It’s a horrible feeling: Damp with sweat, your skin clinging to the sheets as you lie awake, seemingly for hours, in a very hot bedroom.
Overheating is really bad for sleep. It disrupts our body’s natural cool-down process that helps us sleep. But luckily for many of us, we can crank up the AC or turn on the fan.
Wild animals don’t have that luxury.
A pair of new studies on mammals in Europe show that extreme heat disrupts their sleep, often significantly. For example, wild boars in the Czech Republic sleep 17 percent less during hot, summer days than during colder months. Papers are one found, “potentially leading to sleep deprivation.” the other Shows that deer fawns in Ireland also get shorter and poorer quality sleep on scorching days.
Among the only studies of sleep in wild animals, the study points to another way climate change will likely reshape the natural world. As summer heats up, animals may find it harder to sleep in the habitat they call home, potentially weakening their immune systems and chances of survival. This can push these animals into new areas, where they can spread disease and disrupt carefully balanced ecosystems.
“These studies point to a novel and potentially ecosphere-wide way that climate change could affect animals,” Sean O’Donnell, a professor of biology at Drexel University, told Vox via email.
What scientists learn when observing snoozing animals
Euan Mortlock spends a lot of time putting animals to sleep. He’s not an animal but a postdoctoral researcher at the University of Bristol, where he studies sleep in animals ranging from large mammals to fruit flies.
“People think of sleep as something that animals do during other interesting things, but I think it’s one of the most interesting behaviors to observe,” said Mortlock, lead author of two new studies, both published this spring.
One of the things that makes sleep so interesting, Mortlock says, is that almost all animals do it (except maybe sea sponges). Seals sleep while diving as deep as 300 meters, one Research has found. Jellyfish sleep, though they have no brain; research shows They pulse less frequently when they are asleep.
Fruit flies also sleep in the lab, Mortlock said. Rather adorablely, they tilt their heads slightly down, he says, and drop their tiny antennae when they nod. Mortlock is interested in how these tiny insects sense threats while they are asleep. His current research aims to determine whether the scent of a predator, say, will determine whether their brain will wake or sleep in response.
Sleep is incredibly important to human and animal health; It strengthens our immune system and brain and provides a range of other benefits. To that end, environmental changes that disrupt sleep can have dire consequences for survival and ecosystems.
Sleep is “essential for physical recovery and memory consolidation,” Daniel Blumstein, a behavioral ecologist at the University of California, Los Angeles, who was not involved in Morlock’s research, told Vox. “Thus, we should document the things that interfere with that.”
Pigs don’t like heat
People have phones and Fitbits and Apple watches that constantly track sleep. But, how do you measure this behavior in wild animals?
One way is to impose these types of technologies on them.
For research on wild boars, Mortlock’s colleagues captured a group of pigs in Europe and had devices called accelerometers attached to their necks. Accelerometer picks up fine movements. Critically, some of these movements correspond precisely to the specific posture of an animal when it is asleep. Every mammal species has a specific sleeping posture, he said. For example, pigs will either lie on their stomachs with their chins resting on the dirt or their heads touching the ground. Accelerometers can pick up this sleep signature.
Starting in early 2019, researchers monitored the pigs for several years, measuring the duration and quality of their sleep. They then compared those measurements to weather data, including temperature and humidity.
Ultimately, they found that sleep was “shorter, more fragmented and of lower quality at higher temperatures,” as they wrote in the study. Meanwhile, snow and rain produced higher quality sleep, probably because it cooled the animals (and didn’t disturb them too much because pigs usually sleep under bushes or trees).
A slightly earlier study of fallow deer in a park near Dublin – found similar results. Also led by Morlock, that paper, which was published in April and is based on more than 300 days of data, found that total sleep time and quality decreased in chicks on hot days. (The team similarly used accelerometers to study these mammals.)
Although Mortlock’s work is among the most comprehensive analyzes of sleep in wild animals, few previous studies have shown how heat disrupts sleep. A particularly dark one 2015 articleFor example, fruit bats in South Africa sleep less on hot days because they spend more time licking their fur, spreading their wings, and cooling off.
Will climate change make animals sleepless?
An obvious concern is that unusually hot days are becoming more common. A Recent reports Climate change has added an average of 26 days of extreme heat globally over the past year, according to the nonprofit Climate Central.
It can fuel insomnia in some animals like this pig to an extent.
“Given the key role of sleep in overall health, our results indicate that global warming, and the associated increase in extreme climate events, may have a negative impact on sleep, and consequently health, in wildlife,” said Isabella Cappellini, a co-author. Wild Boar’s paper and researcher at Queen’s University Belfast, said In a press release
Lack of sleep may mean that pigs are more likely to get sick or spend less time caring for their young, the authors wrote.
“We know that climate change causes a variety of stressors on animals, and this study reveals a new axis of stress that animals may experience as a result,” Briana Abrahams, an animal behavior and ecology expert at the University of Washington who was not involved in Morlock’s research, said in an email. via told Vox. “Animals (and humans) need sleep to recover from other stressors, so this study suggests that the effects of warmer temperatures on sleep may add to other negative effects of climate change on wildlife.”
It is also important to remember that many species are highly adaptable, especially wild boar. They won’t stop sleeping as the planet warms. Perhaps, they will change their behavior – they will spend more time bathing to cool off, for example, or move to colder areas. That could bring these animals closer to human communities, Mortlock said, where they’ve been known to litter, damage crops and tear up golf courses.
When wild animals migrate, they can also trigger cascades of ecosystem change by adding or subtracting key parts of an area’s food web.
Extreme heat undoubtedly presents all kinds of challenges for wildlife, many of which are already under siege from deforestation and other threats like poaching. It is wreaking havoc, for example, on coral reefs. Yet the specific problems associated with sleeping in hot conditions remain poorly studied and largely unknown.
“There is a huge gap in our understanding of sleep in the wild,” Mortlock said. “But with new methods, we can start to peek behind the scenes.”
