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.

We determined the optimum transect length and spacing for detecting snowshoe hare (Lepus americanus) from snow-track surveys in a fixed area. We also evaluated the utility of the most reliable and efficient designs for indexing hare density. We constructed enclosures ($6.1 ha) at 2 locations in the Upper Peninsula of Michigan, USA, and populated the enclosures with radiocollared hares. Hare densities ranged from 0.2 to 1.5 hares/ha in the enclosures, comparable to low and high densities recorded at the southern extent of snowshoe hare range. During winters of 2012-2014, we conducted snow-track surveys along 9 transects spaced 25 m apart in the enclosures 12-65 hr after a snowfall and mapped the location of every track that intersected a transect. After standardizing the track maps by time since last snowfall, we simulated different transect lengths and spacing and evaluated whether hares were documented on the resultant transect segments. We deemed transect configurations reliable if >90% of the 10,000 simulations correctly denoted the site as occupied. Of the 28 possible transect configurations, only 10 combinations were found to reliably detect hares. We refined the 10 reliable configurations based on efficiency, where efficiency was based on the distance traversed by a surveyor. We recommend using transects that are 150 m in length with 100-m or 75-m spacing, or 125 m in length with 75-m spacing to reliably and efficiently survey a fixed area for snowshoe hares. Ó 2016 The Wildlife Society.