Animal Life in South Africa. 47 



thirty thousand and forty thousand at starting,* does not exceed 

 the truth. On certain seasons, generally recurring* about once in 

 ten years, there is a vast increase in numbers which causes 

 the movement to take some of the features of an American 

 " stampede." We have ourselves witnessed instances on 

 these occasions, when the animals hurried along and seemingly 

 bewildered by the numbers round them have allowed them- 

 selves to be caught by the hand. 



It is to these larger occasional migrations that the Dutch 

 Boers more especially apply the term 6 \ trek bokkens." 



A scarcity of food in certain seasons inducing greater 

 numbers thus to migrate, is the cause usually assigned to these 

 movements, but there is another which we think may have 

 at least an equal share in producing them. These animals are 

 polygamous, consorting in the proportion of four or five females 

 to one male. Now it has been asserted with apparent truth, 

 in the case of animals in a state of domestication that the 

 proportion of the sexes born in different years varies con- 

 siderably, and it is we think likely that these '"''trek bokkens" 

 take place when the numbers have been increased by a large 

 preponderance of females born a few seasons previously. 



Dr. Livingstone assigns another cause, viz., the wary habits 

 of the animals which induce them to leave the high and rank 

 grass and choose more open feeding grounds, an instinct by 

 the way, often displayed by domestic oxen. 



Wherever the herds of antelope are found, whether the 

 numbers be large or small, they appear materially to influence 

 the herbage of the district they frequent. Their close, 

 cropping bite resembling that of sheep, opens out a place for 

 the young shoots, while their droppings not only fertilize the 

 ground, but return to it the seeds in the form most suitable 

 for fecundation. 



Dr. Livingstone has related some instances where the game 

 having been destroyed, the grass totally disappeared, being 

 succeeded by a growth of mesembryanthemum-like plants, 

 a change, which it is needless to say, would materially affect 

 the water supply of a scantily watered country.f 



* They have never been noticed returning to the desert. 



f The difference in the quality of the flesh of different closely allied varieties 

 of antelope feeding on the same herbage is noteworthy ; while the flesh of some 

 is tolerable venison (as the spring bok), that of others (as the rhei bok) is rank 

 carrion. This reminds us that the Dutch colonists have a curious idea respecting 

 the varieties of the common hare, which are very numerous. These animals, 

 they maintain, feed on garbage, an idea certainly confirmed by the places they 

 appear to frequent. To give an example of this habit in a herbivorous animal, the 

 writer remembers many years ago in Lisbon, seeing the goats feeding in the 

 vicinity of the city muzzled, which he was informed was done with a view to 

 prevent their feeding, as they would, if possible, on the offal and impurities that 

 fill the purlieus of that dirtiest of dirty cities. 



