There is a very large old maple tree 30ft off from my house and it has a large naught/hole in it as seen in the photo. Looks like animals or insects are using it as a point of entry. I am concerned about the tree and wonder if there is anything to be worried about and if so what can I do to fix/prevent further damage to the tree. The tree seems healthy besides this all the branches are green and healthy looking, besides a few select dead ones. I don't know much about trees please help, thanks!

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.

Adding on from what John said, here is how to find an ISA arborist in your area:

http://www.isa-arbor.com/finda...

I would have a big concern about the large branch going off and to the left in the picture. From the pic, it looks like that hollowed out part could destabilize that other branch given the proper conditions for failure. It'd be wise to follow the advice of VV.

It certainly does look suspicious and John is right... don't take chances with this tree. We had to remove our oak tree recently and it had a much smaller opening that yours, about as big as a large man's fist. From all outward appearances the tree looked to be healthy, but we discovered it was hollow inside. After rigging up a light bulb to stick in the tree hole, my daughter taped her phone on a stick, put the phone on video, and put the phone inside the hole to see how much of it was hollow. It was awful! We called the local arborist and he said that given the fact that it was so close to our house, he recommended taking it down.

The entire tree needs taken down before it lands on your house. Do not replace it with a Silver Maple, they are bad yard trees.

Thanks for all the advice guys, I am having it taken down.

Sigh indeed as it will likely cost a lot. Good luck to you and make sure to replace it with something quality