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Steller watch : timing of weaning and seasonal patterns in numbers and activities of Steller sea lions.. Marcotte, Michelle 2006

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S T E L L E R W A T C H : TIMING OF WEANING A N D S E A S O N A L P A T T E R N S IN N U M B E R S A N D A C T I V I T I E S O F S T E L L E R S E A LIONS {EUMETOPIAS JUBATUS) A T A Y E A R - R O U N D H A U L O U T SITE IN S O U T H E A S T A L A S K A  by Michelle Marcotte B.Sc. Animal Biology, University of British Columbia, 2003  THESIS S U B M I T T E D IN P A R T I A L F U L F I L M E N T O F THE REQUIREMENTS FOR THE D E G R E E OF  M A S T E R OF SCIENCE in T H E F A C U L T Y OF G R A D U A T E STUDIES (Zoology)  T H E UNIVERSITY OF BRITISH C O L U M B I A November 2006  © Michelle Marcotte, 2006  Abstract Variability i n length o f lactation and maternal association allows otariids flexibility to buffer their young against changes i n nutrition. It also increases the chance o f their young surviving to sexual maturity, which is particularly important i n a declining species such as Steller sea lions {Eumetopias jubatus).  T i m i n g o f weaning is a critically important  event i n mammalian development that can affect subsequent aspects o f an animal's adult life, and may hold the key to understanding the population dynamics o f Steller sea lions. Unfortunately no studies have yet fully documented the behavioural ecology o f Steller sea lions outside o f the breeding season. The goal o f m y study was to document suckling behaviour over 13 consecutive months to determine the timing o f weaning for male and female Steller sea lions under three years o f age at Southwest Brothers Island, Southeast Alaska (July 2004 - July 2005). I also wanted to ascertain the haulout patterns and activity levels o f the colony i n relation to season, prey availability, time o f day, and weather.  Finally, I sought to  evaluate the feasibility o f using an automated, time-lapse camera system to monitor sea lions and its potential for future use. Male Steller sea lions were found to suckle longer than females, with a greater proportion o f males than females suckling at one year. Time spent suckling declined with age suggesting that the animals became more independent as they grew older, most likely as they increased their ability to forage successfully on their own. M a l e sea lions that remained with their mother for longer than one year may have had reduced exposure to predation, and obtained more calories with less energy expenditure from milk, compared to females that became nutritionally independent sooner. A s a result, this may provide males with a chance to grow as b i g as possible, as fast as possible, and increase their ability to hold a territory and have access to mates later i n life. The number o f sea lions onshore at Southwest Brothers Island was influenced by weather on a daily time-scale, but also displayed seasonal changes that may have been related to prey availability and the timing o f breeding. The colony abandoned the island mid-March to m i d - A p r i l , coinciding with the herring spawn and eulachon runs, which are high-fat species and spatio-temporally predictable prey. H i g h daily variability i n numbers n  o f animals at Southwest Brothers likely reflected movement o f animals to and from other nearby haulouts.  Activity levels varied throughout the year, with proportionally more  animals resting i n the summer and more animals engaged i n low activities i n the winter. This suggests a higher behavioural expenditure o f energy i n the winter, contributing to their need for high quality nutrition. June and July is an optimum time to assess sea lion numbers due to the high number o f animals onshore at that time and a greater predictability in sea lion behaviour.  The  counts obtained from the automated time-lapse camera system's digital images correlated with counts obtained from direct observation (r = 0.99). 2  The direct counts were on  average 22% greater than the digital images. W h i l e direct observation is the best method for obtaining a greater variety o f data, the camera systems have a good potential to be used to monitor Steller sea lions and other species when researchers cannot be physically present.  iii  Table of Contents Abstract Table o f Contents List o f Tables List o f Figures Acknowledgements  ii iv vi vii viii  Chapter 1: General introduction: Weaning behaviour and haulout patterns of a colony of Steller sea lions in an increasing population 1 Weaning behaviour Haulout patterns Automated time-lapse camera systems Overview  1 ...3 4 4  Chapter 2: Mama's boys and independent females: Sex-biased weaning behaviour in a sexually dimorphic species, the Steller sea lion 6 Introduction 6 Study site 9 Methods 9 Data analysis 11 Results 12 Proportion of animals engaged in suckling behaviour & the influence of season 12 Time spent suckling & the influence of season 16 Parent-offspring conflict 17 Reproductive failure— abortions 18 Discussion 19 Biases 20 Male versus female 20 Parent-offspring conflict 21 When to wean? 23 Population dynamics 25 Summary 26  Chapter 3: Year-long observations of haulout patterns and activity levels of Steller sea lions at a year-round haulout site in Southeast Alaska 28 Introduction Methods Data analysis Age/sex composition on the haulout Haulout trends Age/sex class and activity state Results General trends  28 29 30 30 31 31 31 31  iv  Age/sex class composition by season Site Fidelity Activity states Time of day Discussion Censusing Steller sea lions Haulout behaviour at Southwest Brothers Summary  33 34 36 37 38 38 39 44  Chapter 4: Steller Watch: Evaluation of an automated time-lapse camera system in relation to direct observation of a gregarious pinniped species, the Steller sea lion .45 Introduction Methods and study site Results and Discussion System performance Comparison of counts Summary Chapter 5: General conclusions  45 46 49 49 51 54 55  Weaning behaviour Haulout behaviour Automated time-lapse camera systems Strengths and weaknesses Future studies  55 55 56 56 57  Literature cited  58  Appendix Appendix Appendix Appendix Appendix Appendix  67 69 70 71 73 74  1. 2. 3. 4. 5. 6.  Focal animal scans data sheets A n i m a l behavioural codes at Southwest Brothers Island Disturbance data sheet Group behaviour scans data sheet (main haulout and other sites) Davis Weatherlink Apparent Temperature Modified Beaufort scale weather codes  List of Tables  Proportion of branded animals observed suckling each month by sex, sample size, and percent of sample size that were male 15  Table 2.1.  T a b l e 2 . 2 . Proportion of branded Steller sea lion pups, yearlings, and two-year olds that were observed suckling each season 16  Proportion of time branded Steller sea lions were observed suckling as a function of time present with their mother and of total time hauled out over the year and by season... 17 T a b l e 2.3.  Table 3.1.  2005  Covariates affecting the number of sea lions hauled out from July 2004 - July : 37  Covariates affecting the number of sea lions hauled out each season from July 2004-July 2005 37 T a b l e 3.2.  Correction factors and standard error (%) for the 5 and 8 megapixel camera systems when numbers of animals were above 50 and between 1-50 51  T a b l e 4.1.  vi  List of Figures Figure 1.1. Location o f Southwest Brothers Island behavioural study site ( 5 7 ° 1 5 ' N , 3 133°55'W)  Figure 2.1. Percent o f branded animals observed suckling at Southwest Brothers Island by age and sex i n 2004/2005 13 Figure 2.2. Sample size and proportion o f animals suckling by sex at Southwest Brothers Island each month 14 Figure 2.3. Number o f eagle events per month from July 04 — July 05 that caused Steller sea lions to react 19  Figure 3.1. M e a n daily number o f animals hauled out from August 04 - 05  32  Figure 3.2. Average seasonal proportions and standard error o f each age/sex class hauled out at Southwest Brothers Island, Alaska from July 04 - August 05 33 Figure 3.3. Number o f marked animals observed at Southwest Brothers Island during consecutive months 34 Figure 3.4. Mean daily proportion o f animals in each activity class, and mean temperature and rainfall 35  Figure 4.1. Outside view o f the automated time-lapse camera system on Southwest Brothers Island 47 Figure 4.2. Inside o f the automated time-lapse camera system on Southwest Brothers Island 48 Figure 4.3. A comparison o f counts taken from direct observation and counts obtained from 8 and 5 megapixel digital images 52  vii  Acknowledgements I am grateful to m y supervisor, Dr. Andrew Trites for taking a chance on me and giving me such a wonderful opportunity to study, learn, and grow. H i s guidance, support, and encouragement were much appreciated. Thank you to m y committee members, Dr. David Rosen and Dr. Patricia Schulte, especially for having the patience and tolerance to come in so late i n the game. I would also like to thank Pamela Rosenbaum for her logistical support, flexibility, and reliability. I would not have been able to complete this study without financial support from the North Pacific Universities Marine M a m m a l Research Consortium, Alaska Fisheries Development Foundation, M c L e a n Fraser Memorial Scholarship, and the M c L e a n Fraser Summer Research Fellowship. Camera equipment and logistics was greatly supported b y A l e x Kulinchenko and Scientific Fisheries Inc. Thank you to Peter Wright for building us a beautiful cabin and blind and helping us with transportation and logistics. M a n y members o f the lab gave advice and helped me through; special thanks goes to Laura K u c e y and K a r i m Soto who saw me through from the beginning. A l s o M . Royerr and E . Gregr for S - P L U S and statistical advice, A . Winship for calculating many numbers, and Tiphaine Jeanniard D u Dot for moral support. A e r i n Jacob and Greg Sharam provided invaluable, constant support and advice. Elaine, you have been there since the beginning. I am greatly appreciative to m y stellar field assistants and lab technicians: M . Davies, B . Campbell, J. Provencher, J. Biro, M . Winterbottom, A . Clark, and N . Vrtacic. Morgan, you especially made the field season, logistics, equipment, and people run smoothly and worry-free. Thank you Josh, for everything you have done and been to me. A n d o f course, m y family who have supported me and allowed me the freedom to succeed i n whatever path I have chosen to follow.  viii  Chapter 1: General introduction: Weaning behaviour and haulout patterns of a colony of Steller sea lions in an increasing population  Weaning behaviour M a n y elements o f the weaning process, such as the role o f the mother or offspring i n initiating weaning, are poorly understood despite the critical importance o f this event i n mammalian development and its affect on subsequent aspects o f the animal's adult life (Counsilman & L i m , 1984; Martin, 1984). Female otariids have a flexible period o f lactation and can forgo pupping i n favour o f nursing their current offspring for an additional one or two years. Part o f this flexibility arises from the mother's ability to alternate foraging trips at sea with nursing sessions on land throughout the offspring's period o f dependence. The majority o f otariid species have been observed nursing juvenile offspring (i.e. > one year) at some point i n time (Bonner, 1984), but none have been seen to successfully raise two at the same time. Energetic constraints likely explain why a Steller sea lion mother does not rear two offspring simultaneously (Winship, Trites & Rosen, 2002). Most Steller sea lions are believed to wean sometime before their first birthday (Pitcher & Calkins, 1981). Females that give birth while nursing a juvenile tend to reject the newborn pup i n favour o f the older sibling (Sandegren, 1970). Anecdotal field reports have noted older Steller sea lions nursing, sometimes up to four years o f age (Sandegren, 1970; Porter, 1997), although no attempt has been made to quantify the proportion o f the population these animals represent. The decline o f Steller sea lions i n the G u l f o f Alaska and Aleutian Islands is thought by some to be caused b y a high mortality o f juveniles at the time o f weaning (York, 1994). A n alternative hypothesis is that the population decline reflects an extended period o f nursing and a corresponding drop i n birth rates (Trites et al, 2006). Both hypotheses are contingent on the weaning process, which is poorly understood i n Steller sea lions. Despite the decline i n the global population o f Steller sea lions (Merrick, Loughlin & Calkins, 1987), the eastern population o f Steller sea lions has been increasing since the 1950s when population surveys began. Trends show that the current population is larger 1  than the historical pre-decline abundance level (Trites & Larkin, 1996). For the past 25 years, the eastern population has been increasing by an average rate o f 3.1% per annum with no sign o f slowing (Pitcher et al, in press). This rate o f increase is still well below the theoretical maximum intrinsic rate o f increase for pinnipeds, suggesting that other factors may limit the population growth rate (Pitcher et al, i n press). It has been proposed that increased juvenile mortality may be a source o f the overall species decline which would have a profound effect on population trajectories  (York, 1994). However,  estimating population trends becomes complicated i f high proportions o f animals are not weaning before each breeding season as previously thought and instead extend their nursing time. Factors that may influence extended lactation i n pinnipeds, such as food availability, have not been thoroughly investigated. Consideration o f circumstances i n which extended lactation occurs w i l l aid i n gaining an understanding  o f population dynamics. In  particular, determining when Steller sea lions wean i n an increasing population may provide insights into the decline o f the western population i n the G u l f o f Alaska and Aleutian Islands. M y study sought to document the timing o f weaning and period o f nursing by observing Steller sea lions for 13 consecutive months at a haulout i n Southeast Alaska (Fig. 1.1) where the population has been increasing at a rate o f 3.1% per annum (Pitcher et al, i n press). Observing a presumed healthy population was believed to offer insight into a critical component o f Steller sea lion life history. I investigated weaning behaviour i n relation to offspring age and sex by recording time spent suckling and termination o f suckling bouts. I also evaluated Trivers' (1974) theory o f parent-offspring conflict by recording all aggressive and passive interactions between mother and offspring during suckling bouts. There has been widespread debate over Trivers' theory (Bateson, 1994; Godfray, 1995) primarily due to conflicting results from previous studies which indicated little to no evidence for increased parent-offspring aggression related to weaning (Martin, 1986; Jensen & Recen, 1989; Packard, M e c h & Ream, 1992; M a l m & Jensen, 1997).  2  F i g u r e 1.1. L o c a t i o n of S o u t h w e s t B r o t h e r s Island b e h a v i o u r a l study site ( 5 7 ° 1 5 ' N , 133°55'W).  