I don't know about your horse, but when I was at one barn, Cloudy would dig a big hole down 3 or 4 ft deep, and then sit on the edge of it with his front legs in the hole. There was something down there he was interested in. Same location in his paddock each time. BO said he had medical issues. I got vet out. No problems. No navicular. (Altho BO had a horse with navicular stance and lame and she'd never let the vet or farrier try to help him.)
After 2 1/2 yrs we moved from that barn. No more hole digging. He didn't whiz in the hole though. Just sat there on the edge of it and meditated.. And I had to fill it every time.
I have a mare that occasionally digs holes in the "beach" (aka sand pit), and I have no idea why she does it. It made me nervous at first, because the only other digging horse I have ever owned would only dig when he was colicking, but she is not colicking, she just feels like digging I guess.
There are friends and faces that may be forgotten, but there are horses that never will be. - Andy Adams
My 7 year old gelding has been digging rather large holes and urinating in them...like a cat. He seems fine otherwise. Any ideas? B/O jokes that he saw a cat and is copying the behavior.
If indeed your gelding is imitating the cat's behavior here is one way to tell for sure. Do something to make your gelding angry. If he walks in front of you and then turns his back to you and very deliberately sits down refusing to look in your direction, then you have been officially disrespected in feline speak.