I just got a puppy pitbull and I noticed the same thing on him. At first I thought it was the cat because he sleeps on my puppys tummy... Then I caught him scratching himself a lot in that area. Although the next day I took him to the vets so he can get shots and they called me the next day because he had a parasite. Its been two days since hes been takin meds and hes still scratching so he could just be itchy there all the time, who knows? Lol. Take your dog to the vets anyway just in case it could be anything.
