The Amphibians of Kenya
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The Amphibians of Kenya Stephen Spawls, Domnick V Wasonga and Robert C Drewes Introduction There are two orders of amphibians in In the early 19th Century, the Kikuyu Kenya; the frogs and the caecilians. Few seer Mugo wa Kibiru prophesied that people are aware of caecilians, as they ‘strangers would come, with skin the are wormlike, burrowing amphibians colour of the banana frog’; he was talking that live in damp soil. However, we know of the Mountain Reed frog, Hyperolius a lot more about frogs. We know the montanus, whose skin is pinkish white. sounds they make; we have seen them The man was right; seemingly predicting at night on wet roads or around our the advent of the colonial era in East outside taps, or by day near the shores of Africa. People sometimes fear frogs and lakes and rivers. And yet little is known toads, believing them to be dangerous. of their lifestyle. The humble chura is a They are not. A few of Kenya’s frogs, for secretive, and yet spectacular creature of example the Red-banded Rubber Frog, the dark and of water, often mysterious, Phrynomantis bifasciatus, and some active only in the rainy season. We hear toads, have toxic skin secretions but them more often than we see them; the these are only dangerous if the skin toxin boom of frogs and toads in the night has accidentally enters a cut. often disturbed our sleep. However, frogs are good for humanity. They eat mostly Kenya’s frogs range widely in size. Females insects; in Kenya’s rice and maize fields it are usually larger than the males, as they is the frogs that keep the insect numbers have to carry the eggs. Our largest frog is down and thus provide more food for us. the huge African Bullfrog, Pyxicephalus Frogs are our friends. edulis, found in Tsavo and Ukambani; this frog can be 14 cm long from snout Frogs are amphibians; that name means to vent, and weigh over a kilogram. Our ‘two lives’, as they live on land and in smallest frog, the Unguja Puddle Frog, water. The first amphibians crawled from Phrynobatrachus ungujae, is only 1.6 cm the lakes and rivers onto land about 370 long as an adult and weights less than million years ago. Some ancient species 2g. Other startling frogs found in Kenya were huge, over 8 m long. Those giant include Peter’s Foam-nest Tree Frog, amphibians are now extinct; we are left which is waterproof, can change colour with three orders; the frogs and toads and lays its eggs in a mass of foam, the (Anura), the salamanders and newts, widespread Senegal Kassina, found from (Caudata) and the poorly-known, worm- Senegal to South Africa, the Northern like caecilians. (Gymnophiona). There are Clawed Frog, which only leaves the water no salamanders or newts in sub-Saharan to migrate in huge numbers, the huge Africa, but Kenya has over 100 species Groove-crowned Bullfrog, which can of frog, and at least seven species of bounce off the water surface as it jumps, caecilian. the exquisite endemic Shimba Hills Reed Frog, and the Mt Elgon Torrent frog, not There are legends and myths about frogs. seen since 1962, never photographed and In many African stories the toad plays possibly extinct. the part of reliable but slow character. 1 Kenya’s caecilians look very much like darkness (frogs are rarely active by day). earthworms, and are usually less than 35 The males usually call at the edge of the cm long. Eight species are known; one of pools, (every species has a different call) which is undescribed. They live largely and the females are attracted; the female in soil and leaf litter in forests along frog finds her male by the specific sound the coast, although one was recently he’s making, if the call isn’t right there’s described from Ngaia Forest near the no attraction. They mate, fertilisation is Nyambene Hills in central Kenya. nearly always external, and the eggs are usually laid in or near the water. They Many of Kenya’s amphibians also occur hatch out into tadpoles. This is a larval in other parts of Africa, but about 20 form quite unlike the adult frog; tadpoles are endemic, found in no other country. have gills like a fish. (a few species do Kenya’s amphibian fauna is quite varied; not have tadpoles, the eggs developing some species are associated with the directly into froglets). The tadpole eats the coastal forests of southeast Africa, algae and detritus, grows rapidly, and others with the arid areas of northern and loses its tail and gills; it turns into a little northeastern Africa, and still others with frog. The small frog eats insects and grows the savannas of southeast and central very rapidly in the remaining water. When Africa and the great forests of central the pool dries up, the frogs either burrow