FISHERY BULLETIN: VOL. 88. NO. 3 



ly marked group of two adults and a caLf, almost cer- 

 tainly the same whales, on 20 August at lat. 70°07'N, 

 long. 131°30'W, which is about 85 km from the place 

 they had been seen 2 wk earlier. This observation 

 suggests that some groups of bowheads are main- 

 tained for at least a few weeks. The observation also 

 suggests that females with calves may sometimes be 

 accompanied by escorts, as has been observed for 

 wintering humpback whales (Herman and Antinoja 

 1977). 



Feeding 



Feeding appeared to occupy much of the time of 

 the bowheads that we observed, but we had to rely 

 on indirect clues, such as observations of swimming 

 with open mouth, mud streaming from the mouth, or 

 presence of feces in the water, to indicate that 

 feeding had taken place. The four possible types of 

 feeding behavior that we identified were 1) water- 

 column feeding; 2) near-bottom feeding; 3) skim 

 feeding; and 4) mud tracking. Of these, the first 

 three rather clearly represented feeding, whereas 

 the function of the last was less certain. As noted 

 above, underwater blowing showed some association 

 with feeding, but the connection was uncertain. 



In 1980, certain feeding behaviors occurred in par- 

 ticular areas: only water-column feeding was seen 

 near the Issungnak artificial island site (Fig. 1), 

 whereas only skim-feeding was seen off the Tukto- 

 yaktuk Peninsula near McKinley Bay. In 1981, there 

 was less evidence for feeding, although we suspect 

 that most feeding occurred in the water column. In 

 1982, when whales dove for long periods (up to 30 

 min), we su.spected water-column feeding to be 

 occurring at almost all times. 



Water-Column Feeding 



Water-column feeding could not be observed 

 directly. Whales were scored as feeding in the water 

 column when they dove for long periods, and when, 

 between long dives, there was much defecation and 

 only slow forward motion. Defecation is simply an in- 

 dication of prior feeding. However, particular 

 behaviors such as a series of long dives usually con- 

 tinued for many hours, so occurrence of defecations 

 between long dives was considered indicative of on- 

 going feeding in the water column. 



The frequency of apparent water-column feeding 

 was not constant. In 1980, we saw bowheads water- 

 column feeding from 3 to 22 August. Thereafter, few 

 whales were present in the area where we had ob- 

 served this behavior, and whales seen elsewhere did 



not seem to feed in the water column. In 1981, when 

 we saw less defecation, we only scored as water- 

 column feeding some adult whales that dove for pro- 

 longed periods on 24 August, while calves remained 

 at the surface. In 1982, most whales made long 

 dives. These whales probably were feeding in the 

 water column, even though we saw little defecation 

 at the surface. Feeding below the surface may have 

 occurred during many other dives besides those that 

 we classified as dives with water-column feeding. 



Observations on 3 August 1980 typify water- 

 column feeding behavior. On this date, bowheads 

 were north of Kugmallit Bay where water depth was 

 18-38 m. The surface water was turbid, brackish 

 water from the Mackenzie River, but beneath this 

 surface layer, there was a second layer of clearer, 

 saline Beaufort Sea water (Griffiths and Buchanan'^). 

 The whales occurred in groups of 2-10 animals, and 

 occasionally as individuals without others nearby. 

 Group members showed a high degree of synchrony, 

 often surfacing very close together and remaining 

 close at least until they dived again. Not only did the 

 members of a group surface and dive synchronously, 

 but various groups spread over an area several 

 kilometers in diameter all tended to be at the surface 

 or beneath it at the same time. 



While the animals were at the surface, they moved 

 slowly forward while taking a series of breaths. As 

 each individual dived, it raised its tail clear of the 

 water, and disappeared from view in the turbid 

 water. Thus, these dives must have taken the whales 

 well below the surface. When the whales were at the 

 surface, they often disturbed the turbid surface 

 layer, exposing dark patches of seawater from 

 deeper depths. However, while submerged after a 

 dive that was preceded by raised flukes, they did not 

 affect the thin surface layer, indicating that they 

 were probably feeding in the underlying clearer 

 ocean water. Defecation was frequent, suggesting 

 that feeding may have taken place recently. The 

 feces clouds were red-orange. 



Bottom Feeding 



On 12 August 1980, we noticed clouds of mud 

 suspended in the water about 25 km west of Issung- 



'Griffiths, W. B., and R. A. Bachanan. 1982. Characteristics 

 of bowhead feeding areas. In W. .1. Richardson (editor), Behavior, 

 disturbance responses and feeding of bowhead whales Balaena 

 myst}cetu.s in the Beaufort Sea. 1980-81, p. 347-455. Unpubl. Rep., 

 456 p. LGL Ecological Research Associates, Inc. Bryan. 

 TX. for Bureau of Land Management, U.S. Department of the In- 

 terior, Washington, DC. Available from Minerals Management 

 Service Alaska DCS Region, P.O. Box 101159, Anchorage, AK 

 99510. 



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