It appears you have an old Silver Maple there - Acer saccharinum - which has more problems that just the hollow illustrated. Note the other large pruning cut on the main trunk that has not closed, either. Animals living in the tree are not the problem; live/intact wood (or lack of it) holding the tree up and together IS something to worry about.
You should pay to have a arborist (professional, insured, and certified by the International Society of Arboriculture) evaluate your tree for risk relative to items of value on your property - primarily your house. Silver Maple trees are notorious for catastrophic failure despite looking just fine and leafy healthy. The physics of how well the tree is attached to its root system - as well as to the rest of its crown - is what is in question. It is not a subject to trifle with, nor take chances on.
