As a representation of the Romantic era, Viola’s contempt for the dead wild cat and Cosimo’s bravery suggests that they’re each going off of different ways of showing bravery and affection. Further, learning to do things for himself—like make his own hat out of fur—suggests that going forward, Cosimo is going to align himself with the natural world available to him from the trees, not the civilized, built world Viola will inhabit (as implied by the fact that she’s going to school, where she’ll learn to be a part of society).