Survival of Steller sea lions in Alaska: a comparison of increasing and decreasing populations

2006 ◽  
Vol 84 (8) ◽  
pp. 1163-1172 ◽  
Author(s):  
Grey W. Pendleton ◽  
Kenneth W. Pitcher ◽  
Lowell W. Fritz ◽  
Anne E. York ◽  
Kimberly L. Raum-Suryan ◽  
...  
Keyword(s):  
Adult Female ◽  
Past Research ◽  
Steller Sea Lion ◽  
Juvenile Survival ◽  
Sea Lion ◽  
Eastern Population ◽  
Western Population ◽  
Survival Probabilities ◽  
Sea Lions ◽  
Female Survival

Steller sea lion ( Eumetopias jubatus (Schreber, 1776)) populations have had differing dynamics in different regions of Alaska over the past 30 years. The western population (west of 144°W, near Cape Suckling) declined by approximately 85% between the 1970s and 2000, while the eastern population has increased at a rate of over 3%/year. Past research has indicated that the decline in the western population likely resulted from decreased juvenile survival and smaller declines in adult female survival and reproduction. Based on repeated observations (1987–2003) of sea lions branded as pups at Marmot Island (58.216°N, 151.840°W; western population; branded in 1987–1988) and at the Forrester Island rookery complex (54.859°N, 133.539°W; eastern population; branded in 1994–1995), we used mark–resight analyses to estimate age-specific survival probabilities. Juvenile sea lion survival probability at Marmot Island from 1988 to 1991 was lower than survival estimates at that location in the 1970s (assumed stable population) and lower than juvenile survival at Forrester Island from 1995 to 1998 (increasing population). Adult female survival at Marmot Island from 1992 to 2003 was only slightly reduced compared with that in the 1970s but was substantially lower than that at Forrester Island (1999–2003). In addition, and contrary to the typical pattern (e.g., Forrester Island), adult female survival probabilities at Marmot Island were indistinguishable from adult male survival probabilities. This suggests that regardless of which factors altered the dynamics of the western Steller sea lion population, they differentially affected females.

scholarly journals Overwintering Steller sea lion (Eumetopias jubatus) pup growth and behavior prior to weaning

2018 ◽  
Vol 96 (2) ◽  
pp. 97-106
Author(s):  
M.J. Rehberg ◽  
L.D. Rea ◽  
C.A. Eischens
Keyword(s):  
Nitrogen Isotope ◽  
Breeding Strategy ◽  
Individual Growth ◽  
Steller Sea Lion ◽  
Diving Behavior ◽  
Eumetopias Jubatus ◽  
Sea Lion ◽  
Sea Lions ◽  
Income Breeding ◽  
Lipid Mass

We measured individual growth, looked for evidence of weaning, and examined the interaction of these changes with diving behavior in young-of-year Steller sea lion (Eumetopias jubatus (Schreber, 1776)) pups in Alaska, USA, during their first winter. Steller sea lions employ an income breeding strategy, in which females provision their young over an individually variable period of months to years. Thus, we set out to identify whether these young sea lions showed evidence of weaning during the challenging winter months, describe the nature of their growth during this time, and examine their behaviors in light of these changes. Between 2005 and 2008, we captured 71 pups during early winter and recaptured 33 of these pups in early spring. Mark–resight and stable nitrogen isotope ratios in vibrissae indicated most pups remained nutritionally dependent on adult females throughout the winter. All pups increased both mass and lipid mass, with half of growth contributed by lipid mass. Changes in behavior were not correlated with growth excepting a weak but significant effect on rate of vertical travel. This study demonstrated that capture–recapture of Steller sea lion pups is possible, provided seasonal timing, locations, and age classes are carefully considered for their likelihood of capture success.

Individual variation in predation on fur seals by southern sea lions (Otaria byronia) in Peru

1993 ◽  
Vol 71 (9) ◽  
pp. 1908-1911 ◽  
Author(s):  
Robert Harcourt
Keyword(s):  
Adult Female ◽  
Individual Variation ◽  
Small Proportion ◽  
South American ◽  
Adult Males ◽  
Sea Lion ◽  
Subadult Male ◽  
Sea Lions ◽  
Hunting Success ◽  
Fur Seals

Southern sea lions (Otaria byronia) were observed to prey on juvenile and adult female South American fur seals (Arctocephalus australis) at Punta San Juan, Peru (15°22′S, 75°12′W) between October 1987 and December 1988. Over the course of the study there were 165 attacks on fur seals with 33 seals killed. While both adult male and subadult male sea lions captured and killed fur seals, adult female and juvenile sea lions never acted aggressively towards fur seals. Adult males attacked fur seals on 82.4% of the occasions when they were present at the rookery, subadults on 52% of occasions. Distinctive pelage characteristics allowed some of the male sea lions to be individually identified, and differences in hunting success were observed between adults and subadults, and between five identifiable adults who hunted on at least five occasions. Motivation for attacks differed for subadults and adults, with subadult males using captured fur seals as female sea lion substitutes, guarding them from others and copulating with them, whilst adult sea lions hunted fur seals as food. However, only a small proportion of adult sea lions hunted fur seals, and with differing rates of success.

