The food factor in hibernation. (Preliminary communication.)

In those animals that hibernate the condition is generally believed to be brought about mainly by a low external temperature; when the winter cold sets in the animal retires to its burrow or nest and remains dormant until spring. Some, on the other hand, hold that a diminished food supply is the chief, or at any rate, an important cause of hibernation, and my experience with a colony of woodchucks (Marmotta monax) during the past winter would appear to support the latter view.

About the middle of September, 1911, eighteen woodchucks, which had been caught in box traps in the neighborhood of Ithaca, and were uninjured, were placed in eight artificial burrows about five feet below the surface of the ground, the object being to study, amongst other things, changes in the nervous system during hibernation. The burrows, which were packed with dry straw, opened into a central court into which food (clover, corn, apples, carrots, etc.) was placed every second day, and it was expected that when the animals began to hibernate the food would cease to be consumed.

In this locality I was told that woodchucks are rarely seen in the open fields later than the first or second week of October, and as the food still continued to disappear after that time, the burrows were opened up and the animals caught and examined to find out their condition, on the following dates.—Oct. 13, Nov. 11 and 27, Dec. 18 and 26. They were found to be quite active on all these occasions, with rectal temperatures somewhere in the neighborhood of 100° F.

The weather up till the end of December had been unusually mild for this climate, and this might possibly have had some influence in maintaining the wakeful condition, but from the beginning of January till the end of March the winter was excessively cold, the air temperature being often below zero fahrenheit, and on two occasions 16° below.