Haulout patterns In addition to documenting the weaning process, a year-long field study also afforded an opportunity to investigate some general assumptions regarding site  fidelity,  haulout  composition, and seasonal activity patterns throughout the year. The time a pinniped spends hauled out on land or foraging at sea has been associated with a number influences including prey availability, predator avoidance, thermoregulation,  social  3  activity, and weather effects ( M i l i n s k i & Heller, 1978; Trillmich & Mohren, 1981; Schneider & Payne, 1983; Gentry & Kooyman, 1986; Costa, Croxall & Duck, 1989; Watts, 1992; Moulton et al, 2002; Nordstrom, 2002; Kucey, 2005; Soto, Trites & AriasSchreiber, 2006). Obtaining an understanding o f individual behaviour provides better insight into community level behavioural strategies. I therefore examined the haulout patterns and activity levels o f Steller sea lions i n relation to environmental factors and season.  Automated time-lapse camera systems Observations o f weaning behaviour and haulout patterns are generally done during the breeding season by directly observing animals from blinds using binoculars. A n alternative approach is to use camera systems that are often used to monitor wildlife and aid i n conducting population surveys.  Cameras provide a means to obtain information  about a great number o f animals over a wide-ranging area and throughout all seasons, but require validation before being widely used. I therefore ran two camera systems that took digital images o f the colony once per hour throughout the year to assess the accuracy o f a local time-lapse camera system. Simultaneous direct counts were also made o f the colony. To assess the accuracy o f this system, I later compared the digital counts with direct counts and created a correction factor to account for animals missed i n the digital images.  Overview The goals o f m y thesis were to 1) determine the timing o f weaning and suckling behaviour o f male and female immature Steller sea lions between four months and three years old; 2) examine seasonal and daily haulout patterns and activity levels o f the animals; and 3) evaluate the effectiveness i n obtaining counts using an automated timelapse camera system compared to direct observation. M y thesis is divided into three main chapters. Chapter 2 examines several aspects o f weaning behaviour such as time spent suckling, parent-offspring conflict, and whether  4  mother or offspring terminated the suckling bout. Chapter 3 investigates the haulout behaviour o f the sea lions seasonally over the course o f one year, paying particular attention to changes i n proportion o f age/sex classes by season, changes i n activity levels, and the influence o f weather variables on the number o f sea lions hauled out through the year. Chapter 4 evaluates the use o f an automated time-lapse camera system with respect to accuracy compared to direct counts and ease o f use, and provides recommendations for future use i n field studies and population monitoring. The three primary chapters were written as independent manuscripts intended for publication i n the primary literature. A s such there is some redundancy as they are all based on the same study methodology, site, and time period. A l l field research was conducted under the U . S . Marine M a m m a l Permit #715-1457 and the University o f British Columbia's A n i m a l Care certificate, Protocol number: A 0 4 0097.  5  Chapter 2 : Mama's boys and independent females: Sex-biased weaning behaviour in a sexually dimorphic species, the Steller sea lion  Introduction M a n y elements o f the weaning process, such as the role o f the mother or offspring i n initiating weaning, are poorly understood despite the importance o f this critical event i n mammalian development (Counsilman & L i m , 1984). The timing o f weaning, which is the end o f parental care and transition to nutritional independence, is believed to affect subsequent aspects o f the animal's adult life (such as survival and reproductive output), and may significantly affect the population dynamics o f species that have variable extended periods o f nursing (i.e. >1 year). M a n y studies have examined cumulative maternal investment and the role o f the mother i n initiating weaning (e.g., Ono, Boness & Oftedal, 1987; Higgins et al,  1988; Trillmich, 1990; Lee, M a j l u f & Gordon, 1991;  Festa-Bianchet & Jorgenson, 1998; Trites & Porter, 2002; Milette & Trites, 2003). Generally, studies o f weaning behaviour have focused on domestic animals and small terrestrial populations (e.g. Martin, 1986; Jensen & Recen, 1989; Packard, M e c h & Ream, 1992; M a l m & Jensen,  1996; M a l m & Jensen,  1997). Few studies  have  investigated the exact time o f weaning and behavioural interactions between mother and offspring i n pinnipeds due to the difficulties involved with studying extended lactation and identifying individual pairs i n w i l d populations (Higgins & Gass, 1993; Rosen & Renouf, 1993; Trites et al, 2006). Unlike most phocids (the 'true seals'), otariids (fur seals and sea lions) have flexible periods o f maternal care because they do not have the body reserves to completely nourish their pups and must conduct periodic foraging trips to replenish their fat stores throughout the entire lactation period (Schulz & Bowen, 2004). A s such, females may suckle their young until shortly before they give birth again. N i n e o f the fifteen species o f otariids show  flexibility  i n individual maternal investment strategies and have been  observed nursing offspring past their first birthday (Bonner, 1984). Three species that do not suckle yearlings are migratory (Northern fur seal Callorhinus ursinus, Subantarctic fur seal Arctocephalus tropicalis, and Antarctic fur seal Arctocephalus gazella). Pups  6  from the previous season are not present on the rookeries o f N e w Zealand fur seals Arctocephalus forsteri and there are incomplete data for two species (Guadalupe fur seal Arctocephalus townsendi and Juan Fernandez fur seal Arctocephalus philippii). Bonner (1984) suggested the flexible lactation time may contribute to the complex social structure o f otariids. The greater sociability and generally larger size o f otariids may result i n terrestrial predators posing less o f a threat than they do for some phocids and therefore reduce pressure to wean quickly. Whether the mother or offspring finally determines the end o f maternal care is uncertain. Trivers'  (1974) theory o f parent-offspring  conflict proposed there would  be  'disagreement' over the amount o f resources transferred to the offspring as termination o f parental care approached. If acquiring more resources gives the offspring an advantage i n terms o f lifetime reproductive success, the offspring is expected to demand more resources than the mother is selected to give. However a mother's own health and future reproductive success may be jeopardized i f she continues to provide increasing amounts o f nutrition. This conflict led Trivers to suggest that a measure o f behavioural conflict between the mother and offspring would indicate the approach to weaning. This conflict over when to wean would likely be exhibited as an increase i n aggression o f the mother toward the young and an increase i n unsuccessful suckling attempts b y the young animal. To date, few mammalian studies have investigated the role o f the offspring i n weaning itself ( M a l m & Jensen, 1997), and only one study has thoroughly investigated the role o f the offspring in weaning itself among otariids (Hasse, 2004). The sex-biased investment theory further suggests that differences may be observed between male and female offspring during weaning (Trivers & Willard, 1973; Maynard Smith, 1980; Clutton-Brock, A l b o n & Guinness, 1981). This theory has been extensively debated (Clutton-Brock & Iason, 1986; Leimar, 1996; Hewison & Gaillard, 1999; Brown, 2001) and has become the basis for a number o f ecological arguments (Cappozzo, Campagna & Monserrat, 1991; Kretzmann, Costa & L e Boeuf, 1993; Birgersson, T i l l b o m & Ekvall, 1998). In a sexually dimorphic species, a large body size i n males is presumed to confer a reproductive advantage that manifests itself i n a higher lifetime reproductive output. Males can sire many young per breeding season while females w i l l always be limited to one at a time. Thus, adult females i n good body condition should 7  invest more heavily i n male offspring over female offspring, while females i n poor condition should invest i n a female offspring rather than produce an average male (Trivers & Willard, 1973). Steller sea lions have long been recognized as one o f the most extreme sexually dimorphic otariids that displays considerable variability in the age o f weaning. M a l e pups are known to be larger on average at birth than female pups (Merrick et al,  1995;  Brandon et al, 2005), with mature males attaining sizes that are on average 1.3 times longer and approximately 2.4 times heavier than females (Winship, Trites & Calkins, 2001). Field observations o f Steller sea lions have noted that some immature animals remain with their mother and continue to suckle for longer than one year (Pitcher & Calkins, 1981; Porter, 1997). If a female continues to nurse her young for an additional year, there are fewer pups i n that year's cohort o f animals. Despite the implications o f extended lactation on population dynamics, only one study has so far attempted to document the timing o f weaning i n Steller sea lions (Trites et al, 2006). Trites et al. (2006) tested a widely held view that Steller sea lions weaned during winter (Jan - Mar). Piecing together a melange o f eight sets o f behavioural observations recorded during the late 1990s from four haulout sites (one i n Southeast Alaska and three in the G u l f o f Alaska) over four years and three seasons (winter, spring, and summer), they concluded that Steller sea lions weaned near their first, second, or third birthdays (June). They also concluded that most immature males during the late 1990s were weaning at age two, with about half o f the females weaning at age one, and the rest at age two. Mark-resight models o f marked animals i n Southeast Alaska (2000 - 2004) suggest that most animals may now be weaning at two years ( K . Pitcher, unpublished, A D F & G ) . M y study was designed to overcome the short-comings o f the meta-analysis reported by Trites et al. (2006) b y continuously observing the weaning behaviour o f Steller sea lions at a year-round haulout for 13 consecutive months. I sought to more precisely document the weaning process and quantify the proportion o f sea lions weaning at one, two, and three years o f age as population growth in Southeast Alaska continues (Pitcher et al, i n press). The extreme case o f sexual dimorphism among Steller sea lions also afforded an opportunity to determine whether sex-biased behavioural differences exist  8  among young animals during this stage o f ontogeny. I aimed to determine the proportion o f animals suckling at one, two, and three years o f age, and whether there were differences between the sexes in the time spent with their mothers throughout the year. Finally, I investigated whether there was observable behavioural evidence o f the mother or offspring initiating the weaning process.  Study site M y study was conducted from 6 July 2004 - 31 July 2005 i n Frederick Sound, Southeast Alaska on Southwest Brothers Island ( 5 7 ° 1 5 ' N , 1 3 3 ° 5 5 ' W ) where a colony o f Steller sea lions consisting o f both sexes and all age classes hauls out year-round (Fig. 1.1). Observations were conducted with the aid o f spotting scopes and an unobstructed view from a hidden blind 125 m from the haulout. This study site was selected based on historical accounts and annual aerial census data, which indicated that high numbers o f animals from both sexes and all age classes were present year-round. The site was also home to a number o f animals that had been branded at breeding sites i n Southeast Alaska with a letter and three digits when they were approximately one month old by the Alaska Department o f Fish and Game ( A D F & G , 1996; Merrick, Loughlin & Calkins, 1996), which provided over 280 uniquely identifiable individuals o f known sex ranging i n age between four months and eleven years during our study.  Methods Direct observations were conducted from 08:00 to 16:00 h each day and resulted i n over 2,800 hours o f observations over 13 months. The behaviour o f all branded individuals and the identity o f their nearest neighbour was recorded every 15 minutes using instantaneous focal scan sampling (Appendix 1) (Altmann, 1974; Martin & Bateson, 1993). Behaviours recorded were resting, low active, playing, swimming, locomotion, aggression, vocalization and suckling (Appendix 2). Behaviours that did not fit into one o f these categories were scored as 'other'. Behaviours that could not be clearly observed  9  were noted as obscured. Suckling was defined as head positioned by teat or actively searching for a nipple. The nearest neighbour to the focal animal was defined as the closest animal within one adult female body length (~2m). The nearest neighbours allowed me to compare time the young animal spent with its mother compared to all other animals and whether it changed over the year. Nearest neighbours were identified by age class as pups, juveniles, adult females, sub-adult males ( S A M s ) , bulls, or mothers. If the focal animal was more than one adult female body length from all other animals, it was recorded as alone. If several animals were equidistant to the focal, then the nearest neighbour was marked as 'other'. The mother o f the focal animal could only be designated as such i f suckling behaviour was observed. This strict definition was used to eliminate the possibility o f misidentifying an animal as being with its mother i f it was simply near another adult female. Except i n rare instances, adult females provide milk only to their biological young and not to other pups or juveniles (Porter & Trites, 2004; Maniscalco et al, i n press). One advantage o f using branded individuals as focal animals was that I could be confident o f the animal's identity throughout the entire year and amongst several observers. Additionally, observers were ' b l i n d ' to the sex o f the animal during observations so no unintentional bias could be introduced. I began classifying the 2004 pups as juveniles (age one - three years) on June 4, the median birthing date o f the pups from the Forrester Island complex where the majority o f the focal animals were branded (Pitcher er al, 2001). Beginning i n February, I recorded whether the offspring or the mother ended the suckling bout. Suckling bouts were defined to end when either the mother or offspring physically left the immediate area (~2m) because that signified the end o f the opportunity to suckle while they were associated. Additionally, I recorded whether each interaction between mother and offspring was 'passive' or 'aggressive'. Direct interactions such as biting or loud vocalizations were considered aggressive, as were indirect interactions such as the mother lying on her stomach or rolling over to prevent access to teats. Passive  10  suckling interactions included all other behaviours such as resting and low active behaviours. All occurrences of abortions were recorded, in addition to all other disturbances (Appendix 3). Events were classified as aircraft, vessel, bird, whale, unknown, and other. Reaction of the animals to events was classified into three categories: detection, alarmed and disturbed. 