Articoli di riviste: "Acinonyx jubatus jubatus (schreber 1776)"

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Veselova, N. A., e E. D. Sinitskaya. "INFLUENCE OF ENVIRONMENTAL FACTORS ON CHEETAHS BEHAVIOR IN MOSCOW ZOO". Theoretical & applied problems of agro-industry 36, n. 3 (2018): 51–55. http://dx.doi.org/10.32935/2221-7312-2018-36-3-51-55.

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Bosman, A. M., M. C. Oosthuizen, M. A. Peirce, E. H. Venter e B. L. Penzhorn. "Babesia lengau sp. nov., a Novel Babesia Species in Cheetah (Acinonyx jubatus, Schreber, 1775) Populations in South Africa". Journal of Clinical Microbiology 48, n. 8 (2 giugno 2010): 2703–8. http://dx.doi.org/10.1128/jcm.02266-09.

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Tsuzuku, Nahoko, e Naoki Kohno. "The oldest record of the Steller sea lion Eumetopias jubatus (Schreber, 1776) from the early Pleistocene of the North Pacific". PeerJ 8 (27 agosto 2020): e9709. http://dx.doi.org/10.7717/peerj.9709.

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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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Eaton, Randall L. "The Predatory Sequence, with Emphasis on Killing Behavior and its Ontogeny, in the Cheetah (Acinonyx jubatus Schreber)". Zeitschrift für Tierpsychologie 27, n. 4 (26 aprile 2010): 492–504. http://dx.doi.org/10.1111/j.1439-0310.1970.tb01883.x.

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Dailey, Murray D., Richard S. Demaree e Richard L. Critchfield. "Galactosomum stelleri sp. n. (Trematoda: Heterophyidae) from the Northern Sea-Lion, Eumetopias jubatus (Schreber, 1776) (Carnivora: Otariidae)". Comparative Parasitology 69, n. 1 (gennaio 2002): 58–61. http://dx.doi.org/10.1654/1525-2647(2002)069[0058:gssnth]2.0.co;2.

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Rehberg, M. J., L. D. Rea e C. A. Eischens. "Overwintering Steller sea lion (Eumetopias jubatus) pup growth and behavior prior to weaning". Canadian Journal of Zoology 96, n. 2 (febbraio 2018): 97–106. http://dx.doi.org/10.1139/cjz-2016-0296.

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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.

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Parker, P., J. T. Harvey, J. M. Maniscalco e S. Atkinson. "Pupping-site fidelity among individual Steller sea lions (Eumetopias jubatus) at Chiswell Island, Alaska". Canadian Journal of Zoology 86, n. 8 (agosto 2008): 826–33. http://dx.doi.org/10.1139/z08-058.

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Pupping-site fidelity (defined as pupping within 5.8 m of a previous location in ≥2 years) in Steller sea lions ( Eumetopias jubatus (Schreber, 1776)) was investigated during the breeding seasons from 2001 to 2005 at Chiswell Island, a small rookery in the Gulf of Alaska. Density of females was minimal with 54–80 pups born. Photo-identification of individuals and GPS points, including elevation of the rookery, were used to determine locations of 297 births. Sixty-four percentage (35/55) of the females exhibited pupping-site fidelity, and mean frequency of site fidelity was greater for females that gave birth >3 times. Fifty percentage of the births occurred at 22% of the locations for all years, indicating that multiple births occurred at some locations throughout the breeding season. Competition or aggression among females for specific pupping locations before birth was not observed, and there was no temporal order of pupping locations used, indicating that the rookery was not overcrowded and that many suitable pupping locations existed. Multiparous females gave birth at significantly greater distances from the surf zone than primiparous females. Long-term monitoring of pupping-site fidelity in combination with other measures of maternal care will ultimately determine which factors have the greatest effect on pup survival.

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Maniscalco, John M., e Pamela Parker. "Maternal and offspring effects on the timing of parturition in western Steller sea lions (Eumetopias jubatus)". Canadian Journal of Zoology 96, n. 4 (aprile 2018): 333–39. http://dx.doi.org/10.1139/cjz-2017-0058.

