A model to predict fasting capacities and utilization of body energy stores in weaned Steller sea lions (Eumetopias jubatus) during periods of reduced prey availability

2009 ◽  
Vol 87 (10) ◽  
pp. 852-864 ◽  
Author(s):  
D. P. Noren ◽  
L. D. Rea ◽  
T. R. Loughlin
Keyword(s):  
Marine Mammals ◽  
Prey Availability ◽  
Population Decline ◽  
Dynamic State ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Variable Model ◽  
Main Site ◽  
Sea Lions ◽  
Fasting Duration

The population decline of Steller sea lions ( Eumetopias jubatus (Schreber, 1776)) may be linked to a decline in juvenile survivorship. Limitations in prey availability may contribute to the decline, thus it is important to understand fasting capacities of Steller sea lions. For most mammals, fat catabolism is the preferred energetic pathway to ensure that protein is spared. However, marine mammals also have a conflicting requirement to conserve fat because the main site of fat storage is the blubber layer, which is also their primary thermal barrier when at sea. We developed a dynamic state variable model to demonstrate how protein and fat reserve utilization and maximum fasting duration are influenced by body condition and time spent foraging. This model was parameterized with respect to conditions faced by juvenile and subadult Steller sea lions foraging unsuccessfully during a period of reduced prey availability. The model accurately predicted changes in fat and protein mass of juvenile and subadult Steller sea lions fasting in captivity. Furthermore, the model demonstrated that body lipid content, body mass, and the proportion of time spent in water influence energy reserve catabolism and maximum fasting durations. Consequently, small, lean individuals are particularly susceptible to reductions in prey availability.

Maternal attendance patterns of Steller sea lions (Eumetopias jubatus) from stable and declining populations in Alaska

2003 ◽  
Vol 81 (2) ◽  
pp. 340-348 ◽  
Author(s):  
Linda L Milette ◽  
Andrew W Trites
Keyword(s):  
Prey Availability ◽  
A Priori ◽  
Population Decline ◽  
Perinatal Period ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
First Feeding ◽  
Attendance Patterns ◽  
The Mean

Maternal attendance patterns of Alaskan Steller sea lions (Eumetopias jubatus) were compared during the summer breeding seasons in 1994 and 1995 at Sugarloaf Island (a declining population) and Lowrie Island (a stable population). Our goal was to determine whether there were differences in maternal attendance between the two populations that were consistent with the hypothesis that lactating Steller sea lions in the area of decline were food-limited during summer. Our a priori expectations were based on well-documented behavioural responses of otariids to reduced prey availability. We found that foraging trips were significantly shorter in the area of population decline, counter to initial predictions. The mean length of foraging trips in the declining area was 19.5 h compared with 24.9 h in the stable area. In contrast, the mean perinatal period (time between parturition and first feeding trip) was significantly longer in the area of decline (9.9 versus 7.9 days), again countering initial predictions. The mean length of shore visits for the declining population was also significantly longer (27.0 h compared with 22.6 h where the population was stable). For both populations, the mean time that mothers foraged increased as pups grew older, whereas the time that they spent on shore with their pups became shorter. Behavioural observations of maternal attendance patterns are inconsistent with the hypothesis that lactating Steller sea lions from the declining population had difficulty obtaining prey during summer.

Variation in maternal attendance patterns and pup behaviour in a declining population of Steller sea lions (Eumetopias jubatus)

1997 ◽  
Vol 75 (8) ◽  
pp. 1241-1246 ◽  
Author(s):  
Wendy R. Hood ◽  
Kathryn A. Ono
Keyword(s):  
Prey Availability ◽  
Population Decline ◽  
High Tide ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Breeding Area ◽  
Foraging Effort ◽  
Sea Lions ◽  
Attendance Patterns ◽  
Breeding Seasons

Maternal attendance patterns of lactating female Steller sea lions (Eumetopias jubatus) and the activity budgets of pups on Año Nuevo Island, California, were compared between the 1973 and 1992 breeding seasons to investigate temporal changes in behaviour that may be associated with population decline. Females were absent from the breeding area longer in 1992, which may reflect increased foraging effort. Pups also spent significantly less time sucking and more time swimming in 1992. Suckling time is correlated with milk intake in some otariid species, thus the decreased amount of time 1992 pups spent sucking could reflect a reduction in the total volume of milk produced by females. Pups in 1992 are likely to have spent more time swimming than pups in 1973 because high tide covered a greater proportion of the study site in 1992 than in 1973. An increase in time females spent at sea and a decrease in time pups spent sucking are consistent with behavioural changes associated with reduced prey availability.

