One of Ben's most obvious characteristics is his inability to communicate with humans for most of the novel. You can use examples of him being unable to talk with his father and brother; even though he talks to his mother, he doesn't say much to her. Another obvious trait is Ben's love of animals and the fact he feels more comfortable with them than he does with humans. You can use how Ben mimics animals or the first time Ben meets the mother badger. You could also use Ben's physical trait of being small for his age. There are several examples of this in the book, such as when Burton picks him, or the fact that he's able to fit in the badger hole. Ben is also a compassionate boy, shown when he tries to keep his father from skinning the father badger. Ben is described as being different from most boys his age. His father's attitude toward him reflects this. Ben is a good friend, shown in his devotion to the badger. Through most of the book, Ben is afraid of humans, shown in his relationship to his father and Burton.
This should give you enough to decide which characteristics best describe Ben. Good luck with your assignment!