SUMMER FORAGING BY LACTATING FEMALE NEW-ZEALAND FUR SEALS (ARCTOCEPHALUS-FORSTERI) OFF OTAGO PENINSULA, NEW-ZEALAND

The behaviour of female New Zealand fur seals (Arctocephalus forsteri) at sea and on land at the rookery of Fuchsia Gully, Otago Peninsula, New Zealand (45 degrees 52'S, 170 degrees 44'E), was examined during t he early stages of lactation in the 1993-1994 breeding season. The att endance patterns of 19 females were investigated using daily observati on at the rookery. Trips to sea to forage ranged from 3.4 h up to 8 da ys (mean 3.26 +/- 1.1 days), and attendance periods at the rookery ran ged from 1 to 13 days (mean 3.09 +/- 1.63 days). At sea, the behaviour of four females was examined by deploying time-depth recorders. Femal es showed a nocturnal pattern of diving, 88.8-97.3% of dives being mad e during the hours of darkness. For all females and each night of fora ging, the deepest dives were completed around dawn and dusk. The deepe st dive recorded was 163 m and all females dove over 100 m deep on at least one dive. The overall median dive depth was considerably less th an this, as around 24:00-03:00, females undertook many shallow dives, and during this time the median dive depth ranged from 5 to 10 m for t he four females. Dives occurred in bouts, but bout duration varied sig nificantly with time of day. Bouts were short during the day and longe r at night, 55% of night bouts lasting throughout the night. Maximum d ive durations ranged from 3.17 to 6.17 min and mean dive durations fro m 0.67 to 1.18 min for individual females. Dive depth was significantl y related to dive duration for all four females. Two of the females al so carried satellite transmitters, and at sea location was determined on three separate nights of foraging. Females were found to be foragin g up to 78 lan from the rookery, but always over the continental shelf (in water shallower than the 200 m depth contour).