330 WHALES 



not necessarily to the same zone, appears clearly from the fact that they 

 are caught in the Antarctic in the summer alone, and in the tropics only 

 in the Avinter. Moreover, their migrations have been observed off the 

 South American and Australian coasts, and investigations of their 

 stomach contents and the thickness of their blubber have shown that their 

 diet is largely of Antarctic origin, and that their blubber is thinner in the 

 tropics. Also, the presence of such parasites as barnacles and Penella and 

 the peculiar scars (probably inflicted by lampreys which attack whales 

 exclusively in warmer waters) (see Chapter 2) are clear evidence of a 

 sojourn in the tropics, while the film of diatoms (especially Cocconeis 

 ceticola Nelson; see also Chapter 2) found particularly on Blue and Fin 

 Whales and occasionally on other species, is clear evidence of a long stay 

 in the Antarctic. Diatom films, which disappear quickly in the tropics, 

 take at least one month to form, and from their thickness together with the 

 presence or absence of spores we can often determine the duration of a 

 whale's stay in the Antarctic more precisely. 



All the above is, however, no more than circumstantial evidence, and 

 for direct proof we must use a technique that has long been applied to the 

 study of the migiation offish, birds and bats, i.e. marking. But before we 

 discuss this technique, we must first mention a recent, promising, depar- 

 ture in the study of the migration of whales and, particularly, of the ques- 

 tion where they spend the winter: the decision, in 1951, by the National 

 Institute of Oceanography to enlist the Royal Navy and the 

 Merchant Navy as whale spotters. Three years later, the Dutch Whale 

 Research Group T.N.O. began a similar project by calling on all Dutch 

 seamen to report any whales they may have spotted on their journeys, and 

 to use special forms for the purpose. Thanks to the co-operation not only 

 of the Royal Dutch Navy and of all Dutch shipping companies, but of all 

 the crews as well, 4,500 completed forms, reporting about 3,500 separate 

 observations, were received in the first three years, and experts are at 

 present at work interpreting them. Since some regions are crossed by ships 

 more frequently than others, the number of whales reported is converted 

 by a factor based on the number of daylight hours a particular ship has 

 spent in a given region. 



The National Institute of Oceanography and also the Dutch Whale 

 Research Group have so far published no more than preliminary reports, 

 from which it appears, inter alia, that at least during certain parts of the 

 year whales congregate in particular regions. Thus, large concentrations 

 of Rorquals were found in the Arabian Sea, the Gulf of Aden, off Dakar, 

 in the Caribbean, and near Newfoundland, no doubt because, as we have 

 seen, these areas are particularly rich in food. Capt. Mörzer Bruins 

 reported the presence of large schools of dolphins in the Gulf of Aden as 



