A foam nest is something that a frog makes for its eggs. The nest stops the eggs from drying out and makes it harder for other animals to eat the eggs. Sometimes the female frog makes the foam nest. Sometimes the male does. It depends on what species the frog is.
The frog makes a chemical in its skin. Then the frog moves its legs to mix the chemical and make bubbles. When the bubbles dry, they become a foam nest. Frog species that live in the same kinds of places have some of the same chemicals in their foam nests, even if they are not closely related. Frog species that are closely related may have different proteins in their foam nests if they live in different kinds of places.
Scientists looked at the living things that are too small to see in the foam nests and saw they were different from the area around the nest and from the tiny things living on the adults frogs' skins. They think having different small living things nearby might help the eggs and tadpoles.
Sometimes, after the eggs hatch, the tadpoles eat the foam nest. Sometimes other animals eat the nest after the tadpoles have gone away.
