Masters Thesis

Distribution and quality of forage in relation to habitat use of female Roosevelt elk in managed forests of the Olympic Peninsula, Washington

I examined the relationship between seasonal habitat use and changes in cover and quality of forage in different vegetation types used by Roosevelt elk (Cervus elaphus roosevelti) in managed forests on the Hoko game management unit, Olympic Peninsula, Washington. Elk were expected to maximize energetic gain by using vegetation types that contained the greatest cover of good quality forage (i.e. high energy and protein content, low tannin content) during each season. Old clear cuts (21 years old) contained poor quality evergreen forage (e.g. Tsuga heterophylla, Gaultheria shallon), and elk used these old clear cuts less than expected given their availability throughout the year. Riparian areas contained good quality deciduous forage (e.g. Rubus spectabilis, Sambucus racemosa, Athyrium filix-femina), and elk used riparian areas more than expected given their availability in spring and fall. Shrub cover was extensive and shrub quality was good across the landscape in summer, and elk used each vegetation type, except old clear cuts, in proportion to its availability during summer. Forage cover was limited and quality was poor across the landscape in winter. Elk used each vegetation type, except old clear cuts, in proportion to its availability during winter. Non-forest areas had greater cover of good quality graminoids and forbs throughout the year than riparian areas and clear cuts, and were used more than expected given their availability. Younger clear cuts (≤ 21 years old) were never used more than expected given their availability, though they contained great cover of deciduous forage. However, they also had less cover of good quality forage than non-forest or riparian areas. In conclusion, when forage cover and quality were similar across vegetation types, elk used vegetation types in proportion to their availabilities. When forage cover and quality were greater in riparian and non-forest areas than in other vegetation types, elk used riparian and non-forest areas more than expected given their availabilities. Therefore, I concluded that elk maximized energetic gain by utilizing vegetation types that contained the greatest cover of good quality forage in each season. However, good quality forage species that have been linked to increased herd reproduction on the study area grew primarily in non-forest and riparian areas. These findings suggest that non-forest and riparian areas are of greater benefit to the nutritional condition and reproduction of Roosevelt elk on the Hoko game management unit than younger clear cuts.

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