'Detection' was scored if one or more animals raised their head and oriented it toward the potential disturbance. 'Alarmed' was scored if one or more animals moved from their resting area but did not enter the water. 'Disturbed' was scored if more than one animal entered the water.  Data analysis  Abundant movements of sea lions to and from my study site limited the consistency of individuals observed. No individual animal was present throughout the entire year. Sample size was also sometimes low due to unexpected seasonal movements that limited the number of animals present during parts of the year. There also tended to be more branded juvenile males present than females. I therefore compared proportions instead of numbers for all statistical analyses. Only animals that were observed at least 10 times per month were included in the statistical analyses to ensure that animals were not misclassified as non-suckling animals due to insufficient observations (Trites et al, 2006). Seven animals were identified as suckling following months when they were scored as non-sucklers. It is unlikely these animals had weaned and then subsequently 'unweaned'. Such animals were therefore rescored as sucklers for the previous months. I calculated the proportion of suckling to non-suckling animals in each age category by month. Percentages were arcsine-transformed and compared using analysis of variance with Tukey tests to determine when and where differences in suckling behaviour were significant (Zar, 1996). I compared immature males and females by month using a paired t-test. An analysis of variance was performed separately on males and females with age in years as the independent variable and the proportion of branded animals that 11  were observed suckling as the dependent variable. I also compared how suckling behaviour and timing o f weaning varied b y age class and season. The proportion o f time that the immature animals engaged i n suckling behaviour was determined as a function o f 1) time spent on shore, and 2) time spent onshore with their mother (Trites et al,  2006). This second method allowed actual time i n suckling  behaviour with mother to be compared with available opportunity. Only those animals seen suckling at least once were included i n the analysis to exclude weaned immature animals and animals that only made a brief appearance at the haulout. Each observed animal contributed a single mean time spent in suckling behaviour for the entire year for his or her corresponding age class. Percentages were arcsine-transformed and analyzed by age class and season using a 2-way A N O V A , and Tukey-Kramer tests were used to determine when and where time i n suckling behaviour differed (Zar, 1996).  Interactions  between mother and offspring during nursing and at the end o f a suckling bout were compared using a Chi-squared test with a Yates continuity correction. A l l statistical tests were performed using S - P L U S (2000).  Results Proportion of animals engaged in suckling behaviour & the influence of season Significant differences were noted among age classes i n the proportions o f males  (F2,24 =  39.24, p < 0.0001) and females (F2,26 = 5.29, p = 0.01) engaged i n suckling behavior (Fig. 2.1. A m o n g females, proportions o f suckling pups  and yearlings did not  differ  significantly, nor was there a difference between the proportions o f yearlings and twoyear olds observed suckling (Tukey test). However, female pups and two-year olds did differ  significantly. In contrast, males showed significant difference between  the  proportion o f pups, yearlings, and two-year olds engaged i n suckling behaviour (Tukey test).  12  T  0  1  2  Age (years)  Figure 2.1. Percent of branded animals observed suckling at Southwest Brothers Island by age and sex in 2004/2005. Capital letters indicate statistical significance for each age class. No statistical significance was found for male and female pups and two-year olds. Male and female one-year olds are statistically different. Bars represent standard error.  No significant difference was noted between males and females when the sexes were compared by age class for pups or two-year olds but a significant difference was found between males and females at one year (Fig. 2.1, paired t-tests, p = 0.04). Less than 100% of pups were observed suckling, possibly due to observer error or because some pups visited our study site without their mothers. Additionally, some pups were observed only during the spring and may have been weaned already. The implication of this is that similar error must be assumed in the proportions of yearling and two-year old age classes observed suckling, such that the estimated proportion of animals suckling are likely underestimated. The proportion of branded animals engaged in suckling behaviour declined during late spring and early summer around their birthday (Fig. 2.2 B,C). Fewer pups and yearlings were observed suckling in the spring. Examining composition by month showed that males were more consistently observed than females (Fig. 2.2 A, Table 2.1).  13  0-1 y (Pups)  6  1.-2 y (Yearlings)  12  18  2-3 y (2,year olds)  24  30  36  Age (months)  Figure 2.2. Sample size and proportion of animals suckling by sex at Southwest Brothers Island each month. (A) Sample size (vertical bars) and the proportion of young males observed (circles). (B, C) Proportion of all branded animals observed suckling that were male and female. Increases in proportions of suckling yearlings and two-year olds following the breeding season is presumed to reflect the return of mothers to the haulout with their dependent offspring. A loess curve illustrates suckling trends (Loess / = 0.25).  14  Table 2.1. Proportion of branded animals observed suckling each month by sex, sample size, and percent of sample size that were male. Month of Age (months) observation 4 Sep 5 Oct Nov 6 7 Dec Jan 8 9 Feb Mar 10 11 Apr 12 May Jun 13 14 Jul 15 Aug 16 Sep 17 Oct Nov 18 19 Dec Jan 20 21 Feb 22 Mar Apr 23 24 May 25 Jun 26 Jul 27 Aug Sep 28 29 Oct 30 Nov Dec 31 32 Jan 33 Feb Mar 34 35 Apr 36 May  0.20 0.00 0.14 0.00 0.60 1.00 0.67 0.40 1.00 1.00 0.00 0.00 0.00 0.25 0.00 0.17 0.25 1.00 0.00 0.00  Females SE 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.08 0.00 0.05 0.00 0.10 0.00 0.16 0.10 0.00 0.00 0.00 0.00 0.00 0.05 0.00 0.06 0.11 0.00 0.00 0.00  -  -  0.00 0.00  0.00 0.00  Mean 1.00 1.00 1.00 1.00 1.00 1.00 0.00  -  n 2 3 4 4 2 1 1 0 5 3 7 1 5 3 3 5 2 1 1 0 2 5 8 2 6 4 1 2 2 0 0 1 5  Mean 1.00 1.00 1.00 1.00 0.80 1.00 1.00 0.67 0.75 0.86 0.50 0.67 0.82 0.88 0.86 1.00 0.80 0.83 0.25 0.00 0.00 0.00 0.25 0.50 0.25 0.00  -  0.00  Males SE 0.00 0.00 0.00 0.00 0.08 0.00 0.00  0.16 0.11 0.05 0.08 0.04 0.04 0.04 0.05 0.00 0.08 0.06 0.11 0.00 0.00 0.00 0.11 0.08 0.11 0.00 0.00  n 2 7 7 7 5 6 2 0 3 4 7 6 12 11 8 7 4 5 6 0 4 6 9 3 4 6 4 2 0 0 0 0 6  Total N 4 10 11 11 7 7 3 0 8 7 14 7 17 14 11 12 6 6 7 0 6 11 17 5 10 10 5 4 2 0 0 1 11  % males 50 70 64 64 71 86 67 38 57 50 86 71 79 73 58 67 83 86 67 55 53 60 40 60 80 50 0 -  0 55  15  Table 2.2. Proportion of branded Steller sea lion pups, yearlings, and two-year olds that were observed suckling each season. Season  Pups SE  % Summer Autumn Winter Spring  100.00 96.00 45.45  0.00 3.92 15.01  n 25 25 11  % 46.43 76.19 79.17 46.15  Yearlings SE 9.42 6.57 8.29 13.83  n  % 6.06 32.00 0.00 0.00  28 42 24 13  Two-year olds SE 4.15 9.33 0.00 0.00  n 33 25 6 12  Calculating proportions o f suckling animals b y age class and season (summer - June, July, August; autumn - September, October, November; winter - December, January, February; and spring - March, A p r i l , M a y ) , a 2-way A N O V A showed a significant effect o f age class (F ,ig = 67.21, p < 0.001) and season (F 2  3 ;  i  8  = 21.77, p < 0.001) but no  interaction between the two (F^is = 2.73, p > 0.05) (Table 2.2). Differences were noted among the proportions o f pups, yearlings and two-year olds observed suckling (Tukey test). A Tukey test further indicated a difference between all seasons except during autumn and winter, and between spring and summer. N o two-year olds were observed suckling after the autumn, and only about half the pups observed i n the spring continued to suckle. Data were not available for pups during summer when they were born on rookeries. Pups were first observed at m y study site at the end o f August when they were brought by their mothers.  Time spent suckling & the influence of season Mean time engaged i n suckling behaviour as a function o f time spent with their mother decreased with age (pups - 56%, yearlings - 51%, and two-year olds - 39%), but the decline was not statistically significant (Table 2.3).  16  Table 2.3. Proportion of time branded Steller sea lions were observed suckling as a function of time present with their mother and of total time hauled out over the year and by season. None of the apparent differences by age class over the year or by season were statistically significant except yearlings with mother in spring and summer.  With Mother year summer autumn winter spring Total Time year summer autumn winter spring  % time 55.88  Pups SE 1.54  14  2.34 3.29 4.85 0.57  12 8 3 16  0.80 0.85 2.42  15 11 4  n  57.40 53.25 62.00 15.94  13.81 16.97 22.30  % time 50.92 45.54 48.75 55.02 74.07 15.39 22.78 14.54 12.85 27.17  Yearlings SE 1.42 3.33 1.98 2.74 5.96 0.55 1.95 0.74 0.89 3.28  n  15 7 11 8 3 18 9 14 9 5  % time 39.29 43.48 38.00  Two-year olds SE 3.49 7.31 3.96  n 4 2 4  12.61 13.79 12.28 -  1.29 2.86 1.44  7 2 6  -  Analyzing time spent suckling as a function o f time the young animals were present with their mother using a 2-way A N O V A showed no significant effect o f age or an interaction between age and season (Table 2.3, p > 0.05). However, there was an effect o f season  (F3 5o ;  = 3.38, p = 0.03). A Tukey test showed the effect due to the difference  between spring and summer. Analyzing time spent suckling as a function o f total time spent hauled out using a 2-way A N O V A revealed no significant difference between the age classes and seasons — nor was any interaction noted between age and season (Table 2.3, p > 0.05). Analyzing time spent with mother as a function o f time spent hauled out revealed no significant difference over the year for each age class (p > 0.05), indicating time spent with mother did not decline significantly over the year.  Parent-offspring conflict A significant percentage (98.9%) o f the 280 interactions recorded between mothers and offspring were passive, with the mothers allowing the offspring to suckle with no hindrance (%f = 267.9, p < 0.001) while the remaining few interactions were recorded as aggressive. The aggressive encounters recorded did not prevent the offspring from suckling, and the offspring was observed suckling directly after the aggressive encounter.  17  Offspring terminated the suckling bout b y physically leaving the mother i n the majority o f situations observed  (91.3%,  X\  =  15.5, p <  0.001)  —  even though the teat  was still available. Terminations o f suckling bouts were recorded 2 3 times and were generally difficult to witness due to the high number o f animals hauled out and the frequent disturbances b y eagles looking for aborted fetuses. Females left the area before their offspring on only 2 o f the 2 3 documented terminations. N o aggressive interactions occurred — rather the females simply got up and entered the water.  Reproductive failure — abortions Eight abortions were witnessed on land over the months o f January, February, and M a r c h when the fetus would have been about three to five months developed. Abortions that occurred overnight were usually detected i n the morning b y the presence o f blood and tissue. However, we have no information on the proportion o f abortions that may have occurred i n the water. Steller sea lions regularly travel to more than one haulout, which makes it difficult to estimate reproductive failure at a population-level or even at a community-level. Eagle disturbances increased during the months o f December - March, ranging from 1 7 - 3 0 per month (Fig. 2 . 3 ) and constituted 8 4 % o f all bird disturbances and 7 8 % o f all disturbances combined (vessels, killer whales, unknown, and aircraft). Eagle disturbances from December - March were associated with eagles flying l o w and landing on the haulout searching for aborted fetuses and associated placentas. Eagle disturbances i n M a y - July were associated with eagles flying to and from their nest and loud territory disputes.  18  Disturbed  25 H  Alarmed Detected  §5 20 CJ) CO  LU  15  10  5H  JUL04 AUG S E P OCT NOV DEC JAN FEB MAR APR MAY JUN JUL05  Month F i g u r e 2 . 3 . N u m b e r of e a g l e e v e n t s p e r month from J u l y 0 4 — J u l y 0 5 that c a u s e d S t e l l e r s e a lions to react. R e a c t i o n of a n i m a l s w a s c l a s s i f i e d a s ' D e t e c t e d ' , A l a r m e d ' , or ' D i s t u r b e d ' . N o t e that f e w s e a lions w e r e present o n the haulout in April.  Discussion Conducting direct behavioural observations o f Steller sea lions at one site for 13 continuous months showed many animals were dependent on their mother until their third year o f life, with a high proportion o f suckling yearlings and a propensity for males to stay longer than females with their mothers. N o significant conflicts were observed between mothers and offspring, and no significant reductions in suckling times was recorded, suggesting that time o f year, rather than age, was a stronger determinant for weaning o f pups and yearlings.  19  Biases M y results must be interpreted i n light o f the limitations associated with the methods used to measure the weaning process, as well as the variables that I was not able to measure such as suckling ability o f the offspring, motivation for suckling, experience and physiology o f the mother, her ability to release milk, non-nutritive suckling, and variation in m i l k composition (see Cameron, 1998, for a full review). Suckling observed during the daytime might also not be an accurate reflection o f what occurs at night. However, such limitations should not impinge upon m y general conclusions given that m y study used behavioural association with the mother as an indicator o f dependence, and m y questions were not related to motivation or actual energy transfer.  Male versus female The proportion o f young males I observed suckling was more variable than that o f the females (compare Figs. 2.2B and 2.2C). This might reflect males being more active than the females, which would have resulted i n them being recorded at the haulout for a shorter duration or a greater likelihood o f being missed all together. The peaks i n proportions o f individuals suckling i n F i g . 