The complex effects of geography, ambient temperature, and north atlantic oscillation on the body size of arctic hares in Greenland

Greenland is one of the coldest areas on earth that are inhabited by animals. In this study, we sought to examine the effect of several environmental factors on skull size of Arctic hares (Lepus arcticus). We measured 263 skulls of Arctic hares, collected in Greenland between 1906 and 1971. We employed two full models: one that includes latitude, longitude, and seasonal surface temperature during collection year and a second that includes the two spatial axes and the North Atlantic Oscillation (NAO) index during collection year. We found complex relationships between the examined parameters and hare skull size, which resemble the trends reported by Post & Forchhammer (2002) between the NAO index and the population dynamics of caribou and musk oxen in Greenland. Our two models provided a similar picture of opposite trends in skull size across Greenland, as reflected by the two- or three-way interactions (between latitude, longitude, and temperature in the first model, and latitude, longitude, and NAO in the second model). This complex picture, in which during both summer and winter the pattern of change in skull size toward north-east Greenland is an inverse of that observed in its south-west, is illustrated in Figure 3. The first and second models explained c. 31% and c. 25%, respectively, of the variation in skull size in both winter and summer. We discuss several possible mechanisms that could affect skull size in such an opposite way across Greenland.