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Identifying factors that affect the timing of parturition among annual breeders is important to aid our understanding of how variations may adversely affect population trends over both short and long temporal scales. We investigated the effect of several parameters on the timing of parturition among individual Steller sea lions (Eumetopias jubatus (Schreber, 1776)) over 6 years between 2005 and 2016 using an information–theoretic approach. In addition to the random effect of year, birth and care of a pup in the previous year had the largest effect on parturition, causing a 2.4 day delay. Maternal age was negatively correlated with timing of parturition and male pups were born nearly a day earlier than female pups, on average. There was limited support for effects of sex and mass, with heavier pups born marginally earlier than lighter ones. This study illustrates some of the complexity of variables that can influence the timing of birth in this species and which should be considered in models that attempt to identify long-term trends in changing marine ecosystems.

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Miller, C. N., L. K. Polasek, A. C. M. Oliveira, C. J. Frost e J. M. Maniscalco. "Milk fatty acid composition of perinatal and foraging Steller sea lions (Eumetopias jubatus): examination from pup stomachs". Canadian Journal of Zoology 96, n. 2 (febbraio 2018): 153–62. http://dx.doi.org/10.1139/cjz-2016-0015.

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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.

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Rehberg, M. J., e J. M. Burns. "Differences in diving and swimming behavior of pup and juvenile Steller sea lions (Eumetopias jubatus) in Alaska". Canadian Journal of Zoology 86, n. 6 (giugno 2008): 539–53. http://dx.doi.org/10.1139/z08-018.

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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.

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Derko, A. A., A. Yu Alekseev, K. A. Sharshov, V. N. Burkanov, J. M. Jamalutdinov, G. N. Abdulgalimova e P. M. Ibnumaskhudova. "MODERN VIEWS ON THE CIRCULATION OF HERPES VIRUSES IN THE OKHOTSK SEA STELLER SEA LION (EUMETOPIAS JUBATUS, SCHREBER, 1776)". South of Russia: ecology, development 14, n. 2 (5 luglio 2019): 35–47. http://dx.doi.org/10.18470/1992-1098-2019-2-35-47.

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Aim. To evaluate the possibility of herpes viruses circulation and possible routes of transmission in population of Steller sea lions of the Sea of Okhotsk by combining a thorough literature study with screening of blood sera samples of Steller sea lion puppies of the Sea of Okhotsk obtained in 2008‐2012.Methods. We investigated 370 blood sera of puppies of the Steller sea lion (2008‐2012) from Tyulenij island, Chkalova island and from the Kurile Islands for the presence of antibodies to two members of the subfamily Alphaherpesvirinae and Gam‐ maherpesvirinae using enzyme‐linked immunosorbent assay (ELISA).Results. The data showed that out of 370 sera samples, 50 contained antibodies to the varicella‐zoster virus (subfamily Alphaherpesvirinae) and 46 – to the Epstein‐Barr virus (subfamily Gammaherpesvirinae).Main conclusions. The literature study revealed that the ecology peculiarities of species contribute to the realization of the main ways of transmission of herpes viruses between individuals. We were also able to identify possible risk factors for the transmission of non‐specific herpes viruses between Steller sea lion and the animals with which they are forced to coexist. The results obtained are in a good agreement with the literature data and indirectly confirm the circulation of herpes viruses in the Steller sea lion of the Kuril Islands, as well as the island Tyulenij. We observe a significant difference in the number of Steller sea lion puppies with the presence of antibodies to gamma‐herpes viruses on the Kuril Islands and the Okhotsk Sea is‐ lands (Р > 99,7). Differences in the number of Steller sea lion puppies with the presence of anti‐ bodies to alpha herpes viruses were not reliably detected.

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Shuert, C. R., J. P. Skinner e J. E. Mellish. "Weighing our measures: approach-appropriate modeling of body composition in juvenile Steller sea lions (Eumetopias jubatus)". Canadian Journal of Zoology 93, n. 3 (marzo 2015): 177–80. http://dx.doi.org/10.1139/cjz-2014-0174.

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While many approaches to modeling body condition exist, ranging from arbitrary morphometric indices to sophisticated cone modeling, few approaches have attempted to develop a standardized, simplified method for determining total body fat and protein in otariids. Our goal was to develop a method for predicting the body condition of juvenile Steller sea lions (Eumetopias jubatus (Schreber, 1776)) using simple morphometrics such as measurements of girth, length, mass, and blubber depth. We compared a candidate set of models to determine which metrics best predicted total body water (TBW) measures obtained by deuterium isotope dilution. Furthermore, we used AICc (Akaike’s information criterion corrected for small sample size) model selection methods and cross-validation to choose and validate the best suite of predictors. TBW was best predicted by a model that included mass, standard length, axial girth with the addition of blubber depths on the lateral side of the neck and dorsal surface of the hip. The results presented here show that blubber depth is an important addition to modeling body composition and may improve upon nonlethal, population-level estimates of nonisotopically derived values of TBW in juvenile Steller sea lions. Additionally, our models present a model development framework for other research efforts for use in determining body condition in otariids.

