Ecology of Deer Range in Alaska

Klein, David

A study was conducted in Southeast Alaska during the summers of 1959, 1960, and 1961, to identify the factors of the environment which alter the plane of nutrition of deer (Odocoileus hemionus sitkensis Merriam) and result in variations in body size. On two islands, Woronkofski and Coronation, suspected to produce deer of wide contrast in body size, 63 deer specimens were collected from which sex, age, weights, and measurements were recorded and samples of rumen contents were collected and analyzed. Specimens were examined to determine levels of parasitism, and the sex and age status of deer that died from natural causes was utilized for additional data. The range vegetation on the two islands was evaluated through the use of line intercept transects and through chemical analyses of major forage species. Results of quantitative analyses of vegetation on the two islands indicate that Woronkofski Island greatly outranks Coronation Island in: (1) plant density and species abundance in the forest and muskeg types (110 to 54 interceptions in the forest type and 297 to 242 interceptions in the muskeg type), (2) total area of subalpine and alpine types (4.72 to 1.82 sq. mi. of subalpine and 5.00 to 0.24 sq. mi. of alpine type) and total area of forest type on an equal density basis (13.05 to 11.6 sq. mi.) and (3) total vegetated area on an equal density basis (24.31 to 16.51 sq. mi.). Qualitative evaluation of forage species through the use of chemical analyses did not show significant differences between islands in comparisons of similar species under comparable site conditions. There were indications that alpine and muskeg vegetation was of higher quality than forest vegetation, and alpine plants appeared to have slightly higher quality than similar species growing on low elevation muskegs. The physiological stage of plant growth apparently is the most important factor in determining nutritive quality of vegetation. Analyses of rumen samples enable a clear separation between Woronkofski and Coronation Islands on the basis of range quality. Nitrogen content in the rumen samples was higher in the Woronkofski group than in those from Coronation Island while an inverse relationship existed with respect to fiber content. Also weights and skeletal measurements of the specimen deer showed growth difference between the two islands which are apparently attributable to differing levels in the annual nutritional regimens of the deer. No statistically significant differences, that could be related to nutritional factors, were found in the levels of parasitism among the deer of the two islands. This may have been a product of the small size of the sample, however when compared with population age structures, levels of Dictyocaulus viviparus appeared to be higher in association with the poorer range conditions on Coronation Island. The sex and age composition of the deer populations on the two islands reflects the quality and quantity of the forage present on the ranges. Woronkofski Island deer, in contrast to those on Coronation Island, had (1) a higher ratio of fawns to adult females, (2) a younger average age, (3) a more even sex ratio both in the living population and among those found dead on the range, and (4) a lower natural mortality composed of primarily young animals.

Ecology of Deer Range in Alaska

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