He probably had hormones before now. Just because the testicles didn’t drop until later does not mean he wasn’t getting a full dose of testosterone. Some bunnies will just ease into the behaviors, becoming more and more sexually frustrated.

Will this continue? Most likely. Will he eventually calm down? Probably. It takes time, but most intact males will calm down as they get older. Most people just can’t wait that long because their bunny is spraying halfway up the walls and aggressively humping things. Neutering stops these behaviors. This is really the only benefit to having a male neutered. It gets rid of the sex-driven behaviors and helps them calm down. Reproductive cancer (like testicular cancer) does exist, but it is rare in males. It isn’t like where spaying a female greatly increases life expectancy since cancer is pretty common among unspayed females.

Not eating or drinking is not usually associated with hormones or puberty… although if he is only interested in mating then I guess it could happen?

I’ve been around 9 year old un-neutered buns who just want to circle and mount my feet, so I wouldn’t really count on it calming down. The best thing to do would be to get him neutered.

If he really stops eating though then there is something else going on, and recommend finding another vet if you don’t trust yours. Is he molting heavily?  A lot of buns will have some GI upset during heavy shedding season.

Well… calm is a relative term here. LOL  I do agree that neutering him is probably the best bet, but I understand that his actual owners are not on board with that.

I must have skipped over the “not eating” part. Is he actually not eating? Or is he just eating less? I mean, hotter temperatures and molting can certainly make a bunny feel bleh and they may be a bit less enthusiastic about food as they normally would be. But I would be concerned if he is not eating at all or if he is exhibiting problems with eating. He’s a bit young for tooth problems yet, but it’s not impossible.