Residencia De Foca Leopardo En Parque Marino Francisco Coloane

Residence of Hydrurga leptonyx in Magallanes: a potencial Subantarctic population that inhabit in Chile?

Jorge Acevedo1 & Francisco Martinez2

1 Centro Regional de Estudios del Cuaternario (Fundación CEQUA). 21 de Mayo 1690, Punta Arenas, Chile.

2 Angel Viano 150, Puerto Natales, Chile.

Abstract

Opportunistic sightings of a solitary leopard seal at Ballena Sound (53°41’S, 72°37’W), in the Magellan region were recorded in six occasions from January to May 2012. Based on the review on photography’s the adult male leopard seal was identified as the same individual by the presence of a distinctive open circle located on the left side of the lower jaw. This finding provide the first evidence of occupation, of at least five months, in a particular channel by a leopard seal, suggesting than the small population that inhabit in the fjords and channel of Chilean Patagonian would not return to Antarctic in spring or summer, remaining year-round in southern localities of Chile.

Key words: Leopard seal, South Patagonia, Residence, Chile, AMCP Francisco Coloane

Introduction

Five species of pinnipeds, South American sea lion Otaria flavescens, southern fur seal Arctocephalus australis, southern elephant seal Mirounga leonina, Antarctic fur seal A. gazella and leopard seal Hydrurga leptonyx, have been recorded in the fjords and channel of Southern Chile (Gibbons et al. 2001, Venegas et al. 2002, Acevedo et al. 2011, Aguayo-Lobo et al. 2011). The latter two species are well outside their normal Antarctic ranges.

The leopard seal (Hydrurga leptonyx de Blainville 1820) is widely distributed on the Antarctic pack ice and south to the edge of the continent, with seasonal northward movements related with ice conditions (Erickson et al. 1971, Kooyman 1981, King 1983). The distribution also includes small permanent concentrations in Antarctic and Subantarctic Islands as Heard (Gwynn 1953, Brown 1957), Auckland, Campbell (King 1983, Reeves et al. 1992) and Kerguelen (Paulin 1952, Bester 1981, Bester & Roux 1986, Borsa 1990). Small seasonal groups are also recorded in Malvinas-Falkland (Hamilton 1939, Bonner & Laws 1964), South Georgia (Hamilton 1939, Laws 1957, Walker et al. 1998, Forcada & Robinson 2006) and Macquarie (Rounsevell & Eberhard 1980) and Marion (Bester et al. 2006) Islands.

Along the coast of Chile, 115 sightings of leopard seals have been reported, mostly distribuited in the South Patagonian (87 individuals), with immature and adult individuals of both sexes and in good condition sighted year-round in glacial areas, especially Tierra del Fuego island (south of 53°43´S) (Aguayo-Lobo et al. 2011). Although the observations presented by last authors shown a year-round presence of leopard seals in the fjords and channels of South America, the data were limited to assessing whether the same individuals who remain year-round. Because, one of the questions to be resolved refers to the rationale for the north or southward dispersion of the individuals. Traditionally, the movement of leopard seals from the Southern Ocean northward of the Antarctic Polar Front has been attributed to the northward extension of the pack ice during winter (Hamilton 1939, Bonner & Laws 1964, Rounsevell & Eberhard 1980, Bester & Roux 1986, Hempel 1990, Testa et al. 1991, Bester et al. 1995, Jessopp et al. 2004), while that the seals would then return back towards the Antarctic continent during austral spring (Brown 1957, Erickson et al. 1971, Siniff & Stone 1985).

This note present information to provide some evidence that, at least, the Chilean Patagonian leopard seal non return to the Antarctic continent, constituting a stable sub-Antarctic population in the marine fauna of Chile.

Materials and Methods

The sightings was recorded by crew members aboard of tourist vessel M/N “Forrest”, which sailing periodically the waters of the Marine and Coastal Protected Area (AMCP) Francisco Coloane (Fig. 1), from December to May. Non scientific crew was aboard the Forrest in those opportunities, therefore these sightings are based on the logbook annotations and photographs of the second author. The sightings were made onboard an inflatable boat of 4,7 m of long with outboard Yamaha engines of 40 hp. The species identification was made by the first author and pelage patterns were also used to identify the seal across the summer/fall months based on the review on several photographys.

Results

A solitary leopard seals was sighted in six occasions in Ballena Sound at 53°41’S, 72°37’W (see Fig. 1) in 15 subsequent visits made from 20 November 2011 to 27 May 2012. Weather conditions at the time of each sighting were optimal with a swell of 0,2-0,5m and a wind speed less of 10 kn.

