The Influence of Vocalization on the Behavior of Beaver, Castor canadensis Kuhl

Abstract

The beaver in North America, Castor canadensis Kuhl, is a secretive animal generally spending much of its life in dens or lodges and is increasingly more confined with increasing latitude. In testing the use of vocalization as a means of social interaction it appeared that sound production had no survival value to such a secretive animal and that when sound was used it was initiated by a visual physical act more associated with their familial or colonial behavior rather than as a means of social control. It was found that there was a decrease in frequencies used with advancing age and age classes could be separated on this basis. INTRODUCTION Beaver are rarely known to vocalize in nature. They are secretive animals with crepuscular habits, which leave their home site, generally a lodge built of mud and sticks at water's edge, only to forage for food. Some occasionally disperse to other areas in search of water and to construct new lodges, but there is no documentation of sounds produced during this activity. In most cases sounds produced by beaver are heard emanating from a lodge and these are largely impossible to categorize. Numerous trappers have reported beaver kits (young of the year) following a canoe and calling plaintively. Tevis (1950) was able to distinguish numerous sound patterns in a family he kept under observation almost continuously for one summer and his opinion was that the young kits vocalized most frequently. Leighton (1933) mentions as many as seven different sound patterns associated with different behavior patterns in penned beaver of various age groups. Almost all study of vocalization and social interaction in mammals has dealt with animals that roamed or could roam at large, among whom sound production could assist in courtship, in delimiting terri- torial boundaries, or in locating other members of the species. This is not the case in the beaver, in which emission of sound would en- danger the individual or the group, and their habits appear to pre- clude sound as a means of social communication. Nevertheless, beaver do produce sound, and an analysis of a group of sounds made by 14 beaver kept in confinement on the University of Saskatchewan cam- pus is presented, with the objective of relating sound production to age in beaver and also to behavior and survival. METHODS The 14 beaver were grouped by weight into four age classes. Two were kits (young of the year), one was a yearling, nine were sub- adults (two- or three-year-olds), and two were adults (four years of age or more). The animals were kept in an insulated room and fed 198