animation during the hottest months of the year also, when their food supply 

 is cut off hy the drought. Their chemical processes at this time are not 

 slowed down as much as in the winter, so that more food material is exhausted. 

 The animals may lose as much weight in two or three weeks summer sleep or 

 aestivation as they do in three months hibernation. 



Unfortunately we know very little about the family life of most of the 

 wild mammals. The actions of caged animals are seldom characteristic, any 

 more than those of a small boy in Sunday school represent his normal, uu' 

 restrained, outdoor activities. Hunters and trappers have been our best source 

 of information, but they too often lack the scientific attitude and, like some 

 nature writers, assign all kinds of human attributes and mental processes to 

 the animals. The beaver has come in for a large share of attention because of 

 its tree-felling exploits and remarkable ability to construct dams. The huge 

 house of logs and mud, which free2,es to form an impenetrable fortress when 

 the icc'Covered lake might make it accessible to lynx or wolf, is an amazing 

 structure. The ubiquitous muskrat, although it builds no dams, has adopted a 

 similar style of architecture, and its conical houses are common landmarks 

 on the marshes. V/herever a steep river bank is available, however, the musk' 

 rat prefers to construct a series of burrows with under-water exits, even digging 

 channels in the stream bed, if necessary, to make these burrows accessible at all 

 times. The otter also digs burrows with under-water openings. Most of 

 the rodents make burrows, many constructing an elaborate series of chambers 

 for bedroom, storage, and other purposes. A few mice make temporary 

 homes by building roofs on abandoned bird nests. The squirrels go them one 

 better by building complete summer homes of leaves and twigs in the tree 

 tops, in addition to their winter homes in hollow trees. Some of the car- 

 nivores and a few of the rodents have dens in caves, in rock crevices and 

 similar places. Such homes are typical of bear, raccoon, porcupine and others. 



Knowledge of mating habits and reproduction in wild mammals is still 

 scanty. Such evident sexual distinctions as the antlers of the male deer, which 

 reach their full development at the time of mating and fall off in the spring 

 when they might injure the young or the nursing mothers, are well known. 

 The tendency of such normally solitary or subterranean animals as the moles 

 and the pocket gophers to wander about above ground during the breeding 

 season in search of companions has also been observed. The larger mammals, 

 having fairly long gestation periods, usually mate in the autumn, the young 

 thus being born in the spring when the food supply is at its maximum and 

 unfavorable weather as far off as possible. The most peculiar adaptation oc 

 curs in the case of bears, since the young, usually two in number, are born in 

 the early spring while the mother is presumably still in hibernation. Possibly 

 because they are secure in the den and are free to feed and grow without 

 interruption for some time after birth, the young are born when very small. 



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