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“If there are fewer prey species, there will be fewer predators. Animals will be dying as a consequence of these conditions.”
Published Dec 09, 2023 • 3 minute read
A rabbit sits in the tall grass in the Bissell Centre parking lot, in downtown Edmonton Wednesday, Nov. 1, 2023. Photo by David Bloom /Postmedia
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Small children with sleds and snowshoe hares are waiting for the snow to come back — but not for the same reasons.
What’s recreational for skiers is life and death for small mammals betrayed by their own changing coats in an El Niño year.
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Dr. Mark Boyce, professor of biological sciences at the University of Alberta, said the driest November now on record at the Edmonton International Airport is having consequences for species that turn colour. The soft white camo uniform that serves them well most winters is a bull’s-eye flag to predators.
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“White-tail jackrabbits and snowshoe rabbits have turned white and they really stand out against the dark background,” he said, noting that white-tailed jackrabbits are showing up on campus in places they don’t usually frequent.
“I think it’s because they’re trying to find some type of cover,” Boyce said. “When the weather is doing strange things, they don’t do so well.”
The culprit is the El Niño cycle’s weather patterns, caused by winds and sea surface temperatures spawned by the Pacific oscillation. All that perturbs mammals that depend on specific conditions, he said.
Last weekend, 10 cm of snow on the ground in Nordegg in west central Alberta disappeared at lower elevations in a bareness that wreaks havoc on Alberta’s small mammals.
Beneath the snowy mantle
Typically, “subnivean” mammals like the marten prey on mice below the snow’s blanket of insulation against the cold.
Without that white blanket, they’re more visible, and vulnerable, to larger predators.
Most winters, the ermine — short-tailed weasel — blends in beautifully in a stunning robe of white.
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But the mice, woodrats, flying squirrels, even small birds on the carnivore’s menu become hip to their predator’s tricks against the brown backdrop on a snowless winter’s day.
Denuded, small mammals are a midnight feast for large winged predators — great grey owls, great horned owls and others “are doing well,” Boyce said.
Coyotes, too, spy stand-out prey from a longer distance — and pick them off accordingly. Sleek, healthy fur and a bright demeanour on coyotes observed on the outskirts of the Henday and on trails in Edmonton’s river valley show signs of a good feeding year.
Edmonton’s 1,500 coyotes have, for the most part, adapted to co-exist with humans, Boyce said.
“They’re doing very well indeed — some focus on wild prey, like jackrabbits, snowshoe hares and small mammals and birds. But there’s some that become garbage specialists and feed on human-left resources,” he said.
Generally, for the moment, until Alberta gets some substantial snow, it’s a predator’s market — but that, too, is cyclical.
“Species that rely on small mammals are going to take a hit because small mammal populations are going to decline because of these strange weather conditions,” Boyce said.
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Eventually, a run on prey animals trickles up to predators, he said.
“If there are fewer prey species, there will be fewer predators. Animals will be dying as a consequence of these conditions.”
Fair foraging, smaller melt
For the moment, the ungulates — deer, moose and elk — enjoy the snowless moment, foraging more easily for plant life that’s closer to the surface.
“Moose are well adapted to the Alberta environment and do fine most years under most conditions,” Boyce said.
In contrast, heavy snow can be hard on the ungulates. If it’s followed by warm weather melt and then another hard freeze, it creates a real barrier for them to access vegetation, he said.
With or without snow, ultimately, last summer’s drought conditions and fewer feet of snow would make life a bit harder for the ungulate crowd, Boyce said.
“The drought will affect the vegetation and the vegetation affects the animals. The ungulates and hares and jackrabbits all feed on vegetation. If you have poor vegetation growth because it’s been dry, that’s going to have a negative effect on the wildlife,” he said.
And in spring, a smaller overall melt would not saturate as well, and as a consequence plants wouldn’t grow as well. That would affect the entire system — humans, crops, the flow downriver — and the wildfire season, because everything would be drier than what’s ideal, Boyce said.
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