Mammal Remains in Owl Pellets

Abstract

The alert field worker has a good deal of the detective in him. He does not need to have an animal in his hands to be aware of its local occurrence, but uses all the clues he can discover. Although his primary interest may be in the welfare of the ruffed grouse or the white-tailed deer, he soon realizes, as Leopold has so well pointed out, that to attain his object he must be an ecologist, aware of the whole series of actions and interactions between all living organisms, and that to increase or decrease the number of any species he must exercise some degree of control over the whole environment. Obviously, any method which will enable him to learn more about the wildlife present in any area will be of value to him. Tracks and tracking methods have been well described by Brunner, Seton, and George F. Mason, identification of hairs by Leon Hausman, and the use of feces or scat as indicators of the presence of certain animals has been suggested by Seton. Still another method of checking the occurrence and seasonal abundance of small mammals, especially rodents, is by the identification of skeletal material found in owl pellets. Owls swallow their prey in large chunks, digest the flesh, and then regurgitate the cleaned bones and fur or feathers. These pellets, from one to six inches long, depending on the kind of owl, may be found under evergreens or wherever owls roost. Once a regular roost or nesting place has been found, one may gather pellets by the hundred. About the only things the beginner might mistake for owl pellets are weathered fox droppings, but the latter almost always contain some vegetable material and, when dry, are definitely dusty, whereas owl pellets contain nothing but clean bone fragments and fur or feathers. Identification of the bones is somewhat complicated by the owl's habit of killing its prey by crushing the back of the skull. Care must be taken, in handling the bone fragments, to see that the teeth do not drop out when the fur packing is removed. Even if the teeth are lost, however, the sockets give some clue to their shape, size and arrangement. The fragmentary condition makes a general key to the identification of skulls, such as that published by the author in his book, Name That Animal, of limited use. The following key has been designed especially for use on owl pellet material, is based on many years of interest in the subject, and has been well tested by people with no special zoological training. It offers two choices under each number. One of these will fit the specimen better than the other, the number at the end of that line indicating the next set of alternatives to be considered, until the name is finally reached. Check lists of local mammals and a check set of skulls of small mammals of the vicinity will, of course, be of much value in verifying the determinations.