The first sighting was made 09:19 AM at 5th January. A solitary leopard seal was seen and photographed resting on a flat rocky platform close to the water (Fig. 2). During the approach with the inflatable boat to the rocky platform, the seal no showed avoidance behavior to human presence. In February 25, a leopard seal was sighted swimming between the ice float near the glacier of Ballena Sound at 10:40 AM. At that time the seal also approached slowly to the inflatable boat for several minutes, shows it head and neck above the sea surface. An hour after the seal was seen resting on the same flat rocky platform previously referred above. On March, five subsequent visits were made to Ballena Sound but not leopard seal was sighted. On April 8th again a leopard seal was seen (10:23 AM) swimming between the ice float near the glacier of Ballena Sound and also was inquisitive swimming very close along and under to the inflatable boat and the leopar seal shows head above the sea surface again. In May another three sightings of a single leopard seal were made on 1st, 22th and 27 th. In the first time the leopard seal was seen resting on the same flat rocky platform previously mentioned and the second sighting the seal was swimming near the flat rocky platform. In the last sightings a leopard seal was seen swimming near a sill of 2 m depth at Ballena Sound. In all cases the seal no showed avoidance behavior to the inflatable boat.

Based on the review on photography’s taken in the six sightings, the leopard seal was identified as the same individual by the presence of a distinctive open circle located on the left side of the lower jaw (see Fig. 2). This individual, a male, was seen in excellent physical conditions and body length was estimated to be 3.0m. No other individuals were observed simultaneously in the area.

Discussion

The movements of leopard seals are difficult to study because of their solitary nature (Borsa 1990). However, a number of leopard seals are thought to displace north from the pack-ice to the sub-Antarctic Islands (ex. Gwynn 1953, Rounsevell & Eberhard 1980; Bester & Roux 1986) or venture even farther north (ex. Rounsevell & Pemberton 1994, Horning & Fenwick 1978, Best 1971). Nevertheless, small numbers of all ages are observed throughout the year at Kerguelen (Bester & Roux 1986, Borsa 1990) and Heard (Gwynn 1953, Brown 1957) Islands, and seasonally on other locations such as Macquarie (Gwynn 1953, Rounsevell & Eberhard 1980) and Bird (Walker et al. 1998, Jessopp et al. 2004, Forcada & Robinson 2006) Islands.

Presence of leopard seals in Chile has been reported mainly to south of 40°S, especially at Parry fjord and D´Agostini Sound, being the oldest record of 1927, meanwhile the first multiple sightings was documented in 1971 (Aguayo-Lobo et al. 2011). The presence of leopard seal at Ballena Sound is occasional with only three sightings documented between 1927 y 2011 (Aguayo-Lobo et al. 2011). Moreover, the authors report the presence in the Fueguian channels of both males and females of all ages (adults and juveniles) and in good condition from summer to spring, suggesting that leopard seals remain year-round. However, the data are limited to solve if these individuals derived from to constant migration from the Antarctic, considering the close proximity of the Fueguian channels area with the Antarctic continent (508 nm) in relation to another continents, or it represent a potential Sub-antarctic population that delayed or suspended their migration to the Antarctic.

All available evidence points to that the leopard seal is primarily an animal of the Antarctic pack-ice (Hamilton 1939, Gwynn 1953). However, the most interesting point which emerges is the evidence on the northward migration of a part of the population outer antarctic and sub-antarctic islands during the winter (Hamilton 1939, Gwynn 1953) that has been attributed to the northward extension of the pack ice during winter (Bonner & Laws 1964, Rounsevell & Eberhard 1980, Bester & Roux 1986, Bester et al. 1995, Jessopp et al. 2004), and then return back towards the Antarctic continent during austral spring (Brown 1957, Erickson et al. 1971, Siniff & Stone 1985) remaining largely within this outer fringe as the pack ice retreats during the austral spring and summer (Bester et al. 1995). Additionally most of the evidence of this northward migration suggests a preponderance of immature animals (Siniff & Stone 1985, Bester et al. 2006) to travel farthest although few older seals also appear to wander so far, but it also is evidence that a large proportion of the adult population never leaves the Antarctic pack-ice (Gwynn 1953, Rogers et al. 2005, Nordøy & Blix 2009).

Although it is not possible to rule out that northward winter dispersion

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