Survival of translocated wild rabbits: importance of habitat, physiological and immune condition

Abstract

European wild rabbit populations are declining in Mediterranean ecosystems, where the species is of special conservation interest, and translocations are one of the most-used tools to recover populations. We evaluated the effects of habitat and physiological and immune condition on the short- and long-term survival of translocated adult wild rabbits. Rabbits were released in four different habitat treatments frequently used in conservation programmes: additional shelter, additional food, additional shelter plus food, predator exclusion and control. Before releasing the rabbits, we determined their physiological condition from body-mass and serum levels of urea, creatinine and total protein, and their immune condition from the concentrations of antibodies against myxomatosis and rabbit haemorrhagic disease. The risk of dying during the first 18 days post-release was two times lower in the predator exclusion treatment than that in the additional shelter, food, shelter plus food treatments and control. Short-term survival was also negative and positively correlated with creatinine and protein levels, respectively. The risk of dying from 19 to 180 days post-release in the additional food treatment was 10 and nine times lower than in predator exclusion and control, respectively, and negatively correlated with the antibody concentration against myxomatosis. The results suggest that short-term survival was related to predation risk and physiological condition, and long-term survival was related to food availability and myxomatosis incidence. We recommend that translocation programmes should consider using soft-release methods to reduce the risk of predation and ensure that all individuals are released in the best possible physiological condition to increase their short-term survival. We also suggest that the habitat be managed to ensure that the environment provides the appropriate conditions (i.e. food and shelter) for individuals and population persistence. Immune condition should be taken into account and translocation programmes should consider the origin of donor populations to reduce the variability of pathogen and virus strains.