We have a 12 week old male and have introduced him to our older 2 year old female. Our smaller pup will grab onto the nake of the older's neck and won't let go. Why?

We have a 12 week old German Shepherd male and have introduced him to our older 2 year old GSD female. When they are together, occasionally our puppy will grab onto the nape of the neck (whale blubber) and hold on and not let go. The 2 year old doesn't do much about it, but what is the puppy doing? I have your videos and have learned a lot. I can only assume this is establishing pack, but it seems really weird to grab a hold and just hang there like a tick. He will hang there until the older dog decides she's finally had enough.

Thanks for your input,
Danielle

p.s. Our female is due to be in heat soon. Can he at such a young age impregnate her?