The realized niche of captive-hatched Houbara Bustards translocated in Morocco meets expectations from the wild

Abstract

The success of translocation programs aiming to boost the effective population size of a declining species is conditioned by the ability of released individuals to survive and breed effectively while they share the ecological niche of wild individuals. Although ecological niche models are increasingly used as tools for conservation translocations, the realized niche of released and wild populations is seldom compared. In this study, we used data from long-term monitoring of a reinforced population of Houbara Bustards in Morocco. We compared the patterns of use of ecological space in the wild by 446 captive-hatched individuals which settled for breeding with the patterns shown by the wild population from the monitoring of 233 wild-hatched adult breeders. We measured the between-sex similarity of the ecological niches and of the geographical distributions. We found that wild-hatched and captive-hatched individuals shared a large part of the ecological space, suggesting a successful integration of captive-hatched mature individuals. The wild-hatched individuals used a broader range of environmental conditions, driven by females that were, on average, older than captive-hatched females and dispersed toward more arid environments. Although the wild- and captive-hatched males had different geographical distributions, they had statistically equivalent ecological niches. This finding suggests that the released Houbaras succeeded in settling new lekking grounds within a similar ecological niche over a larger spatial extent. Such feedback from post-release monitoring is still rare and appears to be a critical validation step for the subsequent use of ENM in translocation programs to assess the quality of release sites.