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

British Antarctic Survey, Cambridge, England, United Kingdom
Antarctic Science (Impact Factor: 1.61). 02/1998; 10(01):75 - 81. DOI: 10.1017/S0954102098000108


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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    • "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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    • " . 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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