Little Chotchy is adorable. He clearly loves you guys- I think the biting is his way of showing that love. At the end, he is paged by one of the girls ( Ochocho- Chan?), so he quickly goes to them to assert his dominance.
My lovely male duck would bite me like that, and it was big and strong and it hurt. But it was still cute, and duck lifehack, wear rubber boots. I think they just love the spongy feeling because it reminds them of eating a slug.