Tymoteusz Ainley
Tymoteusz Ainley voted up HappyTwo BeHereTwo's answer

Beavers, mice, squirrels, porcupines, deer, bear...  It's a huge list!  This might help you identify your culprit.

http://www.forestry.gov.uk/fr/infd-6k4kaf

It's from the UK, brb with a US link.

Edit:  this one shows a picture of beaver damage where they just ate the bark.

https://www.americanforests.org/magazine/article/the-language-of-bark/

Tymoteusz Ainley
Tymoteusz Ainley voted up Sincerity Annabell's answer

Deer !!!!!  They actually are rubbing up against it to scratch their bodies from itching from tiny bugs in their fur.. That causes them to damage the tree trunk and eventually the tree WILL die.

Our family's landscape company has tried many times to keep deer from those trees. Best to loosely wrap it 5 feet … Read more