Seasonal occurrence and diet of leopard seals (Hydrurga leonina) at Bird Island, South Georgia

Antarctic Science (Impact Factor: 1.61). 02/1998; 10(01):75 - 81. DOI: 10.1017/S0954102098000108

ABSTRACT Seasonal haul-out patterns and diet of individually marked leopard seals (Hydrurga
leptonyx) were investigated at Bird Island, South Georgia during the 1983–96 winters. A total of 2956 leopard seal sightings were made, and 121 seals were tagged during the study, mainly between 1993 and 1996. Photographs of scars and pelage patterns were also used to identify a subset of these individuals across years, which provided no evidence of tag loss between or within years. Leopard seals were observed between April and November; the mean time between the first and last sightings in each year was 208 d (s d ± 48). Between 1993–96, eight seals were resident around the island for more than 100 d, and the longest recorded residence was 130 d. The proportion of tagged seals resighted was 0.35 and 0.17 in 1995 and 1996 respectively. Based on estimates of body length, <5% of the seals were juveniles (0–1 years) and >70% were not sexually mature. There was considerable inter-annual variation in abundance, with a maximum of 502 sightings during 1994, compared with a minimum of 21 during 1986 and 1989. Antarctic fur seals (Arctocephalus
gazella) were the main prey item (58% of kills observed and 53% of scats). Other items included penguins (28% of kills observed and 20% of scats) and fish (24% of scats). Antarctic krill (Euphausia
superba), southern elephant seals (Mirounga
leonina) and seabirds other than penguins were also present in the diet in small quantities.

