Sorry, no, it won't re-grow. Those holes will always be there.

Resin

I've never seen anything like that. Those must be some very hungry squirrels! As resin said, the branches will not regenerate. But to a degree, subsequent growth and filling out of the remaining branches will cover up the bare spots a bit.

+oM

wow, you have my sympathy. I have 12 thujas going in the ground this spring. We also have an abundance of big grey squirrel. I feel this is not a common problem with squirrels, but could be wrong. I do hope your trees fill back in.

Thank you, everyone, for the feedback. Every now and then there is one particularly destructive gray squirrel which decides to tear a bunch of nesting material from my conifers. A few years ago it was a Taxus that had almost all of the branches on one side ripped off.

Once I had an Acer palmatum 'Dissectum' growing in the garden. It was a grafted plant. Had I not seen the squirrel removing the last piece above the graft line, I would never have believed it! My $ 25 investment ( years ago) was gone.