Selection of artificial warrens following the restocking of an endangered keystone prey

Abstract

The European rabbit (Oryctolagus cuniculus) is an endangered species native to the Iberian Peninsula, playing a vital ecological role in Mediterranean ecosystems as prey for several threatened predators. Conservation efforts have been implemented to halt its decline, with a particular focus on the Iberian rabbit subspecies (Oryctolagus cuniculus algirus). Many conservation programmes involve restocking and habitat management, including the construction of artificial warrens to provide essential refuge sites. In this study, we examined the use of four types of artificial warrens (logs, Mayoral®, pallets and tubes) by a restocked Iberian rabbit population within a fenced park in southern Portugal. We investigated the factors influencing warren use, basing our analysis on faecal pellet counts at the entrances of artificial warrens. We analysed spatial and temporal patterns in warren use using a generalised additive mixed model. Additionally, we determined the efficiency of each type of artificial warren by computing the ratio between the costs of building the warren and the level of warren use by the rabbits. Our results indicate that Mayoral, tube and log warrens are significantly less used compared to pallet warrens (Logs: β=–0.171±0.041; Mayoral: β=–0.149±0.058; Tube: β=–0.240±0.071). Moreover, pallet warrens were found to be more cost-effective compared to other types analysed. Furthermore, rabbits preferred artificial warrens surrounded by a higher proportion of shrubs (β=0.132±0.037). Artificial warren use exhibited seasonal variation, declining gradually during the winter and early spring, and recovering in late spring, coinciding with the expected breeding peak. Based on our findings, we recommend the implementation of pallet warrens in rabbit restocking programmes to provide immediate shelter and breeding sites for the released rabbits. Furthermore, artificial warrens should be strategically located near shrub patches to facilitate safe access to vital resources such as food and water.