Discovery and Characterization of High-frequency Calls in North American Flying Squirrels (Glaucomys sabrinus and G. volans): Implications for Ecology, Behavior, and Conservation

Abstract

Studies of bioacoustics of vertebrates primarily have focused on amphibians and birds. Comparatively, the acoustic repertoire of mammals is poorly understood, and even less is known about the production of high-frequency sound. Thus far, the study of ultrasound in mammals has focused largely on echolocating abilities of bats and odontocete whales. Studies examining high-frequency sounds used for communication generally have been limited to laboratory experiments with mice and rats. Considerably less is known about high-frequency sound in other mammalian taxa. Similarly, most studies of bioacoustics focus on a single type of call emitted by a species. There are few studies describing the repertoire of calls of mammals. I describe the first known ultrasonic calls in North American flying squirrels (Glaucomys sabrinus and G. volans) and demonstrate a complex repertoire of calls within both species spanning both sonic and ultrasonic ranges. Passive recordings were collected from captive G. sabrinus and G. volans to generate a library of calls for each species. The acoustic model accurately classified calls correctly 92.2% of time. To test the library using natural populations, acoustic surveys were conducted in the Piedmont Plateau and Coastal Plains of Alabama where G. volans occur, and in the Appalachian Mountains of western North Carolina where southern flying squirrels and endangered Carolina northern flying squirrels (G. s. coloratus) occur. Recordings of flying squirrels from acoustic surveys conducted in the wild were quantified and discriminant-function analysis was used to compare recordings from the wild to calls of animals in captivity. Acoustic surveys in the wild detected squirrels at 86 of 180 sites sampled for 47.8% success of detection. The discovery of high-frequency calls in North American flying squirrels may be useful for behavioral studies addressing function of varying types of calls, evolution of ultrasound in gliding mammals, and for detecting, identifying, and monitoring species by using acoustical surveys.