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Available from: Tony Robert Walker, Sep 27, 2015
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    • "have also been regularly observed on many sub-Antarctic Islands including, Marion Island (Bester et al. 2006), Kerguelen Island (Paulin 1952; Bester and Roux 1986; Borsa 1990), Heard Island (Gwynn 1953; Brown 1957), Macquarie Island (Csordas 1963; Rounsevell and Eberhard 1980), South Georgia (Hamilton 1939; Walker et al. 1998; Jessopp et al. 2004), the South Orkney Islands (Hamilton 1939), the Falkland Islands (Hamilton 1939), the Juan Fernandez Islands (Torres and Aguayo-Lobo 1971; Torres 1987), and Easter Island (Aguayo-Lobo et al. 2011). The most northern records previously reported for leopard seals were in the western South Pacific at the Cook "
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    ABSTRACT: Leopard seals are distributed around the Antarctic continent principally between 50A degrees S and 80A degrees S though they are known to wander even farther north, particularly to Australia, New Zealand, South America, and South Africa, and several sub-Antarctic Islands. Seasonal movements of leopard seals have been correlated with seasonal changes in the distribution of sea ice with seals moving north as sea ice develops in spring and winter and southward toward the Antarctic continent as it melts in late autumn and winter. On August 9, 2013, an emaciated juvenile male leopard seal was observed swimming in Bounty Bay at Pitcairn Island (25A degrees 4'S, 130A degrees 6'W). It was found ashore at a boat ramp in the bay the next day. Because of the seal's apparent distress, it was promptly shot and killed humanely by an island police officer and then dumped at sea before any measurements or additional observations could be made. We estimated the seal to be a 10-month-old pup, about 1.8-2 m long. The appearance of this leopard seal at Pitcairn Island is only slightly farther south than the most northern record (the Cook Islands, 21A degrees 25'S, 159A degrees 8'W) for the species, but it is the most remote occurrence yet documented worldwide and correlates with the all-time record for sea ice coverage in the Antarctic in winter 2013.
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    • "The significant difference in the gut microbiota of wild and captive leopard seals may be influenced in part by the distinct OTUs associated with their particular prey items. In captivity , leopard seals are fed a diet of fish caught off Sydney, Australia, while wild leopard seals feed on a variety of dietary items including krill, penguins, and fish (Walker et al., 1998; Hall-Aspland and Rogers, 2004; Casaux et al., 2009). Changes in the gut microbiota of the Atlantic cod, Gadus morhua, were observed after six weeks in response to artificial feeding of the fish, i.e. a change in diet, when moved from a wild to a captive "
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    ABSTRACT: The gut microbiota of mammals underpins the metabolic capacity and health of the host. Our understanding of what influences the composition of this community has been limited primarily to evidence from captive and terrestrial mammals. Therefore, the gut microbiota of southern elephant seals, Mirounga leonina, and leopard seals, Hydrurga leptonyx, inhabiting Antarctica were compared with captive leopard seals. Each seal exhibited a gut microbiota dominated by four phyla: Firmicutes (41.5 ± 4.0%), Fusobacteria (25.6 ± 3.9%), Proteobacteria (17.0 ± 3.2%) and Bacteroidetes (14.1 ± 1.7%). Species, age, sex and captivity were strong drivers of the composition of the gut microbiota, which can be attributed to differences in diet, gut length and physiology and social interactions. Differences in particular prey items consumed by seal species could contribute to the observed differences in the gut microbiota. The longer gut of the southern elephant seal provides a habitat reduced in available oxygen and more suitable to members of the phyla Bacteroidetes compared with other hosts. Among wild seals, 16 'core' bacterial community members were present in the gut of at least 50% of individuals. As identified between southern elephant seal mother-pup pairs, 'core' members are passed on via vertical transmission from a young age and persist through to adulthood. Our study suggests that these hosts have co-evolved with their gut microbiota and core members may provide some benefit to the host, such as developing the immune system. Further evidence of their strong evolutionary history is provided with the presence of 18 shared 'core' members in the gut microbiota of related seals living in the Arctic. The influence of diet and other factors, particularly in captivity, influences the composition of the community considerably. This study suggests that the gut microbiota has co-evolved with wild mammals as is evident in the shared presence of 'core' members.
    Environmental Microbiology 10/2012; 15(4). DOI:10.1111/1462-2920.12022 · 6.20 Impact Factor
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    • " . Collec - tively , these observations may foretell an adaptive tactic that maintains high rates of provisioning when investment in current reproduction is high , and when only one parent is provisioning in what can be highly unpredictable polar environments ( e . g . , the Southern Ocean ) , where multiple stressors occur ( e . g . , predation [ Walker et al . 1998 ] , ex - treme weather [ Romero et al . 2000 ] , and high thermo - regulatory costs [ Romero 2002 ] ) . These data are consistent with the idea that continuous , phenotypic variation in plasma corticosterone , as a homeostatic , metabolic regu - lator , is positively correlated with individual variation in current reproductive effort , "
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    ABSTRACT: Corticosterone has received considerable attention as the principal hormonal mediator of allostasis or physiological stress in wild animals. More recently, it has also been implicated in the regulation of parental care in breeding birds, particularly with respect to individual variation in foraging behavior and provisioning effort. There is also evidence that prolactin can work either inversely or additively with corticosterone to achieve this. Here we test the hypothesis that endogenous corticosterone plays a key physiological role in the control of foraging behavior and parental care, using a combination of exogenous corticosterone treatment, time-depth telemetry, and physiological sampling of female macaroni penguins (Eudyptes chrysolophus) during the brood-guard period of chick rearing, while simultaneously monitoring patterns of prolactin secretion. Plasma corticosterone levels were significantly higher in females given exogenous implants relative to those receiving sham implants. Increased corticosterone levels were associated with significantly higher levels of foraging and diving activity and greater mass gain in implanted females. Elevated plasma corticosterone was also associated with an apparent fitness benefit in the form of increased chick mass. Plasma prolactin levels did not correlate with corticosterone levels at any time, nor was prolactin correlated with any measure of foraging behavior or parental care. Our results provide support for the corticosterone-adaptation hypothesis, which predicts that higher corticosterone levels support increased foraging activity and parental effort.
    The American Naturalist 07/2012; 180(1):E31-41. DOI:10.1086/666001 · 3.83 Impact Factor
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