Effect of the environment, predation and life history on reproductive synchrony in Perissodactyla

Synchronising birth timing with the adequate environmental conditions as well as with congeners can affect juvenile survival and at a later stage, recruitment. In the case of endangered species, understanding the factors driving birth phenology is therefore critical to implement effective conservation and reintroduction policies. Currently, 75% of the Perissodactyla species (odd-toed ungulates) are threatened and some even already had to be reintroduced in their natural habitat. Using a comparative analysis framework, we investigated the effect of nine environmental, life history and predation factors on the synchrony of births in 27 populations of wild Perissodactyla across Africa and Asia. We confirmed the positive effect of environmental seasonality and latitude, as well as the negative effect of environmental productivity on birth synchrony, but we found no significant effect of environmental unpredictability. Life history traits had limited effects on birth synchrony in this order: the intensity of daily reproductive effort and pace of life were non-significant, and migratory behaviour had an unexpected positive association with birth synchrony, suggesting that the link between migration and reproduction might be more complex than the relief of environmental constraints initially expected. We found a positive effect of group size on birth synchrony, in line with the swamping hypothesis to reduce predation risk on neonates, but we found no strong support for a positive effect of predation exposure, measured as a qualitative index combining species-specific sensitivity to predation and site-specific predator abundance. Overall, our findings suggest that individuals adjust reproductive cycles in response to local ecological and social conditions, suggesting that conservation efforts such as reintroductions could benefit from taking into account the extent of the differences between the site of origin and the reintroduction site.