On rainy nights in spring and autumn, great numbers of northern leopard frogs will migrate en masse, sometimes overrunning lawns and roadways in low-lying areas. For winter hibernation, frogs may rest on the surface of mud, etc., often in little hollows, in streams or lakes that do not freeze solid. In spring they disperse to freshwater pond and marshes, and the breeding season begins. A female can lay 3,000 to 5,000 eggs in one season. This fecundity helps offset the high mortality rate. Their call is a long "snore", often followed by a series of short "chuckles". They are found in every province.