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New research reveals how extreme heat affects animal behavior.(Image credit: Mario Tama via Getty Images)Share this article 0Join the conversationFollow usAdd us as a preferred source on GoogleSubscribe to our newsletter
On a sweltering day in South Africa, female southern pied babblers find their thinking impaired. These medium-sized black-and-white birds are attempting to reach delectable mealworms placed behind a transparent barrier. On milder days, the birds can swiftly deduce that they simply need to navigate around the small plastic wall. However, when temperatures soar, the birds persist in futilely pecking at the barrier.
This experiment is part of an expanding volume of research demonstrating that animals experience cognitive disruption during heat waves. When the weather is hot, birds encounter difficulties in learning, canines exhibit increased biting incidents, and goat-like chamois become more prone to altercations. This poses a significant problem not only for those who encounter agitated canines. Amanda Ridley, a behavioral ecologist at the University of Western Australia and co-author of the pied babbler study, states that if animals cannot maintain sufficient alertness to locate sustenance or evade adversaries, their survival prospects diminish.
As climate change contributes to more frequent heat waves, such cognitive impairments across the animal kingdom could have cascading effects throughout entire ecosystems, elevating the risks for already vulnerable species. If pollinators lose their capacity to identify the correct blossoms, crops and wild flora may falter. If birds struggle to procure food with ease, their offspring may not survive. On a warming planet, a sharp intellect is progressively more crucial. Ridley remarks, “A shifting climate implies that your capacity for behavioral adaptation becomes even more vital.”
Hotheaded
There is considerable evidence indicating that animals are adversely impacted by heat. Birds, for instance, dedicate less time to foraging and nurturing their young; they even reduce their vocalizations. Instead, they will remain still for extended periods with their wings outstretched to radiate heat, and respire with their beaks agape. Some creatures seek refuge in shaded areas or retreat into cool burrows, foregoing meals in the process. Meanwhile, bees have been observed splashing water droplets on their faces mid-flight during intensely hot weather. Emily Baird, a neuroscientist at Stockholm University, explains that this method “provides convective cooling for their brain.”
However, some of the initial indicators that elevated temperatures can disrupt cognitive function emerged from studies involving humans. In the 1800s, Belgian astronomer Adolphe Quetelet observed a correlation between summer months and peaks in violent crime across France. Subsequent investigations have linked high ambient temperatures to incidents of gun violence, increased hospital admissions for mental health conditions, elevated suicide rates, and a rise in gambling activities. When it is hot, individuals experience difficulties with decision-making, and their memory recall is compromised. A study revealed that for students attending schools lacking air conditioning, an increase of just one degree Fahrenheit in the school year led to a 1 percent reduction in test scores.
There is growing evidence suggesting that other species may also display heightened aggression as temperatures climb. A 2023 study that analyzed nearly 70,000 reports of dog bites on humans across eight US cities, ranging from Chicago to Baltimore, found that such events were more probable on hot, sunny, and smoggy days. The likelihood of an incident was 10 percent greater on a 90-degree day compared to a 60-degree day—this finding persisted even after accounting for seasonal variations in human outdoor activity, as researchers controlled for these effects in their data.
Nevertheless, the researchers were unable to definitively determine whether dogs become more aggressive due to the heat, or if irritable humans provoke more attacks. Clas Linnman, a neuroscientist at the University of Miami and a co-author of the study, commented, “It is probable that both humans and dogs experience heightened stress and irritability at elevated temperatures.”
Furthermore, this phenomenon is not exclusive to canines: A 2025 study conducted in China indicated that a variety of animals, including snakes and felines, exhibit a greater propensity to bite humans during warmer periods.
Animals also appear to exhibit increased irritability towards one another, particularly when resources like food are involved. Scientists utilized binoculars and spotting scopes to observe wild goat-like chamois that subsist on protein-rich vegetation on the slopes of the Italian Apennine Mountains. Over 1,600 hours of observation spanning two summers revealed that as temperatures rose from 54 to 64 degrees Fahrenheit, vegetation became scarcer, leading to a surge in chamois aggression. The animals became territorial over food patches, displayed threatening postures, and engaged in pursuits, with some altercations escalating. The study’s authors project that chamois aggression will escalate by 50 percent by 2080 as a consequence of climate change.
The small tropical fish known as the golden julie also displays confrontational behavior in warmer conditions. Typically, when a golden julie is presented with a mirror, it perceives its reflection as an unfamiliar individual and exhibits some degree of hostility, such as raising its fin. However, if the water temperature, normally maintained at 78 degrees, is elevated to a hot 84 degrees, the fish is more inclined to become aggressive, potentially biting and thrashing its tail against the mirror in an attempt to intimidate or attack its reflected image.
