TIME BUDGETS AND FORAGING CHARACTERISTICS OF LACTATING ANTARCTIC FUR SEALS

(1) We investigated time allocation to parental care ashore and foraging at sea by lactating Antarctic fur seals at Bird Island, South Georgia, during 1988-89 and 1989-90 and related this to foraging behaviour measured in terms of diving performance at sea and growth of pups. (2) The mean duration of foraging trips was 121 h and 100 h in 1988-89 and 1989-90, respectively, while periods ashore were 55 h and 45 h, respectively in the two years. There was a significant difference between these variables in the two years but there was no significant difference in the percentage of time spent at sea. In both years, there was significant variation between individuals in the foraging-attendance time budget. (3) There was a positive correlation between mean time spent ashore and mean time spent at sea for individual seals. The foraging-attendance patterns of seals changed significantly with time through lactation in one year of the study but not in the other. There was no effect of maternal age or size on foraging-attendance time budget. Duration of foraging trips or the period spent ashore had no effect on pup growth rate. (4) During short foraging trips (1-2 d) seals dived for a greater proportion of the time available for foraging than during longer foraging trips (> 3 d). Seals fed predominantly on krill during both years. Most foraging occurred at night and this was reflected in diel variation in times of arrival and departure of seals from the pupping colony. Based on estimated swimming speed and travel times to and from Bird Island, it was estimated that seals were normally feeding between 60 and 90 km from Bird Island.