Surfacing times and dive rates for narwhals (Monodon monoceros) and belugas (Delphinapterus leucas)

Time spent at and near the sea surface was measured for 25 narwhals, Monodo n monoceros, and 39 belugas or white whales, Delphinapterus leucas, in West Greenland and Canada from 1993 through 1999, using satellite-linked data r ecorders. Narwhals spent less time at the surface than belugas did, and the surfacing time of belugas also varied between localities. No clear differe nces in surfacing time were associated with the time of day, but belugas te nded to make more dives during the night than during the day. Despite large variability in surfacing behaviour among individual whales, time spent at the surface by both species declined from August through November. The few data collected from narwhals from November to February indicate that surfac ing times remained low during this period although more than 25% of each 6 h period was spent at the surface. Whales made between 2 and 20 dives per h our. and narwhals made significantly fewer dives than did belugas, for whic h number of dives varied with locality. The number of dives deeper than 8 i n declined substantially during the autumn for belugas and narwhals that we re moving offshore. When travelling, the whales apparently made fewer dives than at other times.