8yr Old Male Rabbit In Heat

[natfab]

I know male rabbits don’t go into “heat” but that’s the best way to describe his behavior. He is not neutered as I adopted him when he was 6 and the vet said he was too old to have the surgery.
He lives with a spayed female rabbit that he has been bonded with for over 2 years now and in the past 3 months he has started peeing all over their pen, grunting, chasing her around the pen nonstop and humping her to no end. Please help!

 

[JBun]

Spring can sometimes bring a surge of hormones in rabbits, and that usually settles down after a few weeks. Another possibility is a health problem causing increased hormonal behavior. If you don't think it's 'spring fever' as this behavior has continued for several months, it might be a good idea to take your bun to be checked by an experienced rabbit vet. Could even consider getting him neutered if there is no health problem causing this, though at 8 it is an increased risk, but if you have an experienced rabbit vet doing it then it can reduce the risks.
https://rabbit.org/vet-listings/