Table 2. — Summary of some estimated reproductive life history data for bowhead whales. 



Life history 

 parameter 



Parameter 



value 



Area data 

 collected 



Reference 



Sexual maturity 

 Males 

 Females 



Calving and 

 mating period 



11m 

 12m 



Chukchi Sea 

 Chukchi Sea 



Mar. -May 

 Mar. -June 



No. Atlantic 

 Bering to Beaufort 

 Seas 



April Chukchi Sea 

 Apr. -June Chukchi Sea 



Durham (text footnote 11) 



Durham (text footnote 11); 



Johnson et al. (1981) 



Eschrichl and Reinhardt (1866) 

 Braham and Krogman (text footnote 2); 



Braham et al. (1979, 1980c); 



Everitt and Krogman (1979) 

 Durham (text footnote 1 1) 

 Maherand Wilimovsky (1963); 



Marquette (1976) 





Apr. -Aug. 



Western and 



Summarized in Marquette 







eastern Arctic 



(text footnote 15) 





May 



Chukchi Sea 



Foote (text footnote 23) 





May-July 



No. Atlantic 



Gray (1886) 



Gestation 



9-10 mo 



No. Atlantic 



Scoresby(1820) 





12 mo 



Chukchi Sea 



Durham (1980) 





13-14mo 



No. Atlantic 



Eschricht and Reinhardt (1866) 



Lactation 



5-6 mo 



Beaufort Sea 



Marquette (text footnote 15) 





12 mo 



No. Atlantic 



Slij per (1962) 





711-851 cm 



— 



Tomilin(1957) 





(calf length) 







Gross annual 



' 1-5.6% 



Chukchi and 



Davis and Koski (1980); 



reproductive 





Beaufort Seas, 



Cubbage and Rugh (1982); 



rate(GARR) 





and eastern 

 Canadian High 

 Arctic 



Marquette etal. (1982) 



Considered a minimum estimate when compared with estimates for other large baleen whales. 



(1936) estimated the length of newborns at 305-366 cm (10-12 

 ft); Eschricht and Reinhardt (1866) reported lengths of 366 to 

 396 cm (13-14 ft). An apparent newborn calf taken at Barrow 

 20 May 1954 was measured by Eskimos at 300-350 cm (10-12 

 ft) (Marquette footnote 14). According to these findings the 

 average length of a newborn bowhead whale is about 360 cm 

 (12 ft). One bowhead calf with attached umbilicus taken at 

 Barrow in 1971 or 1972, was estimated (no measurements 

 made) by resident Eskimo whalers to be about "20 ft" long, 

 or 615 cm. 28 This is unusually large for a newborn, if the 

 estimate was accurate. 



Information on the duration of the lactation period in 

 bowheads is scant and variable. Slijper (1962) reported the 

 lactation period to be 12 mo. Marquette (footnote 14) stated 

 that since lactating females have not been recorded in the 

 autumn take near Barrow, lactation may last only 5 or 6 mo. 

 Tomilin (1957) reported that lactation ends and calves are 

 weaned at a length of 711-851 cm (23-28 ft). Although incon- 

 clusive, it appears that bowheads have a 6-12 mo lactation 

 period. Since yearlings are not seen in very close association 

 with adults in spring, it seems unlikely that lactation lasts 1 yr. 

 Lactation in gray whales last approximately 4 mo (Rice and 

 Wolman 1971). 



Based on the estimated lactation and gestation periods, the 

 calculated calving interval for female bowhead whales is at 

 least 2 yr and is likely to be longer. Large, long-lived mam- 

 mals are characterized in having calving intervals of more 

 than 2 yr (Fowler and Smith 1973; Goodman 1978). 



"O. Leavitt and J. Adams, Alaska Eskimo Whaling Commission, Barrow 

 Alaska, pers. commun. 15 May 1978. 



Food Habits 



Nemoto (1976) classified the bowhead whale as a bottom 

 skimmer, and although individuals have been observed feeding 

 in shallow waters, bowhead probably feed throughout the 

 water column. A comprehensive study of bowhead feeding has 

 not been conducted; however, the small data base from the 

 available literature indicated that pelagic arthropods (euphau- 

 siids, mysids, pteropods, copepods, and amphipods) are the 

 prey species mostly taken, and, to a lesser extent, annelids, 

 molluscs, and echinoderms (Mitchell 1975; Marquette footnote 

 14; Lowry et al. 1978). Johnson et al. (1966) examined the stom- 

 ach contents of three bowhead whales taken by Point Hope Es- 

 kimos in the spring. The stomachs were empty and the third 

 contained fragmentary remains of polychaetes, reptantia, gas- 

 tropods, crustaceans, echinoids, and sand and gravel. Lowry et 

 al. (1978) analyzed the stomach contents of two bowhead whales 

 taken at Point Barrow in the fall of 1977 and found that together 

 they contained (by volume) 90.3% euphausiids (Thysanoessa 

 raschii), 6.9% gammarid amphipods (Gammarus zaddachi, 

 Acanthostepheia behringiensis, Monculoides zernovi, and 

 Rozinante fragilis), and 2.7% hyperiid amphipods (Para- 

 themisto libellula). Five bowheads taken by Kaktovik whalers 

 off Barter Island in autumn 1979 had primarily euphausiids 

 and copepods (Calanus spp.) in their stomachs (Lowry and 

 Burns 1980). A 1-yr study of bowhead feeding contracted by 

 us to the Alaska Department of Fish and Game, Fairbanks, 

 determined that competition for food with Arctic cod may be 

 important in some years if food is limiting (Frost and Lowry 



21 



