1 98 1 )-*. Of the 17 bowhead whale stomachs and intestinal 

 tracts examined to date from whales landed at Barrow and 

 Kaktovik with discernable prey items present, the following 

 proportions in the bowhead diet were: Euphausiids 65%; 

 copepods 30%; hyperiid amphipods 1%; and all others, pri- 

 marily including amphipods, 4% (see Marquette et al. 1982 

 for a summary of Frost and Lowry footnote 29). 



Behavior 



Essentially all bowheads progress steadily through the near- 

 shore lead during the spring migration along the northwest coast 

 of Alaska, following a fairly straight course towards the north- 

 east (20°-30° magnetic north). Since the NMFS ice camp studies 

 were initiated in 1976, < 1% of all bowheads were seen going 

 southwest in the spring (Carroll and Smithhisler 1980). The rare 

 exceptions occurred when the lead was obstructed by ice, or 

 when the whales were resting, feeding (presumably), courting, 

 mating, or breaching. Most whales progressed past the ice camp 

 at a rate of 1.9-7.5 km/h (1.0-4.0 nmi/h) depending on the 

 direction of the current; this rate of travel was confirmed by 

 studies at Cape Lisburne (Rugh and Cubbage 1980). 



Bowheads do not travel in close association with one an- 

 other. Of 2,406 bowhead observations recorded between 

 1976 and 1978, 1,815 (75.4%) were singles, 470 (19.5%) were 

 in pairs, 105 (4.4%) were in groups of three, and 16 (0.7%) 

 were in groups of 4. There were noticeable peaks during the 

 course of the migration, sometimes related to ice conditions, 

 but also at times when the whales had free movement in the 

 lead. 



When bowheads come to the surface to breathe, they usu- 

 ally break the water surface from 1 to 14 times, with each 

 surfacing (roll) interrupted by a short shallow dive. Exhala- 

 tion is not always observed during each roll. A completed 

 series of rolls is termed a rise ( = total number of rolls visible 

 during a passage of one whale in front of an observer). The 

 mean number of rolls per rise recorded from 1975 to 1977 

 was 6.57 (SD = 3.08; n = 63), while the mean in 1978 was 

 6.53 (SD = 2.84; n = 41) (Carroll and Smithhisler 1980). 



Each time a bowhead rolled it was on the surface for a 

 mean of 4.7 s (SD = 2.0). The average time below the sur- 

 face between blows (= rolls) was 10.8 s (SD = 5.2). From 

 this we calculated that the average amount of time a bow- 

 head was above the surface per rise was about 31 s. The 

 average duration of a rise between the first roll and the sound- 

 ing dive was 1.5 min. 



The duration of sounding dives varied from 3.0 to 26.7 

 min. The mean dive time recorded during the 1975-77 spring 

 seasons was 15.2 min (SD = 4.4). Of 51 dives times in 1978 

 the mean was 15.6 min (SD = 5.2). Combining these with 

 the 1.5 min mean rise time, a time of 17.1 min was calculated 

 for the complete cycle. On the basis of these data, we esti- 

 mate that during their migration near Barrow, bowhead 

 whales were visible above the water surface 3.1% of the time 

 within the field of view of our ice camp observer(s). Using 



the same basic calculations, bowheads were visible to aircraft 

 observers for approximately 8.4% of the time they were 

 under observation. 



The surfacing pattern of a cow and calf pair seems to be 

 related to the calf's activity. Of three cow and calf pairs 

 timed, mean dive time was 6.6 min (range 5.9-7.0 min). Calves 

 often blew two times during each roll. Very small calves were 

 seen during the migration, usually traveling very close to the 

 accompanying adult. We judged these calves to be recently 

 born. 



Bowheads move steadily through partially closed leads by 

 adjusting their diving and surfacing sequences to the size and 

 location of open water in the pack ice. They take fewer breaths 

 per rise and make shorter dives. A whale coming to a small 

 polynya will roll as many times as it has time, while traveling 

 at a normal speed, then dive when it comes to the distant 

 edge. 



Occasionally, the ice cover was so complete that the whales' 

 progress was hindered and they were seen milling in polynyas. 

 It appears that the whales dive, search, and, if they do not 

 find another polynya close enough, return to the original 

 hole. Sea ice is more flexible than freshwater ice and both 

 bowheads and white whales push up on the ice to breathe, 

 forming hummocks. Bowheads have been heard exhaling 

 under the ice when no apparent open water is available." 



Apparently bowheads are not always successful in finding 

 open water or in being able to lift pack ice to breathe. Tomi- 

 lin (1957) and Southwell (1898) both cited instances of bow- 

 heads perishing in the ice, and Sleptsov (1961) stated that 

 there was a mass mortality of several dozen bowheads in 

 Karaginsky Bay in 1932. Cook (1926) also reported bow- 

 heads perishing under ice during the autumn in the Beaufort 

 Sea. Unfortunately, the details of these events were not re- 

 ported. 



Bowheads do not seem habituated to small boats. The 

 sound of an outboard motor will cause a bowhead to vacate 

 an area. The normal reaction to being pursued is escape. 

 If a bowhead is injured, it will often dive under the ice. Re- 

 action to airplanes flying overhead seems mixed. Few whales 

 have reacted vigorously to our presence when we fly between 

 130 and 300 m. On a few occasions we have flown above 

 whales at 65 m without obvious disturbance (c.f. photos in 

 Everitt and Krogman 1979 where altitudes were down to 65 

 m). In 160 encounters using a Coast Guard helicopter and 

 flying at elevations below 300 m only 17 (11%) bowheads ap- 

 peared to react noticeably to the aircraft noise. The same re- 

 sults occurred at altitudes down to 130 m (Braham et al. 

 1980c). It appears then that fright reaction to noise varies 

 greatly, depending upon the source, time of year, environ- 

 mental conditions, and activity of the animals. Surface noises 

 in water appear to cause more frequent fright reactions by 

 bowheads than noises originating above them in the air. 



Occasionally bowheads show considerable exuberance. We 

 have observed them breaching, tail lobbing, flipper slapping, 

 swimming on their backs and sides, and demonstrating other 

 behavior. Along with numerous tail lobs and flipper slaps, a 

 whale seen off Point Hope in 1977 breached 57 times in 96 

 min. We do not know the significance of these kinds of 



"Frost, K., and L. Lowry. 1981. Feeding and trophic relationships of bow- 

 head whales and other vertebrate consumers in the Beaufort Sea. Final report to 

 Natl. Mar. Mammal Lab., Contract No. 80-ABC-00160, 106 p. Northwest and 

 Alaska Fish. Cent., Natl. Mar. Fish. Serv., NOAA. Unpubl. manuscr., Alaska 

 Dep. Fish Game, 1300 College Road, Fairbanks, AK 99701. 



"Eskimo whalers, pers. commun. 1976-79. 



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