2.2B and especially 2.2C likely reflect the return o f mothers from rookeries with their dependent one- and two-year olds at the end o f summer. Proportionally more males than females were observed suckling as they approached their first birthdays (Fig. 2.2), suggesting that females tended to wean earlier than males. Males may have stayed longer because their energy needs were higher than females, and they could not obtain sufficient energy from foraging on their o w n (Trites et al, 2006). The apparent longer-term association between mothers and sons may have provided males with more time to learn to forage, more calories with less energy expenditure for increased growth, and may have reduced their exposure to predation. Testosterone may further allow males to assimilate the energy i n milk more efficiently than females (Glucksman, 1981; Kretzmann, Costa & L e Boeuf, 1993), which would mean that even a small amount o f milk would provide a greater benefit to males.  20  Differences i n the way that males and females allocate energy towards growth have been reported for Australian fur seals (Arctocephalus pusillus doriferus) and Antarctic fur seals  (Arctocephalus gazella) (Arnould,  Boyd  & Socha,  1996; Guinet, L e a &  Goldsworthy, 2000; Arnould & Hindell, 2002). It appears that males preferentially allocate energy toward building lean body mass, while females allocate more energy towards the buildup o f lipid stores. O n average, males o f both species have higher weights than females even though males and females consume similar amounts o f m i l k (Arnould, B o y d & Socha, 1996; Arnould & Hindell, 2002). This suggests there is little, i f any, apparent difference i n maternal investment with regards to nutrition — although some have cited the observations o f males being heavier than females as evidence o f sexbiased maternal investment (Trillmich, 1986; Cappozzo, Campagna & Monserrat, 1991). The sex-specific difference i n how young fur seals allocate energy suggests that females w i l l have proportionally more lipid stores than males at the time o f nutritional independence. This i n turn might result i n a differential tolerance to environmental variation. A young female that has difficulty finding or obtaining food w i l l catabolize her greater lipid stores, which provide twice the energy o f protein catabolism (Randall, Burggren & French, 1997) and therefore could increase her chances o f survival. Males may pay higher thermoregulatory costs during activities such as swimming because they have proportionally less lipid for energy storage. The differences i n growth strategies between males and females may further mean that it is more beneficial for males to stay with their mother for as long as possible to supplement their diet, enhance their growth, and buffer against environmental variation. The fact that Steller sea lions are the most dimorphic otariid species (with male pups being larger on average than females at birth [Winship, Trites & Calkins, 2001; Brandon et al, 2005]) may also mean that this male strategy has been selected to obtain the added resources they require to grow to such a large size.  Parent-offspring conflict Bioenergetic models estimate that a nursing female Steller sea lion would require 70% more food than a non-nursing female i f her young were completely dependent on her for 21  nutrition (Winship, Trites & Rosen, 2002). The lack o f observed aggression between mother and offspring suggests the young obtained adequate nutrition either from the m i l k alone, or by supplementing their m i l k intake with solid food. The absence o f conflict between the two i n m y study suggests that the mother and young obtained the nutrition that each required such that there was no 'disagreement' over allocation o f limited resources as predicted b y Trivers (1974). A variety o f animals have demonstrated little to no evidence o f maternal aggression or indirect behavioural conflict between mothers and dependent young around the time o f weaning (e.g. cats: Martin, 1986; pigs: Jensen & Recen, 1989; arctic wolves: Packard, M e c h & Ream, 1992;  dogs: M a l m & Jensen, 1997). Offspring o f such species have  generally been observed to terminate suckling bouts as opposed to their mother ending them, indicating that opportunity to suckle was not a limiting factor. In the case o f young sea lions, those that had stomachs full o f milk and/or solid food would have had less motivation to stay for more suckling opportunities. Observations o f N e w Zealand fur seals have shown that pups terminate the suckling bouts the majority o f the time (Hasse, 2004). Similarly, anecdotal observations from Porter's (1997) winter study on Steller sea lions revealed offspring leaving the mother more often during nursing bouts. I also found no evidence for increases in parent-offspring conflict i n the Steller sea lion to occur as the time to the next breeding season approached. N o r did I note any decrease i n access to mother's teats and suckling opportunities as the amount o f time spent with their mother did not decrease over the year. It therefore seems that Steller sea lion offspring wean themselves. Further evidence that Steller sea lions wean themselves comes from the observed difference i n timing o f weaning o f males and females. Mothers are unlikely to be aware o f the sex o f their offspring and preferentially decide to wean females early and keep males for an extra year. It seems more probable that males elect to stay with their mothers because they can more readily meet their daily energy needs from m i l k rather than from fish and cephalopds.  22  When to wean? Part o f deciding when to begin taking solid food, how much to take, and when to cease suckling completely is related to the relative cost-benefit ratio associated with suckling versus obtaining and digesting solid food (Jensen & Recen, 1989; M a l m & Jensen, 1996). Animals may begin to forage on their own to fulfill their growing caloric needs i f milk does not provide the required nutrition and calories. Compensating with solid food has been predicted to occur i n pinnipeds, primates, and ungulates when the offspring reach 2.1 times their birth mass with weaning predicted to occur when they reach 4.0 times their birth mass (Lee, M a j l u f & Gordon, 1991). A p p l y i n g standardized growth curves (Winship, Trites & Calkins, 2001) suggests that male Steller sea lions should start to wean when they are 46 k g (2.8 months old) and be fully weaned when they are 88 k g (7.7 months old) — and that females should start to wean when they are 42 k g (3.8 months old) and be fully weaned when they are 80 k g (10.4 months old). Contrary to the theoretical predictions, males weaning on their birthdays are on average 5.7 times their birth weight at one year, 7.0 times at two years and 8.6 times at three years, while females that wean on their birthdays are an average o f 4.5 times their birth weight at one year, 6.4 times at two years, and 7.8 times at three years. Thus there is considerable disparity between the theoretical limits and the field observations. A t one year o f age, male yearlings require 15.0 ± 3.8 k g o f prey on a mixed diet o f fish species, while females require 11.0 ± 2.7 k g (Winship, Trites & Rosen, 2002). Expressed as a percentage o f body weight, male yearlings require about 12 ± 3% o f their body weight per day, while females require 13 ± 3%. A t two years, energy requirements relative to body mass per day on a diet o f mixed species drop to 11 ± 2% for males and females but increase in kilograms to 16.9 ± 3.1 k g and 14.1 ± 2.6 k g respectively. A further decrease occurs at age three: 9 ± 2% for males and 10 ± 2 % for females (increase of 17.0 ± 3.8 k g and 15.6 ± 3.1 k g respectively). Rosen and Trites (2004) estimate that the maximum average amount o f food a yearling sea lion can consume is equivalent to 14-16% o f their body mass and that young animals may not be able to meet their daily energy needs i f they were to consume primarily low energy prey species. They hypothesize that even consuming moderately energy dense prey, juveniles are living energetically on the edge. B y prolonging weaning and providing her offspring with m i l k 23  during this time, the adult female may buffer her young against nutritional hardship. The greater relative energy needs o f males may move them closer to the energetic edge and may explain why more males than females elect to stay with their mothers for an extra year. Lactation is regarded as the most expensive aspect o f maternal care (Gittleman & Thompson, 1988) and is a period that mothers may wish to limit despite the clear benefits for young animals to obtain more milk. However, Pond (1977) pointed out that extended lactation might be preferred over extended gestation for species whose food sources are scattered and o f l o w nutritional content. A longer lactation period should also be preferred i f the mother must travel long distances to obtain prey, and i f the species must rely heavily on speed and agility to capture prey and elude predators (Pond, 1977). Extending lactation beyond the next breeding season is not a rare event among the otariids and can impact their future reproductive success. For example, 2 9 % o f mature Australian sea lions (Neophoca cinered) were observed i n one study to not pup each breeding season, and opted to nurse their juvenile until the next breeding season (Higgins & Gass, 1993). The Galapagos fur seal (Arctocephalus galapagoensis) observed i n another study with a dependent yearling or two-year old was less likely to give birth than those females without dependent young (Trillmich, 1986). In contrast, Maniscalco et al. (2005) found Steller sea lions that did not pup or had lost their pup were less likely to give birth the following season. Extended lactation also occurs among terrestrial species. For example, observations o f red deer suggest that mothers that did not conceive would continue to nurse their young calf the following breeding period, whereas she would likely wean the calf before she gave birth i f she did conceive (Clutton-Brock, Guiness & A l b o n , 1982). Time spent i n suckling behaviour did not change significantly over the year, suggesting that time o f year was a stronger driving factor i n determining the final stage o f weaning i n Steller sea lions than was age o f the animal. This is consistent with the observations o f Raum-Suryan et al. (2004). I observed a sharp decline i n the proportion o f animals suckling when 12 and 24 months old (Fig. 2.2B,C) suggesting that animals suckled the entire year until their next birthday. Two-year olds (>24 months) were an 24  exception and were not observed suckling beyond autumn when 28 months old. This suggests the two-year olds may have been completely independent b y this time. Mothers that w i l l produce another pup while still nursing an offspring from a previous year might abandon the yearling just before they return to the rookery to give birth. Immature animals that accompany their mothers to rookeries may be forced to wean or the yearling may out-compete their new sibling. The limited information available on the behaviour o f juveniles at the rookeries indicates that many o f the females were accompanied by nursing juveniles and that females that lost their pup were re-joined by their juvenile — and that pups were occasionally rejected in favour o f the juvenile (Sandegren, 1970).  Population dynamics A n accurate estimate o f the proportion o f the breeding population producing pups is key to assessing population trajectories. M y study has shown that sea lions at the Southwest Brothers haulout were suckling up to age three but that most were weaned by age two. If this site is representative o f the larger population i n Southeast Alaska, many females are not having new pups each year (possibly due to reproductive failure as shown by the observed abortions) and may be nursing their current young longer (possibly to buffer them against environmental fluctuations). The eastern population o f Steller sea lions has been increasing since the 1950s when surveys began and trends show that the current population is the highest recorded (Trites & Larkin, 1996). For the past 25 years, the eastern population has increased at an average rate o f 3.1% per annum as new rookeries have been established with some influx o f animals from the G u l f o f Alaska (Pitcher et al., in press). This rate o f increase is still well below the theoretical maximum intrinsic rate o f increase for pinnipeds, suggesting that other factors may limit population growth (Pitcher et al, i n press). Increased juvenile mortality has been suggested as a source o f the overall species decline, which would have a profound effect on population trajectories (York, 1994; Trites & Donnelly, 2003). However, the low numbers o f juveniles i n the population could also be explained i f these animals were simply not being born due to their mothers continuing to nurse their 25  juvenile and a high rate o f reproductive failure (Trites et al, 2006). Additionally, about 45% o f the population do not travel to rookeries (Trites & Larkin, 1996) and not all females that remain at the haulouts have dependent young. Identifying the factors that extend lactation and weaning help to decipher the dynamics o f Steller sea lion populations. Results from m y study also provide baseline data for comparison with future trends and with other populations. M y data indicate that many females are nursing juveniles and are not raising a new pup each year. This factor needs to be considered when estimating future population trends. Future studies should investigate the causes o f reproductive failure and w h y the sex differences in weaning behaviour exist. In addition, weaning o f juveniles at the rookery should be investigated, and the proportion o f females that do not invest i n raising offspring each year should be determined. Finally, a concerted effort should be made to determine these parameters i n both increasing and decreasing populations to fully assess the role that delayed age at weaning has played i n the decline and lack o f recovery o f sea lions i n the G u l f o f Alaska and Aleutian Islands.  Summary Behavioural observations related to weaning o f Steller sea lions (Eumetopias jubatus) were recorded for 13 consecutive months (July 2004 - July 2005) at Southwest Brothers Island i n Southeast Alaska to 1) document the age at weaning, 2) establish whether parent-offspring conflict influenced the timing o f weaning, and 3) determine whether there was sex-biased investment by mothers. Recorded observations included proportions o f known-aged animals suckling, antagonistic behaviours between mothers and their young, and frequency o f observed abortions. M y observations were the first to be made over an entire year and revealed a high number o f late-term abortions associated with a high proportion o f young continuing to suckle beyond their first birthday. The proportion o f males (75%) compared to females (44%) observed suckling at one year old suggests that most females were weaned just before their first birthday, while males were not weaned until just before their second birthday. The insignificant level o f conflict between mother and offspring and the observation that offspring tended to end all suckling bouts, 26  suggests considerable responsibility for self-weaning. A l l noted abortions  occurred  during the winter months when the fetus was approximately three to five months developed. Providing m i l k for an additional year presumably enhances the chance o f the juveniles surviving to sexual maturity. Having fewer, but healthier pups, may increase the lifetime reproductive fitness o f the adult female. Approximately half o f female Steller sea lions i n Southeast Alaska may thus be giving birth biennially rather than annually as previously thought. Such a reduction i n birth rates could significantly curtail population growth and have a profound effect on estimated population trajectories.  