Spatial and Energy Requirements of Beavers

The relationship between energy intake and metabolic requirements of beavers {Castor canadensis) is discussed in regard to the spatial requirements of three colonies. A 26pound yearling beaver requires 850 kcal of digestible energy, or 1.5 lb of fresh aspen per day, to maintain its daily metabolic processes with no additional growth. In order for such a beaver to attain maximum growth, 2040 kcal or 3.6 lb of fresh aspen/day are required. An acre of aspen produces 5,840 lb of food, so there: would be sufficient energy to maintain a population of 10 beavers for 442 days if no growth of beavers occured. If one acre of aspen would maintain the population for one year, there would be 2.8 lb of fresh aspen/day which could be utilized for growth within the population. This study investigated the spatial and energy requirements of beavers (Castor canadensis) in three colonies in Crawford County, Pennsylvania. The period of investigation was from 1 January 1959 through 1 January 1962. Data concerning energy intake of individual beavers per day were based mainly on the daily food consumption per beaver per day previously reported by Brenner (1962). Other authors have reported on the movements of beavers (Beer, 1955; Hodgdon and Hunt, 1955); the current study, however, attempted to determine the feeding ranges during the period when the individuals in the colonies were establishing their winter food cache. The relationship between the energy intake of beavers and the metabolic requirements of the species under natural conditions has also not been discussed previously. In the current study, the energy requirements were investigated in relationship to the feeding ranges of the colonies.