On an extremely hot day in South Africa, female southern pied babblers seem to lose their problem-solving edge. These medium-sized black-and-white birds are offered mealworms placed behind a clear barrier. When the weather is mild, they quickly work out that the easiest way to reach the food is to walk around the plastic wall. But once temperatures rise, many of them repeatedly peck at the barrier instead, unable to adjust their behavior.
This experiment is part of a wider body of research suggesting that heat does more than make animals uncomfortable — it can interfere with how they think. During hot spells, birds may struggle to learn, dogs appear more likely to bite, and chamois, goat-like animals found in European mountains, become more aggressive. These effects matter because an animal that cannot think clearly may have a harder time finding food, avoiding predators, or protecting its young.
As climate change makes extreme heat more frequent, these mental disruptions could have consequences across entire ecosystems. Pollinators that fail to remember which flowers provide food may affect plant reproduction and crop production. Birds that cannot forage efficiently may struggle to raise chicks. In a rapidly changing climate, the ability to adapt behaviorally is becoming increasingly important.
Animals Under Heat Stress
There is already strong evidence that heat changes animal behavior. Birds often spend less time searching for food and feeding their young when temperatures rise. Some reduce their singing and instead sit with wings spread, panting to cool themselves. Other animals hide in shade or underground burrows, even if that means missing meals. Bees have also been observed using water droplets while flying, which helps cool their heads and brains.
Early clues that heat can affect thinking came from studies of humans. In the 19th century, Belgian statistician Adolphe Quetelet noticed that violent crime in France increased during summer. Later research connected high temperatures with more gun violence, mental-health-related hospital visits, suicide, and risky decision-making. Heat can also weaken memory and judgment. One study found that students in schools without air conditioning performed worse during hotter school years.
Research now suggests that many other species may also become more reactive in hot conditions. A 2023 study analyzing nearly 70,000 dog-bite reports from eight U.S. cities found that bites were more common on hot, sunny, polluted days. The risk of being bitten was higher on a 90-degree Fahrenheit day than on a 60-degree day. Scientists could not say for certain whether dogs themselves became more aggressive, or whether overheated humans were more likely to provoke them. Most likely, both people and dogs experience more stress in extreme heat.
Other animals show similar patterns. A 2025 study from China found that several species, including snakes and cats, were more likely to bite humans during hot weather.
Heat can also intensify conflict between animals, especially when food is limited. Researchers studying wild chamois in the Italian Apennine Mountains observed them for more than 1,600 hours over two summers. As temperatures rose and vegetation became scarcer, the animals became more territorial. They threatened, chased, and sometimes attacked one another over feeding areas. Scientists predicted that climate change could increase chamois aggression by about 50 percent by 2080.
The golden julie, a small tropical fish, also becomes more confrontational in warmer water. Normally, when placed in front of a mirror, it reacts to its reflection as though facing another fish. But when the water temperature rises from its usual 78 degrees Fahrenheit to around 84 degrees, the fish becomes more aggressive, sometimes biting at the mirror or slapping it with its tail.
Heat and Learning Problems
Extreme heat can also reduce animals’ ability to learn. Amanda Ridley and her colleagues found this in southern pied babblers. In one experiment, the birds were given a wooden block with two covered holes. One hole contained a mealworm, while the other was empty. The lids were different shades of the same color. In cooler weather, the birds learned which shade signaled the food. During heat waves, however, they needed about twice as many attempts to learn the same rule.
Zebra finches show similar difficulties. When researchers gave these Australian songbirds a mealworm inside a transparent tube with one open end, the birds had to figure out how to reach the food. In high temperatures, they often kept pecking at the closed surface instead of using the opening, repeating an ineffective strategy.
Other studies have found that mice exposed to heat have trouble navigating mazes and remembering objects they had seen before. Male guppies also struggle with maze tasks after spending several days in unusually warm water, even when the reward is access to a female.
Animals such as fish and insects may be especially vulnerable because they cannot regulate their body temperature internally the way mammals and birds can. When the surrounding air or water heats up, their brain temperature can rise too. A warmer brain may interfere with nerve function, which can affect sensing, memory, and learning.
Experiments with bumblebees show this clearly. Researchers trained bees to associate sweet sucrose with the color blue and bitter quinine with yellow. At 77 degrees Fahrenheit, most bees learned the difference. At 90 degrees, fewer than half succeeded. In the wild, this could be serious. If bees forget which flowers are useful or how to return home with nectar, both pollinators and the plants they support may suffer.
Reduced Awareness of Danger
Heat may also make animals less alert to threats. In Ridley’s experiments in the Kalahari Desert, pied babblers became worse at responding to predators once temperatures reached about 96 degrees Fahrenheit. Researchers lured birds toward a hidden object using worms, then revealed either a taxidermied genet, a cat-like predator, or a harmless wooden box of similar size and color.
In cooler conditions, the birds reacted strongly to the genet. They called out, scanned the area, or fled. In hotter conditions, they responded almost the same way to the predator and the box. That suggests heat may reduce their ability to recognize danger, which could increase the risk of being killed by predators.
These findings are not only theoretical. In the Kalahari, where pied babblers depend on intelligence to find food and avoid threats, temperatures are rising twice as fast as the global average. In tropical rivers, where guppies search for mates, heat waves are becoming longer and stronger. Around the world, rising temperatures may be quietly weakening animals’ ability to think, learn, and survive.
Scientists warn that the true impact of heat on animal minds may still be underestimated, especially in places such as cities, where temperatures are often even higher than in surrounding natural areas. As the planet warms, the mental strain on wildlife could become another serious challenge for species already under pressure.