By making pets of wild animals much can be learned of their habits, dispositions, and characteristics. Especially their food habits, which, in the wild state, exert so much influence in the economy of nature as checks to the undue increase of other species of animals, insects, or plants. [Illustration: FROM COL. CHI. ACAD. SCIENCES. COMMON GROUND HOG. 1/4 Life-size. COPYRIGHT 1899, NATURE STUDY PUB. CO., CHICAGO.] THE WOODCHUCK. Very similar in its bodily structure to the marmot, of which it is said to be the nearest American relative, is the woodchuck or ground-hog (_Arctomys monax_). It is about eighteen inches in length, including the tail. The body is stout, the head broad and flat, the legs short and thick, the fur blackish or grizzled on the upper portion and of a chestnut red on the under surface of the body. The ground-hog is found in all parts of the region extending from the Atlantic coast west to the Missouri, Iowa, and Minnesota. It inhabits woods, prairies, and meadows, lives on roots, vegetables, and herbs, and is especially fond of red clover. Its burrows are large excavations, and in the early autumn it busies itself in storing provisions for its long winter retreat. It is said to be one of the first hibernating animals to retire to winter quarters and one of the earliest to come forth in the spring, the length of its retirement varying with the locality, and being shorter in the south than in the north. In the northern United States it usually retires about the first of October and reappears about the middle of March. A recent writer and close observer says that woodchucks hibernate in pairs, but he never knew one of these proverbially sleepy creatures to leave its hole until warm weather came--in spite of the alleged practice it has of coming out invariably on the second day of February to fix the weather for the rest of the winter. He took the trouble once to dig into a woodchuck's burrow on a Candlemas day--and a warm, cloudy day it was; just such a day as the ground-hog is said to choose to come out of his hole and stay out. He found two woodchucks in the burrow, with no more sign of life about them than if they had been shot. From all outward appearances he could have taken them out and had a game of football with them without their knowing it. When the animal begins its hibernation it carefully closes the entrance to its burrow. Dr. Bachmann, who had marked a burrow to which he knew a pair of woodchucks had retired, caused it to be opened early in November, and found the two animals, perfectly dormant, lying coiled up close together in a nest of dry grass, twenty-five feet from the entrance. The young woodchucks, of which there are from four to six in a litter, are born about the end of April. The mother takes tender care of them until they are able to shift for themselves.