Symbolism, Imagery, Allegory
It's no surprise that the mastiff bat—the kind that bit Derek on his tongue—would be a symbol. The narrator tells us, "The mastiff bat that Derek Badger slowly lowered toward his gaping maw wasn't vicious. She simply didn't want to be eaten. And so she acted defensively and without hesitation" (15.80, 81). Can't say we blame her, but what can we learn from this bat? First off—and this is a big one—nature isn't personal. The bat did not go after Derek, but acted in self-defense.
We also learn that wild animals make sense, that—like people—there is a logic to their reactions. Therefore, not only can nature not be controlled, it really doesn't need to be. Additionally, any feelings of ownership over nature are incorrect… as poor Derek shows us when the bat bites back.