22 VERTEBRATE REPRODUCTIVE CYCLES 



their farm and domestic animals, and for sentiment's 

 sake they also took an astounding variety of wild animals. 

 Captain Cook, who was the first European to set foot in 

 New Zealand, introduced pigs, and those animals which 

 now run wild in the South Island are supposed to be 

 their descendants. Since that day the widest variety of 

 mammals and birds have been taken there, as well as 

 some five species of frogs and toads and several fresh 

 water fishes including the brown trout. ^^ 



Such animal movements have provided valuable 

 information concerning the control of reproductive 

 seasons, though a great deal of the data has not yet been 

 analysed. The first serious attempt at such an analysis 

 was that of Marshall, i^o, 131 and later, together with the 

 Duke of Bedford, he made a further study of the 

 situation as it affects the mammals. 22 The general 

 conclusion arising from these surveys is that any 

 animal with a fixed breeding season in temperate 

 latitudes reverses this season to conform with the new 

 conditions when it is transported to the other hemisphere. 

 Sometimes this reversal is slow as in the case of a pony 

 brought to Scotland from Timor in the southern 

 hemisphere. In its first year it came on heat in the 

 autumn, but afterwards it adjusted itself to breeding in 

 the spring. 130 



It is also reported that when the chital, or spotted 

 deer of India was introduced into Europe, it was at 

 first in danger of extinction because the calves continued 

 to be born in mid-winter when the unsuitable conditions 

 proved fatal, but later they adapted themselves and the 

 young were born at the appropriate season, ^^o 



Commonly, however, the change in timing is imme- 

 diate so that individual animals may experience two 

 breeding seasons in the year in which the journey is 

 made. An example of this is provided by the ferrets 

 which were taken from England to the zoological 

 gardens in Pretoria, South Africa, in 1937. The trans- 

 ference took place from the late northern summer to the 



