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People often call temperatures "stupid hot" when they are too high. This phrase makes sense because heat really does make animal brains struggle to work properly. In South Africa, scientists studied southern pied babblers. These are medium-sized birds with black and white feathers. The researchers placed the birds near a clear plastic wall with mealworms hidden behind it. On cool days, the birds quickly flew around the wall to get the food. However, when the heat rose, the birds became very confused. They kept pecking at the clear plastic instead of going around it.
This experiment is part of new research showing that heat waves cloud animal minds. When temperatures increase, birds have trouble learning. Dogs tend to bite more often. Chamois, which are goat-like animals in the mountains, start fighting. This loss of mental sharpness is bad news for pet owners. It is also dangerous for the animals themselves. If creatures cannot stay alert enough to find food or avoid predators, their chances of survival drop significantly. Amanda Ridley, a behavioral ecologist, co-authored the study and warns about these serious risks.
With climate change, heat waves are becoming more common. This means these cognitive problems can spread through entire ecosystems. This puts fragile species at even greater risk. For example, if pollinators forget which flowers to visit, crops may fail. If birds cannot find food easily, their young may not survive. Mental sharpness is vital for adapting to a warming planet. "A changing climate means that your ability to behaviorally adapt is even more important," Ridley says.
Heat affects animal behavior in many ways. Birds spend less time looking for food. They also sing less. Instead, they sit with wings spread to release heat or pant with open beaks. Some animals hide in cool burrows and skip meals. Bees show strange behaviors in sizzling weather. They splash water on their faces to cool their brains. Emily Baird, a neuroscientist, explains that this helps them cool down.
Early hints that heat damages minds came from studies on humans. In the 1800s, a Belgian astronomer noticed that violent crime in France peaked in summer. Later studies linked high temperatures to gun violence and mental health issues. When it is hot, people struggle to make decisions and remember things. For students in schools without air conditioning, a year that is just one degree hotter can lower test scores.
Other species also become more aggressive when temperatures rise. A 2023 study analyzed nearly 70,000 dog bite reports in eight U.S. cities. The study found that attacks were more likely on hot, sunny, and smoggy days. The risk was ten percent higher on a 90-degree day than on a 60-degree day. This increase was not just because people take dogs out more often. Researchers controlled for these seasonal effects.
Scientists are unsure if dogs become aggressive from heat or if cranky humans provoke attacks. Clas Linnman, a neuroscientist, suggests both humans and dogs get stressed in high temperatures. This aggression is not limited to dogs. A 2025 study from China showed that snakes and cats also bite more when it gets hot.
Animals also lose their cool with each other, especially over food. Scientists observed wild chamois in the Italian Apennine Mountains. These animals feed on plants on steep slopes. When temperatures rose, vegetation became scarcer. Chamois aggression shot up. The animals became territorial and chased each other. Some attacks turned into physical fights. The study authors predict that chamois aggression will increase by fifty percent by 2080 due to climate change.
Small tropical fish called golden jules also become confrontational in the heat. Ordinarily, they show mild hostility to their reflection. But if the water temperature rises from 78 to 84 degrees, the fish becomes much more aggressive. It may bite the mirror and slap its tail against the glass.
Heat waves also hamper the ability of animals to learn. Ridley and her colleagues tested southern pied babblers again. The birds faced a wooden block with two holes covered by lids. Pecking a lid revealed either an empty hole or a mealworm. During heat waves, the birds needed twice as many trials to learn where the food was.
Another group tested zebra finches in Australia. High temperatures caused similar cognitive problems. The birds kept pecking at a see-through tube instead of reaching in for the worm. Elizabeth Derryberry, a biologist, described this as the bird equivalent of "banging your head against a brick wall."
For animals that cannot control their body temperature, heat waves are very harmful. Baird notes that changes in air temperature affect brain temperature. A hotter brain can hinder nerve function. This might affect sensing, memory, and learning.
When Baird tried to teach bumblebees to associate colors with sweet or bitter tastes, most bees learned at 77 degrees. However, fewer than half succeeded at 90 degrees. This impaired cognition poses serious risks. If insects forget which flowers to pollinate, both insects and human agriculture suffer.
Heat also diminishes animal vigilance. In Ridley’s experiments, pied babblers lost their ability to respond to predators when temperatures reached 96 degrees. They behaved the same way whether facing a real cat or a wooden box. This lack of fear could lead to fatal attacks.
These studies are not just abstract concepts. In the Kalahari, where pied babblers live, temperatures are rising twice as fast as the global average. Heat waves are growing longer and more intense. As temperatures climb, animal thinking becomes strained. Ridley suggests, "We are probably underestimating the impacts of increased heat on animal minds."