Climate factors related to localized changes in snowshoe hare (Lepus americanus) occupancy

Abstract

Information on climate that influences snowshoe hares (Lepus americanus Erxleben, 1777) can inform adaptation strategies. We identified climate factors correlated with localized changes in occupancy of snowshoe hares in Michigan, USA. A change in occupancy occurred if a site (∼7.5 ha) knowingly occupied by hares sometime in the past became unoccupied. We used local ecological knowledge to map sites where hares historically occurred and to assign a year of last-known occupancy. At 134 historically occupied sites, we conducted snow track surveys in 2013 to determine current occupancy status. We identified climate variables having relevance to hare population demographics and modeled the likelihood that those variables influenced current occupancy status. The top-ranking model included maximum temperature from 15 May to 19 January; as maximum temperature increased, the likelihood of a site becoming unoccupied increased. The second-ranked model included total number of days with measurable snow on the ground; as days with snow on the ground decreased, the likelihood of a site becoming unoccupied increased. Our data indicated that site occupancy status of hares can be described by climate variables and that the southern edge of snowshoe hare distribution in Michigan shifted northward by ∼45 km over the last 20 years.