We found a stray dog, and he has bumps on the top of his head and neck. What is it and is it contageous to our other dogs?

Maybe the dog has been in a fight and what you are feeling is the wounds healing from it. To know for sure, you know you would have to take it to the vet. Good luck!

make sure it doesn't have ticks. it may have tumors that are not contagious. it would be recommended to take it to the vet. and make sure that it hasn't been harmed.