Environmental seasonality and group size drive birth timing synchrony in wild odd-toed ungulates
A comparative analysis of 27 wild Perissodactyla populations across Africa and Asia identified key drivers of birth synchrony, including environmental seasonality, latitude, and group size. The study examined nine factors spanning environmental conditions, life history traits, and predation pressure in a group where 75% of species are currently threatened. Findings suggest conservation and reintroduction programs could improve outcomes by accounting for ecological and social differences between origin and destination sites.
Researchers used a comparative analysis framework to investigate what drives the synchronization of births across 27 populations of wild Perissodactyla — the odd-toed ungulates including horses, rhinos, and tapirs — spanning Africa and Asia. The study confirmed that greater environmental seasonality and higher latitude are associated with tighter birth synchrony, while higher environmental productivity reduces it; environmental unpredictability, however, showed no significant effect. Life history traits played a limited role: neither the intensity of daily reproductive effort nor pace-of-life metrics reached significance, and migratory behavior showed an unexpected positive association with birth synchrony rather than the relaxation of constraints that theory would predict. Group size had a positive effect on birth synchrony, consistent with the 'swamping' hypothesis — the idea that flooding the environment with vulnerable neonates simultaneously reduces individual predation risk — though a qualitative predation exposure index combining species sensitivity and local predator abundance did not show strong support. Because 75% of Perissodactyla species are threatened and some have already required reintroduction, the authors argue that understanding these drivers is practically important: reintroduction programs may benefit from carefully matching ecological and social conditions between source and destination populations to preserve adaptive birth timing.
What's missing
As a preprint posted to bioRxiv, this study has not yet undergone formal peer review, so findings should be interpreted with caution. The authors acknowledge that their predation exposure index is qualitative rather than quantitative, which may limit its statistical power. The study does not address how captive breeding conditions — common for many threatened Perissodactyla — may alter birth synchrony patterns relevant to reintroduction planning. The mechanisms linking migratory behavior to increased birth synchrony remain unexplained and are flagged by the authors as an open question.
What different sources said
- bioRxivCenter
Effect of the environment, predation and life history on reproductive synchrony in Perissodactyla
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