Prey Cycles

a group of ptarmigan in the grass

NPS Photo / Kent Miller


Why Study Prey Cycles

  • Snowshoe hare and willow ptarmigan populations change in sync with each other. Both species go through cycles, or alternating periods of high and low population.
  • Hares and ptarmigans are the primary food source for Denali’s golden eagles. More golden eagles lay eggs and successfully raise young in years where hare and ptarmigan populations are high.
  • Golden eagle population cycles correlate with hare and ptarmigan cycles in a bottom-up process. In other words, the population of prey controls the number of predators.
  • Weather and climate have a strong impact on the population of hares and ptarmigans in Denali.

Research in the Park

Park scientists have been monitoring snowshoe hare and willow ptarmigan populations in Denali since 1988. This data shows long-term changes experienced by both species. Hare and ptarmigan populations will continue to be monitored as part of routine field work.

Peer-reviewed Publications

Holder K and Others. 2004. Genetic diversity and management of Nearctic rock ptarmigan (Lagopus mutus). Canadian Journal of Zoology. 82(4):564-575


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    Last updated: July 17, 2019

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