What's out there?

At school the annual batch of baby rabbits has arrived. We have four in our classroom and they are giving much joy to everyone. One of them is tiny and rather unhealthy looking. Two of it's siblings huddled around it trying to keep it warm. Suddenly the fourth bounded along, leapt on top of the other three, as if to declare " oi, what about me, I want to play too!". It could have smothered it!