Age Structure and Reproductive Activity in a Kansas Beaver Population

Abstract

Age structure and reproductive activity of beavers in Kansas were determined by examining carcasses collected from trappers. Kits and yearlings comprised 49% of the sample, and none of these were reproductively active. The mean number of embryos and/or placental scars in the uteri of female beavers older than yearlings was 2.9, and the litter size varied with age. Data produced by this study indicated that the beaver population sampled was not overexploited. Although many general aspects of beaver (Castor canadensis) ecology and behavior have been studied, relatively little is known about age structures and reproductive activity in beaver populations throughout much of North America. Most of the existing data on beaver population age structure and productivity are two or three decades old. Osborn (1953) reported on age structure and productivity of beavers in the montane areas of Wyoming and Leege and Williams (1967) provided similar data from a beaver population in Idaho. Productivity of beavers in Ohio was assessed by Henry and Bookout (1969), in Maryland by Larson (1967), and in Pennsylvania by Brenner (1964). More recently, studies by Wigley et al. (1983) and Payne (1984) have provided pertinent data from beaver populations in Mississippi and Newfoundland, respectively. However, no age structure or age-specific reproductive data have been reported for beaver populations in the Central Plains