WI'KSK; KT A1..: HKIl.WKiKOF HOVVMKAlt WIIAI.KS 



openings of the mouth contrasted sharjaly with the 

 sustained large gajjes observed in 1980 and 1981, and 

 probably did not represent feeding. In southern right 

 whales, Payne (pers. obs.) has observed mouth open- 

 ing that he interprets as yawning following sleep. 



Mud Tracking 



Mud tracking occurred when whales swimming in 

 shallow water (< 12 m depth) disturbed the bottom 

 sediments with each fluke beat, producing clouds of 

 mud joined by a narrower trail of muddy water. 

 These elongated clouds of mud were different from 

 mud clouds produced during presumed bottom feed- 

 ing. Although we often could not see the whales, in 

 at least a few instances their mouths were open. We 

 saw mud tracking during only three flights in the 

 third week of August 1980. 



Mud tracking probably represented incidental 

 disturbance of bottom sediments by a whale feeding 

 near the bottom in shallow water. We saw no 

 evidence that bowheads ever turned and swam back 

 along a mud track made previously. The mud tracks 

 tended to be straight, and some extended for well 

 over 1 km. At certain times, clouds of mud streamed 

 from the whale's body as it swam near the surface. In 

 this case, we suspect that the whales had contacted 

 the bottom, and that the mud had stuck to their 

 bodies. Sometimes, mud-tracking whales exhaled 

 while submerged, producing a characteristic burst of 

 bubbles (see section on The Underwater Blow). 



Defecation 



Defecation usually was evident as a cloud (2-3 m 

 diameter) of red-orange feces near the surface. 

 Whales almost invariably were moving forward or 

 diving when they defecated, and over 50% of the 

 bowheads observed defecating in 1980 did so while 

 the tail was arched up high out of the water just 

 before the dive. The anus was thus close to or at the 

 surface. No part of the body appeared to touch the 

 feces cloud, which was visible at the surface for up to 

 10 min. When whales moved forward while defecat- 

 ing, the feces were more dispersed and disappeared 

 within 1-2 min. Brown (1868) noted that feces of 

 eastern arctic bowheads were also red. Renaud and 

 Davis* observed red clouds of feces off the Tuktoyak- 

 tuk Peninsula in 1980. 



Defecation was seen more often in 1980 (23 cases 

 during 30.4 h over whales) than in 1981 (11 cases 

 during 30.8 h over whales). The difference is statis- 

 tically significant (x^ = 4.39, df = 1, 0.025 <P < 

 0.05), and may be related to year-to-year differences 

 in feeding patterns. In 1982, we saw only one defec- 

 ation (by a lone whale playing with a log). Because 

 we can only observe defecations by whales at the sur- 

 face, we compared the rates in reference to the num- 

 ber of whale-hours of observation at the surface. In 

 1980, there were 2.29 defecations/whale-hour at the 

 surface, as opposed to 0.73 in 1981, and 0.09 in 1982 

 (X^ = 27.58, df = 2, P < 0.001). This decrease could 

 result either from decreased defecation (indicative of 

 less feeding), or from an increasing tendency to 

 defecate under the surface where we could not ob- 

 serve it. During 1982, dives were longer than in the 

 2 previous years (Wiirsig et al. 1984), and we suspect 

 that much water-column feeding was taking place. 



Adult-Calf Pairs 



Calves of the year are a light tan color, distinct 

 from the dark black of noncalf bowheads. An adult 

 that remained close to a calf was assumed to be the 

 calf s mother. For the closely related southern right 

 whale in winter, Payne and Dorsey (1983) found that 

 in unambiguous adult-calf pairs, the adult was always 

 a female, and that identified calves were always seen 

 with the same individually identified female. At 

 times, we saw apparent nursing as calves submerged 

 briefly, oriented toward the teat region of the adult. 

 In 1982, we made longer observations of calves than 

 in either 1980 or 1981. 



The relative lengths of six calves measured from 

 videotape sequences recorded during August 1981 

 were a mean of 0.57 ± SD 0.052 adult body lengths. 

 Many of the calves we observed in August 1982 ap- 

 peared to be smaller, about one-third adult size. This 

 is corroborated by the fact that 14 calves measured 

 via photogrammetry in August-early September 

 1982 were 4.1-7.6 m long, or 33-45% (mean 41%) of 

 the length of the accompanying adult (Davis et al.^). 

 It may be that births occurred earlier in the year in 

 1981 than in 1982, or that the females videotaped in 

 1981 were smaller, on average, than those measured 

 in 1982. 



* Renaud, W. E., and R. A. Davis. 1981. Aerial surveys of bow- 

 head whales and other marine mammals off the Tuktoyaktuk Penin- 

 sula, N.W.T., August-September 1980. Unpubl. Rep., 55 p. LGL 

 Ltd., Toronto, for Dome Petroleum Ltd., Box 200, Calgary, Alberta 

 T2P 2H8, Canada. 



sDavis, R. A., W. R. Koski, and G. W. Miller. 1983. Prelim- 

 inary assessment of the length- frequency distribution and gross an- 

 nual reproductive rate of the western arctic bowhead whale as 

 determined with low-level aerial photography, with comments on 

 life history. Unpubl. Rep., 91 p. LGL Ltd., ToronU), for National 

 Marine Mammal Laboratorv, National Marine Fisheries Service, 

 NOAA, 7600 Sand Point Way N.E., BIN C15700, Seattle, WA 

 98115. 



367 