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Permyakov, P. A., S. D. Ryazanov, A. M. Trukhin, E. G. Mamaev e V. N. Burkanov. "The reproductive success of the Steller sea lion Eumetopias jubatus (Schreber, 1776) on Brat Chirpoev and Medny islands in 2001–2011". Russian Journal of Marine Biology 40, n. 6 (novembre 2014): 440–46. http://dx.doi.org/10.1134/s1063074014060182.

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Parker, Pamela, e John M. Maniscalco. "A long-term study reveals multiple reproductive behavior strategies among territorial adult male Steller sea lions (Eumetopias jubatus)". Canadian Journal of Zoology 92, n. 5 (maggio 2014): 405–15. http://dx.doi.org/10.1139/cjz-2013-0099.

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We conducted a long-term study to assess how tenure and territorial behaviors influence reproductive success among male Steller sea lions (Eumetopias jubatus (Schreber, 1776)). Copulations by males (n = 44) that maintained territories on a rookery in the Gulf of Alaska from 2001 to 2009 were observed using a remote video system. Approximately half of postpartum females copulated with a male in a different territory from where they gave birth. Nearly two-thirds of territorial males with known tenure were unsuccessful in copulating during their first year. Number of copulations for territorial males increased from acquisition year to year 2 with no change in subsequent years. Cluster analysis of tenure and territorial tactic variables for 15 males with observed lifetime reproductive success was used to describe multiple reproductive strategies. Characteristics of the two most successful strategies were the following: (i) males typically copulated in their first year, retained the same territories for 3–5 years, and occupied centrally located coastal territories where the highest percentage of females gave birth and (ii) males did not copulate until at least their third year and occupied peripheral territories with fewer births for a longer tenure of 7–8 years. Results indicated that lifetime reproductive success was not achieved solely by time on the breeding area; rather, it was achieved from a combination of tenure and territorial tactics.

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Stegall, Vicki K., Sean D. Farley, Lorrie D. Rea, Kenneth W. Pitcher, Robert O. Rye, Cynthia L. Kester, Craig A. Stricker e Carleton R. Bern. "Discrimination of carbon and nitrogen isotopes from milk to serum and vibrissae in Alaska Steller sea lions (Eumetopias jubatus)". Canadian Journal of Zoology 86, n. 1 (gennaio 2008): 17–23. http://dx.doi.org/10.1139/z07-115.

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Knowledge of diet–tissue stable isotope discrimination is required to properly interpret stable isotope values and to identify possible diet shifts, such as might be expected from nursing through weaning. This study compared δ13C and δ15Ν οf paired serum and vibrissal roots with those of ingested milk (n = 52) from free-ranging Steller sea lion ( Eumetopias jubatus (Schreber, 1776)) pups (1–11 months) and juveniles (14–27 months) to estimate diet–tissue discrimination. Mean 15N enrichment from ingested milk to serum was 2.1‰ ± 0.6‰ and δ15Ν at the root of the vibrissae (representing current growth) were not significantly different from serum values. Milk was enriched for mean 13C by 5.0‰ ± 1.0‰ and 7.3‰ ± 1.2‰ relative to serum and vibrissal roots, respectively, which was due to the presence of 13C-depleted lipids in milk. This was confirmed by lipid extraction from a subset of milk and serum samples, resulting in a 5.8‰ ± 1.0‰ change only in milk. This study established that vibrissal roots and serum are reflective of a milk diet with approximately 2.0‰ 15N enrichment, and vibrissal roots reflect serum and lipid-extracted milk values with approximately 2.0‰ 13C enrichment. These discrimination factors are important to establish for stable isotope studies assessing diet shifts.

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Waite, J. N., V. N. Burkanov e R. D. Andrews. "Prey competition between sympatric Steller sea lions (Eumetopias jubatus) and northern fur seals (Callorhinus ursinus) on Lovushki Island, Russia". Canadian Journal of Zoology 90, n. 1 (gennaio 2012): 110–27. http://dx.doi.org/10.1139/z11-117.

