Do we have a duty to protect a human prey from a predator? Should xenotransplantation be prohibited? Those two moral dilemmas about predation and organ transplantation create an underestimated threat to consistent animal rights ethics. I point at two specific problems following from those dilemmas, indicate that answers given by anthropocentric and animal rights philosophers are not satisfying, and introduce three hypothetical principles to solve both problems. The principle of tolerated choice equality refers to a possibility to make intuitive judgments not in contradiction with antispeciesism. The principle of ecological uncertainty aversion and the triple-N-principle (which refers to the three criteria of a carnist ideology: normal, natural and necessary) can be used to make a morally relevant distinction between predation and transplantation. I demonstrate that this triple-N-principle is in agreement with the moral intuitions of many animal rights ethicists and correlates with the moral value of biodiversity. With these three principles animal rights ethics might become more coherent than speciesist ethics.