Behavior of gray whales summering near St. Lawrence Island, Bering Sea

The behavior of gray whales was studied near St. Lawrence Island, Alaska, in July and September 1982. Most behavior involved apparent benthic feeding, as evidenced by mud plumes around surfacing whales and kittiwakes landing near whales at the surface. There was little socializing by whales in July, but more in late September. Numbers of blows per surfacing, durations of surfacings, and durations of dives were all correlated. Percent of time at the surface was about 21% in July and 23% in September. There were fewer blows per surfacing, shorter surface times, and shorter dive times when whales were not feeding than when they were feeding. Intervals between successive blows were longer in nonfeeding whales; however, the blow rate (number of blows per minute) did not differ between feeding and nonfeeding whales. Number of blows per surfacing and duration of surfacing increased with increasing water depth (from < 20 to 80 m). Dive duration did not change appreciably with depth in July, but did so in September. Blow rates by feeding whales increased in deeper water, indicating the need for whales to respire more as depth of dives increased. Time of day affected surfacing–dive–respiration characteristics differently in different months. Whales fed more from 1800 to 2100 local Bering Sea time than at other times of day. During an average surfacing, feeding whales moved about 50 m; during a dive, their net horizontal movements were 90–100 m. Speed averaged around 2 km/h and was twice as fast at the surface (3.4 km/h) as compared with net underwater speed (1.7 km/h).