Long-term diving records of an adult female northern elephant seal

Abstract

Seventy-three days long diving record of an adult female northern elephant seal (Mirounga angustirostris) was obtained using the long-term time depth recorder which was developed for Antarctic seal research by the National Institute of Polar Research, Tokyo. It was observed that the female northern elephant seal dived to a great depth continuously for a long period. It dived 5024 times during 73 days, 2.9 times per hour on the average. The mean dive depth and duration were 463.9±147m and 17.1±3.4min, the maximum values being 934m and 33.5min. The dive depth increased gradually on the first 4 days. After that, it fluctuated diurnally, while the dive duration remained rather stable. Following the extended surface intervals (ESIs : defined as surface intervals longer than 10min) dives were shallow but the depth increased gradually.