Loren Michael Mortimer
recently posted at Early Canadian History on bear and squirrel migrations across the St. Lawrence River in the late 18th century:
In September of 1759, great armies were on the move through the upper St. Lawrence Valley. Not the military forces under the command of Montcalm and Wolfe en-route to their climactic showdown on the Plains of Abraham, but an army of black bears migrating en-masse southward from Canada into Britain’s Atlantic colonies. During that autumn, newspapers from New England and New York recorded a southern migration of bears, accompanied by an equally mysterious appearance of thousands of black squirrels. Bears were reported in the city of Boston for the first time in a century—a large bear “the size of small cow” was shot on a Boston wharf as it swam across the harbor from Dorchester Neck.
Bears were “spreading mischief” on colonial farms from the New England frontier to the lower Hudson Valley, devouring fields of “Indian corn” and destroying stocks of hogs, sheep, and calves. British army officers bemoaned frequent bear sightings near General Jeffery Amherst’s field headquarters on Lake Champlain. Newspapers printed lurid tales of a bear attacking and eating two children as they picked beans in a field in Brentwood, New Hampshire. One bear reportedly attacked a female colonist walking near her house, but only made off with the “hind part” of her gown. As much as these armies of marauding bears and squirrels vexed Anglo-American colonists, they provided a critical windfall for indigenous hunters residing beyond New England in the Canadian borderlands and the vast St. Lawrence watershed to the north.
There's a legal angle to this, as well: