10 University of California Publications in Zoology [Vol. 27 
A case is cited under Bufo woodhousii where an entire population of 
toads turned its attention to one particular source of food supply. 
Adults of Rana a. draytonii will regularly devour smaller individuals 
of their own kind if available; a successful ‘frog farm’ in California 
was maintained on the basis of this habit, it being easy to rear the 
young animals under artificial conditions. Yet in nature the same 
procedure on the part of the adults would lead rapidly to the extinc- 
tion of the species. We cannot believe, therefore, that amphibians 
choose their food in the same sense that birds and mammals are known 
to do. Certain limitations in food are imposed by the sort of territory 
(ecologic niches) occupied by different species of amphibians; but 
differences arising in this manner are not to be considered matters 
of choice on the part of the animals themselves. The prime require- 
ment of amphibians (except larval Salientia) in the matter of food 
seems to be that it shall be moving , that is, living. 
The presence of safe, or better in the case of amphibians, suitable, 
breeding places is a factor of prime importance. As pointed out 
again and again in the accounts which follow, the adults of one species 
may occupy widely varying sorts of country, but they seek a par- 
ticular kind of place in which to breed. A single pond may be the 
breeding place for three different Species, provided, however, it is 
varied enough to offer the three special kinds of immediate surround- 
ings which these species of amphibians require. Again, adult am- 
phibians of certain species may live successfully, as individuals, in 
places where they do not have proper breeding facilities. Individual 
toads may live successfully in greenhouses or gardens in a closely 
built up city, but they cannot reproduce as a species unless suitable 
breeding places are available. Appropriate breeding facilities may 
not be available to a species every year; for example, certain ponds 
tenanted by Amby stoma calif orniense in 1922 and 1923 were com- 
pletely dry in the winter of 1923-24. Yet if pools form, and persist 
for a sufficient period one or more times during the life-span of one 
group of mature individuals, the species will be able to persist. At 
Davis, Yolo County, in the spring of 1922, a particularly favorable 
pool produced an unusually large number of Bufo b. halophilus, for 
the bulk of the population seen in various daytime refuges in and 
about that tow T n during the spring of 1924 consisted of two-year-old 
animals. 
