Vagrant Subantarctic fur seals at Bouvetøya G.J.G. Hofmeyr*, M.N. Bester & S.P. Kirkman Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, 0002 South Africa Received 25 February 2005. Accepted 26 July 2005
Three vagrant Subantarctic fur seals, Arctocephalus tropicalis, were seen amongst a colony of Antarctic fur seals, A. gazella, at the isolated subantarctic island, Bouvetøya. Possible sources of the vagrants are populations at either Gough Island or the Prince Edward Islands Archipelago. Key words: Arctocephalus tropicalis, Bouvetøya, vagrants, subantarctic.
hree sightings of Subantarctic fur seals, Arctocephalus tropicalis, were recorded at Bouvetøya (54°25’S, 3°20’E), an isolated island in the South Atlantic Ocean. The first was a subadult male that was seen on 19 January 1997 on a narrow beach just to the north of the coastal platform Nyrøysa (O.A.W. Huyser, pers. comm.). It fled into the sea when disturbed and was not seen again. The second animal was a large adult male seen on the northern section of Nyrøysa between 9 and 12 February 1997. It was not wary of human observers and showed territorial behaviour, with appropriate calls (St Clair-Hill et al. 2001), at two different locations. The third sighting was of an adult male seen on 10, 11 and 14 February 1999. This animal was also not wary of observers and showed territorial behaviour. It was found very close to where the adult male was seen two years previously. While it was possibly the same animal, the colouring of the coat was different. All three animals appeared to be healthy. No other Subantarctic fur seals were seen over the course of four visits to Bouvetøya in the 1996/97, 1998/99, 2000/01 and 2001/02 summers, each approximately three months in duration. During this time extensive fieldwork took place at the rookery on Nyrøysa, ensuring that most parts were visited or observed regularly. Bouvetøya is home to the second largest population of Antarctic fur seals A. gazella (Boyd 1993, Hofmeyr et al. 2005). The great majority of an annual pup production of some 15 000 takes place on the coastal platform of Nyrøysa (Hofmeyr et al. 2005). Subantarctic fur seals have not previously been recorded at Bouvetøya. While early
T
*Author for correspondence. E-mail:
[email protected]
publications referred to the species of the fur seal population present on Bouvetøya as A. tropicalis (Muller et al. 1967) or A. tropicalis gazella (Holdgate et al. 1968), this was prior to the two species being recognized as separate (Repenning et al. 1971). Fevolden & Somme (1977) erroneously referred to Bouvetøya fur seals as A. tropicalis, possibly based on previous literature. The closest population of Subantarctic fur seals to Bouvetøya is at Gough Island (40°20’S, 9°54’W), some 1750 km to the northwest. This is the largest breeding population of this species, with a pup production in excess of 50 000 (Bester 1987, 1990). The second largest breeding population, with a pup production of approximately 30 000 (Bester et al. 2003; Hofmeyr et al., in press), is at the Prince Edward Islands Archipelago (PEIA), approximately 2700 km to the east. While either of these populations could be a source of the vagrants recorded at Bouvetøya, seals from Gough Island would only have had to swim across the Antarctic Circumpolar Current to reach this destination, whereas seals from the PEIA would have had to swim against this current. The second alternative is by no means unrealistic, considering that a Subantarctic fur seal tagged at the PEIA was sighted on the coast of South Africa (Bester 1989). This individual would have had to swim against the Agulhas Return Current to reach this destination directly. These observations were recorded during a study financed by the Norwegian Polar Institute and NORAD. Further support was provided by the Mammal Research Institute of the University of Pretoria and the Percy Fitzpatrick Institute of African Ornithology of the University of Cape Town. We thank Kit Kovacs, Christian Lydersen and Ian Gjertz for their administrative contributions to the fur seal work at Bouvetøya. We are grateful to Kjell Isaksen for his assistance and Onno Huyser of the Percy Fitzpatrick Institute of African Ornithology, University of Cape Town, for permission to quote observations on vagrant Subantarctic fur seals. We are also grateful to two anonymous referees for their comments. REFERENCES BESTER, M.N. 1987. Subantarctic fur seal Arctocephalus
African Zoology 41(1): 145–146 (April 2006)
146
African Zoology Vol. 41, No. 1, April 2006
tropicalis at Gough Island (Tristan da Cunha Group). In: Status, Biology and Ecology of Fur Seals, (eds) J.P. Croxall & R.L. Gentry. NOAA Technical Report NMFS 51: 57–60. BESTER, M.N. 1989. Movements of southern elephant seals and Subantarctic fur seals in relation to Marion Island. Marine Mammal Science. 5: 257–265. BESTER, M.N. 1990. Population trends of Subantarctic fur seals and southern elephant seals at Gough Island. South African Journal of Antarctic Research 20: 9–12. BESTER, M.N., RYAN, P.G. & DYER, B.M. 2003. Population numbers of fur seals at Prince Edward Island, Southern Ocean. African Journal of Marine Science 25: 549–554. BOYD, I.L. 1993. Pup production and distribution of breeding Antarctic fur seals (Arctocephalus gazella) at South Georgia. Antarctic Science 5: 17–24 FEVOLDEN, S. & SOMME, L. 1977. Observations on birds and seals at Bouvetøya. Norsk Polarinstitutt Årbok 1976: 367–371. HOFMEYR, G.J.G., KRAFFT, B.A., KIRKMAN, S.P., BESTER, M.N., LYDERSEN, C., KOVACS, K.M. (2005)
Population changes of Antarctic fur seals at Nyrøysa, Bouvetøya. Polar Biology 28: 725–731. HOFMEYR, G.J.G., BESTER, M.N., MAKHADO, A.B. & PISTORIUS, P.A. (In press) Population change of Subantarctic and Antarctic fur seals at Marion Island. South African Journal of Wildlife Research. HOLDGATE, M.W., TILBROOK, P.J. & VAUGHAN, R.W. 1968. The biology of Bouvetøya. British Antarctic Survey Bulletin 15: 1–7. MULLER, D.B., SCHOEMAN, F.R. & VAN ZINDERENBAKKER, E.M. 1967. Some notes on a biological reconnaissance of Bouvetøya (Antarctic). South African Journal of Science 63: 260–263. REPENNING, G.A., PETERSON, R.S. & HUBBS, C.L. 1971. Contributions to the systematics of southern fur seals, with particular reference to the Juan Fernandez and Guadaloupe species. Antarctic Research Series 18: 1–34. ST CLAIR-HILL, M., FERGUSON, J.W.H., BESTER, M.N. & KERLEY, G.I.H. 2001. Preliminary comparison of calls of the hybridizing fur seals, Arctocephalus tropicalis and A. gazella. African Zoology 36: 45–53.
