Gryffindor: Bats- (some) risk significant chance of being eaten every night to bring food to their young.

Ravenclaw: Owls- as an animal they are very well designed (from their feather texture to their facial arrangement), and are good at what they do

Hufflepuff: Fireflies- you may not think much of them during the day, but when the light fades you see just how impressive they can be

Slytherin: Leopards- If you've ever seen a leopard decide to drag a large animal up a tree, you know the kind of steely determination they have