Scorching summers may be turning Alberta cows into night owls, a new study suggests, which could mean greater losses for farmers.
Rangeland ecology professor Edward Bork and his team at the University of Alberta published a study last March on how extreme heat affects cattle movement.
Bork said he and his team stumbled upon their latest results during another study at the U of A’s Roy Berg Kinsella Research Ranch in 2021. As part of that study, the team strapped pedometers to the legs of 58 cows and heifers to track how and when they moved.
“I kind of equate them to an Apple Watch but for cows,” he said.
The summer of 2021 was extremely hot, with heat domes scorching much of western Canada and contributing to the wildfire that destroyed Lytton, B.C. When the team looked at the cattle’s step counts that summer, they noticed some strange patterns.
The team expected the cattle to become less active overall because of the extreme heat, Bork said. Instead, the pedometers showed that the cattle moved more, taking about 14 per cent more steps and lying down 1.5 per cent less on extreme heat days compared to normal ones.
They also shifted when they walked. Instead of roaming around in the day, Bork said the cattle did most of their extra walking from 11 p.m. to 4 a.m. and from 11 a.m. to 1:30 p.m., with the mornings and afternoons spent lying down.
And they changed where they walked. The team found the cattle hung around open areas such as riparian zones at night and marched into forests — which they normally avoid — during the afternoon on high heat days.
Midnight munchies?
These patterns suggest the cattle had shifted their feeding times, Bork said — they ate at night when it was cooler and lounged around during the hot afternoons. That noontime spike in movement likely happened when the cattle were forced to move to get water; cattle drink about 35 litres a day while on pasture. The cattle likely went into forests in the afternoon to find shade.
Bork said the team found cows (females with calves) walked less than heifers (females without calves) in the summer when it was hot, with the reverse happening in the fall. The team suspects this was because cows had to stick around their calves more in the summer; by fall, their babies were bigger, so the moms could move and eat more.
Delton Jubinville, who raises cattle just north of St. Albert, said he was a bit surprised by this study’s findings on cattle movement.
“Usually, they don’t move around much at night,” he said, although he noticed his cattle move a bit more in the evening during hot times.
While cattle have excellent night vision compared to humans, Jubinville said nighttime feeding could make them more vulnerable to predators, as they would spread out to eat instead of huddling up for safety. Sticking to shade can cause cattle to overgraze shaded areas and limit the amount of food they can take in.
“They just can’t consume enough to get the good gains.”
Climate change means ranchers can expect more extreme heat, and their cattle will need ways to keep cool, Bork said. That means providing trees and windbreak boards for shade and plenty of water, and could mean breeding heat-resistant cattle — perhaps ones with shorter hair and lighter coats.
To help cattle beat the heat, Jubinville said farmers should practise rotational grazing and preserve forested areas to make their fields drought-resistant. They can also put wire fences around forests so the cattle can enjoy their shade without rubbing against and killing the trees.
Bork’s study was published in the International Journal of Biometeorology in March 2025.
