The Ottawa Citizen published this article on the eastern grey squirrel.
Despite the subhead that blames squirrels for damaging attics and electrical wires and calls them “pests,” the article had lots information on the history of this species.
For example, the article claims that the grey squirrel which is so common in Canadian cities today was actually rare in the early 20th century, so much so that a sighting of one in Toronto in 1901 caused people to go on safari to the “sleepy backwater of Leaside” in the hopes of spotting the animal again.
The article notes that in the city squirrels have few predators, other than cars, and the accompanying photo gallery of a grey squirrel retrieving hamburgers and fries from a trash suggests that they find many feeding opportunities in the city.
I would bet that one acre of urban land can support a lot more grey squirrels than one acre of hardwood forest, which is their original habitat.