) i n 2000, and 5 A u g (2.0 SE) the fo l l ow ing year. M e a n end dates were 22 N o v (11.0 SE) for the pups i n 2000 and 29 Oct (6.1 SE) for the year l ings i n 2001. In contrast, the mean start date for sea l ions aged 3+ y (n=4) was 28 Jul (21.8 SE) i n 2000 and 7 A u g (3.4 SE) i n 2001; wh i l e their respective mean end dates were 2 N o v (34.9 SE) i n 2000 and 14 Dec (8.1 SE) i n 2001 (Table 3.3). M o u l t progress ion var ied more among the captive Steller sea l ions than i n the w i l d . General ly , an imals began mou l t i ng on their rumps, fo l l owed by the foref l ipper/shoulder reg ion and the neck. N e w hair then appeared on the head, fo l lowed by the ven t rum and f ina l ly the sides and do r sum. Wh i l e there was some var iab i l i ty to this progression, the area that seemed to f in i sh mou l t i ng the fastest appeared to be the ventra l region, wh i ch went qu i ck l y f r om no new hair be ing present to be ing complete ly mou l ted pr ior to other areas mou l t ing . 48 Table 3.3. Mean date that moulting started and ended for captive Steller sea lions by age class in consecutive years, 2000 and 2001. Mean S E t df P Start Pups 2000 yearlings 2001 24-Aug-00 5-Aug-01 4.2 2.0 -74.31 6 <0.001 age 3+ 2000 age 3+ 2001 28-Jul-00 7-Aug-01 21.8 3.4 -16.99 3 <0.001 End Pups 2000 yearlings 2001 22-Nov-OO 29-Oct-01 11.0 6.1 -27.05 6 <0.001 age 3+ 2000 age 3+ 2001 2-Nov-00 14-Dec-01 34.9 8.1 -11.36 3 <0.001 49 Discussion The dura t ion of mou l t for captive Steller sea l ions for a l l years combined was 83.5 days. Before 2000, mean mou l t durat ion was 64.9 days, wh i l e after 2000 mean mou l t dura t ion was 93.3 days. The mou l t dura t ion for capt ive animals was signif icant ly longer than the mou l t durat ion observed i n the w i l d animals. W h y the two groups of an imals shou ld differ is not obvious. One poss ib i l i ty is that it reflects observat ional error. However , a more l ike ly exp lanat ion is that the mou l t of captive animals was affected by the condit ions of capt iv i ty (e.g., water quality, food, temperatures, etc.). Captive Moult Duration It is not clear w h y the t im ing of mou l t di f fered so m u c h across years i n captive animals. One poss ib i l i ty is that more attention was g i ven to mou l t start dates i n 2000 and 2001 due to the s imultaneous w i l d s tudy counterpart (Chapter 2). The major i ty of the records removed f rom the analyses were f r om the first years of observations and the qual i ty of observations also increased w i t h time, w i t h more detai led sketches i n the later years. The increase i n qua l i ty cou ld also be due to increased recogni t ion of the moul t . Ear l ier years of observations often had questions associated w i t h them, suggest ing that the observers were not as fami l iar w i t h di f ferent iat ing o ld and new hair. Di f ferent iat ion between o ld and new hair is easi ly made w h e n the pelage is un i f o rm ly wet or dry, but is di f f icult if wet and d r y hair are interspersed. Observat ions made i n later years were taken after an imals were hosed w i t h water and the pelage was un i f o rm in colour and texture. It is also possible that the onset of the first mou l t i ng animals was over looked i n past years, since the mou l t start date is the same for a l l animals, wh i l e the degree of the mou l t progress ion differs among ind i v i dua l s for the first 5 0 moul t date ind icated o n the data sheets (i.e. some animals are more advanced i n the amount of new hai r present than others). Wh i l e the difference i n the mou l t durat ion m igh t be part ia l ly exp la ined by the increased attent ion to detai l by observers, it seems to be too great an increase to be expla ined by observat ional error alone. Ano the r poss ib i l i ty is that a change in lat itude m igh t result i n a difference i n photoper iod exposure and may have inf luenced the t im ing