Satiation and compensation for short-term changes in food quality and availability in young Steller sea lions (Eumetopias jubatus)

2004 ◽  
Vol 82 (7) ◽  
pp. 1061-1069 ◽  
Author(s):  
David A.S Rosen ◽  
Andrew W Trites
Keyword(s):  
Food Intake ◽  
Prey Availability ◽  
Energy Content ◽  
High Energy ◽  
Daily Basis ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Short Term ◽  
Sea Lions ◽  
Gross Energy

Foraging theory predicts that animals should proportionately increase their food intake to compensate for reduced food energy content and (or) prey availability. However, the theoretical intake levels will, at some point, exceed the digestive capacity of the predator. We tested the ability of Steller sea lions, Eumetopias jubatus (Schreber, 1776), to compensate for short-term changes in prey energy density and availability, and quantified the maximum amount of food a young sea lion could consume. Five 1–2-year-old captive Steller sea lions were offered either herring (high energy) or capelin (low energy) each day or every second day. When prey were available on a daily basis, the sea lions compensated for differences in the energy content of herring and capelin by consuming sufficient quantities of each (8.3 vs. 14.0 kg·d–1, respectively) to maintain equivalent gross energy intakes. When herring was available only on alternate days, the sea lions increased their consumption by 52% to 11.5 kg·d–1, which was not sufficient to maintain an average gross intake equal to that maintained when herring was available every day. When capelin was available only on alternate days, some animals increased their intake for a few days, but average intake (15.2 kg·d–1) was far below levels observed during daily feeding. Generally, the sea lions appeared to reach their digestive limit at a level equivalent to 14%–16% of their body mass. Our findings suggest that Steller sea lions can alter their food intake in response to short-term changes in prey quality or availability, but that these variables can quickly combine to necessitate food intake levels that exceed the physiological digestive capacities of young animals.

Differences in diving and swimming behavior of pup and juvenile Steller sea lions (Eumetopias jubatus) in Alaska

2008 ◽  
Vol 86 (6) ◽  
pp. 539-553 ◽  
Author(s):  
M. J. Rehberg ◽  
J. M. Burns
Keyword(s):  
Prey Availability ◽  
Activity Patterns ◽  
Diving Behavior ◽  
Juvenile Survival ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Female Fecundity ◽  
Sea Lions ◽  
Prey Behavior ◽  
Prey Depletion

Reduced juvenile survival caused by prey depletion is one hypothesis for the decline in the western Alaska population of Steller sea lions ( Eumetopias jubatus (Schreber, 1776)). To understand the exposure of young sea lions to these depletions, the swimming and diving behavior of pups, juveniles, and subadults was evaluated relative to prey behavior. Pups made shorter and shallower dives (13 m, 0.9 min) than juveniles or subadults, as expected based on physiological limitations, but juveniles and subadults dived to similar depths and durations (29 m, 1.7 min and 38 m, 2.0 min, respectively). Activity patterns of juveniles and subadults reflected diurnal prey migrations, while pup activity did not. Longitudinal trends in pup dive behavior reflected both physiological and behavioral development, while juvenile dive behaviors reflected seasonal changes in prey availability. Results suggest that adult females must continue to provide nutritional support to pups during winter because of the limited diving ability of these young animals. For this reason, the flexible lactation strategies that allow for longer nursing periods during periods of low prey availability and reduce female fecundity may improve juvenile survival.

