Jun 08, 2026 12:00:00

Extreme heat reduces animals' learning ability.

Many people find that when it gets too hot, their minds become foggy and they can't think straight. In fact, studies have reported that

extreme heat can impair cognitive function , but Marta Zaraska, a freelance writer living in France, has compiled various research findings suggesting that this decline in cognitive function due to heatwaves is not limited to humans but also affects animals.

Heat waves make animals stupid and aggressive | Knowable Magazine
https://knowablemagazine.org/content/article/living-world/2026/heat-waves-scramble-animal-minds-trigger-aggression

In the 1800s, Belgian astronomer Adolphe Quetelet noticed that violent crime in France peaked during the summer . Subsequent research has pointed to a link between high temperatures and gun violence , mental illness-related hospitalizations , suicide , and gambling .

When it's too hot, people have difficulty making decisions and their memory suffers. A 2018 study showed that students living in dormitories without air conditioning performed worse on cognitive tests compared to students living in dormitories with air conditioning.

Research shows cognitive abilities decline in rooms without air conditioning; how much does it affect performance? - GIGAZINE

In recent years, numerous studies have reported that extreme heat negatively impacts not only humans but also animals' cognitive abilities. A research team led by behavioral ecologist Amanda Ridley of the University of Western Australia investigated the effects of extreme heat on cognitive function using the Black- and-white Bush Warbler , a passerine bird that inhabits the savannas of southern Africa.

When the behavior of wild Black-and-white Bush Warbler birds was studied under various thermal conditions, it was found that when the temperature exceeded 35.4°C, they increased heat-dissipating behaviors such as opening their beaks wide, breathing heavily, and spreading their wings.

The research team also placed mealworms, a favorite food of the Black-and-white Bush Warbler, on the other side of a transparent wall and observed whether the birds could correctly go around the wall to obtain the mealworms. In this experiment, the Black-and-white Bush Warbler realized that they could eat the mealworms if they went around the transparent wall when it was cool, but as the temperature rose, they had difficulty realizing this and continued to peck at the transparent wall with their beaks.

In

another experiment conducted by Ridley et al., they gave black-and-white bush borers wooden boards with a 'light-colored lid' and a 'dark-colored lid.' The lids were designed so that the bush borers could open them with their beaks, and there was a pattern in which mealworms were always hidden under the 'dark-colored lid.' However, at higher temperatures, it took the bush borers about twice as many trials to notice this pattern.

It's not just the Black-and-white Bush Warbler that experiences cognitive problems in high temperatures. For example,

a 2023 study that examined approximately 70,000 reported cases of dogs biting people in eight US cities found that these incidents were more likely to occur on hot, sunny, and smoggy days. The risk of dogs biting people was 10% higher on days with temperatures of around 32.2°C compared to days with temperatures of around 15.5°C.

Animals often lose their composure, especially when food is involved. A 2023 study that observed serows feeding on plants in the Italian mountains for over 1600 hours found that when the temperature rose from 12.2°C to 17.8°C, the vegetation became sparser, and the serows' aggression increased sharply as a result. The study reported that as food became scarce, the serows became more territorial in their search for food, adopting threatening postures and chasing each other.

Furthermore, it is known that the golden julii , a fish native to Africa, recognizes its own reflection in a mirror as an unfamiliar individual and displays a certain degree of hostility, such as raising its fins. However, experiments have shown that when the water temperature rises from the usual 25.6°C to around 28.9°C, the golden julii's aggression increases, and they may try to bite their own reflection in the mirror or try to hit it with their tail fin.

This increase in aggression and decreased learning ability can be particularly harmful to fish and insects that cannot regulate their body temperature. In a 2022 study by neuroscientist Emily Baird and colleagues at Stockholm University, bumblebees , which are beneficial pollinators, were trained to associate sweet sucrose with blue and bitter quinine with yellow. Most bumblebees learned this association at temperatures below 25°C, but less than half were able to learn it at 32.2°C.

Baird pointed out that temperature changes affect the brain temperature of animals, which can disrupt nerve function and potentially lead to problems with sensation, memory, and learning. He argued that if bumblebees' cognitive function declines and they forget which flowers they should be feeding on, it could negatively impact tomato and blueberry cultivation, which rely on bumblebees as pollinators.

Furthermore, the decline in cognitive function due to rising temperatures also alters animals' responses to predators. In an experiment by Ridley et al., when black-and-white bush robins were shown either a harmless wooden box or a stuffed specimen of the harmful predator, the European genet (genet) , they showed a stronger reaction to the genet under lower temperature conditions, while their reaction to the genet became less pronounced at higher temperatures.

Ridley pointed out that rising temperatures increase the likelihood of deadly attacks by predators, which could negatively impact the populations of prey such as the black-and-white bush borer. 'We may be underestimating the impact that rising temperatures have on the mental health of animals,' he said.