During the long rains of 1992 in the Arabuko-Sokoke, scientists were able to document frog species in this forest emerging at different times to begin breeding; thus, there are "early" breeders and "late" breeders. On the night of August 27, 1987 Academy scientists watched as a spiny reed frog approached a foam nest as it was being constructed by two male and a female foam-nest treefrogs, about 8' above the water.
The spiny reed frog actually thrust the entire forward half of its body into the foam nest and appeared to be eating eggs within the nest. This behavior was unexpected as frogs usually eat living insects. the stomach contents of this frog and other spiny reed frogs collected during that season, plus more collected during the rains of 1992 were examined.
The scientists found some insects but mostly the eggs of other frogs, embryos of other frogs and something they called "mystery stuff".
Excised spiny reed frog stomach containing embryos of foam-nest frog.
Scanning electron micrograph of "mystery stuff" from spiny reed frog stomach. This turned out to be the spiny reed frog's own shed skin. Frogs often eat their own shed skins when recently emerged from long periods of inactivity like hibernation or estivation.
These results indicated that the spiny reed frog is the first terrestrial amphibian known to be a predator on the eggs and larvae of other frogs species. It is also the first African frog known to prey on the eggs of members of its own species, a phenomenon called "heterocannibalism".