Does anybody else's dog do this?

We just got a kitten that's maybe 8 weeks old a week ago. Our 65 lb male APBT likes to put the kitten's whole head in his mouth. It doesn't scare me because the kitten shows no fear and he is very gentle when doing this. He is INFATUATED with the kitten. He constantly follows it and always seems to want to be near it. The mouth thing has me baffled though. Anyone know why he does this?