Jacobs, Paul JuanBennett, Nigel CharlesDu Plessis, L.Hart, Daniel William2026-02-132026-02-132025-03Jacobs, P.J., Bennett, N.C., Du Plessis, L. et al. 2025, 'Fertility up in flames : reduced fertility indices as a consequence of a simulated heatwave on small African mammals', Journal of Zoology, vol. 325, pp. 254-266. DOI: 10.1111/jzo.13247.0952-8369 (print)1469-7998 (online)10.1111/jzo.13247http://hdl.handle.net/2263/108250DATA AVAILABILITY STATEMENT : All data are presented in the manuscript and Data S1.With the increasing frequency and intensity of heatwaves due to climate change, the survival and reproductive success of mammals could be under significant threat. However, the specific effects of these environmental stressors on mammalian reproductive fitness remain insufficiently explored. This study investigates the impact of a simulated heatwave on male fertility indices in two African rodent species: the mesic four-striped field mouse (Rhabdomys dilectus) and the Namaqua rock mouse (Micaelamys namaquensis) during the breeding season. We measured key indicators of male fertility, including testes mass, testes volume, seminiferous tubule diameter, the presence of sperm, and plasma testosterone levels. Our findings reveal that both species experienced significant effects on male fertility indices, with the smaller R. dilectus showing a decline in all fertility indices following a simulated heatwave. These results suggest that the projected increase in heatwave events may compromise the reproductive success of small mammals, potentially leading to population declines. Finally, this study highlights the need for focused studies on the effect of heatwaves on long-term reproductive success in both males and females.en© 2025 The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND).Climate changeRodentReproductionTestesTestosteroneGlobal warmingHeatwavesTemperatureArticle