Heat waves can be especially harmful to animals such as fish and insects that cannot regulate their body temperature. “Changes in air temperature will affect brain temperature,” says Baird. An overheated brain can interfere with the functioning of nerves and this, she says, “can affect sensation, memory and learning.”
Cross section shows bands of cells in the mouse hippocampus.
Credit: Raunak Basu/University of Utah, Salt Lake City
Cross section shows bands of cells in the mouse hippocampus.
Credit: Raunak Basu/University of Utah, Salt Lake City
When Baird and colleagues tried to teach bumblebees to associate sweet sucrose with blue and bitter quinine with yellow, most bumblebees learned the trick at 77°, but less than half managed to do so at 90°. Such impaired knowledge could spell trouble in the field: If insects forget which flowers they are supposed to pollinate (in the case of bumblebees, these include tomatoes and blueberries) or how to return home with nectar, not only will pollinators be harmed, but human agriculture will suffer as well, Baird says.
Heat also appears to dangerously reduce animals’ alertness. In Ridley’s recent experiments, once the mercury reached 96° Fahrenheit in the Kalahari Desert, spotted chicks lost their ability to respond appropriately to predators. In their study, the researchers used insects as bait to attract birds to a mysterious shape covered in a sandy-colored blanket. Once a grizzly came close, the scientists would reveal what lay hidden beneath: either a taxidermied cat-like carnivore called Janet, or a similarly shaped and colored wooden box. Birds became frightened by Janet in cold temperatures – they would scream, inspect their surroundings, or simply run away. But once the heat increased, they behaved the same whether they were facing a carnivore or a cannibal. Ridley suggests that this could increase the likelihood of lethal predator attacks as the heat increases, which could harm populations of babblers and other prey species.
These studies are not merely abstract. In the Kalahari, where southern spottedbills use their intelligence to find insects, temperatures are rising twice as fast as the global average. In tropical rivers, where male guppies search for mates, heat waves are becoming longer and more intense. It’s the same story across much of the planet – temperatures rise, and animals’ thinking becomes stressful, potentially putting species at risk. The impact may be magnified in some areas, such as cities, which often exhibit hotter temperatures than non-urban areas. If anything, Ridley says, “we’re probably underestimating the impact of increasing heat on animals’ brains.”
This story originally appeared on Knoebel Magazine.
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