Africa. The study of such historical and deep in the mud, to where it will remain current distribution of organisms is called damp, or find some other moist retreat, biogeography. such as a hole or deep in a big log. There they remain, waiting for the arrival of Amphibians need water; their skins are another rainy season. not waterproof, with one exception (Foam-nest frogs, Chiromantis). Water Frogs are ectotherms, or ‘cold-blooded’, is lost by evaporation through the skin; meaning the heat for life processes if it is not replaced the frog will die by must come from the environment. Thus, desiccation. Invariably, frogs also need in Kenya, the greatest variety of frogs moisture in some form to breed, for eggs occurs where it is regularly warm and to develop, and for their larvae (tadpoles) wet such as along the coast, where over to exist in the aquatic stage, prior to 40 species occur. But even in cold places metamorphosis. Within these constraints, there are frogs; so long as there is water. Africa’s frogs have adapted to exist in Nearly 20 species can be found on the difficult situations. Although a few live on cool Kinangop plateau, at altitudes over the shores of lakes and rivers, most live in 2000m, and a similar number around areas without permanent water and have Nairobi at 1600m elevation. Conversely evolved astonishing lifestyles to avoid at Wajir, at low altitude but in Kenya’s arid dehydration and breed. In the dry season, sub-desert north, only six species of frog many retreat underground where the are known. soil remains moist, and some even form sealed cocoons. When the rain falls and The presence or absence of frogs can be creates temporary pools, frogs emerge; an excellent indicator of environmental they may appear in such numbers that health. Because of their permeable people are convinced they have dropped (leaky) skins, frogs are highly sensitive to from the sky. A frenzy of activity begins at environmental conditions and pollution; 2 they are rapidly affected by toxins which occur) and the mountain national parks enter through their skin. Healthy water such as Mt Elgon, Mt Kenya and the bodies and wetlands will have healthy Aberdares. Moreover, there are some populations of frogs. If frogs are dying off, important areas with unique amphibians this may be an early warning of pollution, species that are not yet protected nor which potentially might affect humans well understood; for example the Taita as well. In many parts of the world, Hills, the Tana River Delta, the Mau amphibian populations are suffering a Forest and the Cherangan’y Hills. At the worrying decline, likely due to factors National Museum in Nairobi, professional such as environmental degradation, herpetologists are actively working on increased ultraviolet radiation and climate documenting and protecting our frogs. change. Moreover, frogs are becoming This can be a difficult task, as many less resistant to pre-existing factors such species are not well described and thus as chytrid fungus. Several species have difficult to identify, in some cases mating become extinct, even in environmentally calls and even DNA analysis may be conscious countries; for example the required. Moreover it is highly likely that Costa Rican Golden Toad and the there are additional amphibian species in Australian Gastric Brooding Frog. Frogs Kenya awaiting discovery and description. not only serve as environmental monitors, Recent advances in molecular biology the skin of some species has been have revealed the fact that the Kenya found to contain complex substances frog fauna is more diverse that previously like peptides, surprisingly useful against thought. There is much more field work various skin conditions in humans It is and laboratory analysis to be undertaken predicted that many additional substances before we have a full understanding of will be found in amphibian skin. So the East African herpetofauna. More everyone can do their bit to help our information is always needed. The frogs. The use of toxic chemicals needs museum herpetologists always welcome to be strictly controlled. Water sources photographs and specimens of Kenya’s should be kept clean. The environment frogs. needs protection. And frogs need to be seen to be Finally, of course, amphibians play a appreciated. So get out there and find fundamental role in all the ecosystems them, and enjoy our wild places. Frogs they inhabit; both as consumers of insects can be found around taps at night, hiding and other arthropods, and themselves as in plants, under ground cover, and by our food sources for secondary consumers rivers and lakes (but sometimes an expert such as mammals, birds, reptiles and even guide is necessary, care must be taken in other amphibians.