27  Chapter 3: Year-long observations of haulout patterns and activity levels of Steller sea lions at a year-round haulout site in Southeast Alaska  Introduction The time that pinnipeds alternate between foraging at sea and resting and socializing onshore can be related to a variety o f factors including prey availability, predator avoidance, thermoregulation, and social activity ( M i l i n s k i & Heller, 1978; T r i l l m i c h & Mohren, 1981; Gentry & Kooyman, 1986; Costa, Croxall & Duck, 1989; Watts, 1992; Moulton et al,  2002; Nordstrom, 2002; Soto, Trites & Arias-Schreiber, 2006).  Environmental covariates such as wind chill, intensity o f solar radiation, cloud cover, precipitation, and tide have also been associated with numbers o f pinnipeds onshore (Schneider & Payne, 1983; Watts, 1992; Rogers & Bryden, 1997; Reder et al, 2003; Kucey, 2005). Understanding the variables that influence haulout patterns is useful for gaining insight into how animals respond to environmental conditions in relation to lifehistory challenges (Trites & Antonelis, 1994; Sepiilveda, O l i v a & Palma, 2001), energetic requirements (Trillmich & Kooyman, 2001), and the effects o f disturbance on Steller sea lion numbers and behaviours (Allen et al, 1984; Kucey, 2005). Understanding how animals respond to climate is also needed to conduct census counts at appropriate times using suitable correction factors that account for the animals not present (Porter, 1997; Frost, L o w r y & V e r Hoef, 1999; Small, Pendleton & Pitcher, 2003). Careful monitoring is crucial to the future and management o f Steller sea lions (Eumetopias jubatus) which have declined globally b y over 85% since the late 1970s (Merrick, Loughlin & Calkins, 1987; Trites & Larkin, 1996; Calkins et al,  1999).  Population surveys provide insight into broad-scale sea lion population trends. However, fine-scale monitoring provides a further understanding into community level behavioural strategies, which may influence population dynamics. Steller sea lions use two types o f terrestrial sites: haulouts and rookeries. Haulouts are primarily non-breeding, year-round sites, whereas rookeries are used only during the summer breeding season to give birth, nurse young, and mate. Most behavioural studies  28  have been conducted at rookeries (Sandegren, 1970; Gentry, 1974; Merrick & Loughlin, 1997; Milette & Trites, 2003) i n contrast to year-round haulouts that have seldom been studied (Porter, 1997; Kucey, 2005) and have never been directly observed for an entire year. Behaviour o f animals at haulouts may provide essential insight and clues into the Steller sea lion decline. I monitored a Steller sea lion haulout constantly for a year to determine the degree o f site fidelity, haulout composition, and seasonal activity patterns. Mature females have generally been believed to leave haulouts to travel to the rookeries to give birth during the summer, and return with their pups i n the fall. Numbers o f juveniles, sub-adult males ( S A M s ) and adult males (bulls) are generally believed to remain relatively constant throughout the year. I sought to test these assumptions, as well as determine the influence o f environmental factors on haulout patterns and activity levels o f Steller sea lions. Previous studies have examined the effect o f different covariates on the number o f sea lions hauled out (Porter, 1997; Kucey, 2005), but none o f these studies had detailed information about weather, relying instead on modified Beaufort scales. Studies investigating haulout patterns o f pinnipeds have often been restricted in space and time and therefore only collect a narrow range o f information. M y study was designed to observe sea lions over thirteen consecutive months to determine the finer effects o f covariates on numbers o f sea lions hauled out as well as the activity level o f each age/sex class and their response to environmental factors, time o f the year, and seasonal prey availability.  Methods M y study was conducted from 6 July 2004 - 31 July 2005 i n Frederick Sound on Southwest Brothers Island, Southeast Alaska ( 5 7 ° 1 5 ' N , 1 3 3 ° 5 5 ' W ) , where a colony o f Steller sea lions consisting o f both sexes and all age classes hauls out year-round (Fig. 1.1). This is one o f the largest haulouts used by Steller sea lions i n Southeast Alaska and was considered to be representative o f other sites used throughout the year. Observations were conducted with the aid o f spotting scopes and an unobstructed view from a hidden blind 125 m from the haulout. 29  Over 2,800 hours o f direct observations were conducted from 08:00 to 16:00 h each day over the study period (the shortest period o f daylight, which ensured a consistent observation period throughout the year). One observer collected data at a time, with 5 observers participating over the 13-month study. Each observer was trained i n the lab and the field prior to data collection to standardize the identification o f age classes and activity categories between observers. A l l visible pups (<1 year), juveniles (1-3 years), adult females, S A M s , and bulls were counted from the blind every 30 minutes and data recorded included total number o f animals and number o f animals i n each activity category (Appendix 3). Activity categories noted for each age/sex class were either active (moving, playing, aggressive displays, intense vocalization, male copulation), low active (small head movements, low level vocalizations, sitting up with eyes open, scratching and grooming, female copulation, nursing), resting (lying down, sleeping, sitting up with eyes closed), or suckling (suckling or searching for nipple). A Davis Vantage Pro weather station (model #6320C) collected detailed weather on the hour and calculated apparent temperature indices (Appendix 4). A s a precaution against technical failure, weather was also estimated three times daily (at 08:00, 12:00, and 16:00 h) using a modified Beaufort scale similar to that used b y Porter (1997) and K u c e y (2005) (Appendix 5). Data from the weather station was downloaded weekly to a laptop computer.  Data analysis Age/sex composition on the haulout Proportions were arcsine-transformed and analyzed using an analysis o f variance and a chi-square test for multiple proportions ( S - P L U S 2000) to compare the proportion o f sea lions hauled out by age/sex class. Proportions o f pups, juveniles, adult females, S A M s and bulls were analyzed separately to determine i f their presence on the haulout varied b y season.  30  Haulout trends Generalized linear models are commonly used to assess haulout trends over time (Calkins et al, 1999; Frost, L o w r y & V e r Hoef, 1999; Small, Pendleton & Pitcher, 2003) and the effects o f environmental variables (Gurnell, 1996; Kucey, 2005). I used a maximum likelihood generalized linear model ( S - P L U S 2000) to investigate the effect that different covariates had on the number o f sea lions hauled out at m y site. Variables investigated included heat index, temperature, wind chill, humidity, rain, rain rate, and T H S W index (temperature/humidity/sun/wind). The generalized linear models were applied to daily averages o f weather variables and counts.  Age/sex class and activity state A daily mean for each activity state (active, low active, resting, and suckling) was calculated for the animals hauled out on shore b y each age/sex class.  Results General trends D a i l y mean numbers o f animals hauled out at the haulout varied greatly throughout the year, from a minimum o f zero animals i n spring to a maximum o f approximately 350 i n summer and fall (Fig. 3.1 A ) .  31  Figure 3.1. Mean daily number of animals hauled out from August 04 - 05. A) total animals B) pups, juveniles, and females C) SAMs and bulls. Data were smoothed with a loess curve (/ = 0.25). The haulout was temporarily abandoned gradually i n mid-March 2005 for no apparent reason. Sea lions slowly began to return i n m i d - A p r i l and were back to their preabandonment (October - December) numbers b y early M a y . Numbers increased again through June until the beginning o f July 2005 at which point the animals began moving to the other side o f Southwest Brothers Island. This shift i n movement o f animals to the opposite side o f the island was observed in both years (i.e. July 2004 and 2005). Overall, sea lions at Southwest Brothers were most abundant from M a y - December, at medium density from January - mid-March, and absent from mid-March - M a y . Considerable variability was noted i n numbers on shore from one day to the next (Fig. 3.1 A ) . Plotting the number o f animals hauled out by age class revealed that trends for pups tended to lag behind those o f adult females i n the fall (Fig. 3. I B ) . Both age groups tended to increase until the early autumn (October/November) reflecting their joint return from the summer rookeries. Juveniles were present i n their highest numbers during summer, and declined steadily throughout the autumn and winter, possibly reflecting the greater 32  tendency for juveniles to disperse (Raum-Suryan et al, 2002). S A M s and bulls were present at consistently low numbers throughout the year and were most abundant during summer (Fig. 3.1C).  Age/sex class composition by season A 2-way A N O V A revealed a significant effect o f age/sex class (F4,2 = 607.87, p < 0.01) and an interaction between season and age/sex class ( F ^ = 63.89, p = 0.02). The proportion o f each age/sex class hauled out differed significantly by season at Southwest Brothers Island for pups (% = 38.42, p < 0.001) and juveniles (% = 14.51, p < 0.01) but 2  2  4  4  not for females (% = 1.12, p > 0.05), sub-adult males (% = 3.69, p > 0.05), or bulls (x 2  2  4  2  4  4  - 2.79, p > 0.05) (Fig. 3.2).  60 Pups . - V .  50  40 to  O CD  30 20  Juveniles  <  10 Bulls 0  SAMs Summer  Autumn  Season  Winter  Spring  F i g u r e 3.2. A v e r a g e s e a s o n a l proportions a n d s t a n d a r d error of e a c h a g e / s e x c l a s s h a u l e d out at S o u t h w e s t B r o t h e r s Island, A l a s k a f r o m J u l y 0 4 - A u g u s t 0 5 .  33  Site Fidelity Numerous marked focal animals visited Southwest Brothers throughout the year — 141 immature (age 0-3), 54 adult females, and 66 males. 98% o f marked males, 94% o f females, and 89% o f immature animals were observed less than six months total. This reflected differences in their overall fidelity to this site — immature ( 1 - 1 1 months), females ( 1 - 7  months), and males ( 1 - 7  months) (Figure 3.3). The number o f  consecutive months the animals were seen varied with each class.  1  2  3  4  5  6  7  8  9  10  11 12  Consecutive Months Figure 3.3. Number of marked animals observed at Southwest Brothers Island during consecutive months. The majority of animals were present for only one month at a time.  34  A. Total  B. Pups ., ./'••• Resting j . . KT^J Low Active !  •« .Active - ••fe-tf-?.-.-,*'Suckling  C. Juveniles  D. Females  E. Temperature  F. Rain  L  —i SEP  IJ  i l l  1  1  OCT  NOV  1—  DEC  I  I  I  JAN  FEB  MAR  APR  —I MAY  JiL.  t. Ill r  JUN  Jlllll I.  .Ii  JUL  Date  Figure 3.4. Mean daily proportion of animals in each activity class, and mean temperature and rainfall. A) Total sea lions, B) Pups, C) Juveniles, D) Adult females, E) Temperature, F) Rain. Activity was classified as resting (thick line), low active (thin line), active (dotted line), and suckling (grey line). Data were smoothed with a loess curve (/ = 0.25).  35  Activity states Seasonal behaviour patterns were generally similar among pups, juveniles, and adult females (Fig. 3.3B,C, and D ) despite seasonal changes i n weather (Fig. 3.3E,F) and numbers onshore (Fig. 3.3A). L o w active behaviours such as sitting with eyes open, head movements, and low vocalizations tended to increase with the onset o f winter, while the proportion o f time spent resting decreased. Little seasonal change was noted throughout the year i n the frequencies o f active behaviours such as moving, biting, and loud vocalizations. Pups suckled consistently throughout the year until their birthdays i n early June (Fig. 3.SBassumed median pupping date o f June 4 at the Forrester complex where most o f our branded animals were born [Pitcher et al., 2001]), at which point they were classified as juveniles. A smaller proportion o f juveniles suckled compared to pups, with a higher frequency o f juveniles suckling i n the winter than i n summer (Fig. 3.3C). Adult females increased the proportion o f time they engaged i n l o w active behaviours and decreased their resting behaviours through the autumn and into the winter (Fig. 3.3D). However, they reversed this trend from spring through summer (Fig. 3.3D). A i r temperatures ranged from a l o w o f -10°C i n January to a high o f 2 1 ° C i n August, with a grand average o f 8°C for the year (Fig. 3.3E). Rainfall totaled 1660 inches for the year with the wettest month i n December (369 inches) and the driest i n August (23.6 inches). Combining air temperature, atmospheric pressure, and wind speeds to calculate humidity, windchill, heat index, and T H S W index (i.e. the weather perceived b y the sea lions) showed positive correlations with numbers o f animals hauled out over the year (Table 3.1). D a i l y rainfall and rain rate were the only variables that were not significant predictors o f numbers o f sea lions hauled out over the year (Table 3.1). However, analysis b y season revealed both rain and rain rate to be significant factors in the summer (Table 3.2). Temperature and indices related to temperature were significant i n winter and spring (Table 3.2).  36  T a b l e 3 . 1 . C o v a r i a t e s affecting t h e n u m b e r of s e a lions h a u l e d out from J u l y 2 0 0 4 - J u l y 2 0 0 5 . Intercepts a n d variable coefficients of t h e g e n e r a l i z e d linear m o d e l s for e a c h r e s p e c t i v e c o v a r i a t e o n t h e r e s p o n s e variable of n u m b e r of s e a lions h a u l e d out (n = 3 4 3 ) . Significant coefficients a r e s h o w n in b o l d . Covariate THSW Index Rain Rain Rate Temperature Humidity Wind Chill Heat Index  Intercept 4.71 4.86 4.86 4.62 3.75 4.72 4.61  Variable Coefficient 0.025 0.007 -0.001 0.031 0.014 0.023 0.033  T a b l e 3.2. C o v a r i a t e s affecting t h e n u m b e r of s e a lions h a u l e d out e a c h s e a s o n f r o m J u l y 2 0 0 4 - J u l y 2 0 0 5 . V a r i a b l e coefficients of t h e g e n e r a l i z e d linear m o d e l s for e a c h r e s p e c t i v e c o v a r i a t e o n t h e r e s p o n s e variable of n u m b e r of s e a lions h a u l e d out. Significant coefficients a r e s h o w n in bold. Covariate THSW Index Rain Rain Rate Temperature Humidity Wind Chill Heat Index  Autumn -0.04 -0.10 -0.04 -0.05 0.01 -0.04 -0.05  Winter 0.05 -0.10 0.00 0.05 0.00 0.05 0.05  Spring 0.30 -1.16 -0.05 0.15 0.00 0.13 0.18  Summer -0.14 0.27 0.07 -0.18 0.03 -0.17 -0.17  Time of day Considerable  daily  variability  w a s noted  i n numbers  o f animals  hauled out  throughout a n y g i v e n d a y . Standard error i n m e a n d a i l y counts r a n g e d f r o m 0.18 to 3 7 . 