It is well known that high temperatures have effects on human behavior. Our brains function less well, and we tend to become more sluggish and grumpy. The same applies to animals, a growing body of research shows.
Emily Baird, lecturer in zoology at Stockholm University, has studied bumblebees and found that heat affects the bumblebees' memory.
Heat makes bumblebees dizzy and careless. They no longer remember which flowers provide the most nectar and if they do, they may not find their way home afterward, Baird says.
The result is that other bumblebees are left without food because one bumblebee can collect food for all its friends in the entire nest.
Important for food supply
"Bumblebees are one of our most important pollinators, and 70 percent of the plants we eat depend on them. If they don't function properly, it will affect many edible plants, such as beans, cucumbers, tomatoes and eggplants," Baird says.
Butterflies are another important pollinator.
When it is hot outside, butterfly larvae do not grow as well and adult butterflies that become heat-stressed have a shorter lifespan, says Lars Pettersson, associate professor of zooecology at Lund University.
If the number of butterflies decreases, there will be less food for birds and other animals that eat butterflies, such as bats, which will also become disoriented by the heat.
When it comes to birds, research shows that they stop looking for food for their young in the heat. They even chirp less. Instead, they sit still with outstretched wings and wide-open beaks to protect themselves from the heat.
Dogs more easily provoked
A study that reviewed nearly 70,000 reports of dogs biting people in eight American cities found that dog bites occurred more frequently on warm, sunny days.
The risk was ten percent higher on a day with a temperature of 32 degrees Celsius than on a day with 15 degrees Celsius. However, the researchers could not determine whether dogs actually become more aggressive, or whether it is people who are irritable from the heat who provoke more bites.
We have not noticed more aggressive dogs, but dogs are generally more sensitive to heat than people because they only sweat through their foot pads, says Janina Pfalzer at the Swedish Kennel Club (SKK).
Even when the temperature goes above 15 degrees Celsius, there is a risk of overheating.
An overheated dog will pant heavily. It may have pursed lips, as if smiling, and its tongue may hang far out of its mouth. The mucous membranes will be bright red or very pink, says Janina Pfalzer.
Facts: How to help animals
Set out shallow bowls of water and cat food for the hedgehogs. Other animals also benefit from being served water.
A birdbath helps birds and insects find relief from the heat. It is advisable to add rocks so that the insects can land without drowning.
Flowers in the garden or on the balcony provide bumblebees with nectar.
Water the lawn so hedgehogs and birds will find worms more easily.
Don't clean the garden too much; leave weeds and wood piles for the sake of insects.
Is asphalt okay to walk your dog on? Do the five-second test: Place the back of your hand on the asphalt. If you can't hold it for five seconds, it's too hot for your dog's paw pads.
If you suspect your dog has heatstroke, always contact a veterinarian. Never put a wet towel over an overheated dog. This traps the heat.
Source: Swedish Kennel Club, Emily Baird, Swedish Board of Agriculture
Cows are easily affected by heat stress. They stop eating and produce less milk.
Many animals, including snakes and cats, are more likely to bite people when it gets hot, according to a study from China in 2025.
Another animal that seems to lose its temper in the heat is the chamois, a type of mountain goat. Observations show that when the temperature rises from 10 to 19 degrees Celsius, the chamois' aggression towards each other increases.
A tropical fish, the Golden Julie, also becomes more confrontational in the heat. When the water temperature rises from 24 to 29 degrees Celsius, the fish is more likely to become aggressive and lash out with its tail.
Zebra finches need twice as many attempts to learn to find a mealworm during a heat wave compared to normal temperatures.
Bats become disoriented and dehydrated from heat.
Hedgehogs and some small rodents are sensitive to dehydration.
Source: Scientific American, AFP
