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A study of the ecology of beaver in central British Columbia Cottle, Walter Henry

Abstract

Prior to the present work no studies had been made of the ecology of beaver in the glaciated areas of the intermountain plateau of British Columbia, Field studies for this study were carried out in the forested areas of the Cariboo and Chilcotln Districts of the Province during the summers of 1949 and 1950. In 1950 these studies were limited to the trapllne of Mr. E. Collier, Meldrum Creek, B. C. Two pair of live beaver were released on Collier's trapline by the British Columbia Game Department in 1942 and by 1950 these had increased to twenty-one colonies in addition to animals harvested in 1950. Studies were made of some conditions affecting this increase. Examination of areas inhabited by beaver showed that although water is apparently important to the animals as protection from the climate and for escape from certain enemies, it also provides the means whereby the beaver store winter food. Records were kept of the water levels of nine beaver ponds and these showed that beaver dams act as a regulating mechanism and tend to prolong the flow of water in Meldrum Creek. A number of techniques were used to determine the food habits of beaver on the study area and these revealed that although beaver consume mostly the bark of aspen and willow, a number of other foods were taken. A study of the conditions affecting the rate of growth and reproduction of aspen was made. Tallies were made of the stumps of the aspen trees cut in 1949 by beaver of twelve colonies and of trees in sample areas in stands available to these colonies. Such tallies showed that beaver cut all sizes of aspen without preference and that the mean weight of barks and twigs made available by cutting was approximately thirty-seven hundred pounds per colony. Studies of the rate of cutting by beaver In relation to the availability and to the rate of reproduction of aspen demonstrated that beaver on the study area occupy two somewhat distinct habitats, namely lakes and streams. Populations on lakes tend to be stable as there is sufficient reproduction in the large stands available to maintain the stand during use by beaver. Populations on creeks eat out their food supplies and are thus forced to emigrate. By developing the aquatic habitat beaver were observed to have increased the habitat suitable to a number of other species of vertebrates.

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