At least 5 million species of plants and animals share the planet earth (Vié, Hilton-Taylor & Stuart 2009) and, in 2011, the human population passed 7 billion, increasing the pressure on every other species. The requirements of wildlife populations for land and resources overlap with those of human populations, thereby leading to human/wildlife conflict (Lamarque et al. 2008). Indeed, advances in transport infrastructure, technology and agricultural practices have meant that remote areas supporting wildlife are increasingly affected by anthropogenic forces. Important habitats are being lost globally and this is the greatest threat to the world’s mammals (Vié, Hilton-Taylor & Stuart 2009). Of the global land mass, 12.7% has been classified as protected areas (IUCN and UNEP-WCMC 2011), although this protection has a mixed effect in conserving biodiversity (Bruner et al. 2001; Craigie et al. 2010). The lack of buffer zones around protected areas and corridors between them result in hard boundaries between wildlife and human populations, which in turn leads to both conflict and habitat fragmentation (Ogutu et al. 2009; Metzger et al. 2010; Kaczensky et al. 2011).
In an effort to mitigate this conflict and conserve wildlife, fences are increasingly used to demarcate land use zones and separate wildlife and livestock (Hayward & Kerley 2009). Yet these fences have the potential to have both positive and negative effects, particularly for large, highly mobile animals which regularly range outside protected areas to meet their seasonal requirements (Homewood et al. 2001; Ferguson & Hanks 2010). Understanding how large migratory herbivores respond to resource heterogeneity and anthropogenic influences will help us to conserve functioning ecosystems and vital habitats whether or not they are inside protected areas (Thirgood et al. 2004; Harris et al. 2009).
ANIMAL MOVEMENT AND RESOURCE USE
Animals move at multiple spatial scales and understanding the causes, patterns, mechanisms and consequences of this movement is integral to managing and conserving ecosystems (Nathan et al. 2008). Migration is one of the most widely observed movement phenomena in nature (see Milner-Gulland, Fryxell & Sinclair 2011), occurring across a variety of invertebrate and vertebrate species (Dingle & Drake 2007) as an adaptive response to spatial and temporal heterogeneity in resources (Holt & Fryxell 2011). Even small levels of seasonality in resource availability can lead to migration (Fryxell 1991), while the act of migration can have significant ecological impacts through interactions with other species and resources (Holdo et al. 2011b). For instance, a loss of large herbivore migration in the Serengeti is predicted to lead to the collapse of the Serengeti ecosystem (Harris et al. 2009). Yet while we can describe the variation in migration patterns for a range of animals, very little is known about migration theoretically (Milner-Gulland, Fryxell & Sinclair 2011). The use of GPS technology (Tomkiewicz et al. 2010) makes it possible to focus more on the individual animals rather than the population so as to help understand the fitness consequences of migratory behaviour (Milner-Gulland, Fryxell & Sinclair 2011). This in turn contributes to the development of successful conservation and management strategies.