EPOW Ecology Picture of the Week -- Oddities of the Ridged Frog

Explanation: I discovered this placid anuran in a pond in a quiet forest some miles south of Kinshasa, the crowded capital of the Democratic Republic of the Congo. This is a "common," "true," or "typical frog" (that's what frogs of family Ranidae are often referred to), but by no means does it have typical behaviors.

For one, when it is disturbed or threatened, it tends to jump away from water, not into water. How this behavior -- rather atypical for frogs -- arose is unknown.

Further, if it is captured, it goes into a "foam and moan" display, by exuding a skin secretion, producing a moaning call, and stiffening its body. But then it readily jumps at any chance to escape. All of these behaviors are to thwart predation, and as far as I can tell, are rather unique to this species.

It is eaten by local people of West Africa.

Mascarene ridged frogs are found widely distributed in central to southern Africa, occurring in swamps and flooded forests. But they also occur rather oddly on the Mascarene Islands (giving the frog its name), as well as Madagascar and Seychelles. Whether they were introduced to these islands, or somehow rafted across oceanic stretches, or occurred there in antiquity during periods of low ocean levels and presence of island-spanning land bridges, is unknown.

For so placid and unassuming a denizen of the swamps, this frog surely raises a lot of mysteries!

Information:
Channing, A. 2001. Amphibians of central and southern Africa. Comstock Publishing Associates, Ithaca and London. 470 pp.

EPOW - Ecology Picture of the Week