Diet diversity of Steller sea lions (Eumetopias jubatus) and their population decline in Alaska: a potential relationship

1997 ◽  
Vol 54 (6) ◽  
pp. 1342-1348 ◽  
Author(s):  
Richard L Merrick ◽  
M Kathryn Chumbley ◽  
G Vernon Byrd
Keyword(s):  
Population Decline ◽  
Gulf Of Alaska ◽  
Walleye Pollock ◽  
Aleutian Islands ◽  
Strong Positive Correlation ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Diet Diversity ◽  
Sea Lions ◽  
Atka Mackerel

We examined the diet of Steller sea lions (Eumetopias jubatus) during June-August 1990-1993 from six areas in the Aleutian Islands and Gulf of Alaska and related these diets to sea lion population changes that occurred during the period. Seven general prey categories were identified, but either walleye pollock (Theragra chalcogramma) or Atka mackerel (Pleurogrammus monopterygius) dominated in every area. The diversity of prey consumed varied among sites. Only the eastern Aleutian Islands area had all seven categories in the diet, and there, walleye pollock and Atka mackerel each made up around 30% of the diet. The remainder was composed mostly of small schooling fish (e.g., Pacific herring (Clupea pallasi) and salmon (Oncorhynchus spp.)). The diet in the Gulf of Alaska included mostly walleye pollock whereas the central and western Aleutian diet was composed mostly of Atka mackerel. Populations in the six areas decreased up to 49% during 1990-1994. A strong positive correlation (r = 0.949, P = 0.004) was found between diet diversity and the amount of decline in an area: as diet diversity decreased, populations decreased. This suggests that sea lions need a variety of prey available, perhaps to buffer significant changes in abundance of any single prey.

Ontogeny of dive performance in pup and juvenile Steller sea lions in Alaska

2005 ◽  
Vol 83 (9) ◽  
pp. 1214-1231 ◽  
Author(s):  
Kenneth W Pitcher ◽  
Michael J Rehberg ◽  
Grey W Pendleton ◽  
Kimberly L Raum-Suryan ◽  
Thomas S Gelatt ◽  
...  
Keyword(s):  
Marine Mammals ◽  
Dive Duration ◽  
Time Of Day ◽  
Predictor Variables ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
Significant Relationships ◽  
Variation Explained ◽  
Response Variables

Development of competent diving ability is critical to obtaining nutritional independence in marine mammals such as Steller sea lions (SSLs), Eumetopias jubatus (Schreber, 1776). We studied diving performance in pup (75) and juvenile (36) SSLs using satellite data recorders. In general, dives by SSLs were brief and shallow. Overall, 82.3% of dives were <2 min long and 86.9% of dives were <10 m deep. Long (>5 min) and deep dives (>100 m) constituted only 2.49% and 0.77%, respectively, of total dives. We used linear mixed-effects models to investigate the relationships between the response variables maximum-daily-depth, time-at-depth, mean-dive-duration, dive rate, and time-at-sea and the predictor variables age, sex, population (eastern and western Alaska populations), time-of-day, and month-of-year. All response variables except dive rate were positively related (P < 0.05) to age. Dive rate declined (P < 0.001) with age. Time-of-day, month, population, sex, and some first-order interactions were all significantly (P < 0.05) related to some measure of diving performance. With large samples we were able to identify significant relationships between the response variables and the predictor variables, even though the total amount of variation explained by the models was low, because most dives were short and shallow regardless of age, sex, population, time-of-day, or month-of-year. Depths and durations of dives by juvenile animals increased throughout the range of ages studied and were similar to or greater than those previously reported for juveniles and adult females. We expect maximum depths and durations to continue to increase with age until body mass plateaus at about 10 years of age. Therefore, we expect older animals to be more efficient foragers, as they would have greater aerobic dive limits as well as more experience locating and capturing prey.

scholarly journals Dive, food, and exercise effects on blood microparticles in Steller sea lions (Eumetopias jubatus): exploring a biomarker for decompression sickness

