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Frogs: Unheralded royalty of South Africa's wetlands

June 15, 2004

  By John Yeld

Frogs and toads have always suffered a bad press, even though myth has it that one of them won a princess's heart by miraculously metamorphosing after a quick peck from the royal lips.

Frogs certainly metamorphose, and in a most astounding variety of ways, but they don't turn into princes.

Rather, they are the unheralded royalty of wetlands, marshes, seasonal vleis, ponds, rivers and even grasslands.

Contrary to popular belief, most frogs do not live in running water and some, like the Cape rain frog, actually hate water and can't even swim.

And all these amphibians play a crucial role in ecosystems as both predators and prey, and - particularly - as important indicators of ecosystem health.

Southern Africa is blessed with a wealth of frogs (there is no scientific distinction between frogs and toads), boasting an astounding 114 species.

The whole of England, by contrast, has just six.

But the bad news is that 20 of our region's 114 species (nearly 20%) are threatened to a greater or lesser extent.

Four of these 20 species are classified as "critically endangered", while eight are "endangered" and another eight are "vulnerable".

A further five frog species are "near threatened" and the status of another eight is "data deficient" because so little is known about their occurrence and life histories.

During the past nine years, the status and habitats of southern Africa's frogs has been meticulously re-
searched and mapped by some 400 people - mostly by a handful of professional herpetologists but also by volunteers - who compiled
42 500 distribution records for all 114 recorded species.

Now, these records have been annotated and interpreted in a comprehensive publication, The Atlas and Red Data Book of the Frogs of South Africa, Lesotho and Swaziland, by a team co-ordinated from the University of Cape Town's Avian Demography Unit (ADU).

The School of Health Sciences at the University of the North and several other universities, museums and conservation agencies around the country also played important roles in the work.

The atlas, co-published by the ADU and America's famous Smithsonian Institution - a partnership described as "the David and Goliath of scientific publishers" - was launched at a function at UCT last week.

It wasn't all plain sailing or easy work for the researchers. Harold Braack, the project's main fieldworker, survived three hijacking attempts in the Transkei, and on one occasion found himself surrounded by a group of angry farmers pointing guns at him - they suspected him of stock theft.

"One of the problems of frog atlasing is that you've got to do it at night and so you automatically look suspicious," said one of the project's co-ordinators, James Harrison.

His colleague Marius Burger, also a professional scientist who did much of the fieldwork, told the audience at the launch that it had been arduous but thoroughly rewarding work.

"You would just stop at a little marsh or every time the road made a dip and then listen, and sometimes you could hear up to 10 different frog species - each has a unique call, and that was one of the most important ways of gathering data."

The main purpose of frogs' calling is to mate, Burger reminded his audience.

Cape Town has a particular conservation responsibility for frogs because two of the four critically endangered species are found on the Cape Peninsula.

These are the Table Mountain Ghost Frog, which is found in only eight streams on the mountain, and the Micro Frog, whose only remaining population on the Cape Flats is in the indigenous vegetation inside the Kenilworth Racetrack.

The other two critically endangered frogs are Hewitt's Ghost Frog, which occurs only in the Elandsberg in the Eastern Cape, and the Mistbelt Moss Frog, which is restricted to the eastern escarpment of KwaZulu-Natal and the Eastern Cape.

Both of these species have their habitats threatened by commercial forestry and invasive alien vegetation.

Another endangered frog is the Cape Platanna, now only found in the Cape Point section of the Table Mountain National Park, Betty's Bay/Kleinmond area and the Agulhas National Park at the southern tip of Africa.

Burger pointed out that more than half of the sub-region's 114 frog species were endemic - they occur naturally only in southern Africa - and that 20 of these had been discovered in the past 40 years.

"And we've been averaging one new species per year over the past 10 years and there are probably another 10 out there that haven't even been named yet!"

Western leopard toad under threat

The Frog Atlas Project has highlighted threats to the endangered Western Leopard Toad, which uses wetland areas on the Cape Peninsula as one of its few remaining breeding sites.

The local population of this beautiful frog was decimated by the building of the Blue Route (M3) freeway. Now, many of the remaining frogs are at risk because of the proposed R300 toll road which will cross one of its breeding strongholds, the Zandvlei wetlands.

Marius Burger, one of the Frog Atlas project's co-ordinators, said wetlands had become South Africa's most endangered habitat type. Although he was not familiar with the exact planned route of the proposed R300 toll toad, he said losing pieces of wetlands "here and there" was a major problem.

"People make the mistake of thinking that rivers and dams or lakes are important to frogs - actually, those are of small importance. The most important habitat for frogs are seasonal marshes and vleis and sometimes just roadside verges filling up: very temporary ponds.

"And development - roads or agriculture or urban development, some manipulation of the land - is the biggest current reason for the decline in frogs in southern Africa.

"Roads have to be built, but they should avoid wetlands as far as possible."



[ posted on 15-Dec-2005 ]

  May 30, 2024, 2:38 am