FISHERY Bl'LLETIN: VOL. 83. NO. 3 



90 m ASL in 1981) on the coast. We used a Wild Tl 

 theodolite with 6-s accuracy and 30-power optics in 

 1980, and a Nikon NT-2A with 20-s accuracy and 

 30-power optics in 1981. Horizontal and vertical 

 bearings were later translated to x and y map coor- 

 dinates. This transiting technique, developed by R. 

 Payne, is described by Wiirsig (1978). The station 

 was in use from 19 August to 1 September 1980, and 

 23 August to 13 September 1981. 



Locations of most whales within a 10 km radius of 

 the theodolite station during fair weather and day- 

 light hours were documented. Unfortunately, whales 

 rarely approached Herschel Island closer than 5 km 

 during the 1980 field season, so details of behavior 

 were difficult to discern. In 1981, fewer whales were 

 seen, but they were closer to shore, allowing more 

 detailed behavioral observations. 



RESULTS 



The Surfacing-Dive Cycle 



In the Beaufort Sea in summer, nonmigrating 

 bowhead whales typically alternate between dives of 

 variable length, depending on activity, and sur- 

 facings within which there are several respirations. 

 This pattern differs slightly from that during migra- 

 tion, when sounding dives (around 15 min long) are 

 separated by periods when several brief surfacings, 

 each with a single respiration, alternate with "series" 

 dives about 15 s long (Rugh and Cubbage 1980; Car- 

 roll and Smithhisler 1980). Presumably, migrating 

 animals dive between respirations to avoid hydro- 

 dynamic drag imposed by the air-water interface. No 

 such submergence is necessary for a whale that is 

 not moving rapidly through the water. However, the 

 basic repertoire of breathing several times in 

 relatively, closely spaced series and then not 

 breathing for many minutes (during the long dive) is 

 similar during both prolonged directed movement 

 and more stationary activity. The pattern extends to 

 some degree even to whales that remain at the sur- 

 face for long periods (up to 30 min or more during 

 surface skim feeding, socializing, or play). They 

 generally breathe several times within a few 

 minutes, and then cease breathing for a longer time, 

 despite their near proximity to the surface and the 

 availability of air. Similar patterns are seen in other 

 whales, including right whales, Eubalaena glacialvi, 

 (Kraus et al. 1982) and gray whales, Eschrichtiua 

 robicstus, (Sumich 1983). Durations of surfacings and 

 dives, intervals between successive blows, and 

 number of blows per surfacing are described in Wur- 

 sig et al. (1984). 



Surfacing and Respiring 



Whales in water deeper than about 30-45 m usual- 

 ly surface head and blowhole first after a sounding 

 dive, with the body oriented at some angle (such as 

 30°) from horizontal. When whales do not dive very 

 deeply (as in shallow water), the surfacing is less due 

 to active swimming upward, and the head and tail 

 surface at approximately the same time. 



A blow is an exhalation of air by a whale. Blows 

 can occur above or below the surface. Surface blows 

 are usually visible as a white cloud of water spray, 

 but may be so weak as to be undetectable. The first 

 blow after a surfacing usually appears strong, prob- 

 ably because it is a more forceful exhalation and 

 because water is present above the blowholes during 

 or just after surfacing. On calm days and when 

 whales lie at the surface with the blowholes exposed, 

 the blowholes are relatively dry, and blows may be 

 difficult to detect. Blows of calves can also be dif- 

 ficult to see. 



Surface exhalations of gray; humpback, Megaptera 

 novaeangliae; fin, Balaenoptera physalus; and 

 southern right whales, Eubalaena australis, are 

 almost always followed immediately by an inhalation 

 (B. Wiirsig, pers. obs.). Hence we suspect, following 

 Scoresby (1820), that exhalations and inhalations 

 generally occur together in bowhead whales as well. 



Diving and Associated Behavior 



The predive flex is a distinctive concave bending of 

 the back seen several seconds before many dives. 

 The whale flexes its back by about 0.5-1 m, so that 

 the snout and tail disrupt the surface. Considerable 

 white water is created at these two points. The whale 

 then straightens its back and lies momentarily still 

 before arching the back convexly as it begins its roll 

 forward and down. The predive flex is seen from low 

 vantage points as an abrupt lifting of the head, 

 because the flukes apparently only touch the water 

 surface from below. 



The predive flex was seen more often during 1980 

 than during 1981 or 1982. Although it occurred 

 previous to dives well over 50% of the time in 1980, 

 it occurred in only 8% of the observations (before 29 

 of 352 dives) in 1981. For 1982, we have especially 

 detailed analyses of predive flexes. In that year, 

 predive flexes occurred in presumably undisturbed 

 noncalves before 32 of 132 dives (24.2%); flexes 

 occurred more often in late August than earlier 

 (Table 1). Dives following predive flexes were, on the 

 average, about twice as long as dives without predive 

 flexes (19.00 ± SD 7.877 min, n = 13, vs. 10.15 ± 



360 



