We've had this dog for 5 years and thought he had been neutered. The rescue centre said he had been done and there were no balls to be seen. He was estimated to be 2.5 then so must now be 7 or 8. This morning he was lying in the sun and I saw a suspicious bulge at the base of his penis - lifted his hind leg and saw testicles. They disappeared again within minutes, but they were definitely there. I prodded them and he stuck his willy out. I was flabbergasted.
Now, Mum saw this when she was dog-sitting about a year ago and we had the vet check him over, but the vet couldn't find anything definite. He was reluctant to do anything - said undescended testes would mean a much bigger operation than normal neutering, and as we hadn't personally seen them then there was a chance Mum had been mistaken. He also said the dog would most likely be sterile (this was in the context of Mum adopting a female puppy) so not to worry about him fathering puppies.
However, it explains so much about his behaviour over the years - most notably his reaction to bitches in heat. You may think we were dreadfully slow on the uptake, but I'd never owned an entire dog before and we had been told he'd been done, so didn't really question it!
My question is: would it be worth neutering him now? It would be a bigger operation and he's getting on a bit. Would his behaviour change? He can be aggressive towards other dogs and sometimes displays protective/aggressive behaviour towards strangers as well, particularly when DH isn't here and it's just me and 4 month old DD.