African dwarf frogs sing to attract mates or to show their excitement. They sing by producing a humming or buzzing sound.
This behavior is mostly associated with mating periods. Male African dwarf frogs usually sing to attract female frogs at night. Sometimes, the female frogs can sing back as well.
However, sometimes you’ll also hear them singing even though the mating period hasn’t begun or when there are no potential mates around. This means your frogs are simply happy or excited, and they’re showing it through their singing.