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Demography of snowshoe hares in relation to regional climate variability during a 10-year population cycle in interior Alaska

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We monitored populations of snowshoe hares (Lepus americanus, Erxleben) in interior Alaska for 10years from 1999 to 2008. During this period, fall densities of hares fluctuated approximately 14-fold. High population growth rates over summer (= 1.83–8.00) were followed by large population declines over winter (= 0.16–0.82). Young-of-the-year hares tended to gain mass over winter, while adult hares tended to loose body mass. The average mass of adult hares was significantly lower during the low phase of the cycle compared with when hares were abundant. Overwinter survival of juveniles relative to adults decreased strongly as a function of the frequency of snowfall events. However, effects of temperature and precipitation on hare demography were season dependent and appear to act as modifiers of the primary controls over population dynamics (predation and food) rather than as direct sources of mortality. The rapid changes in green-up and snow-up in interior Alaska may affect forage conditions as well as the timing of molt in snowshoe hares. The strength of these interactions may increase in importance if the asynchrony of environmental seasonality and life history traits of snowshoe hares becomes more pronounced as the climate continues to change.

Nous avons effectué un suivi annuel des populations de lièvre d’Amérique (Lepus americanus, Erxleben) de l’intérieur de l’Alaska de 1999 à 2008. Au cours de cette période, la densité automnale du lièvre a fluctué d’un facteur 14. Les taux élevés de croissance des populations en été (= 1,83–8,00) ont été suivis d’importants déclins des populations en hiver (= 0,16–0,82). Les levreaux tendaient à augmenter leur masse corporelle en hiver tandis que les adultes tendaient à la voir diminuer. La masse moyenne des lièvres adultes était significativement plus faible durant le creux du cycle que durant la période d’abondance. La fréquence des chutes de neige influençait davantage la survie hivernale des juvéniles que celle des adultes. Toutefois, les effets de la température et des précipitations sur la démographie du lièvre dépendaient de la saison et semblaient agir comme agents modificateurs des principaux facteurs de la dynamique des populations (prédation et nourriture) plutôt que comme causes directes de mortalité. Les transitions rapides entre les saisons avec et sans neige à l’intérieur de l’Alaska peuvent influencer les conditions d’alimentation ainsi que la période de mue du lièvre d’Amérique. L’intensité de ces interactions pourrait s’amplifier si l’asynchronie entre la phénologie et les caractéristiques du cycle biologique du lièvre d’Amérique s’accentue en lien avec la progression des changements climatiques.

Document Type: Research Article

Publication date: 2010-07-01

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  • Published since 1971, this monthly journal features articles, reviews, notes and commentaries on all aspects of forest science, including biometrics and mensuration, conservation, disturbance, ecology, economics, entomology, fire, genetics, management, operations, pathology, physiology, policy, remote sensing, social science, soil, silviculture, wildlife and wood science, contributed by internationally respected scientists. It also publishes special issues dedicated to a topic of current interest.
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