This study was concerned with analysis of the habitat of beaver (Castor canadensis Kuhl). The hypothesis that an animal's condition reflects the adequacy of its environment was used as a basis for the evaluation. The growth rates of beaver on two different habitat types in Prince Albert National Park, Saskatchewan, are compared and the habitats are classified accordingly. Beaver were raised under experimental conditions at the University of British Columbia and the growth rates and feed consumptions were recorded. The bioenergetics of the beaver are calculated and the results, combined with qualitative and quantitative measures of the habitats on the study areas, are used to elucidate the energy relations of the natural colonies of beaver under study. The relative growth of some organ weights and body measurements are described. Unsuccessful attempts are made to derive a condition index for beaver by using all measurements available and subjecting them to various analyses. Finally, the sequential measurements of beaver on the study areas are compared for both summer and winter seasons. These studies indicated that the condition of a beaver, whether measured by growth rate or relative growth, accurately designates the value of its habitat. Differences in condition of beaver occurred most prominently during the winter as a result of the strict limitations in the quality and quantity of available food. Fourteen beaver livers were analyzed to determine whether a chemical change of liver tissue accompanies a change in the condition of the animal. Over the period studied, May 2 to October 15, no progressive change could be found. The reproductive rates of beaver from Elk Island National Park, Alberta, and Prince Albert National Park, Saskatchewan, are compared. Beaver from the former park showed a significantly higher reproductive rate. This was correlated with habitat differences between the two areas indicating that the reproductive rate is another attribute of the animal which will reflect the adequacy of the environment. / Science, Faculty of / Zoology, Department of / Graduate