Extreme heat is muddling animals’ brains—and even triggering aggression | Scientific American
June 24, 2026<br>6 min read<br>Add Us On GoogleAdd SciAm<br>Extreme heat is muddling animals’ brains—and even triggering aggression
As temperatures rise, some creatures pick fights while others struggle to learn
By Marta Zaraska & Knowable Magazine
Paul Biris/Getty Images
On a blazing hot day in South Africa, female southern pied babblers can’t think straight. The medium-sized black-and-white birds are trying to get at tasty mealworms behind a see-through barrier. On cooler days, the birds can quickly figure out that all they have to do is go around the small wall of plastic. But when the mercury goes up, the birds just keep stubbornly pecking at the barrier.<br>That experiment is part of a growing body of research showing that animals get their minds muddled during heat waves. When it’s hot outside, birds struggle to learn, dogs bite more often, goat-like chamois pick fights. This is bad news not just for those who get on Fido’s toasted nerves. If the animals can’t stay alert enough to find food or avoid predators, their chances of survival go downhill, says Amanda Ridley, a behavioral ecologist at the University of Western Australia who coauthored the pied babbler study.<br>With climate change making heat waves more common, such cognitive impairments across the animal kingdom could ripple through entire ecosystems, putting already fragile species at greater risk. If pollinators forget which flowers to visit, crops and wild plants may fail. If birds can’t find food as easily, their young may not survive. And on a warming planet, a sharp mind is particularly vital. “A changing climate means that your ability to behaviorally adapt is even more important,” Ridley says.<br>On supporting science journalism<br>If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.<br>Hotheaded<br>There is plenty of evidence that animals are affected by heat. Birds, for example, spend less time looking for food and feeding their young; they even sing less. Instead, they’ll sit around for hours with wings spread to dissipate the heat, and pant with their beaks wide open. Some animals retreat to shade or hide in cool burrows — again, skipping meals. Bees, meanwhile, splash their faces with droplets of water midflight when the weather is sizzling. This way, “they get convective cooling for their brain,” says Emily Baird, a neuroscientist at Stockholm University.<br>Some of the first hints that hot temperatures can mess up minds, however, came from studies on humans. Back in the 1800s, Belgian astronomer Adolphe Quetelet noticed that violent crime in France peaked in the summer. Later studies linked high temperatures with gun violence, mental-health-related hospital admissions, suicide and gambling. When it’s hot, people have trouble making decisions, and their memory suffers. For students at schools without air conditioning, a school year just one degree Fahrenheit hotter reduces test scores by 1 percent, a study found.<br>Increasingly there’s evidence that other species may also be more aggressive when mercury shoots up. A 2023 study that combed through nearly 70,000 reports of dogs biting people across eight US cities, from Chicago to Baltimore, found that such incidents were more likely to happen on hot, sunny and smoggy days. The risk was 10 percent higher on a 90-degree day than on a 60-degree day — and not only because people are more apt to venture out for walks when the sun is shining (the researchers controlled for seasonal effects in their data).<br>Still, the scientists were unable to determine whether dogs get more aggressive as it gets hot, or if cranky humans provoke more attacks. “It’s likely that both humans and dogs get stressed and more irate at higher temperatures,” said Clas Linnman, a neuroscientist at the University of Miami and a coauthor on the study.<br>And it’s not only dogs: A 2025 study out of China showed that many animals, including snakes and cats, are more inclined to bite people when it gets hot.<br>Animals also seem to lose their cool with each other, especially if there is food involved. Scientists used binoculars and spotting scopes to spy on wild goat-like chamois that feed on protein-rich plants on the slopes of the Italian Apennine Mountains. More than 1,600 hours of observations over two summers revealed that when temperatures rose from 54 to 64 degrees Fahrenheit, vegetation grew scarcer, and chamois aggression in turn shot up. The animals became territorial over patches of food, they assumed threatening postures, chased each other — attacks that, at times, escalated. The study authors predict that chamois aggression will go up 50 percent by 2080 due...