Hotter temperatures spark aggression in species from salamanders to monkeys
When the Heat Turns Up, So Do Tempers — Even in Salamanders
Humans aren’t the only ones who lose their cool in hot weather. Back in 2016, ecologist Kristen Cecala watched a surprising scene unfold inside a lab incubator: black-bellied salamanders lunging at one another like tiny brawlers. Barely the length of a hand, these Appalachian stream dwellers became territorial and combative, snapping at rivals with unexpected ferocity.
Cecala, of the University of the South in Tennessee, nicknamed the setup “salamander fight club.” Her goal was to test how rising temperatures influence amphibian behavior. The results were striking — salamanders at 25° Celsius were almost four times as likely to attack compared to those kept at cooler, more natural conditions of 15° or 20°.
And salamanders aren’t alone. Across the animal kingdom — from ants and minnows to monkeys and mice — research shows that higher temperatures often fuel aggression.
A Rising Trend With Rising Heat
As global temperatures climb, scientists warn that these subtle behavioral shifts could ripple through ecosystems. More fights among minnows, for instance, could fracture shoals and make them easier prey. Salamanders defending territories more fiercely might spread out, lowering population density and making them more vulnerable to decline. Ants growing bolder in warmer alpine regions might expand their colonies at the expense of rivals.
The pattern isn’t universal — some species remain unfazed — but for many ectotherms (cold-blooded creatures that rely on external heat to regulate body temperature), the link is clear. Heat boosts their metabolisms, burning calories faster and heightening competition for food.
“For salamanders, when resources feel limited, they’re less willing to let anyone else in,” Cecala explains.
In ants, the effect may be even simpler. Warmer weather brings more honeydew from aphids, providing surplus energy — some of which is apparently spent on fighting.
What About Warm-Blooded Animals?
Endotherms, like mammals and birds, can regulate their body temperature through sweating, panting, or seeking shade. Still, studies suggest they aren’t immune. Research has tied hotter days to aggression in monkeys, rodents, dogs — and even humans.
“Uncomfortable, stressful heat affects a number of psychological and physiological processes that can lead to increased aggression,” says environmental neuroscientist Kim Meidenbauer of Washington State University.
Some scientists point to calorie loss and metabolic strain, while others suggest the simple irritability of overheating. In humans, debates continue over whether crime spikes in hot weather reflect biological stress or just more people being outside. But as neuroscientist Clas Linnman of Massachusetts General Hospital notes: “Because this correlation is consistent across species, purely sociological explanations fall short.”
Fight Clubs of the Future
The bigger question now is what happens as animals adapt — or fail to adapt — to a warming world. Will aggression settle once species adjust, or will it reshape ecosystems entirely?
For Cecala’s Appalachian salamanders, the stakes are high. A little extra heat in their mountain streams might mean a lot more fighting. And that’s a reminder that climate change doesn’t just melt ice caps or shift weather patterns — it can reach right into the behavior of even the smallest creatures, turning peaceful streams into battlegrounds.