My two year old colt did that last year, or at least I'm assuming he did as the outside layers of my other gelding's wonderful thick tail slowly disappeared until he looked like I'd banged it off at his hocks.
I never saw the colt touching it but it wasn't stuck in the fences either and it certainly was going somewhere!
Considering I'd had the other gelding for five years at that point and had never had a problem the obvious culprit was the new horse. I immediately started him on regular doses of Sand Clear in hopes of getting the hair out of his gut and bagged what remained of Kody's tail. I also tried spraying it with a bitter spray I bought at the tack store but I'm not sure that did much. It was hard to tell as he nibbled it off a bit at a time and of course it was taking a long time to grow back so I couldn't tell if he'd stopped.
I made the mistake of discontinuing the bagging and the several inches of progress I'd made in regrowing it mysterious vanished one night a few weeks later. I could have killed him! Despite my annoyance I never seemed to get around to rebagging the tail or spraying it with nasty stuff again but he must have grown out of the habit (please God?
) as Kody's tail is finally beginning to look respectable again. Thankfully the colt never did eat the hairs at the center so you wouldn't have noticed Kody was missing his tail at first glance in the ring but it was definitely thin and really unbalanced the picture he made.
I'm crossing my fingers as it continues to lengthen and by the end of this summer I'm hopeful he'll have that glorious roan tail back.
I wish I'd thought of a grazing muzzle! Since my boys are dry-lotted anyway that would have worked nicely. That or putting some sort of mesh barrier across the bottom of both my farm gates. I think the colt was reaching through the lower bars at about knee-height and nibbling what he could reach of his buddy's tail as being the only part of him he could get ahold of. He wanted to rough-house but of course couldn't when they were separated. Thankfully Kody would never tolerate him nibbling on his mane or forelock but I think the tail wiggling behind him while he relaxed by the gate was below his reaction threshold.
Leia
P.S.- I'd been occasionally finding tail hairs in Turbo's poo but no longer did after using the Sand Clear several times. I'm hopeful that means it cleared him out but I live in fear that he's got half a tail lurking in his gut!