ARGOS Tracking Data of Fur Seals from Macquarie Island in 1997-1999
The populations of fur seals on Australia's two subantarctic islands were exterminated by uncontrolled sealing in the 19th century. Only in the latter half of the 20th century have populations commenced recovering. This project provides key information on the status and trends of recovering fur seal populations in the Southern Ocean, including information on the distribution of foraging effort, food and energy requirements, oceanographic determinants of demographic performance, ecological interactions with commercial fisheries, the extent, trends, processes and implications of hybridisation at Macquarie Island, and the status and trends in numbers of the threatened subantarctic fur seal.
This dataset represents ARGOS tracking data of fur seals from Macquarie Island during 1997-1999. The tracking data are comprised of 28 data profiles.
Taken from the abstract of the referenced paper:
Antarctic Arctocephalus gazella and subantarctic Arctocephalus tropicalis fur seals breed sympatrically at Macquarie Island. The two species have different lactation strategies, the former rearing its pup in 4 months and the latter taking 10 months. The diet and at-sea foraging behaviour of these sympatric species was compared during the austral summer period when their pup rearing period overlapped. The prey of the two fur seal species was very similar, with fish dominating the diet. Themyctophid, Electrona subaspera, was the main prey item (93.9%) in all months of the study. There were no major differences in the diving behaviour between species. Both species foraged north of the island parallel to the Macquarie Ridge. Foraging activity was concentrated at two sites: (i) within 30 km north of the island; and (ii) at 60 km north. Most locations for overnight foraging trips were within 10 km of the colonies. The different lactation strategies of A. gazella and A. tropicalis allowed for flexibility in foraging behaviour. At Macquarie Island, the local marine environmental conditions have resulted in similar foraging behaviour for both species.
Energetics of Lactation and Foraging in Antarctic and Subantarctic Fur Seals at Macquarie Island
Metadata record for data from ASAC Project 100
See the link below for public details on this project.
From the abstract of one of the referenced papers:
Between November 1988 and March 1989, scats were collected from three species of fur seals (Arctocephalus forsteri, A. gazella and A. tropicalis) at the northern end of Macquarie Island and from A. forsteri between January and March 1989 at the southern end. All fed mainly on fish. For A. gazella/A. tropicalis an average of 99.2% of scats in monthly collections contained fish remains, while for A. forsteri the figure for North Head was 100% and for Hurd Point was 94.9%. Arctocephalus forsteri at Hurd Point took less fish and more penguins than at North Head and there were significant differences in the composiiton of the fish diet in two of three months. At North Head, the fish diet of A. gazella/A. tropicalis differed significantly from that of A. forsteri in three of the five months studied. Food resources for fur seals around Macquarie Island are considered to be less available than they are around Heard Island.
Maternal Attendance and Pup Growth in Fur Seals (Arctocephalus spp.) at Macquarie and Heard Islands
Taken from the abstract of the referenced papers:
Maternal attendance behaviour was studies in Antarctic (Arctocephalus gazella) and subantarctic fur seals (Arctocephalus tropicalis) which breed sympatrically at subantarctic Macquarie Island. Data on attendance were obtained using telemetric methods. Both species undertook two types of foraging trips: overnight foraging tips which were of less than 1 day duration and occurred exclusively overnight, and extended foraging trips which lasted longer 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 and extended foraging trips did not differ significantly between species. Two types of shore attendance bouts that differed in duration were also observed in these species. Short attendance bouts lasted less than 0.9 days, while long attendance bouts lasted longer than 0.9 days. Short attendance bouts lasted 0.4 and 0.5 days, while long attendance bouts lasted 1.6 and 1.7 days in A. gazella and A. tropicalis, respectively, and did not differ significantly between species. The most significant differences between the attendance behaviour of both species was in the percentage of foraging time allocated to overnight foraging trips (15% and 25% in A. gazella and A. tropicalis, respectively), and the percentage of time spent ashore (30% and 38% in A. gazella and A. tropicalis, respectively). The nearness of pelagic waters to Macquarie Island is considered to be the main reason that lactating females are able to undertake overnight foraging trips. These trips may be used by females as a means of optimising the costs of fasting and nursing ashore. Females may be able to save energy by only nursing pups when milk transfer efficiencies are high, and reduce the time and energy costs of fasting ashore when milk transfer efficiency is low. Of the female A. gazella that still carried transmitters at the end of lactation, 83% continued regular attendance for between 21 and 150 days post-lactation (when data collection ceased). Overwintering of A. gazella females at breeding sites has not been previously reported in other populations.
Breeding colonies of the Antarctic fur seal Arctocephalus gazella on Heard Island (53.18S, 73.5E) are situated on the sheltered northern and eastern coasts on flat vegetated terrain near streams and pools. Pupping in the 1987/88 summer began on 21 November, with 90% of births in 26 d. The median birth date was 11 December. Pup counts at Heard Island made in seven breeding seasons from 1962/63 to 1987/88 show an exponential rate of increase of 21%, which may be inflated due to undercounting in early years. The total of 248 births in 1987/88 represents an exponential increase of 37% since the previous year, but pups may have been undercounted then. Based on the number of pups born, the breeding population is estimated at 870-1,120. During the breeding season, the largest number of animals ashore was 835. Many non-breeding fur seals began hauling out from early January and 15,000 animals were estimated to be ashore by late February, a far larger number than expected from the size of the breeding population. Both the breeding and non-breeding components of the population may be augmented by immigration. The source of immigrants may be undiscovered breeding colonies of this species in the northwestern sector of the Kerguelen Archipelago or the concentration at South Georgia. Further censuses are required at Heard Island to monitor the population growth.