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 popu- lations at either Gough Island or the Prince Edward Islands Archipelago. Key words: Arctocephalus tropicalis, Bouvetøya, vagrants, subantarctic. T hree sightings of Subantarctic fur seals, Arcto- cephalus 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 appropri- ate 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 terri- torial behaviour. It was found very close to where the adult male was seen two years previously. While it was possibly the same animal, the colour- ing 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 popula- tion 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 previ- ously been recorded at Bouvetøya. While early 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), approxi- mately 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 destina- tion 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 Uni- versity of Cape Town. We thank Kit Kovacs, Christian Lydersen and Ian Gjertz for their administrative contri- butions 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, Uni- versity of Cape Town, for permission to quote observa- tions 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) *Author for correspondence. E-mail: ghofmeyr@zoology.up.ac.za