THE FUTURE OF WHALES AND WHALING 4O5 



off New Zealand, does not agree with this opinion, and points out that 

 two of the animals marked by him were caught twelve and nineteen 

 months later in unimpaired condition. In one of these, the actual age at 

 capture, i.e. about three years, could be established with a fair amount 

 of accuracy, and investigations of the baleen plates and the ear plugs 

 indicated that one ring was laid down annually in the baleen, and 

 two in the ear plugs. This was confirmed by the data provided by a 

 Humpback marked one year old in 1954 and captured in 1959 (Chittle- 

 borough, i960). Five earplugs taken at Japanese floating factories from 

 marked Fin Whales of an age of at least 27 years indicated, however, 

 that the annual rate of deposition is less than 2 and nearer i. We must 

 wait for further results before we finally make up our minds. 



Until recently, the age determination of Odontocetes by examination 

 of layers in the dentine was not verified by examination of an animal of 

 known age. But in 1959, Sergeant, inspecting the teeth of four Bottlenoses 

 of known age in the Marineland Aquarium (Florida) concluded that, for 

 reasons not yet fully understood, the number of years concurred with the 

 number of layers in each tooth. Belugas, Pilot Whales, and Sperm Whales, 

 on the other hand, are said to form two layers of dentine a year. 



While our theories of the age of whales remain as vague as they are, 

 we can have no certainty about their life expectancy either. Even so, we 

 have some idea, which is, however, diametrically opposed to common 

 belief and also to the opinion of the great Cuvier, who, in his Histoire 

 naturelle des Cétacés (1936), said: 'La durée de leur vie doit être considerable si 

 Von en juge par analogue avec celle des autres animaux a manwielles' (The 

 duration of their lives, judged by that of other mammals, must be con- 

 siderable). In saying so Cuvier - and most people have this tendency - 

 was thinking exclusively of their dimensions. Now it is generally correct to 

 say that large animals grow older than small animals, but not quite to the 

 extent that popular belief would have it. Thus elephants certainly never 

 groAv older than seventy years. Moreover, there are exceptions to this 

 general rule, e.g. bats which live until they are twenty years old, and this 

 despite their small size, from which we might have inferred that their life 

 expectancy was three years at most (the maximum age of mice). The 

 explanation for all this is probably that maximum age is determined 

 largely by the metabolic rate, which decreases with increasing size (see 

 Chapters 9 and 11). In bats, however, the high metabolic rate which 

 normally goes with small dimensions is reduced during long periods of 

 hibernation and also during ordinary sleep in the summer - hence their 

 relatively long life. 



Whales, on the other hand, use all the strength they have most of the time, 

 moving about even when they are 'asleep' (see p. 189). Their metabolic 