of mou l t i ng i n captiv ity. Breed ing aggregations of Steller sea l ions exhibit synchronous pupp ing , but the start of p upp i n g varies between sites (Pitcher et al. 2001). Relat ive to the Forrester Is land breed ing complex, animals located bo th nor th and south are bo rn later. The apparent cl ine i n t iming of p upp i n g m igh t be m i r ro red by a s imi lar cl ine i n the t im ing of moult . If so, animals taken f r om south of Forrester at the Scott Islands and brought further south to Vancouver m ight be expected to beg in mou l t i ng later than those observed at Forrester. There may also be some effect on hormones that altered t iming of mou l t du r i ng their first year i n capt iv i ty i n Vancouver . A l l told, these factors shou ld have resulted i n the captive animals mou l t i ng later than their w i l d counterparts on Low r i e Island, wh i c h was not the case. Wild and Captive Moult Duration Comparison I found that the durat ions of mou l t for both pups and adu l t females were s imi lar i n the w i l d . Howeve r , their t im ing di f fered f r om that observed i n captivity. In studies of other captive p inn ipeds, mou l t du ra t i on and t im ing has deviated greatly f r om what is expected i n the w i l d , albeit a l l based on smal l sample sizes. Ha rbou r seal mou l t durat ions (Ashwe l l -E r i ckson et al. 1986) were longer (by two to three times) i n capt iv i ty than wha t has been observed i n the w i l d ( A D F G , Tug idak Is land unpub l i shed data). S imi lar ly , capt ive gray seals started mou l t i ng 2 months earl ier than their w i l d counterparts (Boi ly 1996). 51 A l ike ly exp lanat ion that may account for the d ispar i ty i n the mou l t durat ions of capt ive and w i l d p inn ipeds may be related to di f fer ing env i ronmenta l condi t ions and the phys io log ica l effects of capt iv i ty. Someth ing as s imple as a difference i n diet cou ld affect the t im ing of mou l t . In the Gu l f of A l a ska for example, ecosystem changes altered the diet of harbour seals, wh i ch in turn affected the t im ing of reproduct ive events, such as the t im ing of pupp i ng (Jemison 1997). D ie ta ry shifts had further cascading effects on other aspects of the harbour seal l ife cycle, i n c lud ing the mou l t i ng per iod (Danie l et al. 2003). Differences i n diet between captive and w i l d sea l ions may therefore exp la in some of the differences in mou l t i ng times or durat ions. A second possib le exp lanat ion is that the different phys i ca l condit ions of the w i l d and capt ive Steller sea l ion env i ronments (e.g., temperature, water p H , salinity) in f luenced the t im ing of mou l t through basic phys io log ica l processes. Ch lor inated water may affect the hair of the animals, and has been shown to negat ively affect the ep idermis of bottlenose do lph ins (Har r i son and Thur ley 1974). Nu t r i t i ona l supp lements and changes in act iv i ty levels may also have affected the sea l i on moul t , as cou ld reproduct ive status. Prevent ing sea l ions f rom conce iv ing cou ld feasibly tr igger the produc t ion of pro lact in or some other potent ia l mou l t mechan ism. The phys io log ica l response to not reproduc ing is an interesting poss ib i l i ty g iven that the mou l t durat ions of sea l ions i n the 3+ y classes were s l ight ly longer than those of younger animals over the same years. The animals i n the capt ive s tudy aged 3+ y were not reproduc ing and were not go ing through changes s imi lar to their w i l d counterparts. In general, the mou l t durat ion for captive animals decreased unt i l age 3, then increased un t i l age 8 (Figure 3.1). The change i n the mou l t dura t ion i n the captive animals contrasts w i t h observations f r om the w i l d w i t h no difference in 52 the mou l t dura t ion of pups and adul t females (Chapter 2). Differences in nutr i t ional intake and