68 



DISCOVERY REPORTS 



The group in Fig. 59 under 9 m. in length represents calves of the current season, 

 that above 9 m. in length those of the previous season. In Fig. 60 the part of the curve 

 on the left-hand side of the month of August represents calves less than a year old, that 

 on the right-hand side those over a year old. Olsen (1914-15) makes a statement that 



PregnancLj once 

 everq two qears 



Iwo pregnancies 

 in three Ljears 



Oestrus Sept- Dec. 



Dioestrus 



after the first 

 sexual season 



Pre^nancu Sep|-Au^ 

 Dec- Nov 



, , . Sept- Dec 

 _actdtion to 



^^ Dec -Feb 



Anoestrus to Usept 

 Feb ' 



Fig. 58. Humpback whale. Diagram of oestrous cycle. 



Fig. 59. Humpback whale. Lengths and dates of immature whales. 



agrees with this conclusion : speaking'of the^Humpbacks arriving off the coast of South 

 Africa on their northward migration, he says that they are often accompanied by calves 

 of the previous year about 30 ft. (9-15 m.) long, and he further states that between the 

 north and south migrations nearly all the Humpbacks caught at Durban are 30-35 or 

 40 ft. (9- 1 5-10-67 or 12-2 m.) long and are sexually immature individuals one to two 

 years old. 