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Approximately 1 000 Steller sea lions ( Eumetopias jubatus (Schreber, 1776); SSL) and 14 000 northern fur seals ( Callorhinus ursinus (L., 1758); NFS) breed sympatrically on Lovushki Island in the Russian Far East, creating the potential for interspecific competition for prey. An additional 13 000 – 14 000 juvenile NFS are present during the breeding season. The diets of breeding SSL and both breeding and juvenile NFS were examined through analysis of scats and spews collected during the breeding seasons of 2003, 2005, and 2007–2008. There were significant overlaps in the prey species and size selection of SSL and juvenile NFS. There were significant differences between the diets of SSL and breeding NFS. SSL and juvenile NFS fed primarily on Atka mackerel ( Pleurogrammus monopterygius (Pallas, 1810)), while breeding NFS fed on cephalopods, salmon (genus Oncorhynchus Suckley, 1861), Atka mackerel, and northern smoothtongue ( Leuroglossus schmidti Rass, 1955). The partitioning of resources between breeding animals has allowed both species to coexist within the same region and likely reflected differences in foraging abilities and provisioning strategies of the adults and the fasting abilities of their pups. However, continued growth of the NFS population may lead to the exclusion of SSL owing to interspecific competition for prey.

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Tollit, Dominic, Lowell Fritz, Ruth Joy, Kristi Miller, Angela Schulze, James Thomason, William Walker, Tonya Zeppelin e Thomas Gelatt. "Diet of endangered Steller sea lions (Eumetopias jubatus) in the Aleutian Islands: new insights from DNA detections and bioenergetic reconstructions". Canadian Journal of Zoology 95, n. 11 (novembre 2017): 853–68. http://dx.doi.org/10.1139/cjz-2016-0253.

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The endangered western stock of Steller sea lion (Eumetopias jubatus (Schreber, 1776)) still declines in the western Aleutian Islands and accurate diet information is vital to test leading hypotheses. We undertook the first bioenergetic diet reconstruction using both molecular and hard part prey identifications from >600 scats collected in March–April 2008 and 2012. Atka mackerel (Pleurogrammus monopterygius (Pallas, 1810)) remained a primary prey (17%–27% by energy), but large (mean 60 cm) Pacific cod (Gadus macrocephalus Tilesius, 1810) also emerged as important prey (20%–24%) in a more diverse diet than previously reported, with Cottidae and smooth lumpsucker (Aptocyclus ventricosus (Pallas, 1769)) also contributing ∼10%. DNA detections highlighted a potentially important and previously underestimated prey, giant Pacific octopus (Enteroctopus dofleini (Wülker, 1910) (diet contribution 2%–15%, dependent on prey size assumptions). Although 504 unique DNA identifications resulted in significant increases for cephalopods, Pacific cod, and smooth lumpsucker, hard part alone species rankings were similar to composite ones and bioenergetic species rankings similar to occurrence-based ones. Retention or regurgitation of large cephalopod beaks, the removal of large cod heads, and skeletal fragility of lumpsuckers may explain these differences. DNA identifications provide valuable comparative and complementary prey occurrence data for pinnipeds, but composite diet estimates are optimal.

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Fritz, L., B. Brost, E. Laman, K. Luxa, K. Sweeney, J. Thomason, D. Tollit, W. Walker e T. Zeppelin. "A re-examination of the relationship between Steller sea lion (Eumetopias jubatus) diet and population trend using data from the Aleutian Islands". Canadian Journal of Zoology 97, n. 12 (dicembre 2019): 1137–55. http://dx.doi.org/10.1139/cjz-2018-0329.

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Prey diversity and energy density have been linked to each other and to population trends in many studies of bird and mammal diets. We re-examined these relationships in Steller sea lions (Eumetopias jubatus (Schreber, 1776)) using data collected from the Aleutian Islands, where there has been a strong longitudinal gradient in population trend. Diet diversity and energy density metrics were similar in the western Aleutians, where sea lion counts declined consistently, and in the easternmost Aleutian area, where population trends improved significantly. We compared traditional deterministic diet diversity metrics with diversity scores based on an occupancy model that accounts for differences in sample size and uncertainty in prey group detection. This analysis indicated that there was no significant change in diet diversity over the 23-year study period or any significant differences across the Aleutian Islands. These results are consistent with prey abundance data from nine groundfish bottom trawl surveys conducted over the same period. While diet studies detail what Steller sea lions eat and provide an estimate of their energy intake, they provide only limited information on the energy expended to obtain their food or the consequences of their diet and foraging ecology on individual or population fitness.

