Page:Popular Science Monthly Volume 77.djvu/363

Rh Earlier or later in the autumn, according to the species, the bats retire to caves and hollow trees and similar places, where they cluster together, hanging by their hind claws, head downward, and clinging to one another as well as to the walls of their retreat. Such masses may comprise various species, yet all species do not retire at the same time.

The noctule is seldom seen abroad later than July—while the pipistrelle may be seen flying any warm evening during the spring, summer and autumn months.

Owing to the difference in the flying season of these different bats, it is only natural to suppose that the hibernation of the former species (noctule) is much deeper and longer than in the latter (pipistrelle), which may feed all the year round. Here in North America some bats may, and probably do, migrate southward to avoid the too intense cold, and among these is probably the noctule, which is the first to come and the first to go. These "flitter mice" are insectivorous, and before discussing some of the other mammalia, it may be advisable to call attention to some points of difference existing, during the hibernating state, between the carnivorous and herbivorous animals.

Bears come out of the hibernating condition as fat, or nearly so, as when they retired in the fall; marmots, ground squirrels, etc., emerge in poor condition, in some cases quite emaciated; this in spite of the fact that they are functionally torpid, while bears and skunks are not. Female bears even bring forth their young while hibernating and suckle them from about the beginning of February to April, while they obtain no nourishment themselves.

The bear and badger, in our northern and western climates, retire to their winter quarters and pass the greater part of their time in sleep, yet neither the brown bear nor the badger falls into a true state of hibernation. On the other hand, the black bear of North America is aroused with difficulty from his winter sleep, and this gives ground for the belief that he differs from the other species of bears in that he hibernates while the others do not.

The most perfect hibernating animal we have in Canada is the ground-hog (woodchuck), which hibernates in a burrow of its own