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Subantarctic Fur Seals Arctocephalus tropicalis at Heard Island. S.D. Goldsworthy* ... the Antarctic Convergence; Prince Edward Islands, Iles. * Current address: ...
Polar Biol (1989) 9:337-339

© Springer-Verlag 1989

Short Note Subantarctic Fur Seals Arctocephalus tropicalis at Heard Island S.D. Goldsworthy* and P.D. Shaughnessy CSIRO Division of Wildlife and Ecology, P.O. Box 84, Lyneham, ACT 2602, Australia Received 18 August 1988; accepted 5 January 1989

Introduction Both the Antarctic fur seal Arctocephalus gazella and the Subantarctic fur seal A. tropicalis breed in the Southern Ocean (Fig. 1). The former species breeds on islands south of the Antarctic Convergence and immediately north of it, the latter on islands north of the Convergence (Bonner 1981). To date, sympatric breeding of the two species has been reported from three localities north of the Antarctic Convergence; Prince Edward Islands, Iles * Current address: Department of Botany and Zoology, Monash University, Clayton, Victoria 3168, Australia

Crozet and Macquarie Island in the South Indian Ocean (Kerley 1983; Jouventin et al. 1982; Shaughnessy et al. 1988b). There is evidence for hybridisation at Marion Island and Macquarie Island. At Heard Island (south of the Convergence at 53 10 S, 73 30 E) the Antarctic fur seal is increasing in numbers and is perhaps recovering from past exploitation (Shaughnessy et al. 1988a). In this note we report sightings of the Subantarctic fur seal at Heard Island in the 1987/1988 summer during an Australian National Antarctic Research Expedition (ANARE) to the Island. In addition, Heard Island is added to the localities where fur seal species breed sympatrically.

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Scale Fig. 1. Breeding localities of Antarctic fur seals and Subantarctic fur seals

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Fig, 2. Map of Heard Island showing places where Subantarctic fur seals were sighted

Methods Censuses, searches for tags and other observations of Antarctic fur seals were conducted at Heard Island by Goldsworthy and other expeditioners between 18 October 1987 and i March 1988. Opportunity was taken to search for Subantarctic fur seals at the eastern end of the Island (Fig. 2). Characteristics used to distinguish between A. gazella and A. tropicalis have been described by Condy (1978) and Shaughnessy et al. (1988b). Briefly, A. tropicalis pups have a uniform black natal coat, whereas A. gazella pups have a grizzled pelage and a paler muzzle. Among adult females (cows) A. tropicalis have a shorter, broader nose and a deeper pup attraction call than A. gazella.

Results and Discussion

In addition to the characteristics noted above for distinguishing between the two species of fur seal, several others were utilised. It was noted that A. tropicalis cows have shorter, stouter necks than A. gazella cows, and creamy yellow chests. Adult and subadult male A. tropicalis were recognized by their creamy yellow chest and face and by their dorsal pelage, which appeared to be darker than in A. gazella possibly from the contrast in coloration between the dorsal and ventral pelage. Large male A. tropicalis also have a dark crest on the top of their head. Juveniles of both species were recognised by their small size and adult type pelage. Those of A. tropicalis could be distinguished from A. gazella juveniles on the basis of combinations of the above characteristics, particularly the shorter nose and neck, and the darker back (which tends to be chocolate brown in A. tropicalis and silver grey in A. gazella). Thirteen sightings of Subantarctic fur seals were made, plus a cow and its pup (Fig. 3) which were seen repeatedly at Skua Beach (Table 1). The male pup weighed 7.1 kg on 7 January and 8.7 kg on 21 January. It was tagged in the trailing edge of each fore flipper with blue Dalton Super-flexi tags (069 right 070 left). The cow and pup were within the territory of an adult male (bull) A. gazella which also contained an A. gazella

cow with its pup. The bull appeared to be equally attentive to both females. This situation with territories containing both A. gazella and A. tropicalis has also been reported at Macquarie and Crozet Islands, whereas at Marion Island the two species were observed to breed separately (Shaughnessy et al. 1988b; Jouventin et al. 1982; Kerley 1983). The territory was 20 m inland of the landward edge of the beach on Azorella selago and Poa cookii vegetation, and 80 m from the nearest fur seal territory. This is an unusual habitat for A. tropicalis which hauls out on rocky shores to breed at Amsterdam, Gough and Marion Islands (Paulian 1964; Bester 1982; Condy 1978). Two of the Subantarctic fur seals had been tagged on Marion Island (Bester, in preparation). The subadult male (RSAF 3262) was tagged at Outcrop Beach as a

Fig. 3. Adult female Subantarctic fur seal with pup at Skua Beach, Heard Island, December 1987

