DIVING BEHAVIOR AND FORAGING LOCATION OF FEMALE SOUTHERN ELEPHANT SEALS FROM PATAGONIA

Our aim was to describe the free-ranging diving pattern and to determi ne the location of foraging of pregnant female southern elephant seals , Mirounga leonina, from Peninsula Valdes, Argentina, This colony is u nusual in two respects: it is removed from deep water by a broad shall ow shelf (345-630 km wide), and colony numbers have been increasing in recent years in contrast to numbers from other southern hemisphere co lonies that are stable or in decline. Microprocessor controlled, geolo cation-time-depth recorders were deployed on four females, recording a total of 15,836 dives (270 dive days) during the period February to A pril, 1992. Departing seals crossed the continental shelf quickly (54. 5-62.1 h) and did not show signs of foraging until reaching deep water , due east of the colony in the South Atlantic Ocean. Diving was virtu ally continuous (93% of the time underwater) with overall mean (+/-S.D .) rates of 2.5 +/- 0.2 dives/h, mean dive durations of 22.8 +/- 7.1 m in (maximum dive duration = 79 min) with 1.6 +/- 0.6 min surface inter vals between dives, and dive depths of 431 +/- 193 m (maximum dive dep th = 1,072 m). The diving pattern of females from Patagonia is similar to that of seals from colonies where numbers are decreasing (Macquari e stock) or are stable (South Georgia Island). Our subjects did not, h owever, feed in or south of the Antarctic Polar Front, or in cold wate rs along the Antarctic coast, where seals from declining or stable col onies forage.