Examining the utility of fishery and survey data to detect prey removal effects on Steller sea lions (Eumetopias jubatus)

2014 ◽  
Vol 71 (8) ◽  
pp. 1229-1242 ◽  
Author(s):  
Paul B. Conn ◽  
Devin S. Johnson ◽  
Lowell W. Fritz ◽  
Brian S. Fadely
Keyword(s):  
Strong Relationship ◽  
Statistical Hypothesis ◽  
Steller Sea Lion ◽  
Eumetopias Jubatus ◽  
Vital Rates ◽  
Hypothesis Tests ◽  
Sea Lion ◽  
Fish Stocks ◽  
Sea Lions ◽  
The Relationship

One focus of mitigation for Steller sea lion (Eumetopias jubatus) declines in Alaska has been to restrict commercial fishery activity around sea lion rookeries and haul-outs. However, a variety of statistical hypothesis tests have failed to relate sea lion population metrics to fish and fishing variables, prompting speculation that regulations may be unwarranted. In this study, we use simulation to show that standard hypothesis tests often have overstated power to detect a relationship between Steller sea lion vital rates and fish or fishing variables. The power and utility of hypothesis tests largely depend on choosing appropriate dependent and independent variables. In particular, pup counts were the most effective for diagnosing fecundity effects, and successive ratios of adult counts were the most effective for diagnosing survival effects. Fish relative abundance was the most effective independent variable, with other choices (e.g., fishery catch) often resulting in misleading inferences. We argue that Bayes factors are best suited for characterizing the relationship between fish abundance and Steller sea lion vital rates and that existing evidence does not preclude a strong relationship between sea lion fecundity and the availability of commercially harvested fish stocks.

Milk fatty acid composition of perinatal and foraging Steller sea lions (Eumetopias jubatus): examination from pup stomachs

2018 ◽  
Vol 96 (2) ◽  
pp. 153-162 ◽  
Author(s):  
C.N. Miller ◽  
L.K. Polasek ◽  
A.C.M. Oliveira ◽  
C.J. Frost ◽  
J.M. Maniscalco
Keyword(s):  
Fatty Acids ◽  
Fatty Acid Composition ◽  
Fatty Acid ◽  
Acid Composition ◽  
Steller Sea Lion ◽  
Milk Fatty Acid ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lion ◽  
Sea Lions

To investigate the milk fatty acid composition of female Steller sea lions (Eumetopias jubatus (Schreber, 1776)) between and within maternal states (i.e., perinatal or foraging), milk samples were collected in 2010 and 2011 via gastric intubation from Steller sea lion pups on a small rookery in the central Gulf of Alaska. Maternal states of lactating females were determined upon reuniting with their sampled pups via remotely operated video cameras on the rookery. Milk fatty acid composition between Steller sea lion maternal states was significantly different, and thus can be utilized to distinguish between perinatal and foraging Steller sea lions of the same geographic region in the absence of direct observation. However, milk fatty acid composition remained relatively constant within perinatal Steller sea lions, suggesting steady mobilization of fatty acids from blubber to milk, and within foraging Steller sea lions, implying females forage on similar prey species within several days after their perinatal period. Differences in milk fatty acid composition between maternal states, including differences in the relative percentages of polyunsaturated fatty acids, may have important implications for growth and development of offspring.

Metabolic response to fasting in 6-week-old Steller sea lion pups (Eumetopias jubatus)

2000 ◽  
Vol 78 (5) ◽  
pp. 890-894 ◽  
Author(s):  
L D Rea ◽  
D AS Rosen ◽  
A W Trites
Keyword(s):  
Metabolic Response ◽  
Blood Chemistry ◽  
Steller Sea Lion ◽  
Metabolic Adaptation ◽  
Eumetopias Jubatus ◽  
Sea Lion ◽  
Sea Lions ◽  
Lipid Catabolism ◽  
In The Wild ◽  
Change In Mean

