We have gray squirrels, that live in trees, and rock squirrels that burrow under stone, pavement and the like. Squirrels eat nuts (especially our acorns), fruit, seeds (they will hang out under bird feeders for snacks) and tree bark. Predators include raccoons, foxes, hawks, owls and snakes. Squirrels have litters of kits in both spring and fall. Babies are born blind and hairless; they live in the nest for months, nursing and totally dependent on the mother squirrel.
Baby squirrels can fall out of nests, especially in windy weather. If you find an uninjured baby on the ground, give the mother squirrel space and time to collect it. She may be busy building a new nest and moving several kits. Keep watch, but stay away and keep pets out of the area, so she feels safe to return for the fallen baby. If the baby is injured or truly orphaned, keep it warm and contact a licensed wildlife rehabber.