St Lawrence 1 

 1,70- 



Figure 31.— Aerial surve> (racklines flown b> \MFS scientists, Seplember 1°74. Bowhead whale sightings in the BeauforC Sea are incorporated into Figure 30. (From 



Fiseus and Marquette text footnote 15.) 



havior in May, as whales passed Point Hope. Copulatory 

 behavior was also reported by Krogman (1977) and Everitt 

 and Krogman (1979) in May north of Point Barrow. Mating 

 behavior of Atlantic bowheads was reported in late summer 

 (Scoresby 1820). Possible copulation was witnessed on 16 

 March 1979 west of St. Matthew Island (Braham et al. 1980c). 

 Mating may therefore occur from late winter to summer, 

 with spring (April-June) being the more probable peak period. 



Gestation is estimated to last 1 yr Scoresby (1820) believed 

 that bowheads have a 9-10 mo gestation period, while Esch- 

 richt and Reinhardt (1866) believed it to be 13-14 mo. Dur- 

 ham (1980, footnote 10) reported from observations of har- 

 vested bowheads taken at Point Hope and Barrow that the 

 gestation period is 12 mo. The actual length, however, is still 

 unknown. Minimum gross annual reproductive rate (calves 

 per total population) has been estimated at 1-5.6% (Davis 

 and Koski 1980; Cubbage and Rugh 1982; Marquette et al. 

 1982). 



The calving period is reported to correspond with the time 

 of mating — early spring to early summer. Cows with calves 

 pass Point Hope and Point Barrow from mid-April to early- 

 June (Maher and Wilimovsky 1963; Marquette 1976; Braham 



et al. 1979). Whalers in the eastern Arctic reported seeing 

 apparent cows with calves from early May to July (Gray 

 1886). Durham (footnote 10) believed that bowhead whales 

 in the western Arctic calve in early April. Eschricht and Rein- 

 hardt (1866) in the eastern Arctic Canada reported calving 

 occurring from late March to early May. Most researchers 

 agree that a single calf is born. 



Although recognizing that parturition has never been ob- 

 served, our scant sightings of calves indicate that bowheads 

 probably give birth in spring, perhaps a few before (February- 

 March) but most during migration (April-June). Marquette 

 (footnote 14), summarizing the known data on calving, pro- 

 vided information that bowheads may calve from April 

 through August. Observations of calves in the spring (Bra- 

 ham et al. 1979, 1980b) and apparent copulatory behavior in 

 the late winter (Braham et al. 1980c) and spring (Everitt and 

 Krogman 1979) with no sightings reported for the autumn, 

 also indicate that the peak period of mating and calving is 

 March-June, with few calves being born in summer or 

 autumn. 



The length of newborn calves has been measured at 305- 

 460 cm (10-15 ft) (Scoresby 1820; Durham 1980). Bodfish 



20 



