Home range emergence through habitat preference and memory: An empirical study on a reintroduced large herbivore population
Home ranges and habitat use are two inter-related ecological properties of animals. In herbivores, they are both the result of multiple drivers, such as feeding needs, anti-predatory tactics, mating system, and memory. Traditionally, habitat use has been investigated at either the landscape scale, or the home range scale. However, resource choice and space use occur ‘step by step’, through a continuous process, based on movement. Individual tracking technologies have recently favoured a ‘trajectory based’ approach to study animals’ space use, but disentangling the effect of the aforementioned multiple factors is still demanding. In this study, we use GPS data from reintroduced individuals of a small deer, the European roe deer Capreolus capreolus, to investigate home range emergence after release in a completely novel environment, i.e. with no initial memory effect. On top of macro-habitat geographic layers, we recorded fine-scale habitat variables in random sampling plots. We fitted a Poisson distribution to frequency of use of sites to assess macro- and micro-habitat selection by individuals in the first six months after release. We then used the main factors to perform step selection functions for cumulative time windows of relocations, thus measuring the variation in habitat preference after release.
Our preliminary results indicate that habitat selection of reintroduced individuals after release in the novel site was affected by few macro-variables which are known to be niche components of the study species, such as canopy cover, and early successional stages of the forest, and by a diversity of fine-scale variables, that respond to specific needs of individuals. For example, short distance hiding cover, rather than mean distance, was positively selected, probably as an anti-predatory tactic; abundance of tree sprouts was a factor positively affecting site use by roe deer, as well as early-stage shrubs, consistently with the feeding strategy of the species- a selective browser with high nutritional requirements. Interestingly, preference for fine-scale variables varied through time since release, whereas preference for macro-habitats was constant throughout. This study provides novel insights on the process at the basis of home range emergence as combination of unvaried (innate?) preference and site-specific, time-variable responses to the environment, with a possible role for memory.