Vocal Sac-Brooding Frogs: Rhinodermatidae

Mostly active during the day, the vocal sac-brooding frogs likely find a spot in the forest or field and settle in to wait for an insect or other small invertebrate to wander by. The frogs then quickly nab the passing meal. The two species are active most of the year, but disappear in cold, winter months. The frogs probably wait for warmer weather from a sheltered spot under a layer of moss or a rotting log, but scientists do not know for sure where the frogs go in the winter. When the Darwin's frog is threatened, it flips onto its back and lies still. This display shows off the frog's bright black-and-white pattern, which may scare off a predator. The Chile Darwin's frog, which also has the black-and-white underside, probably does the same thing.

Once spring comes, the frogs again appear in the woods and meadows. Each male performs his nighttime calls from land and draws in a female. Darwin's frog calls quickly repeat a "pi-i-i-i-ip" over and over again. The male Chile Darwin's frog sings a fast "pip-pip-pip-pip" and waits a few seconds before repeating the short call. In both species, the female lays her eggs on the ground and leaves the parenting job to the male. A female Chile Darwin frog lays one or two dozen small eggs, while a female Darwin's frog lays three to seven larger eggs. The male in both species stays with the eggs until they are almost ready to hatch, then scoops them up with his mouth. The eggs slide back into his vocal sac, a balloon-like structure in the areas of his throat and chest that inflates and deflates when he calls. Since he has already mated and no longer needs to use the vocal sac to call in females, it provides a safe spot for the eggs to hatch into tadpoles. In about eight days, the male Chile Darwin's frog hops over to a stream or pool, and the young tadpoles squirm out of his vocal sac and into the water, where they later turn into froglets. In Darwin's frog, the tadpoles remain in the male's vocal sac for 50 to 70 days until they turn into froglets. Only then do they crawl outside.