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Rosen, David A. S., e Andrew W. Trites. "Satiation and compensation for short-term changes in food quality and availability in young Steller sea lions (Eumetopias jubatus)". Canadian Journal of Zoology 82, n. 7 (1 luglio 2004): 1061–69. http://dx.doi.org/10.1139/z04-082.

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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.

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York, A. E., J. R. Thomason, E. H. Sinclair e K. A. Hobson. "Stable carbon and nitrogen isotope values in teeth of Steller sea lions: age of weaning and the impact of the 1975–1976 regime shift in the North Pacific Ocean". Canadian Journal of Zoology 86, n. 1 (gennaio 2008): 33–44. http://dx.doi.org/10.1139/z07-108.

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We measured δ15N and δ13C values and tooth width from the first 4 years’ dentinal growth layer groups (GLGs) in the teeth of 113 female Steller sea lions ( Eumetopias jubatus (Schreber, 1776)) born between 1960 and 1983, a period that included a large population decrease and a climate regime shift. A linear discriminant analysis on the δ13C and δ15N values estimated 60% of Steller sea lions were weaned in their 1st year, 30% in their 2nd year, and 8% in their 3rd year. GLG-1 was wider in “weaned” animals than those still “nursing” in their 2nd year, suggesting that faster growing pups weaned earlier. Except during the regime shift, the average age at weaning increased and the size of GLG-1 in weaned animals decreased. We suggest that during the regime shift a greater proportion of pups which survived (to have their teeth sampled for this study) grew faster and were weaned by the end of their 1st year. We hypothesize that the long-term weaning age increase and growth rate decrease are consistent with a change in relative mortality of weaned pups and those that continued to nurse, possibly caused by a reduction in available resources, characterized as a switch from a “live-fast” to a “live-slow” life history.

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Noren, D. P., L. D. Rea e T. R. Loughlin. "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". Canadian Journal of Zoology 87, n. 10 (ottobre 2009): 852–64. http://dx.doi.org/10.1139/z09-074.

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Abstract (sommario):

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.

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Tollit, D. J., S. G. Heaslip, R. L. Barrick e A. W. Trites. "Impact of diet-index selection and the digestion of prey hard remains on determining the diet of the Steller sea lion (Eumetopias jubatus)". Canadian Journal of Zoology 85, n. 1 (gennaio 2007): 1–15. http://dx.doi.org/10.1139/z06-174.

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Abstract (sommario):

Nine prey species (n = 7431) were fed to four captive female Steller sea lions ( Eumetopias jubatus (Schreber, 1776)) in 11 feeding trials over 75 days to investigate the effectiveness of different methods used to determine diet from prey hard remains. Trials aimed to replicate short (1–2 days) and long feeding bouts, and consisted of single species and mixed daily diets. Overall, 25.2% ± 22.2% (mean ± SD, range 0%–83%) otoliths were recovered, but recovery rates varied by species (ANOVA, P = 0.01) and were linearly related to otolith robustness (R2 = 0.88). Squid beaks were recovered at higher frequencies (mean 96%) than the otoliths of all species. Enumerating both non-otolith skeletal structures and otoliths (together termed bones) increased species recovery rates by twofold, on average (P < 0.001), with increases up to 2.5 times for Pacific herring ( Clupea pallasii Valenciennes in Cuvier and Valenciennes, 1847) and 3–4 times for salmonids. Using bones reduced interspecific differences (P = 0.08), but recovery varied among sea lions. Bones were distributed over more scats per meal (mean 2.9 scats, range 0–5) than otoliths (mean 1.9 scats, range 0–4). In three different 15-day mixed diet trials, biomass reconstruction (BR) indices performed better than frequency of occurrence indices in predicting diet fed. Applying our experimentally derived numerical correction factors (to account for species differences in complete prey digestion) further improved BR estimates, resulting in all 12 unweighted comparisons within 5% (for otoliths) and 12% (for bones) of the actual diet fed.

