Ecosystem Engineering Effects of European Rabbits in a Mediterranean Habitat

Beyond their role as primary consumers, herbivore activities can play a key part in spatial processes at the ecosystem level (e.g., McNaughton 1983; McInnes et al. 1992; De Miguel et al. 1997). Environmental factors such as geomorphology, soil and vegetation characteristics, slope, aspect etc., affect the spatial distribution of the resources they need, mainly refuge, food, and water. Therefore, a particular set of habitat characteristics influences the use of different areas for specific activities by a given herbivore species. In turn, the use of habitats by herbivores may affect such characteristics at different scales. This is the case of many sedentary herbivores which, after establishing themselves in a particular area of an ecosystem, begin their modification. Pond construction by beavers not only changes river-flow patterns and surrounding vegetation, but also nutrient cycling (Naiman et al. 1994; Pollock et al. 1995). Excavating mammals, such as prairie dogs and pocket gophers, can also have profound impacts upon soil processes and the vegetation surrounding their burrow systems (see Whitford and Kay 1999; Huntly and Reichman 1994 for thorough reviews). Species that can have significant effects on the spatial structure of the landscape and the distribution of resources, both for themselves and other organisms, are considered ecosystem engineers (Jones et al. 1994). These species can be important patch creators through their activities or structures, and these patches can be exploited by different animal and plant species, thus increasing biodiversity and potentially controlling many processes and affecting ecosystems at different scales.