Intact Male Behaving Oddly

We have an intact 10-12 year old rescued GSD mix who has never had the issues that usually come with having an intact male dog. No marking problems, no escape attempts, no chasing after females. He's been a fantastic dog.

We recently got a female puppy who was spayed pretty early due to the fact that it's the state law for shelters to send their animals out fixed. We adopted her 5/21/21. The two got along fantastically.

As of 10/10/21 our male has become absolutely infatuated. They live together almost 5 months and were great, but he now has started following her around whining and trying to hump her. He'll lay on the floor in front of a couch she's on and just drool and whine. We've been trying to keep them separated because we're tired of telling him to leave her along, but whenever they're apart he just sits and cries. It's beginning to really set the whole household on edge.

The GSD of course has bad hips and a bad back and we're scared he'll hurt himself trying to mount the pup. Not only that, but the female, not even a year old, already has severe hip dysplasia and can not support a dog twice her weight.

We are at our witts end. We would hate to neuter him this late in life, but we don't know what else to try. Any advice would be much appreciated.