African Frogs - Things that croak in the night

As amphibians, frogs are typified by having a dual life cycle - they are usually aquatic during egg and larval stages and terrestrial during adulthood. Despite a dependence on a moist environment, frogs have adapted to a host of ecological situations. They occur in grasslands, savanna, forests, deserts and high mountains, in all continents except Antarctica. Africa is blessed with a remarkable variety of frogs of all shapes and sizes.

Like birds, each frog species has a unique call to attract mates. This call is often their most recognisable feature - to other frogs as well as to humans. In the breeding season, which differs from species to species, male frogs emit a loud advertisement call that, among other things, serves to attract a mate. Female frogs in the vicinity respond to the calling male by moving towards the source of the noise. The biggest and loudest males call from the most suitable places for egg laying. Most males are hostile to one another, but in some species, males actually form a chorus, pausing to allow a rival to call between their own croaks, pips or whistles. This may seem counterproductive, but the collective noise is likely to attract suitable females from further afield and thus increase mating opportunities.

Tadpoles are mostly herbivorous (feeding on algae) but adult frogs are carnivorous, preying on the larvae and adult of insects and spiders, snails and earthworms. Some species have a sticky, extendible tongue like that of a chameleon. They are themselves preyed upon by snakes, otters, predatory fishes, herons, kingfishers and many other creatures. One of the biggest enemies of most African frogs is the odd-looking Hamerkop which stands patiently by the waterside - all day if need be - until a frog moves. . . The large bullfrogs prey on smaller frogs, baby birds and small rodents as well as large insects. Whenever there is mass emergence of winged termites from a nest, frogs are liable to show up for the easy and highly nutritious pickings.

Gone Frogging . . .

Frogs are fascinating creatures to find and observe. The fun activity of "frogging" is now catching on around the world. This basically involves going out after dark with a bright torch, gumboots and a tape recorder. Frogs may be calling all around, but actually locating them can be difficult as most are shy and secretive. With patience and practice, and the help of a companion, you'll soon get to know how best to approach wetlands and marshes and in which micro-habitats to look for various species. Peak frog activity in Africa is during and immediately after rain, when males call most vigorously and many species are on the move. See this month's REVIEWS section for details of an exciting new book - Frogs and Frogging in Southern Africa.

Frog Heavyweight

On the South African highveld plateau, the enormous Giant Bullfrog buries itself underground during the cold, dry winter, dressed in a protective transparent skin. When the first major thunderstorms arrive and the ground becomes waterlogged, these huge amphibians emerge from their burrows and occupy rain pools in the veld. Here the mighty males call, jostle and fight for supremacy, and fertilise the eggs of all females which are attracted to the site. Males measure 20cm in length - about the size of a man's hand and weigh over half a kilogram. Parental care and cannibalism have been recorded in this remarkable species.

All Together now

The Foamnest Frog occurs in the warmer, low-lying parts of the continent. It gets its name from the bizarre and distinctive nests which resemble egg foam or meringue. These ball-shaped foamy masses are secreted onto tree branches above water, often temporary rain pools, and contain eggs and developing tadpoles. The nests serve as insulation from the cold and heat in the manner of a polystyrene cooler box, and after about five days, the tadpoles drop from their arboreal nest into the water below, where they develop quickly and leave the water for a life in the trees. The foam in which the eggs develop is created not only by a mating pair, but also by several other males which give "group sex" a new meaning by depositing their own sperm and using their long hind legs to beat it up into a froth. These sexually adventurous and charming frogs are frequently seen around buildings, especially in winter, when they turn chalky white and take up a warm position on a light fitting, lampshade or (in the author's home) the back of the television set!

Conservation

Sadly, the populations of many frog species around the world are declining. In many cases, the cause is obvious; as wetlands are drained for agriculture and forests are felled. Whenever a natural habitat is destroyed, one or more species of frog is bound to suffer. Because their skin is thin and porous, frogs are highly vulnerable to chemical pollution of water bodies and aerial pesticides. In recent years, conservationists have been alarmed at the decline (and sometimes disappearance) of some frogs from seemingly pristine habitats, with no obvious explanation. Global warming and acid rain are two explanations offered. You can play a small part in frog conservation by making your own garden frog-friendly: a small pool or a corner of the garden which is left undisturbed with branches, rocks and fallen leaves, is enough to provide refuge for one or more species. Driving cautiously on roads during and after rain, not only increases your own chances of survival but also that of the many frogs which have to negotiate these hazards when searching for mates.

Where to see Frogs at andBEYOND lodges

A variety of frogs can be seen at all andBEYOND properties, but most are heard more often than seen. The nocturnal chorus of several species is a characteristic and evocative sound of Africa. Perhaps the finest frogging destination is Phinda, where over thirty species have been recorded, and gumboots are available for enthusiasts. Tiny and colourful reed frogs - some no longer than a match - frequently enter rooms to feed on mosquitoes and care should be taken when closing doors or windows.

- Duncan Butchart -

Posted: Other by CC Africa, Date: 21 November 2006