HABITS OF MAMMALS 829 



" flying squirrels," such as Pteromys, among Rodents ; 

 '' flying lemurs " (Galeopithecus), allied to Insectivores. 

 Not a few are aquatic — all the Cetaceans, the two Sirenians, 

 and the Pinniped Carnivores, such as seals and walruses ; 

 while water-voles, beavers, otters, polar bear, and many 

 others are also at home in the water. Burrowers are well 

 represented by moles and rabbits ; arboreal forms by 

 squirrels and monkeys. 



As to diet, man, many monkeys, the pigs, and many 

 others, may be called omnivorous ; kangaroos, hoofed 

 animals, and most rodents are herbivorous ; the Echidna, 

 the ant-eaters, hedgehogs and shrews, and most bats, are 

 insectivorous ; most of the Carnivora are carnivorous ; 

 dolphins and seals feed chiefly on fishes ; but in most cases 

 the diet varies not a little with the available food-supply. 



The struggle for existence among Mammals is sometimes 

 keen among fellows of the same kind ; thus the brown rat 

 {Mus decummius) tends to drive away the black rat (M. 

 rattus) ; but stress, due to over-population, is sometimes 

 mitigated by migration, as in the case of the lemmings. 

 The struggle seems to be keener between foes of different 

 kinds, between carnivores and herbivores, between birds 

 of prey and small mammals ; but combination for mutual 

 defence often mitigates the intensity of the conflict. Teeth 

 and claws, hoofs and horns, are the chief weapons, while the 

 scales of pangolins, the bony shields of armadillos, the 

 spines of hedgehogs and porcupines, and the thick hide of 

 the rhinoceros, may be regarded as protective armature. 

 In keeping their foothold some Mammals are helped by the 

 harmony between their colouring and that of their surround- 

 ings ; thus the white Arctic fox and hare are inconspicuous 

 on the snow, the striped tiger is hidden in the jungle, and 

 many tawny animals harmonise with the sandy background 

 of the desert. 



The majority of Mammals are gregarious ; witness the 

 herds of herbivores, the cities of the prairie-dogs, the packs 

 of wolves, the schools of porpoises, the bands of monkeys. 

 Combinations for attack and for defence are common ; 

 sentinels are posted and social conventions are respected ; 

 such migrations as those of the lemming and reindeer are 

 characteristically social. In the beaver village and among 



