Evolutionary and ecological determinants of the phenology of births in wild large herbivores, a systematic review

1. Introduction Timing of birth is a major determinant of individuals’ reproductive success and phenotypic performances, driven by multiple factors. However, there is currently no quantitative assessment of the support received by the drivers of the phenology of births in mammals. 2. Aims our objective was to identify the drivers tested for their effect on the phenology of births in large herbivores and how much empirical support they received, as well as determine thematic, taxonomic and spatial gaps in the literature. 3. Methods We conducted a systematic review focusing on the drivers of the phenology of births in large herbivores. We extracted the outcomes of 124 articles and assessed the reliability of their findings using a general index based on the quality of the data and methods used. 4. Results and Discussion We identified a major research gap in Asian and South and Central American species. The effect of population and individual characteristics remained marginally accounted for, even though there was evidence of their importance in the determination of the phenology of births. The two dominant hypotheses (seasonality and predation) received good to moderate empirical support regarding their effect on birth timing and synchrony, respectively. Given the strong geographic and methodological biases, these hypotheses should be considered as most consistently supported in the existing literature rather than definitively established across systems. 5. Conclusions We encourage research in these understudied domains, as well as large scale multi-species comparative analyses to fill in these gaps and improve our understanding of reproductive phenology. Graphical Abstract This semi-systematic review supports the two dominant drivers of birth phenology, the seasonality and predation hypotheses. Even though there is evidence of their importance, the effects of female, offspring and population characteristics remain marginally accounted for. Asian and South and Central American species are currently understudied.