Hi I have a 8 1/2 year old male husky, (de-sexed) the past 12 months he randomly attacks chews a wooden gate and digging under it, during the night or day when I'm home when I'm not home, it's all really random Moments and has hurt himself badly once doing it, does it for a week then might have a week of nothing, he has been put on anxiety medication but it doesn't seem to have helped him, he has lived with another dog since a puppy, walked/run everyday and he isn't an overly hypo dog so isn't boredom or anything down that track, he's breathing really deeply and heart beating fast when doing it, really Fretting but can't figure out why, any help or ways to stop this would be greatly appreciated. He has a great temperament and other than this has been a great and well behaved dog. Here's a photo of him getting photo bombed by his best mate..

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As the gate attaching. The only thing I can really think of is something is around that gate, whether it's a cat that walks by it or a mole digging in the ground on the other side. Check for signs of anything that could be coming up or near the gate. Keep track of the days that he does it and see if they line up with the moon cycles any. Example: he's doing it during a full moon or close to it.