With the onset of summer, large white meringue-like balls start appearing on logs and branches at our waterholes and pans – but what is this? The large balls of foam are actually the work of a frog known as the Southern Foam Nest Frog (Chiromantis xerampelina), and as the name suggests, these are actually nests offering protection and protein to the tadpoles in their early stages of development. These nests are formed by the female foam-nest frog producing an oviduct secretion, which the mating pair then churn with their hind legs to create this foam-like substance. Their privacy is then short-lived as a whole host of other males (in some instances up to 12!) start arriving and jostling for position close to the female in an attempt to mate and fertilize as many eggs as they can, in turn helping churn them into foam. The nest takes 7 hours to build (usually in the evening) during which time the female will re-enter the pond 2-4 times to rehydrate and usually return to mate with a new partner. The following day’s sunlight hardens the nest’s outer surface in order to help protect the tadpoles and eggs, and after about 4-6 days the 1cm tadpoles fall from the bottom of the nest into the water below and thus their transition from aquatic tadpole to terrestrial frog begins. But these nests are not the only thing fascinating about these frogs – they are actually able to change their colour like a chameleon, something done not only to blend in and avoid predation but also to help thermo-regulate. They also have large pads at the end of each toe to help them clamber around foliage and assist them in their arboreal lifestyle. On top of that they secrete a wax-like substance to avoid dehydration and they conserve water by concentrating their urine, helping make it possible for them to spend so much time on land. The promiscuous nature of these frogs helps them diversify their gene pool and assist in the fertilizing of as many as possible of the 12000 eggs that the female will lay! Here at KwaMbili these frogs are regular visitors and their quiet innocent nature makes them a must-see.
Report by Andi
