ZOOLOGY 227 



work on the fluctuation in numbers of wild rodents, is discussed 

 in Chapter XVI, p. 536. 



Apart from work on South African rodents, there have been no 

 other studies on the periodicity of African animals. Isolated obser- 

 vations, however, suggest that zebra in East Africa suffer periodic 

 outbreaks of lung-worm. Again, epizootics of unknown cause 

 among hippopotami have been recorded from the Congo. In 

 Uganda, also, at the south end of Lake Albert in 1932 and in Lake 

 George in 1933, similar hippopotamus epizootics occurred, which 

 started and ended so suddenly that the cause and actual disease 

 were never discovered. As data slowly accumulate, analyses may 

 show that the principle of cyclic fluctuations in numbers is widely 

 applicable, and other important disease relations between wild 

 animals, stock, and humans will doubtless be found. Clearly it can- 

 not be assumed that cyclic fluctuations of northern and of tropical 

 animals are due to similar causes. In this connection the eleven- 

 year sunspot cycle, which appears to be prominent in tropical 

 regions, as was pointed out in Chapter IV, may influence animal 

 and plant periodicity in Africa. Mr. Elton is at present collecting 

 all data from the African continent bearing on variations in animal 

 numbers with a view to testing this hypothesis. Another of Mr. 

 Elton's activities is to edit the Journal of Animal Ecology, in which 

 many papers bearing on the ecology of Africa have been published 

 in recent years. 



Animal ecology is of great scientific and economic importance, 

 but at present there is very little provision for it. The whole future 

 of the conservation of game animals in Africa depends on it, so an 

 organization may be envisaged when research officers are attached 

 to the several game departments and all results are correlated at 

 some central institution such as Amani, for this is a branch of study 

 in which correlation over wide areas is a necessity. 



CONSERVATION OF WILD ANIMALS 



Areas in which wild life is protected may be divided into three 

 grades : (i) Preserves, in which wild animals are protected for shoot- 

 ing purposes against all except a strictly limited number of favoured 

 individuals. Present-day ideals favour the enjoyment of animals by 



