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Population Biology of Snowshoe Hares. I. Demography of Food-Supplemented Populations in the Southern Yukon, 1976-84

Charles J. Krebs, B. S. Gilbert, S. Boutin, A. R. E. Sinclair and J. N. M. Smith
Journal of Animal Ecology
Vol. 55, No. 3 (Oct., 1986), pp. 963-982
DOI: 10.2307/4427
Stable URL: http://www.jstor.org/stable/4427
Page Count: 20
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Population Biology of Snowshoe Hares. I. Demography of Food-Supplemented Populations in the Southern Yukon, 1976-84
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Abstract

(1) We studied the population dynamics of snowshoe hares (Lepus americanus) in the Kluane Lake region of the Yukon by live-trapping nine areas year-round. We provided rabbit chow as winter food to three of these populations from September to May, 1977 to 1984. (2) Peak densities were reached in 1980 and 1981 on all areas except Jacquot Island. Two areas with extra winter food maintained densities three times that of their controls, while one food-supplemented area on Jacquot Island showed little effect of improved feeding on hare density. (3) Supplementary food did not prevent the cyclic decline and all areas reached low densities by 1984. The beginning of the decline was delayed 6 months on one food area but not delayed on the other. (4) The amplitude of the cycle was 141-fold based on spring numbers and 268-fold based on August numbers. This is considerably higher than the amplitudes measured in Minnesota and Alberta. (5) The hare cycle was caused by changes in recruitment (probably determined by losses during the first 8 weeks of life), juvenile survival in autumn, and adult survival in autumn. Survival rates gradually decreased during the cycle, and were lowest in its decline phase. (6) Extra winter food did not prevent the drop in survival that occurs during the decline phase of the hare cycle, nor did it prevent the low recruitment rate that occurs during the decline.

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