Sometimes animals do the strangest things. Like building a nest out of foam. It just seems like a strange choice of places to lay your eggs, but hey, if it ain’t broken, don’t fix it. Anyway, today’s animal, the grey foam-nest frog, chooses this method to reproduce. I guess that makes sense, given the frog’s name.
Foam-nest frogs are found in Africa, pretty much everywhere south of the Democratic Republic of the Congo. They live in tropical and subtropical forests in the north, and in drier savanna in the south. Dry areas are not the best habitats for frogs, who lose moisture through their skins, but the foam-nest frog has some key adaptations to deal with this.
One of the ways the frog conserves moisture is by tucking its legs under itself, keeping its surface area low. It also has impermeable skin, unlike most amphibians, which lose water freely though their skin. This allows the foam-nest frog to produce uric acid as excrement instead of urine, which saves a ton of water. Finally, the frog is able to secrete a waterproof cocoon in the dry season to further minimize the amount of water lost.
When these frogs mate, however, all attempts at conserving moisture are thrown out the window. Defenestrated, even. The female secretes some nasty fluid from her cloaca, on a branch or structure overhanging some water. Males then join the female, and whip up the secretion into a foam. Many males can join the party, and sometimes multiple females will also show up. The females have to return to the water multiple times during this process to get enough liquid to build a suitable nest.
Once the nest is prepared, which can take up to seven hours, the female lays her eggs in the foam. Anywhere from 500 to 1300 eggs can be laid in a single nest. The eggs hatch in the nest and in three to five days the tadpoles drop out of the nest and into the pond.
Why these frogs choose to build nests out of foam I do not know, but my guess is that the frogs want to keep the eggs moist, but out of pond where predators might have their way with them. That may not be why, but at least the foam nest thing makes these frogs super cool!