Wildlife response to infrastructure: the problem with confounding factors

Abstract

Understanding the effects of human infrastructure on wildlife is important for conservation and management and therefore widely studied. Challenges of many such studies are that they are often conducted after infrastructure establishment, when the exact consequence of the structure may be difficult to disentangle from other determinants of animal spatial use. To highlight these challenges, we use a case study of semi-domestic reindeer (Rangifer tarandus tarandus) spatial use within 5–6 km from an existing and a planned power line, using faecal pellet group counts in two areas in northern Norway. We found no relationship between pellet group density and distance to the existing power line, while the density of pellet groups decreased with increasing distance from the planned power line. Vegetation type was the main predictor of reindeer spatial use in the power line area, while elevation and vegetation cover accounted for the occurrence of reindeer in the area without power lines. Our results show that reindeer spatial use is a function of many aspects of the landscape, but not all of these are possible to control for. When this power line is built, what will an after-study of reindeer space use reveal? We underscore the importance of recording wildlife spatial use prior to, and after, infrastructure establishment for sound conclusions about animal response or lack thereof.