The northern interior grizzly bear Ursus arctos L

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Fifty-three different grizzly bears were captured on a 1,110 km² study area in southwestern Yukon Territory. At least 41 were considered residents and possibly as many as 49, or a density of one grizzly per 27.1 or 22.7 km² respectively. The age composition of the population showed a high percentage (76 per cent) of adult animals. Productivity was relatively low with an average litter size of 1.7 cubs and 1.5 yearlings, late maturation of females (6.5 to 8.5 years), and a minimum of 3 years between litters. A definitive technique of age determination was proven by counting cementum annuli in the teeth. The increase in breadth of skull was correlated with age and an acceptable, much simpler age determination technique was developed. Specimen material was collected from 320 grizzly bears and age data from 239 were used to prepare sex specific life tables. Mortality was generally higher in adult females than in adult males and higher in adults than in the young and subadult classes. The northern interior grizzly is a rather small ecotype in stature. I found that the average weight was 139 and 95 kg for adult males and adult females, respectively. Maximum weights were 240 and 125 kg, respectively. Weight loss over the winter was as great as 43 per cent of the pre-denning weight. The animals added weight rapidly in the autumn when feeding on soapberries (Shepherdia canadensis). Information was collected on general colour, moult patterns and colour changes, food habits and habitat selection, behaviour, activity patterns and home range movements, and den site characteristics. The harvest of grizzlies in the Yukon was analysed in detail. Information obtained during the study was synthesized and used as a basis for management proposals. An estimate of the total population of grizzlies in the Yukon Territory was extrapolated from the available data.

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Reference Code: A75PEA02IDUS

Full Citation: Pearson, A. M. 1975. The northern interior grizzly bear Ursus arctos L. Canadian Wildlife Service Report Series Number 34. Canadian Wildlife Service, Ottawa. 84 pp.

Location: ANIMAL EF: URSUS ARCTOS