Two's A Crowd

I thought I saw the water ruffled in an ice pool under the fallen willow. Training my 100-400 in that direction I was surprised to see a muskrat out of the water chewing on something. Then to my amazement another popped up next to it. They engaged in mutual grooming before dipping back in and swimming towards me.

Emerging onto this sheet of ice for a short while allowed me to photograph them before they disappeared. The light was very poor and I'm surprised the image is not too bad. Of course cropped and sharpened.

I thought they might be beavers at first because nearby there's a tree gnawed around the base of the trunk. But I've seen the muskrat here before and the tail is a giveaway. Do muskrats gnaw trees I wonder?