WHALES 



surface. The dolphins react by jumphig right out of the water. Whether 

 this game, which, by the way, the cormorants also like to play with ducks, 

 is entirely to the dolphins' liking is open to discussion, though dolphins 

 are known to deal summarily with other nuisances. Caldwell (1956) 

 reports that one of the Bottlenose Dolphins in The Living Sea Gulfarium 

 repeatedly picked up a turtle which tried to steal fish from it and dropped 

 it at the other side of the tank. 



Another helpful factor in the training of Bottlenose Dolphins is the fact 

 that, just like seals and sea-lions, they are diurnal animals, i.e. they eat 

 and play during the day and rest by night. Hence, like monkeys, horses 

 and dogs, they are closer to man's daily rhythm than, say, hedgehogs or 

 cats which are most active in the dusk or at night. Not that these dolphins 

 are fully awake throughout the day, for after each feed they usually 

 snatch about an hour's 'sleep', the cows floating with their blowhole 

 above water, and the bulls just a little below the surface, to come up for 

 air every so often, and usually opening their eyes as they do so. At night, 

 when they do not feed, they usually sleep for much longer periods. 

 Naturally, wild dolphins may have quite a different diurnal rhythm, 

 possibly influenced by the tides, since, during high water, they enter 

 creeks and bays in search of fish. Layne has stated that Boutus are active 

 day and night, but the porpoise which was kept in Texel for some months 

 used to spend a great deal of its time dozing at the surface. Vincent (i960) 

 reports that the Common Dolphins in Monaco had a daily respiratory 

 rhythm of six and a nightly rhythm of three to four blows per minute. 



In any case, the Marineland aquarium has clearly shown that some 

 Cetaceans are in fact nocturnal animals, since when Pilot Whales were 

 first taken there, they spent practically the whole day floating near the 

 surface, their eyes closed and their blowhole, front part of the back and 

 dorsal fin just protruding above the water. For this reason, these animals 

 had to be fed at night-time, though the Pilot Whale which stayed in the 

 aquarium for nine months gradually began to become more active during 

 the day, thus adapting itself to the general pattern. However, when the 

 dolphins started to attack it, it quickly returned to its old nocturnal ways. 

 At Marineland, California, too, a Pilot Whale used to sleep both during 

 the day and during the night, dozing either horizontally or vertically near 

 the surface. Whether this difference between dolphins and Pilot Whales is 

 connected with their diet - the former feeding predominantly on fish and 

 the latter predominantly on cuttlefish - will have to be investigated 

 further. In any case, it appears that the Gangetic Dolphin, which is 

 practically blind, and which feeds off the slimy bottom of the Ganges and 

 its tributaries, is another nocturnal animal, and so, apparently, is the 

 Little Piked Whale, though Kimura and Nemoto ( 1 956) , who observed 