0 0 for the entire year. T h e greatest v a r i a b i l i t y i n h o u r l y counts o c c u r r e d i n J u n e ( 1 0 9 - 3 6 8 sea l i o n s ) , a n d the least i n M a r c h ; h o w e v e r there w a s n o seasonal trend i n d a i l y v a r i a b i l i t y i n n u m b e r s onshore. N o d i s t i n g u i s h a b l e y e a r l y o r seasonal d i u r n a l pattern w a s detectable d u r i n g the hours o f 0 8 : 0 0 a n d 1 6 : 0 0 at this site, consistent w i t h p r e v i o u s sites p e c i f i c results ( K u c e y , 2 0 0 5 ) .  37  Discussion Southwest Brothers Island was chosen as a representative year-round Steller sea lion haulout site where animals could be observed for 365 consecutive days to document seasonal changes in sea lion behaviours and numbers that have bearing on assessing population status.  It is one o f nearly 600 haulouts used by sea lions throughout their  range (283 i n Southeast Alaska), and is the first to be observed for a consecutive 13 months. Some o f the conclusions drawn are likely specific to Southwest Brothers (i.e., abandonment i n mid-March and movement i n July), while other observations can likely be applied range wide (i.e., variability o f numbers onshore and the effect o f weather on sea lion behavior). Although classified as a year-round haulout, there was considerable seasonal variation i n numbers o f sea lions that used the Southwest Brothers haulout, including a period o f time when sea lions abandoned it altogether. In all likelihood other Alaskan haulouts that are classified as year-round use sites are also equally dynamic with numbers generally declining as the summer breeding season approaches, and increasing again i n the fall as adult females return with their newborn pups.  Censusing Steller sea lions Estimating population size o f Steller sea lions is a core component o f population management that requires knowing when to census and what factors can influence the numbers observed onshore. Observations from Southwest Brothers suggest time o f day and prevailing weather conditions had little effect on sea lion numbers, but that seasonal shifts i n sea lion distribution were most significant. M a x i m u m numbers o f sea lions tended to be on shore during the breeding season (i.e. June) making this an optimum time to count — and is when the majority o f censuses take place (Loughlin, Perlov & Vladimirov, 1992; Fritz & Stinchcomb, 2005). A second period o f relative stability i n sea lion numbers was noted during winter (February), during which time a greater proportion o f animals were likely at sea feeding. The reduction i n numbers on shore during winter points to the need to apply appropriate correction factors to estimate total population size and account for missing animals. 38  Current surveys take place during the breeding season on rookeries and haulouts using a variety o f methods, depending on the location (aerial, land, or boat-based) (Loughlin, Perlov & Vladimirov, 1992). Correction factors for numbers o f animals missed during the survey have been estimated based on life-tables and mathematical models (Trites & Larkin, 1996), however, trends i n the size o f the population are commonly determined by using counts o f pups and non-pups over time by consistently surveying specific 'trend' sites (Fritz & Stinchcomb, 2005). Numbers o f sea lions at haulouts are more variable than numbers at rookeries, and site-specific variability is considerable (Kucey, 2005). It may be that trend sites are more informative than rangewide correction factors to determine the health o f the global population until site-specific correction factors can be determined.  Haulout behaviour at Southwest Brothers The temporary abandonment  o f Southwest Brothers Island in mid-February was  unexpected and may have been related to the seasonal availability o f prey that was outside the normal foraging range o f m y study animals. Most pinnipeds use terrestrial sites outside o f the breeding season to rest, moult, nurse and/or conserve energy (Thompson, 1989; Thompson et al, 1989). In the case o f Steller sea lions, haulout sites are believed to be situated close to waters that are relatively shallow and well-mixed, with higher average tidal speeds and less-steep bottom slopes (Ban, 2005).  T o have  animals abandon a regularly used site presumably reflects a deliberate foraging strategy rather than a random, opportunistic event. Steller sea lions are known to target prey that are i n dense spawning or migrating groups such as Pacific herring (Clupea harengus pallasi), cod (Gadus macrocephalus), salmon, sandlance (Ammodytes hexapterus), and eulachon (Thaleichthys pacificus Girad) (Sinclair & Zeppelin, 2002; Sigler, W o m b l e & Vollenweider, 2004). Eulachon have an unusually high energy content, spatio-temporal predictability, and accessibility (40-150m depth), and are thought to be an important seasonal prey item for Steller sea lions (Sinclair & Zeppelin, 2002; Sigler, W o m b l e & Vollenweider, 2004) at a critical time o f  39  the year when energy demands are the highest such as winter (Winship, Trites & Rosen, 2002; Kumagai, Rosen & Trites, 2006). Eulachon are abundant i n most major drainages from Southeast Alaska and generally spawn from M a r c h to M a y (Womble et al, 2005), and may be what drew sea lions away in mid-March. A l o n g these lines, it is noteworthy that over 1000 animals were reported i n L y n n Canal i n late M a r c h ( L . Jemison, A D F & G , pers comm), when both the herring spawn and eulachon runs generally occur (Sigler, Womble & Vollenweider, 2004; Gende & Sigler, 2006). It is also noteworthy that other predators including harbour seals and seabirds aggregate around eulachon runs (Marston, W i l l s o n & Gende, 2002) and that high variations o f harbour seals hauled out at different sites throughout the year is believed to be related to the presence o f eulachon smelt (Thompson, 1989). Eulachon spawning runs are known to draw significant aggregations  o f Steller sea lions i n  Southeast Alaska and may increase the energy intake o f sea lions b y as much as 90% (Sigler, Womble & Vollenweider, 2004). The second unexpected change i n sea lion numbers occurred during July 2004 and July 2005, when animals slowly shifted to hauling out on the opposite side o f the island. This new haulout area featured a west-facing, shallow-sloping gravel beach, and was i n sharp contrast to the jagged rocks and steep slope o f their main haulout site. The new site appeared to provide ample room for the juveniles to interact with each other and the S A M s , which may have facilitated play, an essential part o f the life-history learning process. Play is a way o f learning specific behavioural patterns for later adult life such as territory defense and fighting bouts, and may allow for a greater behavioural flexibility later in life (Gentry, 1974). The first year the sea lions exhibited this shift i n local site fidelity, I assumed there were some unusual cause or motivation, but the following year, approximately a week later, they began to move again. There were no major disturbances or severe weather observed at the main site and the sea lions moved over gradually, with the bulls and S A M s hauling out first, followed slowly by the rest o f the colony. The shift i n animal abundance from the main haulout parallels to some extent the shift i n breeding animals from rookeries to nearby haulouts. Mature bulls have been noted to hold territories at  40  haulouts during summer and have been observed to copulate with females (Coombs & Trites, 2006) and similar behaviour was noted at Southwest Brothers. Thus it is conceivable that the breakdown o f the main haulout might have reflected the movement away from the territorial males towards immature males and less aggressive interactions. Sea lions are a gregarious species and preferentially haul out together (Gentry, 1970), which may explain the gradual movement to the other site — the more animals that hauled out, the increased likelihood that others would haul out there too. A number o f pinniped species have shown diurnal patterns i n numbers on shore thought to be associated with foraging and air temperature (i.e., Thompson, 1989 - Phoca vitulina; Lydersen, 1991 - Phoca hispida; Bengtson & Stewart, 1992 - Lobodon carcinophagus; Horning & Trillmich, 1999 - Artocephalus galapagoensis; Soto, Trites & Arias-Schreiber, 2006 - Otaria flavescens). In contrast, studies o f other species have not found any evidence o f diurnal foraging patterns (i.e. ringed seals- Born, Teilmann & Riget, 2002), with dives occurring at all times o f the day and night (i.e. Australian fur seal- Hindell & Pemberton, 1997). Some studies have found daily haulout patterns which suggest the cycle o f arrival and departures observed is indicative o f Steller sea lions foraging at night (Sandegren, 1970; Withrow, 1982). K u c e y (2005) found mixed results, with time o f day significantly influencing the number o f sea lions hauled out at some sites, but not others. However, only a weak trend was found at Southwest Brothers during daylight hours (08:00 - 16:00), even during winter when daylight was restricted to this period. Numbers o f animals hauled out at each hour o f the observed day did not differ over the year or b y season, indicating no diurnal pattern, which might be indicative o f a diversity o f prey at all times. The high thermoconductivity o f water (which is 25x that o f air, [Berta & Sumich, 1999]) means that thermoregulation is a particular challenge for warm-blooded animals inhabiting the ocean. The challenge for pinnipeds i n particular is to conserve heat i n the water and dissipate heat i n air. Time o f day, intensity o f solar radiation, wind chill, cloud cover, and precipitation all play a role i n perceived ambient temperature and have been found to correlate with the number o f pinnipeds hauled out on various occasions (Porter, 1997; Reder et al, 2003). Studies o f pinnipeds have found differing results on the effect  41  o f weather on the number o f animals hauled out, at times finding no correlations (Grellier, Thompson & Corpe, 1996). In general the effect o f weather on pinnipeds appears to be site and latitude specific. A t low latitudes, warm, dry, calm weather appears to have the greatest influence (Schneider & Payne, 1983; Reder et al, 2003), while haulout behaviour at high latitudes generally correlates negatively with wind-chill index, and numbers hauled out correlate with mid-day when the temperature tends to be the warmest (Lake, Burton & Hindell, 1997; Rogers & Bryden, 1997; Moulton et al,  2002; Reder et al,  2003). Haulout  behaviour appears to be species and site specific, which could complicate wide-ranging population surveys. The highest numbers o f animals were present at Southwest Brothers Island i n the summer months, which was also the warmest weather. Proportions o f animals engaged i n low active behaviours increased during the winter while the proportion i n resting behaviours decreased dramatically for females  and  juveniles, with pups displaying a similar but weaker trend. Weather conditions were more extreme i n winter than i n the summer, and the animals appeared to be bothered b y sudden changes in weather conditions, as anecdotally reported i n previous studies (i.e., Sandegren, 1970; Withrow, 1982; Porter, 1997). Summer was the driest season and sea lions numbers were affected b y rain and rate o f rainfall at this time. Major disturbances due primarily to eagles looking for aborted fetuses and associated placentas occurred almost daily during the winter (Fig. 2.3). The constant disturbances from eagles caused major behavioural changes on the haulout, often causing animals to be more restless and vigilant. Diurnal cycles and weather can often be trumped by more pressing behavioural requirements such as a female's need to nurse her young, and for her young to suckle i n a safe place (Allen et al,  1984; Thompson et al,  1989; Lake, Burton & Hindell, 1997).  During the worst weather when the haulout was covered i n ice, the few animals hauled out were often female-pup nursing pairs. Haulout patterns o f pinnipeds are often seasonal and can be correlated with reproductive stage or other life-history stages such as molting (Thompson et al, 1989) and may vary with age class (Harkonen, Harding & Lunneryd, 1999). For example, male and non-breeding female harbour seals spend longer periods o f  42  time ashore during the molt than females who have just pupped and are motivated to regain fat stores (Thompson et al, 1989). Inter- and intra-specific variability i n haulout patterns can be considerable (Godsell, 1988; Thompson et al, 1989; Born, Teilmann & Riget, 2002). Some animals w i l l always be away from the haulout foraging, travelling, rafting, or playing. Different age and sex classes often have different behaviours, which may make them more or less likely to be observed (McLaren & Smith, 1985; Harkonen, Harding & Lunneryd, 1999; Reder et al, 2003). Numbers o f Steller sea lions found on shore are influenced by a multitude o f factors at various times o f the year and i n differing ways. A t this particular site, which was previously thought to be a year-round haulout, I discovered the animals abandoned it possibly i n favour o f a seasonally available, high fat prey. In contrast to the predictable haulout patterns at rookeries that reflect strong site fidelity and the presence o f females with dependent pups and bulls maintaining breeding territories (Gentry, 1970; Sandegren, 1970), winter haulouts are more unpredictable, possibly due to seasonal access to prey and a more flexible relationship with dependent offspring (Porter, 1997). Site-fidelity at this site varied with each class o f animals, the immature animals exhibiting the strongest fidelity, followed b y females and lastly males, most likely due to a combination o f dependence and other accessible sites nearby. The local movement  around the  island was particularly surprising and  the  topographic features were the only obvious differences between the two locations on the small island. The weather predictors justify the timing o f annual aerial surveys during summer and also showed that the level o f detail on weather factors may not i n fact be required. The animals appeared to spend proportionally more time i n low active behaviours than resting during the winter compared with the rest o f the year, which may have implications for nutritional requirements.  