You can protect the remaining one
with hardware 1/4 or 1/2 inch grid by putting it around the tree
probably 2-3 feet high.
You may want to call animal control and see if they can trap it. This
may be a new one just wandering for new land.
Wes Dukes (wdukes.pobox@com) Swap the . and the @ to email me please.

I think they will only kill beaver, not trap and relocate (depending
on your county). If you go the kill route, please be sure they use
the instantaneous "humane" method, and not the hour long drowning
method (they can hold breath, struggling, for 20 minutes).
Anyway, I have successfully saved all the trees I managed to get to
before THEY did, by simply making a ring of 4 ft. width chickenwire,
with a few inches play for tree growth. I nailed it to the root, so
they couldn't hike it up with their noses. It is still working 9
years later.
Kira