According to my recollection of the words of a tour guide in Vancouver, Canada, those big, dark squirrels we see around here were brought to Stanley Park from New York. Then they multiplied and kind of outcompeted the small native squirrels.

Someone's related blog: https://www.miss604.com/2015/03/grey-squirrels-of-stanley-pa...

Quote: So how did this squirrel get here just over 100 years ago? Some reports say that the squirrels were a gift from the Mayor of New York City in 1909 but Jolene from Stanley Park History found that in 1909 Vancouver Park Boar Chair, Charles Tisdall, wrote to various American cities in search of purchasing “grey squirrels” for Stanley Park.

> In more remote places and in the mountains where the winters are harsher you still see the small red native squirrels though.

And here I was thinking milder winters would benefit the red squirrels because they would have a better chance getting through those without food supplies/fat reserves. Guess it's actually more of an even playground in terms of food supplies, where things like the grey's parapoxvirus tip the balance in favor of more greys surviving.

Are harsher winter conditions harder on the grey squirrels? Maybe their fat-reserves give them a mobility disadvantage that becomes crippling in harsher winter conditions? Or maybe those remote places are so remote that grey squirrels merely haven't made it there, yet.