energy expenditures seem to be the most l ike ly explanat ion for these observed differences. Summary M o u l t dura t ion was determined for capt ive Steller sea l ions and contrasted to the mou l t durat ion found i n w i l d animals. The mean mou l t durat ion for a l l capt ive animals was 83.5 days w i t h a l l comb ined years and ages (n=33). M e a n mou l t dura t ion d i d not s ignif icant ly differ between males and females. Differences were found by age class and b y year. Before 2000 the average mou l t dura t ion was 64.9 days, wh i c h increased s igni f icant ly to 93.3 days i n 2000 and 104.7 days i n 2001. The increase may not be attr ibuted to an increase i n age alone, as the pups of the year also had longer mou l t durat ions. In 2001, the mean dura t ion was 85.6 days for animals under age 3 y, and was 128.5 days for those animals 3+ y. These results differ s ignif icant ly f r om the mean mou l t durat ions of w i l d Steller sea l ions i n Southeast A laska . Possib le explanat ions for the difference i n mou l t durat ion between w i l d and capt ive animals might be direct ly related to the phys i ca l characteristics of their env i ronments. 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Journa l of Mamma l ogy , 82: 500-519. 60 Winsh ip , A.J., Trites, A .W. , and Rosen, D.A.S. 2002. A bioenergetic mode l for est imat ing the food requirements of Steller sea l ions Eumetopias jubatus i n A laska , U S A . Ma r i ne Eco logy Progress Series, 229: 291-312. Young , J.Z. 1957. L i fe of Mamma l s . C la rendon Press, Ox fo rd . 61 APPENDIX Append i x 1. Data forms for Steller sea l i on mou l t i ng s tudy (Chapter 2). STELLER SEA LION MOULTING DATA FORM C PUP) D A T E : S T U D Y S I T E : O B S E R V E R S : J dorsum CcO Appendix 2. Captive moult observations used in Chapter 3. Age Duration Duration Sea lion Year (years) Sex Start Moult End Moult (days) (weeks) Adak 1993 0 m 5-Nov-93 14-Jan-94 70 10.0 Adak 1994 1 m Adak 1995 2 m 20-Nov-95 Adak 1996 3 m 22-Oct-96 Boni 2000 0 f 31-Aug-00 27-Dec-00 118 16.9 Boni 2001 1 f 10-Aug-01 2-Nov-01 84 12.0 Eden 2000 0 f 15-Aug-00 26-Oct-00 72 10.3 Eden 2001 • 1 f 2-Aug-01 ll-dct-01 70 10.0 Hazy 1997 0 i 28-Nov-97 Hazy 1998 1 f 14-Aug-98 22-Sep-98 39 5.6 Hazy 1999 2 f 16-Jul-99 16-Sep-99 62 8.9 Hazy 2000 3 f 9-Jul-00 23-Sep-00 76 10.9 Hazy 2001 4 f 2-Aug-01 30-Nov-Ol 120 17.1 Kiska 1993 0 f 13-Oct-93 24-Dec-93 72 10.3 Kiska 1995 2 f 24-Oct-95 Kiska 1996 3 f 15-Oct-96 Kiska 1997 4 f l-Nov-97 Kodiak 1997 0 m 7-Oct-97 12-Dec-97 66 9.4 Kodiak 1998 1 m 4-Sep-98 Kodiak 1999 2 m 29-Jun-99 2-Sep-99 65 9.3 Kodiak 2000 3 m 3-Jul-00 13-Oct-00 102 14.6 Kodiak 2001 4 m 16-Aug-01 28-Dec-01 134 19.1 Nuka 2000 0 f 21-Aug-00 8-Dec-00 109 15.6 Nuka 2001 1 f 10-Aug-01 17-Nov-Ol 99 14.1 Sade 1994 0 f Sade 1995 1 f 20-Nov-95 Sade 1996 2 f 7-Oct-96 Sitka 1997 0 f 7-Oct-97 5-Dec-97 59 8.4 Sitka 1998 1 f 15-Sep-98 Sitka 1999 2 f 29-Jun-99 16-Sep-99 79 11.3 Sitka 2000 3 f 9-Jul-00 21-Sep-00 74 10.6 Sitka 2001 4 f 2-Aug-01 30-Nov-Ol 120 17.1 Sugar 1993 0 f ll-Nov-93 63 Age Duration Duration Sea lion Year (years) Sex Start Moult End Moult (days) (weeks) Sugar 1995 2 f 3-Oct-95 20-Nov-95 48 6.9 Sugar 1996 3 f 7-Oct-96 Sugar 1997 4 f ll-Sep-97 l-Nov-97 51 7.3 Tag 1993 0 m 5-Nov-93 31-Jan-94 87 12.4 Tag 1994 1 m Tag 1995 2 m 20-Nov-95 Tag 1996 3 m 6-Sep-96 25-Nov-96 80 11.4 Tag 1997 4 m 8-Sep-97 Tag 1998 5 m Tag 2000 7 m 2-Oct-00 14-Feb-01 135 19.3 Tag 2001 8 m 10-Aug-01 28-Dec-01 140 20.0 Tasu 2000 0 f 6-Sep-00 16-Nov-OO 71 10.1 Tasu 2001 1 f 2-Aug-01 2-Nov-Ol 92 13.1 Timber 1997 0 m 7-Oct-97 12-Dec-97 66 9.4 Timber 1998 1 m 14-Aug-98 22-Sep-98 39 5.6 Timber 1999 2 m 29-Jun-99 16-Sep-99 79 11.3 Woody 1993 0 m Woody 1994 1 m 23-Sep-94 Woody 1995 2 m l-Nov-95 Woody 1996 3 m Woody 1997 4 m ll-Sep-97 l-Nov-97 51 7.3 Yasha 2000 0 f 17-Aug-00 8-Nov-00 83 11.9 Yasha 2001 1 f 2-Aug-01 24-Oct-01 83 11.9

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