It also bars larger cavity users that would otherwise compete for a particular cavity. The great crested flycatcher often hangs a snake skin in the cavity entrance. The skin works like a scarecrow, frightening away other cavity nesters. Mammals Squirrels, opossums and raccoons den in hollow trees. Other mammals, including bats, striped skunks, mink, gray foxes and black bears also will roost or den in tree cavities.
Hollow trees provide shelter from the elements, as well as sites for raising young.
Raccoons prefer an opening 4 to 10 inches wide that is located 10 to 40 feet above ground. Gray foxes occasionally den in hollow trees and even climb them. They are known to climb vertical tree trunks to heights of 60 feet. They back down a vertical trunk or turn around and run down a sloping one. Black bears often den under tree roots, debris piles and hollow logs, but sometimes prefer elevated dens in hollow trees because they offer better protection from cold winter rains.