How does Darwin’s frog care for developing young in its vocal sac?

Darwin’s frog (Rhinoderma darwinii) exhibits a unique form of parental care known as mouth-brooding. After an amplectic pair deposits 20 to 30 eggs on moist ground, the male waits until the embryos are nearly ready to hatch and begin moving.1

The male then picks up the eggs with his tongue, causing them to pass through the vocal slits in the floor of his mouth and into his large vocal sac. The eggs hatch within this sac, where the larvae remain to complete their development. Once the young have undergone metamorphosis, they emerge from the male’s mouth as fully developed frogs.1