Maternal attendance behaviour of sympatrically breeding Antarctic and subantarctic fur seals, Arctocephalus spp., at Macquarie Island

Maternal attendance behaviour was studied in Antarctic (Arctocephalus gazel la) and subantarctic fur seals (Arctocephalus tropicalis) which breed sympa trically at subantarctic Macquarie Island. Data on attendance were obtained using telemetric methods. Both species undertook two types of foraging tri ps: overnight foraging trips which were of less than 1 day duration and occ urred exclusively overnight, and extended foraging trips which lasted longe r than 1 day. The mean duration of overnight foraging trips was 0.43 and 0. 39 days, while the duration of extended foraging trips was 3.6 and 3.8 days in A. gazella and A. tropicalis, respectively. The duration of overnight a nd extended foraging trips did not differ significantly between species. Tw o types of shore attendance bouts that differed in duration were also obser ved in these species. Short attendance bouts lasted less than 0.9 days, whi le long attendance bouts lasted longer than 0.9 days. Short attendance bout s lasted 0.4 and 0.5 days, while long attendance bouts lasted 1.6 and 1.7 d ays in A. gazella and A. tropicalis, respectively, and did not differ signi ficantly between species. The most significant differences between the atte ndance behaviour of both species was in the percentage of foraging time all ocated to overnight foraging trips (15% and 25% in A. gazella and A. tropic alis, respectively), and the percentage of time spent ashore (30% and 38% i n A. gazella and A. tropicalis, respectively). The nearness of pelagic wate rs to Macquarie Island is considered to be the main reason that lactating f emales are able to undertake overnight foraging trips. These trips may be u sed by females as a means of optimising the costs of fasting and nursing as hore. Females may be able to save energy by only nursing pups when milk tra nsfer efficiencies are high, and reduce the time and energy costs of fastin g ashore when milk transfer efficiency is low. Of the female A. gazella tha t still carried transmitters at the end of lactation, 83% continued regular attendance for between 21 and 150 days post-lactation (when data collectio n ceased). Overwintering of A. gazella females at breeding sites has not be en previously reported in other populations.