First assessment of the potential introduction by hunters of eastern cottontail rabbits (Sylvilagus floridanus) in Spain

Context. Humans have introduced lagomorph species in areas outside their native ranges for their meat, fur or value as game species. Assessing the rate of success of lagomorph introductions is vital to address the ecological damage they may cause. Cases of failed lagomorph introductions in apparently suitable areas may also shed light on mechanisms that may deter invasion, which are useful in developing strategies for population control. In Spain, it has been suggested that hunters introduced the non-native eastern cottontail (Sylvilagus floridanus) to compensate for the recent drastic declines of the native European rabbit (Oryctolagus cuniculus). Aims. Our main goals were to investigate (1) whether Sylvilagus rabbits have indeed been introduced by hunters across Spain, and (2) whether the species has become established in Spanish ecosystems. Methods. We interviewed 311 hunters or naturalists across Spain. The questionnaires inquired about the characteristics of game management in each locality, including the frequency of rabbit restocking, and particularly whether Sylvilagus rabbits had been released in the surveyed localities. In addition, we sampled 192 rabbit populations (n = 3974 individuals) across Spain by using molecular analysis to determine whether Sylvilagus rabbits were present in these areas. Key results. Our interview results suggest that Sylvilagus rabbits may have been released in 6% of the 311 localities surveyed. However, molecular analyses failed to confirm their persistence, because all samples belonged to O. cuniculus. Conclusions. We infer that Sylvilagus rabbits failed to establish themselves in Spain, although interviewees reported their introduction. Several reasons may explain the unsuccessful establishment of this species, such as a low propagule pressure, competition with native species, predation, inability to cope with local pathogens and unsuitable climatic conditions.