PROBLEMS OF WINTER 
in the midst of civilization, and provide a constant supply of 
flesh for carnivorous mammals, birds, and reptiles. 
The storing of winter provender is a feature of animal economy 
well worth consideration. It has been forced upon small ani- 
mals wherever the climate, either by reason of cold, problems 
snowy winters or very hot, dry summers, causes an  % Winter. 
annual failure of the food supply for a time. A moment’s 
thought will show how, by the falling of the leaves, the drying 
of bark, the death of green herbage, and the hardening and 
burial of land and water under ice and snow, a northern winter 
cuts off more or less completely all means of making a living 
from most of the smaller rodents and from various other animals. 
If regions with such a climate are to retain their animals, some 
extraordinary means must be found for avoiding or enduring this 
season. The insects die, but leave inert larve to revive in the 
ensuing spring and so continue the race. Many of the lower 
animals, as snails, reptiles, etc., go into the ground or the mud 
of swamps and ponds and rest in a more or less torpid condition. 
Fishes and the aquatic life generally seek the deeper parts of 
their home waters, and exist beneath the ice, or go down to lake 
or sea. Most of the insect-eating birds migrate to southern 
regions, where food is constantly procurable. 
None of these methods is wholly available to the nervous, 
warm-blooded mammals, which, unless they have acquired a 
strength, hardihood, and breadth of taste which belong to only 
a few of the rodents, must either be able to go into the cold- 
trance of hibernation or else save enough from their plenty of 
autumn to keep them alive during the following months of 
famine. The same difficulty arises from opposite causes in 
deserts, where the excessive drought and heat of midsummer 
destroy the food of some mammals so completely that they 
must go into a heat trance (estivation) or else, like the mole 
rat, must stock their burrows with enough bulbs or other proper 
edibles to last them until the next rains begin. 
2G 449 