Four Steller sea lions (Eumetopias jubatus) aged 6 weeks were fasted for 2.5 d to determine how young pups mobilize energy reserves during short periods of fasting similar to those experienced in the wild. At 6 weeks of age, the pups lost 5.1 ± 0.3% of their body mass during 2 d of fasting, with an average daily mass loss of 0.7 ± 0.1 kg·d-1. Plasma blood urea nitrogen (BUN) concentration increased significantly from 3.0 ± 0.1 mM, after an overnight fast, to 4.8 ± 0.5 mM, after 2.5 d of fasting. It is apparent that BUN levels are quickly depressed, since after only an overnight fast, these pups showed BUN levels 2- to 4-fold lower than those measured after the same pups, when 9 months of age, had recently been fed fish. Plasma ketone body (β-HBA) concentrations of the 6-week-old pups increased significantly from 0.32 ± 0.08 to 0.42 ± 0.08 mM between 0.5 and 1.5 d of fasting. There was no significant change in mean plasma concentration beyond 1.5 d, owing to variable individual responses to extended fasting. Plasma β-HBA levels at 9 months of age ranged from 0.07 to 0.18 mM. Six-week-old Steller sea lion pups showed blood chemistry consistent with metabolic adaptation to fasting within 16 h but were unable to sustain a protein-sparing metabolism for a prolonged period. The pups appeared to revert to protein catabolism after only 2.5 d of fasting. This infers a decrease in lipid catabolism that might be due to the depletion of available lipid resources.

Temporal records of diet diversity dynamics in individual adult female Steller sea lion (Eumetopias jubatus) vibrissae

Oecologia ◽  
2018 ◽  
Vol 188 (1) ◽  
pp. 263-275 ◽  
Author(s):  
A. C. Doll ◽  
B. D. Taras ◽  
C. A. Stricker ◽  
L. D. Rea ◽  
T. M. O’Hara ◽  
...  
Keyword(s):  
Adult Female ◽  
Steller Sea Lion ◽  
Eumetopias Jubatus ◽  
Sea Lion ◽  
Diet Diversity ◽  
Diversity Dynamics ◽  
Individual Adult

Long-term survival and reproductive success of New Zealand sea lions (Phocarctos hookeri) treated with ivermectin as pups

2015 ◽  
Vol 42 (8) ◽  
pp. 660 ◽  
Author(s):  
S. A. Michael ◽  
B. L. Chilvers ◽  
W. D. Roe ◽  
B. D. Gartrell
Keyword(s):  
New Zealand ◽  
Management Tool ◽  
Juvenile Survival ◽  
Sea Lion ◽  
Term Survival ◽  
Long Term Survival ◽  
Growth And Survival ◽  
Sea Lions ◽  
Phocarctos Hookeri

Context Hookworms (Uncinaria spp.) are a common parasite of neonatal fur seals and sea lions around the world and may contribute to decreased pup growth and survival. Removal of these parasitic burdens by administration of the anthelmintic ivermectin has been trialled in New Zealand (NZ) sea lion (Phocarctos hookeri) pups at Sandy Bay, Enderby Island, with initial benefits in growth and survival reported. Long-term effects, however, are not known. Aims To determine the impact of ivermectin treatment administered in the first month of life, on long-term survival and fecundity in a sample of NZ sea lion pups. Methods For a sample of treated and control pups born between 2002 and 2004, resighting data to 2012 was assessed with the Cox proportional hazards analysis to evaluate survival to maturity and fecundity. Key results Sample size was a limiting factor as juvenile survival was very low, but a trend of improved survival was observed in the ivermectin-treated group. Year of birth was significant due to the effects of a bacterial epizootic in the first year of the trial. Reproductive rate was not significantly different between groups. Conclusions The effect of disease and parasitism on the survival of NZ sea lions is apparent, contributing to early pup mortality, with potentially wider-ranging implications for juvenile survival and beyond. Implications Further research is warranted to investigate anthelmintic treatment of NZ sea lion pups as a safe and effective management tool to improve survival and recruitment in declining populations.

Regional variation in trophic ecology of adult female Australian sea lions inferred from stable isotopes in whiskers

2013 ◽  
Vol 40 (4) ◽  
pp. 303 ◽  
Author(s):  
A. D. Lowther ◽  
R. G. Harcourt ◽  
S. D. Goldsworthy
Keyword(s):  
Adult Female ◽  
Regional Variation ◽  
Foraging Ecology ◽  
Isotope Ratios ◽  
Western Coast ◽  
Sea Lion ◽  
Δ13c Values ◽  
Sea Lions ◽  
Australian Sea Lion ◽  
Δ15n And Δ13c