2016 ◽  
Vol 310 (7) ◽  
pp. R596-R601 ◽  
Author(s):  
Andreas Fahlman ◽  
Michael J. Moore ◽  
Andrew W. Trites ◽  
David A. S. Rosen ◽  
Martin Haulena ◽  
...  
Keyword(s):  
Marine Mammals ◽  
Decompression Sickness ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sampling Protocol ◽  
Sea Lions ◽  
Terrestrial Mammals ◽  
Diving Depth ◽  
Decompression Stress ◽  
Effect Of Feeding

Recent studies of stranded marine mammals indicate that exposure to underwater military sonar may induce pathophysiological responses consistent with decompression sickness (DCS). However, DCS has been difficult to diagnose in marine mammals. We investigated whether blood microparticles (MPs, measured as number/μl plasma), which increase in response to decompression stress in terrestrial mammals, are a suitable biomarker for DCS in marine mammals. We obtained blood samples from trained Steller sea lions ( Eumetopias jubatus, 4 adult females) wearing time-depth recorders that dove to predetermined depths (either 5 or 50 meters). We hypothesized that MPs would be positively related to decompression stress (depth and duration underwater). We also tested the effect of feeding and exercise in isolation on MPs using the same blood sampling protocol. We found that feeding and exercise had no effect on blood MP levels, but that diving caused MPs to increase. However, blood MP levels did not correlate with diving depth, relative time underwater, and presumed decompression stress, possibly indicating acclimation following repeated exposure to depth.

Diet composition of Steller sea lions (Eumetopias jubatus) in Frederick Sound, southeast Alaska: a comparison of quantification methods using scats to describe temporal and spatial variabilities

2015 ◽  
Vol 93 (5) ◽  
pp. 361-376 ◽  
Author(s):  
D.J. Tollit ◽  
M.A. Wong ◽  
A.W. Trites
Keyword(s):  
Pacific Salmon ◽  
Biomass Energy ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Southeast Alaska ◽  
Merluccius Productus ◽  
Sea Lions ◽  
Sampling Protocols ◽  
Dietary Indices

We compared eight dietary indices used to describe the diet of Steller sea lions (Eumetopias jubatus (Schreber, 1776)) from 2001 to 2004 in Frederick Sound, southeast Alaska. Remains (n = 9666 items) from 59+ species categories were identified from 1684 fecal samples (scats) from 14 collection periods. The most frequently occurring prey were walleye pollock (Theragra chalcogramma (Pallas, 1814) = Gadus chalcogrammus Pallas, 1814; 95%), Pacific herring (Clupea pallasii Valenciennes in Cuvier and Valenciennes, 1847; 30%), Pacific hake (Merluccius productus (Ayres, 1855); 29%), and arrowtooth flounder (Atheresthes stomias (Jordan and Gilbert, 1880) = Reinhardtius stomias (Jordan and Gilbert, 1880); 21%). These species, along with Pacific salmon (genus Oncorhynchus Suckley, 1861) and skate (genus Raja L., 1758), accounted for 80%–90% of the reconstructed biomass and energy contribution, with pollock contributing 37%–60%. Overall, 80% of fish were 14–42 cm long and mainly pelagic, though 40% of scats contained benthic-associated prey. Steller sea lions switched from adult pollock to strong cohorts of juvenile pollock, and took advantage of spawning concentrations of salmon in autumn and herring in late spring and summer, as well as a climate-driven increase in hake availability. Observed temporal and site differences in diet confirm the need for robust long-term scat sampling protocols. All major indices similarly tracked key temporal changes, despite differences in occurrence and biomass-energy-based diet estimates linked to prey size and energy-density effects and the application of correction factors.

High diving metabolism results in a short aerobic dive limit for Steller sea lions (Eumetopias jubatus)

2013 ◽  
Vol 183 (5) ◽  
pp. 699-708 ◽  
Author(s):  
Carling D. Gerlinsky ◽  
David A. S. Rosen ◽  
Andrew W. Trites
Keyword(s):  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
Sea Lions ◽  
Aerobic Dive Limit
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