Colours of Wildlife: Bubbling Kassina
Created | Updated Mar 2, 2014
Bubbling Kassina
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!"
Time for another froggie! This is the Bubbling Kassina, Kassina senegalensis. It is a close relative of reed frogs and tree frogs, but is itself fully terrestrial. It is sometimes called a Running Frog, from its habit of running or walking rather than hopping. It is found in savannah regions all over sub-Saharan Africa; indeed it is one of the most widespread and abundant amphibians on the continent.
This is a frog I know very well! It is not at all rare around Polokwane, and sometimes they stray into my garden or even my house. But my fondest memory of these frogs come not from having seen them, but from having heard them. It was when I was a teenager and hiking in the veld just outside town. I suddenly heard sounds, very charming sounds, which I knew not to be any of the local birds, and didn't sound like insects either. But I was in the veld amidst the thorny trees and shrubs and the dry grass … what else could it be? I hiked in the direction of the sounds, and I stumbled on a vast marshland! It was a large area of flooded grassland, with the water only a couple of inches deep. And over the entire marsh the calls resounded and I knew now that they were frogs! There were two in particular that struck me. The first was a low, purring 'prrrrrr'-sound, and the other, fit 'around' these, was a bubbling 'boip-boip' sound. I didn't know what frogs made these at the time, but when I returned home I went to the library and got a book about South African frogs. At the back of the book was a small vinyl record with frog calls on it. I played it and identified the calls! The 'prrrr'-sound was made by the Banded Rubber Frog, and the 'boip-boip' sounds were the calls of the Bubbling Kassina! Since then I've heard these frogs on a few other occasions, and every time it brought back to me the magic of that first experience of coming across the frog marsh in the veld.
The bubbling kassina is a small frog, reaching only 5 cm/2" in snout-to-vent length. It has front and back legs of comparable length. Its toes have very little webbing. It can be recognized by its shape, its eye like a cat's with a vertical slit pupil, and its stripes. One other frog in South Africa looks rather similar, the Rattling Frog, Semnodactylus wealii, but that one has black stripes sub-divided length-wise by pale stripes, and a somewhat different shape and face. There's also the Red-legged Kassina, Kassina maculata, but that one is spotted rather than striped, with expanded tips to its toes, and grows a bit bigger. There are other, similar kassinas in tropical Africa, but in South Africa it is unlikely to be confused with anything else. It is a smooth-skinned frog, with a ground colour that can be cream, yellow, olive-green, grayish or any hue in between. It always has a dark stripe down the midline of its back. It typically has dark stripes down its sides and across its legs as well, but these are often broken into segments or spots. Its belly is whitish, except for the dark flap that covers the male's vocal sac. When the male calls and the vocal sac expands, the dark area divides into two black patches on either side of the vocal sac. This 'breaks up' the surface of the inflated sac, which along with the black stripes helps to disguise the little frog calling amidst the grass and reeds.
Like all savannah frogs, bubbling kassinas have lives marked by long periods of dormancy and short periods of activity. For the entire dry winter and autumn these frogs will stay underground, usually in burrows excavated by other creatures. The first substantial storm will fill the temporary pans and marshes with shallow water. The moisture will prompt the kassinas into activity, and the males start calling. In the early afternoon they will call from amidst the grass, but towards late afternoon they will move out to the nearest marsh or pond and congregate at the water's edge. Here the chorus will become very intense. The females will hone in on the males with the best and most insistent calls. They will get into the mating position, the male on the female's back with his arms clasped around her chest just under her armpits. She lays her eggs in the water where they cling to the submerged portions of grass stems and other plants. Each clutch can contain as many as 400 eggs. The male fertilizes them as they come out. From the eggs the tadpoles emerge; they grow up to 8 cm/a bit over 3" in length. So they are longer than the adult frogs, but of course they have long, swimming tails that they lose upon metamorphosis. The tadpoles are dark in colour with red or golden patches and a high tail fin. They metamorphose in two to three months, and a new generation of kassinas will spend a short period of time fattening up by catching insects before burying themselves as well to wait for the next rain season.
Kassinas are of scientific interest. Their bodies contain a substance known as kassinin, one of the tachykinin peptides, which are proteins that prompt activity of nerves and also help nerve cells communicate with each other . These substances can influence the brain and behavior, stimulate secretion of other substances, cause blood vessels to expand and the smooth muscle of intestinal tissue to contract. Studying these substances can tell us much about how the chemistry of the body influences its workings.
