Understanding the demography of a reinforced population: Long-term survival of captive-bred and wild-born houbara bustards in Morocco

Translocation of captive-bred animals to reinforce threatened populations is widely used as a conservation strategy for small and declining wildlife populations. A fundamental goal of these interventions is that trans- located animals will survive and improve the future viability of populations. To evaluate this goal, we need to estimate the long-term survival of both captive-bred and wild-born animals in reinforced populations in order to best assess the relative contribution of translocated individuals to population growth. Here, we used tracking data from a large-scale, long-term translocation program in Morocco to estimate long-term survival in a rein- forced population of houbara bustards (Chlamydotis undulata undulata). We estimated annual survival rates of captive-bred and wild-born houbara, and considered sources of individual and temporal variation in survival, including how age-specific rates vary between captive-bred and wild-born birds. Our results reveal key differ- ences in how survival varied with age between captive-bred and wild-born houbara. Survival of wild-born houbara was relatively high and constant beyond the first year of life, while survival of captive-bred birds increased more gradually in early years, approaching that of wild-born individuals in older ages. These results suggest that captive-bred houbara have high potential to contribute to the growth and persistence of houbara populations. Our estimates also highlight the importance of considering sources of individual variation in de- mographic rates when assessing the contribution of reinforcements to population growth. Finally, these analyses emphasise the need to estimate long-term survival when predicting the future viability of reinforced populations.