Short-term impacts of large re-stocking on European hare population dynamics in a grassland landscape

Context The current rate of biodiversity loss increasingly motivates population reinforcement efforts. If reinforcement aims at increasing population abundance, the factors that influence the success of such operations remain poorly understood. Moreover, unintended side effects may lead to the opposite outcome such as a decrease in abundance following reinforcement. The abundance of European hare (Lepus europaeus) in France has been repeatedly reported to be in decline since the 1960s, especially in grassland landscapes. Although past studies have investigated the effects of hare translocation operations (i.e. reintroduction and re-stocking) on post-release survival rates, whether these wildlife management actions have led to an increase in the population abundance of European hare remains unclear. Aims Our objectives were to assess the impact of re-stocking operations on the population dynamics of European hare in a grassland landscape in the Jura Mountains (France), where hare populations are declining in numbers, and to determine whether these actions effectively enhance local abundance. Methods We investigated here the effects of hare re-stocking on (1) the rate and causes of mortality of 103 released individuals (51 in 2021 and 52 in 2022) and (2) the overall spatial and temporal impact of releases on local population dynamics by analysing the variation of hare abundance estimated from nocturnal point counts. Key results Despite the large number of released individuals, we report a limited short-term temporal impact of re-stocking on local population abundance of European hare. Overall survival rates of released hares were low (<10% after 1 year) owing to predation (57%), roadkill (20%), and diseases (12%), although the relative contribution of each cause varied over time after release. Conclusion Our results suggest that re-stockings had limited benefits for the mitigation of European hare decline, primarily owing to high post-release mortality, which is likely being driven by predator attraction to released individuals, especially in the days following release. Implications Reinforcement operations, especially for prey species, should perhaps consider strategies such as acclimatisation, soft-release, and anti-predator training, to reduce predation risk and improve the success of these interventions.