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Habitat utilization by mule deer in relation to cattle and California bighorn sheep in the Ashnola River Valley, British Columbia Morrison, Douglas Charles

Abstract

Habitat use by mule deer, particularly in relation to use by cattle and by California bighorn sheep on the bighorn winter-spring ranges of Flatiron Mountain was studied from January 1968 through November 1969. Observations were made of (1) food habits, (2) forage production and utilization, (3) the effect of spring and summer utilization on subsequent forage production and (4) spatial and temporal distribution of range use. The results indicate that competition for forage between the native ungulates, deer and sheep, is largely obviated by differential habitat use. This may point to long term evolutionary ecological niche specialization. Some competition for forage occurs for a short period in the early spring when both ungulate species seek succulent new grass, the supply of which is at first limited. Cattle use of the winter-spring ranges was excessive and the diets of cattle and the native ungulates are similar, with the exception that utilization of grass by deer was less. Range use by cattle contributed to intra-specific cattle-deer competition on the grasslands in the spring and cattle-bighorn competition on the grasslands during the winter. The study of spring range utilization indicated that deer use was not detrimental to the 1969 annual forage production in areas used by deer. Spring range utilization by bighorn or bighorn in combination with deer reduced the standing crop of forage produced on the Agropyron spicatum dominated winter-spring ranges. Sheep utilization on South Slope during the summer, when forage growth was declining, further reduced the amount of forage available to the wintering bighorn population.

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