A "wolf effect" is at work in Saskatchewan and Manitoba that seems to control how many foxes and coyotes there are in different regions, a new scientific report says.
Thomas Newsome and William Ripple, researchers with the Oregon State University's department of forest ecosystems and society, studied 30 years' worth of fur trapping records in the two provinces.
They also studied similar records in Alaska, Yukon, Northwest Territories, Maine, New Brunswick and Nova Scotia.
"Our hypothesis is that in areas where wolves are present, we should get more red foxes than coyotes," Newsome said.
Similarly, in areas where there are no wolves, there should be lots of coyotes and relatively fewer foxes, he said.
According to the results, published this week in the Journal of Animal Ecology by the British Ecological Society, the hypothesis was supported by the data.
In Saskatchewan and Manitoba, where wolves are mostly absent in the southern agricultural regions of each province, coyotes outnumber foxes on average by 3-to-1.
However, in the north, where wolves are abundant, it's a different story — foxes outnumber coyotes by an average of 4-1, with one spot having a 500-to-1 ratio. Wolves are said to be "suppressing" coyotes in these areas by outcompeting the smaller predators for prey.
Between the wolf and no-wolf areas in Saskatchewan and Manitoba is a 200-kilometre-wide transition zone where there are are some wolves, but not enough to change the balance between coyotes and foxes.
Newsome, who is a Fulbright scholar from Australia, says animal trapping records reveal a strong wolf effect across North America.
The researchers' findings could be important as efforts to reintroduce wolves continue in some areas of the United States.
Newsome thinks the results are also relevant outside North America, including with respect to dingoes in Australia.
There, the canine animals are the top predators in some areas, but are considered pests by livestock producers.
The North American data suggests that if dingo numbers are reduced, it could yield unintended consequences to other predators — such as creating a boom in feral cats and red foxes — and in general being harmful to the ecology, Newsome said.