Cognitive problems
Heat waves can also impede an animal’s capacity for learning, as observed by Ridley and her colleagues in their work with southern pied babblers. In one of their experimental setups, the birds were given a straightforward wooden block featuring two apertures, each covered by a lid. When a bird pecked at a lid, it would pivot, revealing either an empty cavity or a desirable mealworm (Ridley notes that babblers are “highly motivated by mealworms”). One lid was dark, while the other was a lighter shade of the same hue. During periods of intense heat, the birds required double the number of trials to ascertain that the mealworm was consistently concealed beneath the lid of the darker shade.
A wild pied babbler investigates a contraption that holds a tasty mealworm beneath one of two lids. The birds can learn to associate a lid of a particular color shade with the mealworm treat, but when it’s very hot, it takes the birds much longer to do so.
(Image credit: C. SORAVIA ET AL / ROYAL SOCIETY OPEN SCIENCE 2025, CC by 4.0)
In a separate study, scientists investigated zebra finches, attractive Australian songbirds, and discovered that elevated temperatures also impair their cognitive abilities. Elizabeth Derryberry, an evolutionary biologist at the University of Tennessee, Knoxville, and a co-author of the study, stated that when trying to figure out how to extract a mealworm from a transparent tube with an opening at one end, the birds would repeatedly peck at the tube. She likened this behavior to “banging your head against a brick wall.”
Adding to this body of evidence, research conducted several years ago indicated that mice exhibit difficulties navigating mazes and tend to forget previously encountered objects when temperatures are high. More recently, investigators found that male guppies, commonly kept as aquarium fish, also struggle to navigate mazes after prolonged exposure to heat-wave-like conditions of 90 degrees Fahrenheit for several days, even when the reward for successful navigation is a receptive female, which they typically find highly appealing.
For ectothermic animals like fish and insects, whose body temperature is regulated by their environment, heat waves could prove especially detrimental. Baird explains, “Environmental temperature fluctuations will influence brain temperature.” An elevated brain temperature could impede nerve function, which, she suggests, “may impact sensory perception, memory, and learning.”
In addition to highlighting behavioral changes, animal studies can also offer insight into how heat meddles with brain cells. Experiments with mice, for example, show that poor performance in hot mazes is linked to inflammation in the hippocampus, the brain’s memory center, and can lead to the death of neurons there.
(Image credit: RAUNAK BASU / UNIVERSITY OF UTAH, SALT LAKE CITY, CC by 2.0)
Baird and her associates attempted to train bumblebees to associate sweet sucrose with the color blue and bitter quinine with yellow. While most bumblebees successfully learned this association at 77 degrees Fahrenheit, fewer than half achieved this at 90 degrees Fahrenheit. Baird notes that such compromised cognitive function could lead to significant issues in natural environments. If insects fail to recall which flowers to pollinate (such as tomatoes and blueberries for bumblebees) or how to return to their nest with nectar, it could adversely affect not only pollinator populations but also human agriculture.
Heat also appears to dangerously reduce animal alertness. In Ridley’s recent investigations, once temperatures in the Kalahari Desert reached 96 degrees Fahrenheit, pied babblers lost their ability to adequately react to predators. During these studies, researchers enticed birds towards a concealed object covered with a sandy-colored blanket, using worms as bait. Upon a babbler’s approach, the scientists would reveal the item: either a taxidermied feline predator known as a genet or a wooden box of similar size and coloration. The birds exhibited fear of the genet in cooler temperatures, emitting alarm calls, scanning their surroundings, or fleeing. However, as temperatures increased, they displayed similar behaviors regardless of whether they encountered the predator or the inanimate box. Ridley posits that this diminished vigilance could result in a higher incidence of fatal predator attacks as temperatures rise, potentially impacting populations of babblers and other prey species.
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These research findings are not merely theoretical. In the Kalahari region, where southern pied babblers rely on their cognitive abilities to locate sustenance, temperatures are escalating at twice the global average rate. In tropical river systems, where male guppies search for mates, heat waves are becoming more protracted and severe. This pattern is consistent across much of the globe: as temperatures climb, animal cognition becomes strained, potentially imperiling various species. The effects may be amplified in specific environments, such as urban areas, which frequently experience even higher temperatures than rural locales. Ridley suggests that “We are likely underestimating the repercussions of increased heat on the minds of animals.”
This article originally appeared in Knowable Magazine, a nonprofit publication committed to disseminating scientific knowledge widely. Subscribe to Knowable Magazine’s newsletter.
