Rabbits as a keystone species in southern Europe

A keystone species is one that is crucial in maintaining the organization and diversity of their ecological communities. We tested the idea that rabbits act as a keystone species in southern Europe by exploring relationships between rabbit abundance and the abundance and diversity of raptor species. At 20 sites in southern Spain we assessed rabbit abundance through counts of animals along transects and assessed the number of raptor individuals and species through watches from vantage points. In a further 120 locations we also derived an index of rabbit abundance, from pellets and compared this to the presence or absence of the critically endangered Spanish imperial eagle. Rabbit abundance was positively associated with the number of observations of raptors, the number of raptor species and the number of species of conservation concern. Sites with the most rabbits had higher conservation value. Moreover, the presence of Spanish imperial eagle was strongly associated with sites where rabbits were at high density. We conclude that rabbits do act as a keystone species and we suggest that conservation efforts should focus on improving the status of this small-game species in southern Europe.