Context The primary selective forces responsible for shaping life-history traits come from the physical and biological environment in which a species resides. Consequently, the limits of a species range may provide a useful measure of adaptive potential to environmental change. The proximity of foraging grounds to terrestrial nursing habitat constrains central-place foragers such as otariid seals in selecting breeding locations. The Australian sea lion (Neophoca cinerea) is an endangered otariid endemic to Australia, whose northern-range extent occurs at a temperate–tropical transition zone on the western coast of Western Australia (WA). Aims Currently, there is a complete absence of data on the foraging ecology of Australian sea lions in WA. We sought to address this critical knowledge gap and provide data on the foraging ecology of adult female Australian sea lions at three isolated breeding colonies in western WA. Methods We used stable-isotope ratios of carbon (δ13C) and nitrogen (δ15N) in the whiskers of pups as proxies to characterise feeding behaviour of 10–28% of all adult female Australian sea lions at each colony. We then compared these geographic data to (1) conspecifics at similar latitude in South Australia (SA) and (2) isotopic data collated from other studies on seabirds that inhabit the region, to place foraging behaviour of adult female Australian sea lions into context. Key results At the southernmost colonies in WA, individual animals were members of one of two distinct isotopic clusters that could be described by differences in δ15N and δ13C values. Individuals at the northernmost colony displayed δ15N values similar to those of seabirds in the same region. Across the study, isotope ratios of adult female Australian sea lions in western WA were between 3‰ and 5‰ lower than those observed at a colony at similar latitude in SA. Conclusions Gross differences in the physical oceanography between WA and SA may in part explain the differences in isotope ratios of individuals between the regions, with lower δ15N and δ13C values in WA probably reflecting the relatively depauperate conditions of the Leeuwin Current. Implications Potential regional differences in trophic structure should be considered when developing appropriate management plans for Australian sea lions and regional variation in the diet of Australian sea lion warrants further investigation.

scholarly journals Steller Sea Lion (Eumetopias jubatus) Response to Non-lethal Hazing at Bonneville Dam

2021 ◽  
Vol 2 ◽  
Author(s):  
Kyle S. Tidwell ◽  
Brett A. Carrothers ◽  
Daniel T. Blumstein ◽  
Zachary A. Schakner
Keyword(s):  
Chinook Salmon ◽  
Steller Sea Lion ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lion ◽  
Sea Lions ◽  
Physical Stimuli ◽  
Multiple Species ◽  
Fisheries Interactions

Protected Steller sea lions (Eumetopias jubatus) aggregate at Bonneville Dam on the Columbia River and prey upon multiple species of endangered salmon ascending the river. Hazing is a non-lethal activity designed to repel sea lions that includes aversive auditory and physical stimuli to deter animals from an area and has been employed with sea lion—fisheries interactions for more than 40 years but sea lion responses to hazing through time is not well-documented. We observed the behavior of Steller sea lions in periods with and without hazing during two spring Chinook salmon passage seasons to evaluate: (1) what effect hazing had on the number of animals present and their foraging behavior, and (2) whether they habituated to hazing. We found that hazing temporarily reduced the number of Steller sea lions, but only when actively hazed. During hazing, Steller sea lions were more likely to move away from hazers on the dam, decreased their foraging, and increased their time investigating the environment. However, these effects were temporary; their behavior returned to initial observation levels once hazing ceased. Furthermore, their responsiveness to hazing declined throughout the season, indicating habituation and raising concern for the application and long-term efficacy of hazing in managing predation on endangered salmon.

scholarly journals The oldest record of the Steller sea lion Eumetopias jubatus (Schreber, 1776) from the early Pleistocene of the North Pacific

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9709
Author(s):  
Nahoko Tsuzuku ◽  
Naoki Kohno
Keyword(s):  
North Pacific ◽  
Japan Sea ◽  
Early Pleistocene ◽  
Steller Sea Lion ◽  
Eumetopias Jubatus ◽  
Sea Lion ◽  
Sea Lions ◽  
The North ◽  
Fur Seals ◽  
The North Pacific

The extant genera of fur seals and sea lions of the family Otariidae (Carnivora: Pinnipedia) are thought to have emerged in the Pliocene or the early Pleistocene in the North Pacific. Among them, the Steller sea lion (Eumetopias jubatus) is the largest and distributed both in the western and eastern North Pacific. In contrast to the limited distribution of the current population around the Japanese Islands that is now only along the coast of Hokkaido, their fossil records have been known from the middle and late Pleistocene of Honshu Island. One such important fossil specimen has been recorded from the upper lower Pleistocene Omma Formation (ca. 1.36–0.83 Ma) in Kanazawa, Ishikawa Prefecture, Japan, which now bears the institutional number GKZ-N 00001. Because GKZ-N 00001 is the earliest fossil having been identified as a species of the sea lion genus Eumetopias, it is of importance to elucidate the evolutionary history of that genus. The morphometric comparisons were made among 51 mandibles of fur seals and sea lions with GKZ-N 00001. As results of bivariate analyses and PCA based on 39 measurements for external morphologies with internal structures by CT scan data, there is almost no difference between GKZ-N 00001 and extant male individuals of E. jubatus. In this regard, GKZ-N 00001 is identified specifically as the Steller sea lion E. jubatus. Consequently, it is recognized as the oldest Steller sea lion in the North Pacific. About 0.8 Ma, the distribution of the Steller sea lion had been already established at least in the Japan Sea side of the western North Pacific.

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