The pups are demonstrating much more control in their walking and balance now (though they don't quite have it all down yet!). They're also becoming aware of the fact that they have siblings.
What you'll see in this clip is some early playfulness and some very preliminary attempts to figure out who's more dominant (litters usually end up with loose pecking orders -- a pack thing). Some of that is established by the vocalizations you hear, and even more by their wrassling. :)
Also, in case you're wondering when you see the clip, the pups can now "feel" their ribbon collars (something neurologically they were unaware of before). They've also become coordinated enough to "scratch" using their hind legs (another milestone). You'll see Mr. Green here "discovering" his collar, and he's not too pleased about it (you'll see him scratch at it several times).
Not to worry. He's very content with it now.
Here they are (still 3.5 weeks old):
Aren't they growing fast?
'til next time,