Editorial NexoScience
A cricket chirps faster on a warm night than on a cold one. A fruit fly courts more quickly when the room heats up. It is tempting to assume that, as the planet warms, animals everywhere will simply mate faster and more often, as if courtship worked like a chemical reaction that speeds up with temperature. Biologists have wondered about this for years, because how a species mates is not a side detail. It shapes which genes get passed on and how well a population can hang on as its environment shifts.
Two researchers at the University of Aberdeen, Natalie Pilakouta and Anaïs Baillet, decided to find out whether that assumption actually holds up across the animal kingdom, not just in a handful of favorite lab species. They pulled together 53 separate studies, covering insects, spiders, crustaceans, fish, amphibians, reptiles and a couple of bird species, and combined them into a single statistical analysis, extracting 29 measurements of how long it took animals to start mating, 29 measurements of how picky they were about a partner, and 58 measurements of whether mating happened at all.
The tidy story does not survive contact with the data. Across all 53 studies combined, there was no consistent effect of temperature on how long courtship took, how choosy animals were, or whether mating succeeded. Some species mated faster in the heat, others slower, and just as many showed no change at all. When the researchers dug into why the results scattered so widely, they found that differences between species, not any universal biological rule, explained the vast majority of the variation, well over 90% in every trait they measured.
One pattern did survive, though, and it is a narrow one. Mating success went up, but only when the heat hit during the mating attempt itself, not when animals had simply grown up in a warmer environment or spent time in the heat beforehand. In other words, a warm moment can nudge two animals toward mating right then and there, but growing up warm does not seem to make a species mate more often over its lifetime. The authors suspect this has to do with metabolism, since warmer bodies process signals and cues faster in the moment, which can tip a borderline encounter toward a successful one.
There is also a real trade-off hiding in a smaller slice of the data. In the 10 studies that tracked both how long courtship took and whether it succeeded in the same animals, the two numbers moved in opposite directions almost every time. When heat shortened the time to mating, success went up. When it stretched courtship out, success dropped. That link was strong, a correlation of −0.77, which suggests that speed and success are tied together within a species even if the overall direction of that speed is unpredictable across species.
The other honest finding is about who has actually been studied. Insects dominate this entire field. Out of 53 studies, only two involved birds, and none involved mammals. That is not a minor gap. It means biologists still cannot say with any confidence whether warm blooded animals respond to heat the same way a beetle or a cricket does, because almost nobody has looked.
None of this means temperature is irrelevant to how animals mate. It means the relationship is not the simple dial that a lot of popular science writing implies, where hotter automatically means more mating or less choosy partners. The honest answer, backed by the largest synthesis of this data to date, is that the effect depends heavily on which species, which life stage, and which exact moment the heat arrives, and that predicting how sexual selection will shift in a warming world is going to require a lot more data outside of insects before anyone can generalize with confidence.
The findings come from Natalie Pilakouta and Anaïs Baillet, published in the Journal of Animal Ecology (2022). DOI: 10.1111/1365-2656.13761.
