DISTRIBUTION AND ABUNDANCE 79 



species. Gadow (1909) pointed out that Salamamira salamandra is not 

 foimd on limestone formations. Noble and Noble (1923) showed that 

 Hyla andersonii is found only in Spliagmim pools, wliich amounts to a 

 geological or chemical connexion, for Sphagnum is only found in acid 

 waters. Wright and Wright (1949) also point out that frogs are 

 apparently affected by geological factors, and that the breeding ponds 

 appear to be dependent on the nature of the surface waters of these 

 areas. 



In Chapter i I pointed out that the evidence existed showing that 

 the species cannot live in areas where the spring temperatures are high. 

 There seems hardly any limit to the cold it can stand, for in the Alps, 

 it is found up to the snow line, and these Alpine frogs and tadpoles are 

 unusually large. I suspect that this is an Alpine or northern species, 

 living in the lowlands in England not quite under optimum conditions. 

 Fig. I shows the distribution as far as it is known, and is largely drawn 

 after Balcells (1956). It can be seen how far north the animal ranges. 

 Many of the countries in which it is found, such as Poland and Finland, 

 have severe winters. Those living in the mild climate of the British 

 Isles must remind themselves that, in those countries, the frog lives in 

 the winter deep under the snow, or at the bottom of ponds thickly 

 covered with ice. They may also recall that the year when there were 

 most tadpoles in the ponds followed a winter of almost continental 

 severity. 



The question of distribution is connected with that of abundance, 

 for obviously, at the boundaries of the range, it is reasonable to expect 

 that the species will become rare, and that, as one proceeds further, 

 it will disappear altogether. But abundance has many other facets, and 

 fluctuations in abundance have attracted the attention of many 

 ecologists, not always with unanimous results. 



Fluctuations in Abundance 



Lack (1954), in the first book entirely devoted to this subject, has 

 given many examples from birds and other animals, but does not 

 include any amphibian. In reading his book, explicitly written to 

 provoke discussion and criticism, I have been interested to compare and 

 contrast the events he describes with those I know in the life of the 

 frog. I fmd some features that seem to confirm his views, but others 

 in which I must differ. 



The fundamental basis of the theory put forward by Lack and his 