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Sinclair, E. H., W. A. Walker e P. J. Gearin. "The diet of free-ranging male Steller sea lions (Eumetopias jubatus) in the eastern Bering Sea: a retrospective analysis based on stomach contents of an endangered pinniped". Canadian Journal of Zoology 97, n. 3 (marzo 2019): 195–202. http://dx.doi.org/10.1139/cjz-2018-0057.

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Abstract (sommario):

This study illuminates historical diet and foraging locations of endangered western U.S. stock Steller sea lions (Eumetopias jubatus (Schreber, 1776)). Prey were identified from stomachs of 22 males collected in the eastern Bering Sea from the ice edge in March 1985 and nearshore St. Paul Island in September–October 1985 and 1986. Percent frequency of occurrence (PFO) and percent number (PN) were highest for walleye pollock (Gadus chalcogrammus Pallas, 1814; PFO 69%, PN 15%, mean length 17 cm), Pacific herring (Clupea pallasii Valenciennes in Cuvier and Valenciennes, 1847; PFO 62%, PN 16%, mean length 26 cm), shorthorn sculpin (Myoxocephalus scorpius (Linnaeus, 1758); PFO 54%, PN 30%), and Pacific giant octopus (Enteroctopus dofleini (Wülker, 1910); PFO 39%, PN 8%, mean weight 31 kg) in spring, and northern rock sole (Lepidopsetta polyxystra Orr and Matarese, 2000; PFO 78%, PN 47%, mean length 35 cm), Pacific cod (Gadus macrocephalus Tilesius, 1810; PFO 56%, PN 12%, mean length 62 cm), walleye pollock (PFO 44%, PN 7%, mean length 49 cm), and red Irish lord (Hemilepidotus hemilepidotus (Tilesius, 1811); PFO 11%, PN 9%) in fall. Species of Cryptacanthidae, Liparidae, and Zoarcidae were highly represented and exclusive to spring collections. Predictable seasonal concentrations and movements of mature prey along frontal boundaries of the continental shelf and ice edge may be critical to male Steller sea lion fitness during the non-breeding season.

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24

Rea, L. D., D. A. S. Rosen e A. W. Trites. "Utilization of stored energy reserves during fasting varies by age and season in Steller sea lions". Canadian Journal of Zoology 85, n. 2 (febbraio 2007): 190–200. http://dx.doi.org/10.1139/z06-204.

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Abstract (sommario):

Nine captive Steller sea lions ( Eumetopias jubatus (Schreber, 1776), 1.75–6 years of age) were fasted for 7–14 d to test the effect of short-term fasting on changes in body mass and body condition. Trials were repeated during both the summer breeding season and the nonbreeding season in seven animals to elucidate whether there was a seasonal component to the ability of Steller sea lions to adapt to limited food resources. Mean percent mass loss per day was higher during the breeding season in juveniles (1.8% ± 0.2%·d–1) than in subadults (1.2% ± 0.1%·d–1), but there were no significant age-related differences during the nonbreeding season (juveniles, 1.5% ± 0.3%·d–1; subadults, 1.7% ± 0.3%·d–1). A decrease in the rate of mass loss occurred after the first 3 d of fasting only in subadults during the breeding season. Percent total body lipid ranged from 11% to 28% of total body mass at the initiation of fasting trials. Animals with lower initial percent total body lipid exhibited higher subsequent rates of mass loss and a lower percentage of tissue catabolism derived from lipid reserves. There was no evidence of metabolic adaptation to fasting in juveniles, which suggests that juvenile sea lions would be more negatively impacted by food limitation during the breeding season than would subadults.

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Tollit, D. J., M. A. Wong e A. W. Trites. "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". Canadian Journal of Zoology 93, n. 5 (maggio 2015): 361–76. http://dx.doi.org/10.1139/cjz-2014-0292.

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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.

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O’Corry-Crowe, G., B. L. Taylor, T. Gelatt, T. R. Loughlin, J. Bickham, M. Basterretche, K. W. Pitcher e D. P. DeMaster. "Demographic independence along ecosystem boundaries in Steller sea lions revealed by mtDNA analysis: implications for management of an endangered species". Canadian Journal of Zoology 84, n. 12 (dicembre 2006): 1796–809. http://dx.doi.org/10.1139/z06-167.