43  Summary Numbers and behaviours o f Steller sea lions were documented for 13 consecutive months (July 2004 - 2005) at Southwest Brothers Island i n Southeast Alaska to test general assumptions about seasonal haulout patterns and the effects o f weather on census counts. Proportions o f females, sub-adult males ( S A M s ) , and bulls on shore did not change significantly by season, unlike the proportions o f pups and juveniles. Contrary to assumptions that the haulout was used 'year-round', animals abandoned the island i n spring and preferentially hauled out on the opposite side o f the island during both summers o f observation. Abandonment o f the haulout was correlated with the timing o f the herring spawn and eulachon run, but movement o f sea lions to the other local site could not be explained. Activity o f animals on shore (active, l o w active, and resting) varied by season, with animals i n general displaying more activity i n the winter than the summer, which i n turn correlated with increased disturbances and extreme weather. Generalized linear models showed that all indices o f weather ( T H S W index, temperature, humidity, wind chill, and heat index) influenced the number o f animals hauled out over the year, except for rainfall. N o diurnal haulout pattern was noted at this site, over the year or by season. Winter haulout patterns are less predictable than at other times o f year due to a combination o f factors including weather, disturbance, seasonal prey availability, and possibly more flexible attendance patterns o f mother-offspring pairs. Surveying animals during the breeding season, i n the summer months may be the most effective way to get accurate population estimates because the highest numbers o f animals are onshore. Although m y study was only conducted at one haulout site, results are likely applicable to other haulout sites as Steller sea lion haulouts share many commonalties.  44  Chapter 4 : Steller Watch: Evaluation of an automated time-lapse camera system in relation to direct observation of a gregarious pinniped species, the Steller sea lion  Introduction  Cameras have long been used to monitor wildlife in the field, and circumvent the need for placing observers in remote and sometimes hostile conditions. Aerial photographs have been commonly taken to monitor population trends in wide-ranging, large groups of animals such as Steller sea lions (Eumetopias californianus),  jubatus)  and California sea lions  (Zalophus  and are generally accepted to be a more accurate method of surveying  animals than counting on land or from boats due to the topography of the haulout (animals obscured by crevices and odd angles), dense aggregations of animals, movement of highly gregarious species, disturbances, and movement of boats (Loughlin, Perlov & Vladimirov, 1992; Westlake, Perryman & Ono, 1997; Lowry, 1999). Video and timelapse photography have also been used to evaluate movements of animals on time scales of hours and days (Allen et al, 1984; Thompson & Harwood, 1990; Maniscalco et al, in press). However, no system has yet been deployed to monitor sea lion numbers on rookeries and haulouts in remote locations over an extended period of time (weeks and months). The goal of my study was to assess the accuracy and reliability of an automated time-lapse camera system developed by Scientific Fisheries Systems Inc., (Anchorage, Alaska), and determine whether it can be used for future research to monitor sites when researchers cannot be physically present. The Scientific Fisheries camera system offers the possibility of collecting census data and identifying marked animals on a longer more site-specific basis than can be presently gathered from aerial photographs. The system was designed to have minimum impact on the environment and the animals, and to sustain severe climate and interference from insects, birds, and mammals.  45  Methods and study site The study was conducted from 6 July 2004 - 31 July 2005 i n Frederick Sound on Southwest Brothers Island ( 5 7 ° 1 5 ' N , 1 3 3 ° 5 5 ' W ) , where a colony o f Steller sea lions consisting o f both sexes and all age classes hauls out year-round (Fig. 1.1). This haulout was selected based on historical accounts and annual aerial census data conducted by the Alaska Department o f Fish and Game ( A D F & G ) , which indicated that animals from both sexes and all age classes were present throughout the year. Direct counts were made with the aid o f spotting scopes b y observers sitting i n a blind next to the cameras. Total counts o f animals hauled out onshore were conducted every hour, on the hour, from 08:00 16:00 daily (Appendix 4). T w o camera systems were bolted to rock 125 m i n front o f the haulout, and were programmed to capture one image per hour, on the hour - coinciding with the direct counts (Fig. 4.1). The two camera systems consisted o f N i k o n C o o l P i x 5700 (5megapixel) digital camera and a DigiSnap 2800 controller (Harbortronics, G i g Harbor, W A ) . They were encased in a splash proof box ( N E M A 4 X rated) containing moistureabsorption packets, and a 6 5 A h gel-cell battery powered the system which was recharged during daylight by a 10W single crystal solar panel (Fig. 4.2). The 125 m distance to the haulout did not allow a single camera to fully cover the haulout. The 5-megapixel cameras (Nikon C o o l P i x 5700) were replaced with 8-megapixel cameras (Nikon C o o l P i x 8700) i n February 2005 to improve image resolution. This allowed the quality o f images taken with these two cameras to be compared. A night vision scope (Multi-Use Minimonocular N V G ) , manufactured b y Insight Technology Incorporated, ( N V M - 0 0 0 - A 1 / A 2 ) was initially attached to one o f the cameras i n order to have a daytime system and a nighttime system. This would have allowed numbers o f sea lions to be recorded on the haulout over a 24-hour period. After encountering significant trouble with the range o f the night scope and the quality o f the images, it was decided to simply have two daytime systems, allowing the two cameras to be angled in such a way that the entire range o f the haulout was photographed.  46  F i g u r e 4.1. O u t s i d e view of the a u t o m a t e d t i m e - l a p s e c a m e r a s y s t e m o n S o u t h w e s t B r o t h e r s Island.  Each day, the operational status of the camera was verified by looking through the plexiglas window of the system to make sure the green light on the DigiSnap controller was blinking. This indicated that the system was working correctly and capturing an image each hour. Once per week, a laptop and U S B connection were used to download the images. The images were then deleted from the camera's memory to allow for maximum storage capacity. Each camera had an 8 G B memory card that could record 4,032 images of normal jpeg compression. Cameras were programmed to take one picture per hour - 24 pictures per day.  47  Figure 4.2. Inside of the automated time-lapse camera system on Southwest Brothers Island. The battery is on the left of the image, the camera and moisture absorption packets on the right.  The number of sea lions in each photo were subsequently counted on a computer screen using Adobe Photoshop 5.0. The images were magnified and a red mark was placed on each animal. Marks were counted to determine total animals present. Overlap between the two images was calculated and subtracted from the grand total. Due to the large quantity of data, I took counts from a select number of images to compare with the direct counts. A two-sample paired t-test was used to check for significant differences in the means between counts obtained from direct observation and those obtained from the digital images. To analyze the accuracy of the system counts under optimal conditions, I excluded images that were of poor quality, where the images did not cover the entire haulout, and images where the overlap of time on the two systems was greater than five minutes. Analysis was conducted on the total number of images counted, on images 48  obtainedfromthe 5- and 8- megapixel cameras separately, and on images containing less than or greater than 50 animals respectively. The last analysis was done to account for disparity in the ability of the observer to count few or many animals. Finally, to test for an effect of experience counting and observing in the field, I compared the photo counts obtainedfroman experienced field counter with counts from an inexperienced counter.  Results and Discussion System performance  Camera positioning in relation to the sun made a noticeable difference in picture clarity. For example, Camera 2 faced southeast and had clearer, "brighter" photos more often than Camera 1. Moisture/rain often accumulated on the outside of the camera box during or following bad weather and partially obscured animals on the haulout. However, all images were clear once the moisture dried. Clarity and resolution of the 5-megapixel camera images were better at dawn, dusk, and early evening when contrast between the animals and haulout was better. There was good coverage per camera of the haulout and the images showed the overall spatial arrangement of the animals well. Nursing/suckling behaviours were sometimes distinguishable in the photographs. In general, the resolution of the 5-megapixel camera was not fine enough to see all of the animals. This meant the images had to be magnified significantly, to the point that the animals in the photographs appeared as a collection of multi-coloured, grainy pixels. The sea lions were often difficult to distinguish from rock on heavily overcast or rainy days, when it was foggy or snowing, when the sun reflected off the water, rocks, and wet animals, when the sea lions were in shadows or in crevices, and when the animals were darkly coloured (i.e., wet or pre-moulted pups). Pups were generally difficult to distinguish in the photographs, especially in early fall when they still had pre-molt dark fur and they were small enough to be obscured by other animals or the topography of the haulout. It was also sometimes difficult to distinguish one sea lion from another when they were in a densely packed, large group.  49  Suckling and nursing behaviours can be obscured i n these situations. M o v i n g sea lions appeared as smudges. Branded animals could occasionally be seen but were generally not legible, and flipper tags were indistinguishable at this resolution. The images from the 8-megapixel camera were noticeably sharper and clearer and individual sea lions were easier to distinguish and required less magnification to be counted. Branded animals were also more easily distinguished and their numbers could sometimes be read i f the branded animal was positioned optimally (at 90 degrees to the observer with left side visible). The 8-megapixel camera solved many o f the problems presented b y the 5-megapixel camera. D a i l y checks o f both systems to see that they were working revealed that the cameras were reliable for most o f the time but occasionally stopped working. Instructions that were provided by Scientific Fisheries for maintaining and changing cameras were well written and comprehensive. The camera systems only lasting impact on the environment were the holes i n the rock left b y bolting the systems down. The casing itself was small and painted grey and was therefore camouflaged from tourists and other people on the water. They were completely waterproof and continued working even with a foot o f snow piled on top o f the solar panel and when buffeted by extremely high wind speeds. The moisture absorption packs that maintained a humidity-free environment inside i n the systems were changed once in the year, and there was no interference with the images or the systems from insects, birds or small mammals. A t one point in the year the sea lions decided to haul out directly beneath the observation blind, and eventually came high enough up the rocks to lay next to (and on top of) the camera systems. A s a result they inadvertently moved the camera boxes so the angle was entirely off. Future deployments o f the cameras should therefore ensure that all bolts are tight enough to prevent movement once the systems are put i n place and set to the desired angle. Another consideration is prevailing weather  conditions while  downloading images. H i g h winds and rain made it difficult to shelter the computer, cords, and connections. The camera systems stopped working on a number o f occasions for no apparent reason. Restarting the system b y pushing the re-boot button on the outside o f the box was 50  rarely successful, which meant manually re-booting the entire system. Manually rebooting worked well except that it could only be done when the weather was dry, because the entire system had to be opened. Re-booting the system often changed  the  programmed times for pictures to be taken b y 5-10 minutes. Trying to coordinate the two camera systems to take their images at the same time was sometimes difficult, since any mistake meant waiting until the next hour to remove and re-program the cameras. Voltage data on the systems was collected to check i f power might have caused the cameras to periodically stop, but did not offer an explanation. N o r did the times the systems stopped working correlate with light and weather conditions.  Comparison of counts In general, counts made from the photograph were consistently lower than counts made by direct observation (Fig. 4.3). Gregarious species can be difficult to count from a still image, as shown by A l l e n et al. (1984) who used a film-based time-lapse camera system with an interval o f one frame per minute and found that the camera was reliable for daily trends but was not a reliable indicator o f the actual number o f seals present. Direct observations have the benefit o f being able to more easily identify behaviours and see shifting animals. Table 4.1. Correction factors and standard error (%) for the 5- and 8-megapixel camera systems when numbers of animals were above 50 and between 1-50.  Camera 5 mgpx 8 mgpx  Counts < 50 & > 1 62.68 70.70  SE 1.25 2.90  Counts >50 70.92 77.76  SE 1.49 0.62  Counts from direct observation and from photographs on both 5- and 8-megapixel cameras differed significantly (p < 0.001). While the 8-megapixel camera made the resolution better for counting the images, the difference between direct and image counts was still significant. Correction factors were determined for the camera counts when compared with the direct counts and were found to be quite good (Table 4.1). If cameras 51  are set up at different sites, correction factors w i l l have to be determined for each site according to the position o f the system and topography o f the haulout. The correction factor between counts o f the 8-megapixel camera was high with an r = 0.99, suggesting the correction factor obtained would be consistently reliable (Figure  4.3).  Figure 4.3. A comparison of counts taken from direct observation and counts obtained from 8 and 5 megapixel digital images.  