In this brief clip, Poof stretches out and yawns before snatching a strand of hay from Belka's mouth. After finishing her nibble she proceeds to scratch herself, then lays down for a nap in her pigloo while Belka looks about for more.
Below is an even shorter closeup of the latter half of Poof's yawn. Just look at that little piggy tongue - and those teeth! It sure is tiring being a pig.