By Joel Tansey, Black Press
On British Columbia’s Gulf Islands, racoons roam without fear.
With large carnivores – cougars, bears and wolves – having been eradicated from the islands about 100 years ago, the area has become a sort of racoon paradise.
This has an effect on local ecosystems.
Typically nocturnal, Gulf Island racoons boldly forage for food day and night. They’ll often venture away from land during low tide, up to a kilometre from shore. This gives them a dangerous level of exposure should any predatory trouble arise, but it never does.
“They spend less than one second of every minute with their heads up, scanning the environment, and 59 seconds with their heads down foraging,” said Liana Zanette, a biology professor at the University of Western Ontario.
Zanette looked at the effects that this lack of fear and clear over-indulgence was having on a racoon’s prey base. She discovered that inter-tidal life was severely affected on islands with significant racoon populations.
“We really wanted to pinpoint whether it was the loss of large carnivores that were driving this cascading effect… and also wanted to determine the extent of which this effect could be driven by fear, or really it’s the lack of fear,” Zanette explained.
Zanette and her team felt this would be a prime location to monitor how racoon behaviour would change should that fear be re-introduced.
That fear didn’t come in the form of actual wolves or cougars, but rather artificial fear that proved to be just as impactful.
The researchers worked on a couple islands over two years, hanging speakers along stretches of shorelines that would broadcast the sounds of barking dogs and seals.
Basically, they created a reason for racoons to be afraid again.
“We found that when they hear the sounds of barking dogs, they reduce their foraging by 66 per cent and that this had a huge effect on the prey base,” Zanette said. “When we restored just the fear of large carnivores back into the system, it reduced the foraging of the racoons, which led to a big increase in the inter-tidal crabs, an increase in the inter-tidal fishes and an increase in the larger red rock crabs as well.”
These effects then cascaded down through the various tiers of the food chain.
A similar study by Zanette has shown that fear manipulation can decrease the number of offspring in songbirds.
While the Kootenays still have intact, large carnivore populations, Zanette believes this type of research can apply to this region as well.
“In terms of managing wildlife populations and the ecosystem, what this is showing is that the presence of large carnivores is definitely important and it’s the fear that they instil in animals that is really driving a lot of responses,” she said.
The B.C. government has taken controversial steps in recent years to protect mountain caribou herds in the South Peace and South Selkirk regions of the province through a wolf cull. The CBC also published an article in February of this year that quoted hunters and ecologists who believe that further culls of regional carnivores may be needed to protect dwindling elk and moose populations in the East Kootenay region.
Zanette didn’t offer an opinion on the government’s wolf cull, but said that it can be beneficial to look at alternative methods as well.
“It’s not like the wolves are going to be completely exterminated…but alternatives could be tried,” she said.
For example, Zanette is hoping to do a manipulation to protect Vancouver Island marmots from cougars through the use of a cougar’s natural fear of humans. Human sounds were shown to instil fear in cougars in California, and Zanette hopes to be able to use this method to protect marmot populations on the Island.
Sound interesting? Zanette will be giving a talk called “Fear of predators as an ecosystem service” at Revelstoke Mountain Resort this Wednesday, April 6, at 7 p.m. It is the keynote speech at a conference on predator prey dynamics being held at the resort this week. Entry to the talk is free for the public.