246 HABITS AND INSTINCTS OP ANIMALS. CHAP. VIII. 



more distant. We shall not here speculate upon the 

 causes of migrations generally, since these simultaneous 

 movements appear to originate from various motives, 

 but of which a necessary supply of food seems to be the 

 chief: our present purpose is to show its effects. 



(263.) As united migration implies a great develop- 

 ment of the social principle, we find it most remarkable 

 among quadrupeds in the class of Ungulata, comprising 

 the ruminants, and all those tribes whose docility to- 

 wards man is most conspicuous. A few instances may 

 be briefly noticed. The Saiga antelopes (Antelope Coins 

 H. Smith) are sociable and migratory, especially in the 

 autumn, when they assemble, sometimes to the number 

 of ten thousand, in a herd, and traverse towards more 

 southerly deserts, returning, in the spring, in smaller 

 troops. They are unwilling to reside far from water; 

 are seldom seen single ; and the herd, when in a state of 

 repose, always keep a few stationed to look out. But 

 perhaps the most striking instance of this instinct is 

 afforded by the springer antelope or springbock of the 

 Cape colonists. This species resides on the plains of 

 Southern Africa, to an unknown distance in the interior, 

 in flocks, assembling in vast herds, and migrating from 

 north to south, and back, with the monsoons. These 

 migrations, which are said to take place, in their most 

 numerous form, only at the intervals of several years, 

 appear to come from the north-east, and in masses of 

 many thousands, devouring, like locusts, every green 

 herb. The foremost of these vast flocks are fat, and 

 the rear exceedingly lean, while the direction continues 

 one way ; but with the change of the monsoon, when 

 they return towards the north, the rear become the 

 leaders, fattening in their turn, and leaving the others 

 to pick up a scanty subsistence.* Mr. Burchell, speak- 

 ing of the same species, observes, that it is one of the 

 most numerous in Africa, sometimes being seen in 

 flocks of two thousand. The most animated account, 

 however, is that of Le Vaillant, which we shall give in 



* H. Smith, Cuv. vol. iv. p. 209. 



