REPRODUCTION 367 



By the time the foetus has grown to about 9 to lo feet, the first lamellae 

 appear on the whalebone ridge (see Chapter 10). 



During the first four months in the uterus, the Cetacean embryo 

 develops at about the same rate as that of other mammals (see p. 364), 

 but in the subsequent three months, the embryo of a Blue Whale may 

 grow from 2 feet to over 6| feet, and its weight may increase from 8 lb. to 

 5 cwt. (Fig. 204; see also Naaktgeboren, Slijper and van Utrecht, i960). 

 Huggett and Widdas (1951), who did extensive research on the intra- 

 uterine development of various mammals, have calculated that the rate 

 of growth during these three months is two and a half times that of most 

 terrestrial mammals and ten times that of men and apes. This is probably 

 due to the fact that the mother (but not the Sperm Whale mother - see 

 p. 364) has adequate supplies of food for only four to five months (Laws, 



1959)- 

 Now let us turn our attention to the termination of pregnancy, i.e. 



birth. The fact that the Cetacean calf (like that of the sea-cow and most 

 hippopotami, but unlike that of seals, sea-lions and sea-otters) is born 

 under water and that the whole process is thus normally invisible to us, 

 makes biologists all the more indebted to such institutions as the Marine- 

 land Aquarium, where they can view, photograph and film the event to 

 their heart's content. (There was only one precedent, viz. in 19 14 when a 

 still-born porpoise saw the light of day in Brighton Aquarium. In 

 Marineland, too, six pregnancies of Bottlenose Whales ended in mis- 

 carriages or still-births, but on seven occasions viable Bottlenose calves 

 were born, while the birth of a viable Spotted Dolphin was also observed.) 

 These studies in the Marineland Aquarium and some of Sleptsov's 

 observations on the birth of dolphins caught in nets off the Black Sea coast 

 together with investigations of cows which obviously died in labour, are, 

 in fact, the only available data on the birth of Cetaceans. No one has ever 

 witnessed the birth of a Rorqual, and all our knowledge is based on 

 examination of three cows which died in labour. 



The abdomens of pregnant Bottlenose Dolphins in the Marineland Aqua- 

 rium are said to protrude in characteristic places a few months before 

 birth. These animals are so tame that they allow divers to place their 

 hands against them and feel clear movements of the foetus. Sometimes 

 these movements can be observed visually as well. During the last months 

 of pregnancy, the cows have a tendency to keep to themselves, and they 

 become far less playful. With the onset of labour, the cow starts to swim 

 very much more slowly than she usually does, while other cows keep 

 constantly by her side, surround her from time to time, and giv^e the 

 impression of being intensely interested in her. Similar behaviour has also 

 been observed in cows and other herd animals, and must be attributed 