There were no significant difference between the counts o f the two inexperienced counters (P = 0.1861). However counts o f sea lions in photographs made b y a person who had previously observed sea lions in the w i l d were significantly higher than counts made by inexperienced counters. The inexperienced counters counted an average o f 86% o f the sea lions seen b y the experienced field counter. Observers who have spent time i n the field counting and recording sea lion behaviour have knowledge o f the subtleties i n sea lion shape and position, and are able to distinguish them from each other and their 52  background. This suggests that experience must be taken into consideration when hiring researchers to count animals i n photographs. Time-lapse digital camera systems may be limited to answering specific questions about general trends i n numbers and distributions and appear to be well suited for monitoring species where humans physically cannot observe and disturbance needs to be at a minimum, such as the cliff-side breeding nests o f sea birds. They provide an index o f abundance within a limited field o f view. A t m y study site, Steller sea lions moved around the island on a consistent basis, often hauling out on tide-exposed rocks and areas other than the main site, and even at one point directly on top o f the camera systems. The systems I tested needed surveillance and monitoring to ensure they were running properly which may not be an acceptable limitation i f they need to be left independently for long periods. A number o f counts would have been missed i f the camera systems had been relied on alone, and other types o f information such as changes i n behaviour, disturbances, predation attempts, re-sighted animals, and human interactions could not be extracted from the images. Placement o f the cameras is an important consideration when deploying automated systems. Distance to haulout must be considered with regards to resolution, clarity, and range o f the image i n relation to the type o f information that is being gathered. A n image taken above a haulout may be better than one pointed directly on, because the topography o f the rocks would not interfere with visibility and the animals would not be hidden behind one another. However, the logistics o f doing this for Steller sea lions are generally difficult and site specific, given that most haulout sites are on remote rocky outcroppings with no trees for mounting cameras (Ban, 2005). Getting the systems high enough to cover the entire space o f the haulout can be equally challenging. Thus, each site w i l l have a  different  set  o f advantages  and limitations and would  have to be  assessed  independently. Sitting and watching animals directly i n the w i l d is an integral part o f formulating questions and gaining insight into life-history strategies. Human senses not only pick up sight, but also sound, smell and touch, which the mind can integrate to provide a more comprehensive, realistic understanding o f the proximate causes o f animal behaviour. 53  Cameras have clear economic benefits over the establishment o f staffed field camps. However, the benefit o f having a computerized system collecting information w i l l often be out-weighed b y the advantages o f human eyes and a brain to think about the ' w h y ' and 'how' questions that drive our curiosity and fuel our motivation for research.  Summary The automated camera system, designed by Scientific Fisheries Systems Inc. was deployed from July 2004 - July 2005 on Southwest Brothers Island i n Southeast Alaska to evaluate its potential to monitor sea lion numbers on rookeries and haulouts over extended periods, i n remote locations. The system had no noticeable impact on the environment or the sea lions, and severe climate and interference from insects, birds, or mammals did not negatively affect it. Counts o f animals from the digital images were consistently lower than direct counts by field biologists, and averaged approximately 78% o f the direct counts under optimal conditions. The linear model o f the two methods of counting animals suggested the correction factor would be consistently reliable (r = 2  0.99). Counts from photographs reflected general site-use trends, but were not completely accurate representations o f actual animal movement due to its limited scope. Specific data such as brand re-sights and individual behaviours such as suckling/nursing w i l l still have to be gathered by direct observation. The camera systems may provide a novel approach i n the future to fill i n gaps i n counts and monitor sites when researchers cannot be physically present.  54  Chapter 5 : General conclusions The goals o f m y study were to document weaning behaviour i n Steller sea lions, record site-fidelity i n relation to seasonal haulout patterns and activity levels, and evaluate an automated time-lapse camera system as a means to monitor use o f local haulouts o f animals. In order to accomplish these goals, I conducted behavioural observations and counts at a colony o f Steller sea lions i n Southeast Alaska for 13 consecutive months. A weather station recorded hourly environmental variables and a time-lapse camera system photographed the haulout every hour.  Weaning  behaviour  M y study revealed a high proportion o f animals suckling beyond their first and even second birthdays, with males showing a tendency to remain associated with their mother longer. I recorded no observable parent-offspring aggression and the offspring ended the suckling bout more frequently than the female. The results shown i n Chapter 2 suggest that many females were not having a new pup each breeding season, opting instead to continue nursing their current offspring. This flexibility i n length o f lactation may reflect the sociability o f this species and fluctuating prey resources, and may significantly affect the population dynamics o f Steller sea lions.  Haulout  behaviour  The haulout patterns and activity levels o f the colony were investigated over 13 consecutive months. The proportion o f pups and juveniles making up the colony varied significantly by season while proportions o f females, S A M s , and bulls remained constant. A l l animals abandoned the site from mid-March to m i d - A p r i l , when herring spawned and eulachon arrived at the mouths o f rivers. These two species are energy dense prey and have a high spatio-temporal predictability. Over both summers o f observation, the animals changed their local site and hauled out on the opposite side o f the island, a topographically different area. N o major disturbance was witnessed and the movement to the new site appeared gradual and deliberate. N o simple explanation for this seasonal  55  movement was apparent. Temperature and other indices were significant indicators o f the number o f animals hauled out onshore. N o diurnal haulout pattern during daylight hours was found, i n agreement with previous studies conducted at this site.  Automated time-lapse camera systems I evaluated the efficacy and accuracy o f the automated time-lapse camera systems when compared with direct counts. Even under optimal conditions, the counts o f photographed sea lions were 22% lower on average than counts made i n the field. The systems generally performed well when the weather was good, and the animals were hauled out i n their normal location. The cameras provide a novel means for future studies to keep track o f site-specific trends o f animals when researchers cannot be physically present.  Strengths and weaknesses Animals that live i n a fluctuating environment need to adapt to constantly changing conditions that affect their abilities to find food, avoid predators, and obtain mates. Behaviour is one o f the primary ways that animals adapt to the conditions they live i n . Behavioural studies are often difficult to carry out due to the often subjective nature o f categorizing what animals do. The behaviours and methods chosen and level o f analysis w i l l influence the interpretation o f results. Data obtained from focal animals may not be entirely representative o f the colony and correspondingly, the colony's behaviour may not be representative o f the entire population o f animals. In m y study, not all animals hauled out at the site were visible from our observation point. I assumed that the animals within view were representative o f the entire colony and that animals were not behaving differently at areas that could not be seen. Despite difficulties i n conducting behavioural studies, m y research is the first study to conduct behavioural observations o f one colony o f Steller sea lions across all seasons consecutively for an entire year. This allowed me the opportunity to have consistency o f site, observers, and animals. The animals were more mobile than expected. It was generally thought that there would be a core group o f animals that would stay at the site  56  consistently throughout the year, with others coming and going. Not only did the animals haul out at other areas and rocks around the island, but also data from our focal animals revealed different animals remained at the site for variable lengths o f time. This most likely reflected seasonal availability o f prey and the proximity o f other haulouts to m y study site.  Future studies Research on weaning behaviour o f otariids i n the future would do well to use satellite tags to track the movement o f female-offspring pairs. This information would clarify whether they forage together and potentially allow the exact time o f permanent separation to be determined. Furthermore, behaviour at the rookeries during the breeding season should be thoroughly investigated with regards to female-juvenile-pup  behaviour,  mother-offspring conflict, reproductive failure/loss o f pup resulting i n extended lactation, and sex-biased behaviour to investigate the strategies o f females that give birth to a new pup and have a dependent offspring present. 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Y o r k , A . E . (1994). The population dynamics o f northern sea lions, 1975-1985. Mar. Mamm. Sci. 10,38-51. Zar, J . H . (1996). Biostatistical analysis. Englewood Cliffs, Prentice-Hall, Inc.  66  Appendix 1. Focal animal scans data sheets F O C A L ANIMAL SCANS S T E L L E R WATCH SW BROTHERS ISLAND 2004-2005 DATE (DD/MM/YY):  Michelle Marcotte  OBSERVER:  First number- behaviour, Second number- association  TIME  8:05  8:20  8:35  8:50  9:05  9:20  9:35  9:50  10:05 10:20 10:35 10:50 11:05 11:20 11:35 11:50  ANIMAL ID  67  FOCAL ANIMAL SCANS  STELLER WATCH DATE (DD/MM/YY): SW BROTHERS ISLAND 2004-2005  Michelle Marcotte  OBSERVER:  First number- behaviour, Second number- association  TIME  12:05 12:20 12:35 12:50 13:05 13:20 13:35 13:50 14:05 14:20 14:35 14:50 15:05 15:20 15:35 15:50  16:05  ANIMAL ID  68  Appendix 2. A n i m a l behavioural codes at Southwest Brothers Island  G R O U P B E H A V I O U R SCANS A C T I V E (A) = moving, playing, aggressive displays, intense vocalization, male copulation R E S T I N G (R) = lying down, sleeping, sitting up with head pointed to sky with eyes closed L O W A C T I V E (LA) = small head movement, low level vocalization, sitting up with eyes open, scratching/grooming, female copulation, nursing. S U C K L I N G = (S) suckling or searching for nipple F O C A L SCANS F O C A L S C A N B E H A V I O U R (1) R = resting -lying down or head up with eyes closed L A = low active -sitting up with eyes open, small head movements, low vocalizations, scratching/grooming P L = play -playing with objects (i.e. kelp) or with others S = suckle -searching for nipple, suckling W a = water -swimming, playing i n water on rock shelves, jumping i n and out M = Movement -moving around haulout, (walking) A = aggressive -biting, hostile interactions, mock fighting, displays V = Vocalization -loud vocalizations O = other 99 = obscured -hard to make out individual, uncertain F O C A L A N I M A L A S S O C I A T I O N (2) (nearest neighbour) 1 alone 2 with juvenile 3 with mother 4 with mature female 5 with bull 6 with S A M 7 with other The measure o f association w i l l be one adult female body length. If the animal is more than one adult female body length from anyone else, it w i l l be considered alone. If there are several animals within on adult body length to the focal, the animal nearest to the focal w i l l be considered its associate. If several animals are equidistant to the focal, then it w i l l be marked as 'other'.  69  Appendix 3. Disturbance data sheet MISC. DISTURBANCE AND EVENTS SW BROTHERS 2004-2005 DATE (DD/MM/YY)  TIME  # % #INTO VOCAL EVENT REACTION HEADS HEADS WATER t ' l * . UP UP  Michelle Marcotte  STELLER WATCH COMMENTS/ INITIALS  EVENT- Aircraft, Vessel, Bird, Whale(s), Unknown, Other REACTION: 1. DETECTION- one or more animals with head raised and oriented toward potential disturbance 2. ALARMED- one or more animal move from its resting area, but did not enter the water 3. DISTURBED- more than one animal entered the water  70  DATE (DD/MM/YY):  GROUP BEHAVIOUR SCANS SW BROTHERS 2004-2005 TIME TOTAL YOUNG OF YEAR c 8:00 8:30 9:00 9:30 10:00 10:30 11:00 11:30 12:00 12:30 13:00 13:30 14:00 14:30 15:00 15:30 16:00  c  S  A  R  Michelle Marcotte  STELLER WATCH FEMALES  JUVENILES c  S  A  R  C  A  R  C  A  COMMENTS/WEATHER  BULLS  SAMS R  C  A  R  INITIALS  DATE (DD/MM/YY):  GROUP BEHAVIOUR SCANS- OTHER SITES  Michelle Marcotte  STELLER WATCH  SW BROTHERS 2004-2005 YOUNG OF  TIME  YEAR ;  C  S  JUVENILES C  S  FEMALES SAMS C  C  BULLS C  FOCALS  BEHAVIOUR/ ASSOCIATION  SITE LOCATION  COMMENTS/WEATHER  INITIALS  Appendix 5. Davis Weatherlink Apparent Temperature  The Davis Weatherlink collects a range o f environmental data including temperature, U V index, wind direction, wind speed, humidity, and calculates a number o f indices o f apparent temperature. These include:  Wind chill- takes into account how the speed o f the wind affects perception o f air temperature. Heat index- uses temperature and relative humidity to determine how hot the air actually 'feels'. When humidity is low, the apparent temperature w i l l be lower than the air temperature, since perspiration evaporates rapidly to cool the body. However, when humidity is high, the apparent temperature is perceived to be higher than the actual air temperature, because perspiration evaporates more slowly. Heat index is insignificant below 14°C. Temperature/Humidity/Sun/Wind (THSW) Index- uses humidity and temperature like the Heat Index, but also includes the heating effects o f sunshine and cooling effects o f wind to calculate an apparent temperature o f what it 'feels' like out i n the sun. Humidity- the amount o f water vapour i n the air, which varies with air temperature and pressure. Relative humidity takes into account these factors and offers a humidity reading which reflects the amount o f water vapour i n the air as a percentage o f the amount the air is capable o f holding. Relative humidity is an important factor i n determining the amount o f evaporation from plants and wet surfaces since warm air with l o w humidity has a large capacity to absorb extra water vapour.  73  J  Appendix 6. Modified Beaufort scale weather codes S K Y (1) 0 clear 1 scattered clouds 2 partly cloudy 3 overcast 4 light fog 5 heavy fog 6 drizzle 7 rain 8 snow 9 hail  -  no clouds, sunny, a few high wisps o f white a few clouds scattered throughout the sky very cloudy but you can still make out the sky in some areas no distinguishable cloud shapes, more o f a homogenous grey not too much, haulout visible view o f haulout and land features is severely limited misty, spitting rain full blown raining flakes solid rain  W I N D (2) 0 calm 1 light breeze 2 moderate breeze 3 strong breeze 4 gale  no wind, smoke would rise vertical wind can be felt on face, leaves are rustling raises paper, small branches are moving large branches moving, would be hard to use an umbrella breaks twigs off trees, generally impedes movement  W A V E (3) 0 flat calm sea is like a mirror 1 peaks, no caps ripples, waves with no white on top 2 white caps waves with white foam on crests 3 white caps greater 2ft 4 white caps greater 6ft  S W E L L (4) 0 less 4 ft 1 greater 4 ft 2 greater 10ft (e.g., Sky = partly cloudy, windy = strong breeze, wave = peaks, no caps, swell = less would be written as, 2210)  

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