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Previous genetic studies indicate Steller sea lions ( Eumetopias jubatus (Schreber, 1776)) comprise three phylogeographically distinct populations. However, differences in population trends and ecology and the limited extent of recorded dispersal suggest structure may be present at smaller scales. We examined sequence variation within a longer segment (531 bp) of the mtDNA control region in greater numbers (n = 1654) of sea lions from across Alaska than earlier investigations to investigate fine-scale dispersal patterns in Steller sea lions. We detected high levels of haplotypic diversity (h = 0.934) and confirmed phylogeographic differentiation between southeastern and western Alaska (Φst = 0.23, P < 0.0001), but also found significant differentiation at regional and local scales. Rookeries in the Gulf of Alaska, eastern Bering Sea, and eastern Aleutians were distinct from rookeries in the central and western Aleutians (Fst = 0.021, P < 0.0001; Φst = 0.017, P < 0.0001). The location of this split coincides with an oceanographic divergence between continental shelf and ocean basin waters and with differences in sea lion foraging ecology and population trends. A number of rookeries were also significantly differentiated from nearby rookeries (Fst = 0.02–0.025, P < 0.05), signifying substantial female-mediated philopatry, in some cases, at local scales. These findings have important implications for understanding the ecology of Steller sea lions in relation to marine ecosystems and the causes of population declines, and they provide guidance for management, including the identification of management stocks.

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Pendleton, Grey W., Kenneth W. Pitcher, Lowell W. Fritz, Anne E. York, Kimberly L. Raum-Suryan, Thomas R. Loughlin, Donald G. Calkins, Kelly K. Hastings e Thomas S. Gelatt. "Survival of Steller sea lions in Alaska: a comparison of increasing and decreasing populations". Canadian Journal of Zoology 84, n. 8 (agosto 2006): 1163–72. http://dx.doi.org/10.1139/z06-103.

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Abstract (sommario):

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.

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Kitts, David D., Minh Dieu Huynh, Chun Hu e Andrew W. Trites. "Season variation in nutrient composition of Alaskan walleye pollock". Canadian Journal of Zoology 82, n. 9 (1 settembre 2004): 1408–15. http://dx.doi.org/10.1139/z04-116.

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A popular hypothesis for the noted steady decline in the population of Steller sea lions, Eumetopias jubatus (Schreber, 1776), in the regions from Prince William Sound through the Aleutian Islands relates to their nutritional status. Sea lion diets appear to have shifted from primarily small schooling fatty fishes to low-fat fish such as walleye pollock, Theragra chalcogramma (Pallas, 1814). We examined the seasonal changes in proximate nutrients of pollock collected in the Bering Sea. Mean energy density (dry mass) of pollock peaked in October then declined and remained low throughout winter. Energy recovery occurred in the summer months with strong recovery observed in female fish caught in July. Contrary to whole fish carcass energy contents, both total protein and moisture contents were at their highest levels in winter (January) when total crude lipid content was at its lowest (p < 0.05). This trend gradually declined to its lowest levels in the fall when lipid content was high. The decline in total lipids during winter seasons appeared to parallel gonad development during the prespawning period. Sex differences in energy densities were not found. Proximate analysis data for moisture, protein, ash, and lipid content also did not show any significant variation between males and females. Protein digestibility of pollock was higher (p < 0.05) in the summer than in the spring, but not different for winter or fall. We concluded that the nutrient content of walleye pollock may have some impact on the Steller sea lions that feed on them, particularly the energetic value that appears to be low during important feeding periods for this marine mammal.

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Pitcher, Kenneth W., Michael J. Rehberg, Grey W. Pendleton, Kimberly L. Raum-Suryan, Thomas S. Gelatt, Una G. Swain e Michael F. Sigler. "Ontogeny of dive performance in pup and juvenile Steller sea lions in Alaska". Canadian Journal of Zoology 83, n. 9 (1 settembre 2005): 1214–31. http://dx.doi.org/10.1139/z05-098.

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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.

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SALEH, M. A., I. HELMY e R. GIEGENGACK. "The Cheetah, Acinonyx jubatus (Schreber, 1776) in Egypt (Felidae, Acinonychinae)". Mammalia 65, n. 2 (2001). http://dx.doi.org/10.1515/mamm.2001.65.2.177.

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HAMDINE, W., T. MEFTAH e A. SEHKI. "Réparation et Statut du guépard (Acinonyx jubatus Schreber, 1776) dans le Sahara central algérien (Ahaggar etTassili)". Mammalia 67, n. 3 (2003). http://dx.doi.org/10.1515/mamm.2003.67.3.439.

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