Charlie only had one testicle decesended when I got him as a pup. I waited and waited hoping the other would make an appearance but it never did so I had him castrated when he was 18 months old as he'd had time to mature (I was told by a previous vet to have it done at 6 months but felt that was far too young). I then got Toby and he only had one, took him to my previous vets and they said he didn't have any, don't know why they said that as the one was definitely there
I was abit worried as I'd planned to show Toby, then not long after he turned 12 months I had a feel and the other had appeared!
So I wouldn't worry too much about Cooper yet as there is still plenty of time for his other to make an appearance.
