DISTRIBUTION AND SEASONAL MOVEMENTS 285 



grounds rather earlier than the younger whales. The emigrant schools of autumn include the nursing 

 cows with calves newly recruited around the Azores during the calving season of the summer months 



(P- 2 70- 



Table 3 1 . Average lengths* and percentages of sexually immature^ zvhales 

 in monthly catches at Horta between 1944 and 1954 

 Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 



* It has been necessary to separate whales measured before and after 9 July 1949, since measurements prior to that date 

 did not include the length of the flukes (see p. 241). 



f For the same reason, no attempt has been made to estimate the proportions of immature animals among whales caught 

 before 9 July 1949. Anatomical material was collected from most of the whales caught afterwards, so it is known whether or 

 not they were mature. The minority which were not examined biologically have been classified by applying the estimates of 

 mean lengths at sexual maturity (p. 262). 



Migrations 

 Matthews (1938, p. 159) has noted that among sperm whales there is a general movement, apparent 

 from Townsend's charts (1935), towards temperate waters in summer and towards low latitudes in 

 winter. Regarding the North Atlantic field these charts show that in winter the old whaleships took 

 plenty of sperm whales at the Cape Verde Islands and few at the Azores, whereas in summer few were 

 taken at the Cape Verdes but plenty in the Azores. Since whales may be expected to migrate in a 

 north-south direction, and since the Cape Verde Islands, lying around 16 N., are to the south of the 

 Azores, it is probable that Townsend's summer and winter charts reflect the migrations responsible 

 for the seasonal changes of the whale stock around the Azores.* To the south-eastward also lies the 

 former winter whaling ground of the Canary Islands, and these may also contribute summer whales 

 to the Azores. Madeira lies between the Canaries and the Azores: from such figures (unsexed) as are 

 available in the annual reports of the Gremio dos Armadores da Pesca da Baleia, I note that the peak 

 of the present Madeiran open boat sperm whale fishery is in spring, three months earlier than in the 

 Azores, and that there are indications of a second abundance in autumn and early winter (Fig. 15). 

 Because males are not distinguished from females in Fig. 15, the significance of the curve is somewhat 

 obscured. Yet its appearance, so markedly different from the cumulative curve for Azores males and 

 females, is not unlikely if Madeira lies in the path of whales spreading seasonally to and fro between 

 the Azores and the Canaries. 



One cannot be certain whether or not many sperm whales of the local stock move northwards beyond 

 the Azores in summer, but the unimodal catch curves (Figs. 13 and 14) at least show that the stock 

 does not move in a body to a higher latitude and return in autumn. If any whales do straggle to the 

 northward they are likely to be males rather than females, for at latitudes higher than those of the 



* In 1889 Beneden anticipated this view that sperm whales caught round the Azores in summer come from the southward. 



