90 ECOLOGY AND LIFE HISTORY OF THE COMMON FROG 



the purpose, but if this does happen, and the tadpoles are given plenty 

 of room and are well cared for, the final mortality may be well much 

 less than the 99 per cent or more that occurs in the ponds. The return 

 of, say, fifty full-grown tadpoles to the pond might serve as a lesson in 

 the conservation of the fauna, and result in more httle frogs than if the 

 clump had never been taken at all. 



I have often watched the behaviour of children at frog-ponds. I do 

 not think they are serious predators. Tadpoles are not "game." 

 Fish, however small, are "game." I think a child with tadpoles in a 

 jar is either very young, or has not been lucky enough to get fish. 

 Children should be taught not to take home whole clumps of spawn. 



Apart from predation, man has many other influences. In the 

 lowlands, almost all ponds are artificial, having at some time been dug 

 by man for watering cattle or as excavations for gravel. Before the 

 rise of agriculture, there may have been marshes but no ponds as we 

 know them. Moreover, the country was largely covered by forests. 

 This species is not a wood frog, and it is quite possible that the present 

 population of frogs owes its existence, except in the mountains and in 

 certain areas with marshes, to the activities of man. 



Conclusion 



In this chapter, I have been following a rather tangled thread, in 

 which abundance, mortality, and distribution have all been considered. 

 They are related subjects, hard to separate into neat compartments, but 

 it may now be possible, in the hght of what I have written, to explain 

 more fully the reservation I made about the theories on the regulation 

 of animal numbers that have occupied the attention of ecologists for 

 at least twenty-five years, and which still give rise to discussion and to 

 controversy. 



In his paper on this subject, Nicholson (1933) began with an analogy 

 which was a description of the way in which a balloon maintains its 

 height. Even if it is displaced by some force, it regains its original 

 position and the larger the displacement the greater is the restoring 

 force. He stated definitely that "only" factors that operate in a similar 

 way, and act more strongly the greater the departure from normal, 

 were capable of acting as controls of animal populations in which 

 "conditions" remained the same. The exclusive form of this statement 

 was not based on ecological facts, such as a failure to find any example 

 of a fluctuation that was not restored by this kind of action, but seems 



