No totally sure. I found a ton of branches in the middle of the tree and some on the floor. I cleaned them all out. I also sprayed fox urine on the tree to hopefully deter the angry squirrel. Never encountered this before….

I have a lot of arbs and squirrels and I have never seen that. My squirrels seem to prefer deciduous leaves for nesting.

Arbs tend to regrow from exposed trunk, but, as stated above, it's a slow process.

We had a large Sweet bay magnolia. All except the very top was clean as a sailboat mast. The top was very healthy.

I puzzled on this for several years until one day I say a squirrel neatly cutting the leaves and twigs She then collected them and took them into another tree where she had a nest.

That is totally bizarre. I've never seen anything like that before. You could stuff a mattress with that much material.

Thuja occidentalis generally will not sprout from bare wood but surrounding branches will fill in and cover up the holes eventually. Probably will never be quite the same but will be a lot less noticeable over time.

in my MI... squirrels make their aeries.. 40 to 50 feet up in deciduous trees .. and i have a hundred or so arbs of various kinds..

and i have never seen a tree rat come down 50 feet.. run over to an arb.. and carry a piece back up 50 feet ..

i agree.. im not buying a squirrel did this for nesting purposes .. you know.. many of them are just asshats.. and do this type of thing for the shear joy of being belligerent.. lol ..

and then i read krn's answer.. go figure.. lol ..

if that arb is in as shady a spot as i looks.. it might take 10 or 20 years before it fills back in.. depending where you are .... big city name ... in my ground freeze mich .. with a 6 month growing season.. see above.. in the PNW with a near year around growing season.. i presume much shorter ...

whether it is wise to remove or replace.. would require more pix of your garden.. as well as seeing what those conifers might be hiding ...

the best option... WAG.. would be plant something else.. to replace this one.. so when it needs to go.. the new one is ready to replace it....

ken

It definitely came from a squirrel. He came back when I was out there.

I have since sprayed w fox urine, and put up a wire cage over the empty section to deter him from creating more damage.

The arb is the far right arb in a privacy shield which consists of about 8 trees. They are all about 12ft tall, and get mostly full sun. They have been thriving, and this was very unfortunate.

At the moment, I don’t feel it is worth replacing. Hopefully, it will somewhat fill in over time.

I would leave it too. if it were say 6' tall, I would likely replace, but 12' is too much.

I have a row of arbs. All are 20+' tall now except one on the very end. Every time it sent up a leader, a deer would rub the leader to death. So, it's currently 5' wide and 2' tall. Not sure if it will ever send up another leader.

Squirrels, like most rodents, have front teeth that continually grow. So they have to frequently gnaw on certain types of bark to keep them in check.

Could be this squirrel found something he liked or worked well for him and so continued coming back to the same tree even same part of the tree to do what he has to do instinctively.

IME, arborvitaes do not have an ability to back bud or produce new growth from bare wood. So no new branches will appear in this area but as mentioned above, existing growth will eventually fill in enough that the squirrel damage will not be as noticeable.

Squirrels mauled my Chamaecyparis pisifera `Baby Blue Ice’ one year and some springs I find a thick mulch of pine branch tips. Yeah, squirrels will do that.

tj

When I was in wooded southwest VA, a squirrel took to chewing holes in my house's wood siding. It didn't do it for very long....