What is he doing with the dogs that could cause hair loss?
It could be a lot of things. It could be related to stress or allergies, alopecia, or general hair loss. Usually hair loss for men starts with the front though. It does seem a bit odd that he has 4 different spots. It may be as simple as changing shampoos. If you continue to worry about it or it gets worse just bring him to the doctor.
It might be Alopecia but I would contact your dermatologist to make sure it isn't something more serious like ringworm. Good luck and feel better.