339 Table 1. Sightings of Subantarctic fur seals at Heard Island, 1987/1988 summer Date

Age-class

Location

Comment

10 Dec 8 7 25 Feb 88 19 Dec 87

Cow with pup

Skua Beach

Subadult male

Fairchild Beach

Observed repeatedly Bearing tag RSAF 3262

25 25 31 15

88 88 88 88

2 subadult males Juvenile Cow Juvenile female

Fairchild Beach Spit Bay Doppler Hill Skua Beach

88 88 88 88 Feb 88

2 juveniles 2 juveniles Juvenile Subadult male Juvenile female

Fairchild Beach Spit Bay Doppler Hill Skua Beach Spit Bay

Jan Jan Jan Feb

15 Feb 16 Feb 16 Feb 25 Feb 2 6 - 27

Bearing tag RSAF 5865

black pup on 7 February 1984 and the juvenile female (RSAF 5865) was tagged at Mixed Pickle Cove as a black pup on 29 January 1985 (Bester, in preparation). These observations provide the first record of the Subantarctic fur seal at Heard Island, and the first pupping record from south o f the Antarctic Convergence. Breeding populations of this species have been increasing this century at Amsterdam, Crozet, Prince Edward and Gough Islands (Hes and Roux 1983; Jouventin et al. 1982; Condy 1978; Bester 1980). A recently established breeding population has been noted at Macquarie Island (Shaughnessy 1988 b), and the species has also been sighted at South Georgia, southern Africa and south-western Australia (Payne 1979; Shaughnessy and Ross 1980; Gales, in preparation). In view of the population increases of Subantarctic fur seals, sightings at other localities can be expected. More importantly, the potential establishment of breeding populations, such as at Heard Island should be monitored. Acknowledgements. We thank the Director, Australian Antarctic Division, for making facilities at Heard Island available, the Station Leader at Heard Island (H.R. Burton) for supporting the project and members

of the 1987/1988 ANARE who assisted with observations. We also thank M.N. Bester, H.R. Burton, J.E. King, R. Kirkwood and G.L. Shaughnessy for comments on the manuscript.

References

Bester MN (1980) Population increase in the Amsterdam Island fur seal Arctocephalus tropicalis at Gough Island. SAJ Zool 15:229-234 Bester MN (1982) Distribution, habitat selection and colony types of the Amsterdam Island fur seal Arctocephalus tropicalis at Gough Island. J Zool, London 196:217-231 Bester MN (in preparation) Movement of southern elephant seals and Subantarctic fur seals in relation to Marion Island Bonner WN (1981) Southern fur seals Arctocephalus (Geoffroy SaintHilaire and Cuvier, 1826). In" Ridgway SH, Harrison RJ (eds) Handbook of marine mammals, vol 1. Academic Press, London, pp 161-208 Condy PR (1978) Distribution, abundance, and annual cycle of fur seals (Arctocephalus spp.) on the Prince Edward Islands. SAJ Wildl Res 8:159-168 Gales NJ (in preparation) Records of Subantarctic fur seals Arctocephalus tropicalis in Australia Hes AD, Roux J-P (1983) Population increase in the sub-Antarctic fur seal Arctocephalus tropicalis at Amsterdam Island. SAJ Antarct Res 13:29- 34 Jouventin P, Stahl JC, Weimerskirch H (1982) La recolonisation des Iles Crozet par les otaries (Arctocephalus tropicalis et A. gazella). Mammalia 46:505-514 Kerley GIH (1983) Relative population sizes and trends, and hybridization of fur seals Arctocephalus tropicalis and A. gazella at the Prince Edward Islands, Southern Ocean. SAJ Zool 18:388-392 Paulian P (1964) Contribution a l'etude de l'otaire de File Amsterdam. Mammalia [Suppl] 28:146 Payne MR (1979) Fur seals Arctocephalus tropicalis and A. gazella crossing the Antarctic Convergence at South Georgia. Mammalia 43:93-98 Shaughnessy PD, Ross GJB (1980) Records of the Subantarctic fur seal (Arctocephalus tropicalis) from South Africa with notes on its biology and some observations of captive animals. Ann S Afr Mus 82:71-89 Shaughnessy PD, Shaughnessy GL, Keage PL (1988a) Fur seals at Heard Island - recovery from past expoitation? In: Augee ML (ed) Marine mammals of Australasia - field biology and captive management. Royal Zool Soc NSW, Sydney, pp 71-77 Shaughnessy PD, Shaughnessy GL, Fletcher L (1988b) Recovery of the fur seal population at Macquarie Island. Pap Proc Soc Tasmania 122:177-187