Figure 1

The hibernation and breeding phenology (2007–2011; mean ± SE) of free-living adult female arctic ground squirrels from two populations living 20 km apart in northern Alaska. A) Female phenology relative to the calendar year; B) Female phenology relative to the timing of spring snowmelt (‘0’ on the x-axis). (a) the time females emerged from hibernation, (b) the date of parturition, (c) the time females entered hibernation. The dashed gray lines represents 100% snowmelt, the solid black lines represents 100% snow-cover.