I can answer only for northern Virginia, which I sppose is warmer than western Canada. If I left an intact ripe fruit on my patio overnght, it would not be intact by morning. A watermelon might be intacter than a cantaloupe, which, when ripe, has an aroma that says "Eat Me" even to creatures with a poor sense of smell, such as humans.

But I have raccooons, foxes, and the occasional coyote in addition to many small nibblers. No rats. And no bears, which would make quick work of fruit left outdoors.

Point of curiosity -- why do you want to leave the fruit in your backyard?

I can answer only for northern Virginia, which I suppose is warmer than western Canada. If I left an intact ripe fruit on my patio overnight, it would not be intact by morning. A watermelon might be more intact than a cantaloupe, which, when ripe, has an aroma that says "Eat Me" even to creatures with a poor sense of smell, such as humans.

But I have raccoons, foxes, and the occasional coyote in addition to many small nibblers. No rats. And no bears, which would make quick work of fruit left outdoors.

Point of curiosity -- why do you want to leave the fruit in your backyard?