Despite the title, I'm not talking about a beaver or something.
I was out in my yard kind of moving some dead branches and stuff... I noticed this one real skinny tree, maybe and inch to an inch and a half in diameter... It was kind of bent over and the top half of the tree was gone... at first glance it looked like someone cut it with a saw or something as it was a smoother separation, not just a break.
So I looked closer. The other half was on the ground. Here's the two halves next to each other.

What it looks like to me is that some insect ate its way around in a spiral towards the center until the tree was cut in half.
Tristan was over today and I was showing this to him... he looked up and noticed a bunch of branches in that area looked like that.
I'll have to try and look into what kind of insect did this... but I thought it was kind of interesting anyway.