Colours of Wildlife: Kloof Frog
Created | Updated Mar 12, 2017
Kloof Frog
Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"
Here you have one of South Africa's rarest and daintiest frog species, a Kloof Frog, Natalobatrachus bonebergi! The scientific name means, basically, 'Boneberg's Frog from Natal'. It occurs mostly in Kwazulu-Natal, but also in the Eastern Cape, at lower elevations – up to 900 m/3000' above sea level. It is also called a 'Diving Frog'. It is small, females reaching 37 mm/1.5" in length, and males only about 25 mm/1".
Tiny Clamberers of the Moist Ravines
Kloof frogs are very habitat-specific: they live in dense, dark forest fringing the gorges many rivers cut through the Eastern Cape and Kwazulu-Natal coastal grasslands, on their way to the sea. This region is peculiar for having many such rivers all flowing roughly in a south-eastern direction, cutting very steep-sided and spectacular riverine gorges, such as the Oribi Gorge. These provide the little kloof frog with excellent safe habitat. First of all, the deep gorges provide shelter for forest trees and lush herbs and shrubs, contrasting with the surrounding open grassland. Second, the gorges themselves have lots of precipitously steep cliffs and banks and lots of rocks. On these steep surfaces, the kloof frogs live. They have special sticky toes, with the tips expanded into lateral flanges like a capital letter T. They can clamber into the trees and bushes as well, and even up smooth, slippery surfaces. The dense, dark and moist kloofs are also perfect for keeping their delicate skins moist – they can't survive in the open sunshine at all. When disturbed, they will leap like high-diving human athletes into the running stream and rapidly lose themselves amidst the pebbles of the riverbed. They're quite hard to spot, being coloured in subdued greys and browns with a pink tint here and there. Like many frogs, they're quite variable, some being much more boldly marked than others, and some being quite light in colour. In the breeding season, the male calls from concealed positions amidst the vegetation or the rocks. His call is just a soft, tinkly click, uttered at irregular intervals.
These frogs is mainly distinguished by the way they breed. Like other frogs, they fertilize their eggs externally, the male climbing onto the female's back and clasping his arms around her. But they don't go into the water like other frogs. Instead, the female lays a big, jelly-like mass of eggs on a twig or branch or on a steep rock wall, overhanging the water. There are about 75-95 eggs in each 'clutch'. The male now fertilizes them. From here, the eggs develop for a while outside of the water, the little tadpoles being seen wriggling around inside them. The female returns to the eggs from time to time, squirting water over them from her cloaca to keep them moist. After six days, the eggs 'hatch': the jelly softens and the little tadpoles drop into the water. They complete their metamorphosis into tiny frogs after two more months.
Sad to say, but the Kloof Frog is today on of South Africa's most threatened amphibian species. It never had a very great range, being completely restricted to these moist, dark, river-gorge forests of Natal and the Eastern Cape. These rivers don't join up but each reaches the ocean separately, carving a separate gorge. This means that these frogs are inhabiting numerous small patches of forest that are not connected to each other. Each population is therefore isolated from the others. (There has to have been a time in the past where forests were much more extensive, to allow the frogs to travel over the in-between country from one gorge to another.) This makes each population – containing only a few adult frogs – very vulnerable to any disturbance. And such disturbances are numerous today. First of all, pollution and siltation of rivers (the latter caused by poor land use leading to soil erosion upriver) make a lot of the streams unsuitable for the frogs. But also, humans have destroyed much suitable habitat. The coastal regions of Kwazulu-Natal, once covered in coastal grassland and forest, have on a large scale been transformed to sugar-cane plantations, where the frogs can't survive. Other forests have been turned into commercial plantations, mostly of pine trees. Again, these foreign trees are not used by the frogs and they thus disappear from these plantations. Lastly, much suitable frog habitat has been destroyed to make way for human settlements, these coastal regions being among the more densely populated parts of South Africa. These little frogs are still decreasing, and need our serious help. We must assure them of both quantity and quality of living space, for them to survive. But there are some nature reserves where they occur. We still need to figure out the effect of their populations being so fragmented. But like all frogs, they need very little to survive, and if we can help them out, they'll certainly be very grateful.
