Vegans also don't eat honey, which is not really a byproduct of animal suffering. And a vegan also wouldn't eat eggs, even if they kept and raised their own free range chickens who were laying unfertilized eggs which were just going to rot if not consumed. Because veganism isn't about the "suffering" of an animal. You could genetically engineer an animal that was incapable of feeling pain or fear and made it so that it felt ecstasy while being butchered, but killing and eating it would still be unethical for a person to do, and still be in violation of veganism's core principles, because it's about conscious beings exploiting the labor or nature of animals without their consent. An animal like a wolf or lion (or in this case a venus fly trap) eating meat is not "unethical" because it exists outside of ethics: it's just a component of an ecosystem in which predation is a natural element. Humans have functionally removed themselves from whatever ecosystem they evolved to be a part of, so our exploitation of animals and their natural behaviors is just that: exploitative.