Altitude, latitude, and climate zone as determinants of mountain hare (Lepus timidus) coat colour change

We utilized images from camera traps that were deployed by the SCANDCAM project (viltkamera.nina.no), originally designed to monitor Eurasian lynx (Lynx lynx). Camera traps were deployed in multiple study areas in an extensive grid with approximately one camera per 50 km2 grid cell (Figure 1). For this study, we selected all mountain hare records from the period between 25th November 2010 and 25th June 2019. Images containing mountain hares were recorded at 678 locations from 2010-2019 spanning a latitudinal gradient from 58°N to 69° N and altitudes from 0 to 841 m a.s.l. in Norway (Figure 1). To reduce pseudo-replication, we discarded observations recorded within 60 minutes of the previous observation. When mountain hares were identified, we classified moulting stage in three categories estimating the proportion of the hares’ coat (excluding the long white belly) which was white. 1) Hares with ≥90% white fur were classified as “white”, 2) hares with ≤10% white fur were classified as “brown”, and 3) all other hares were classified as “moulting”. All images were accessed on viltkamera.nina.no and were visually classified by one of two observers, and quality controlled whenever the observer was uncertain of how to classify the images.