Dr. Libokov: Certain islands near New Zealand are home to the tuatara, reptiles that are the sole surviving members of the sphenodontidans. Sphenodontidans were plentiful throughout the world during the age of the dinosaurs. But the survival of sphenodontidans near New Zealand, and their total disappearance elsewhere, is no mystery. New Zealand and nearby islands have no native land mammals. Land mammals, plentiful elsewhere, undoubtedly became major predators of sphenodontidans and their eggs, leading to their extinction. Dr. Santos: In fact, the tuatara thrive only on a few islands near New Zealand. On all those where land mammals, such as rats, dogs, or cats, have been introduced in recent years, the tuatara are now extinct or nearly so.
Dr. Santos' response provides additional evidence in support of Dr. Libokov's hypothesis.