An investigation of the factors affecting carrying capacity of selected areas in Newfoundland for the beaver, Castor Canadensis caecator bangs, 1913

Northcott, Thomas Henry A. (1964) An investigation of the factors affecting carrying capacity of selected areas in Newfoundland for the beaver, Castor Canadensis caecator bangs, 1913. Masters thesis, Memorial University of Newfoundland.

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Abstract

Factors which influence the carrying capacity of habitat for beavers, Castor canadensis, in Newfoundland were investigated in two study areas of dissimilar habitat types. One area had served previously as a study area for other aspects of beaver ecology and here tagged beavers with known territories were an aid to the present study. -- Topography determines the type and availability of water for beaver colonization. Highest densities in Newfoundland are found in areas where many small ponds and streams of gradient less than 3 per cent occur in conjunction with hardwoods. Alder is the most important plant species, both as food and as building material. More than 90 per cent of all tree species cut are in the 1-3 inch diameter class. Aquatic vegetation, particularly the water lily, is the major constituent of the beavers' summer diet. -- Logging and forest fires are beneficial to beaver since they create conditions necessary for an invasion of hardwoods. Most species of vegetation flooded by beavers are killed in one or two years. Abnormal fluctuating water levels, as found in areas of logging operations, normally precludes beaver occupancy of these areas. -- Competition by moose and muskrat on aquatic vegetation is relatively heavy, but does not adversely effect the beaver. Moose browsing of alder is the only serious competitive influence to beavers and may cause colony abandonment. Main cause of abandonment is lack of food. Harassment by man or natural predators does not normally have a serious effect on the colony. -- Factors determining size of colony territory are: type of water, availability of food, age of colony and intraspecific conflict. These combine to determine the population density of any area. Scarcity of food caused much summer movement in one study area. Census counts from 1958-I963 revealed that beavers adjust their numbers to keep the population in balance with a changing food supply. -- Maximum carrying capacity of Newfoundland beaver habitat is probably 1 active lodge per square mile. A carrying capacity index of high, medium and low (1, .5 - 1> and < .5 active lodges per square mile) is suggested. Three habitat types are proposed with the water and food requirements and population potential of each.

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