Wood frogs in amplexus

Photo: © Scott Egan

When reptiles, birds, and mammals mate, the male fertilizes the eggs inside the female's body. Like fish, almost all frogs fertilize the eggs on the outside. The male holds the female around the waist in a mating hug called amplexus. He fertilizes the eggs as the female lays them. Amplexus can last hours or days—one pair of Andean toads stayed in amplexus for four months!