Mark Elderkin said that in the United States the squirrels primarily eat mast, nuts from hardwood trees like oak and beech. But in Nova Scotia, a few years can go by with not a lot of production from those trees, and the squirrels become urban animals in order to thrive.
“It’s pretty clear that what’s allowing them to survive here is not just the mast,” Elderkin said.
“They’d never make it through the winters; our winters are just too severe. It’s bird feeders.”
He said squirrels have a “pretty specialized size and quantity of food” that they need to survive.
That means grey squirrels — which, at half a kilogram and 30 centimetres in length not including the tail, are twice as big or more than red squirrels — compete for food with smaller squirrels, chipmunks and birds. They will also eat bird eggs and nestlings.
“When you add an animal of that size into a food-limited environment, it’s going to compete in a major way,” Elderkin said.
When people have issues with grey squirrels there is almost always a bird feeder nearby, he said.
“I tell them to shut down the feeder and usually within a week they are gone.”
Elderkin said the introduction of foreign trees like black walnuts is also a drawing card.
Because of their size, he said, only the great horned owl and a couple of bigger raptors can take a grey squirrel. And because it’s less likely that foxes, coyotes and minks will be in urban areas, the lack of predation can help populations stay established.
“A weasel would certainly be outclassed by them; there’s no way it could tussle with them unless they were incapacitated in some way. They’re a pretty big, nasty bit of business with their teeth.”
The grey squirrel, which can also be black, or grey with red, became well-established in Annapolis and Digby counties about 60 years ago and has been steadily moving east through the Valley and beyond. Seeing the animals running through trees or flattened on the road is becoming more common in many communities.
Elderkin said the earliest record of the animal in Nova Scotia was when several were brought here in the mid-1800s as a gift from the United States. They were put in a cage outside Province House and later released, but a population wasn’t established.
It wasn’t until the 1930s that they were noted again, with scattered reports up to the 1960s. But those were mostly anecdotal, with reports of individual animals, Elderkin said.
After 1960, “things started to spike,” he said.
“The reports became pretty regular and predictable, and almost all of them were focused around the Digby-Annapolis area.”
He said almost all the reports were around CFB Cornwallis. The theory is that squirrels hitched rides on trucks going to the base from CFB Gagetown in New Brunswick, home to one of the oldest established sites for the animal in the Maritimes.
Elderkin said the squirrel is known as one of the top invasive species in the world.
“One of the incredible things about them is their legendary long-distance dispersal, which usually happens in late summer.”
Elderkin said he once stopped while driving near Bridgetown and watched a squirrel go along the road ahead of him for two kilometres.
“That squirrel never stopped. It stayed right on the side of the road and was running in a straight line.”
Still, they don’t seem to be establishing themselves along the Atlantic coast.
“I don’t have many reports of them along there, so the coastal environment might be limiting to them,” Elderkin said.
The squirrels have been reported from Yarmouth through Truro and to New Glasgow and Amherst.
“I don’t think they would survive on Cape Breton Island,” said Elderkin.
“It’s just too lean, with not enough mast growth there to sustain them through the summer months.”
Elderkin said there are no plans to do anything to deal with the population.
“There’s general concern, but (it requires) the public’s will to understand at the individual level what their role is in maintaining natural biodiversity in cities and towns.
“There’s a selfish streak in a lot of people who say, ‘I want to have my birds.’” He said that lack of understanding and insistence on feeding birds is causing plenty of trouble, not just by maintaining the grey squirrel but by spreading diseases that kill off birds.