382 





Figure 215. Humpback suckling tws 

 calves. From a drawing by Scammon. 

 {Norman and Fraser, 1928.) 



nipple, Avhich has meanwhile emerged from its slit. Since the calf lacks 

 proper lips, it has to seize the nipple between the tongue and the tip of its 

 palate. We have seen that the tongues particvilarly of young Mysticetes 

 are very much more muscular than those of older specimens, and that their 

 tips are free. With this free tip, which in some Odontocetes has a scalloped 

 edge, the calf presses the nipple from beneath and from the sides against 

 the palate. In this way, and also because of the arrangement of the muscles 

 in the tongue, the tongue becomes doubled up so that the milk can spout 

 straight into the throat. Once the calf lets go, the milk often continues to 

 spout from the teat for a further six seconds or so, so that we gain the 

 clear impression that the milk flows under fairly great pressure, probably 

 due to contraction of the cutaneous muscles with which the mammary 

 gland is surrounded, or else because the lobes themselves are filled with a 

 surfeit of milk, which contractions of the myo-epithelial cells surrounding 

 the individual lobuli force through the nipple. (The presence of myo- 

 epithelial cells in the mammary glands of Cetaceans was established by 

 W. A. Smit.) While most Cetacean calves squeeze the nipple between 

 tongue and palate. Sperm Whales may well form the exception, since, 

 because of the peculiar shape of their heads and lower jaws, it seems 

 unlikely that they can do so. They probably seize the nipple with the 

 corners of their mouths, but no one has ever reported seeing them do so. 

 The Bottlenoses in the Marineland Aquarium usually start looking for 

 their mothers' nipples some seventy-five minutes after birth, though some 

 took as long as four hours about it. The first feed was taken fifteen to thirty 

 minutes after the first attempt, and for the first two weeks the calf was 

 suckled roughly once every twenty-six minutes, day and night. Sheep feed 

 their young at about the same rate (twenty-two times in sixteen hours of 

 daylight), while piglets are suckled once every hour or so. During each 

 feed, the young Bottlenose took one to nine sucks, each lasting for only a 

 few seconds, since the calf cannot stay under water for more than half a 

 m.inute at a time. Other mammals suck for far longer periods, e.g. newly- 

 born lambs, which take from 50 to 250 seconds (older lambs - 30 

 seconds), but in Cetaceans, in which the cow spouts her milk into the 

 calf's mouth, thus obviating the need for sucking, the calf obtains a 



