Treats. This one fell on a piece of carpet, so you don't actually hear it falling (and it's pretty small, so you might not have seen it, either). I have other clips of him chasing treats where you can actually hear them clattering onto the floor. They're shorter, though, and I love the way he's burrowing in this particular one -- that's so him ... provided he's chasing after something he really, really wants, that is!
(Same for the other two.)
Still comes equipped with sharp claws, though! :)