Cape Town - Froggie went a-courtin’ and he did ride, uh-huh…
As the lyrics of this mid-16th century folksong that has been covered by scores of artists as varied as Bruce Springsteen, Bob Dylan and Elvis Presley, can attest, the mating habits of amphibians are of enduring interest to people.
But what many Capetonians don’t know is that the Western Cape in general and the Cape Peninsula in particular is a hot spot of frog diversity of global significance. And unfortunately, several of this region’s endemic frog species are restricted to a diminishing number and size of breeding sites, and the frogs are becoming increasingly threatened as a result.
The Western Leopard Toad is one of the IUCN endangered species that has attracted significant attention over the past decade, but there are other species that are equally, if not more, at risk of extinction. Fortunately, most of them occur within the Table Mountain National Park, but even here their future is not secure. This was made clear during an evening excursion in the Cape of Good Hope (Cape Point) area of the park this week to highlight the park’s current amphibian conservation projects.
One of those involved is herpetologist Dr John Measey of Stellenbosch University’s Centre for Invasion Biology, who has been working on Africa’s amphibians for the past 20 years.
He says South Africa has an “amazing variety” of frogs, ranging from the massive African Bullfrog that is so heavy you need two hands to pick it up, to the minute Micro Frog (or Cape Flats Frog). There are 12 frog families represented in South Africa and currently 125 species, but this number is constantly increasing as genetic discoveries demand taxonomic changes and as new species are found.
Half of these families are represented in the Cape’s fynbos region, making it “very special”, and there is a particular concentration of threatened frog species on the Cape Peninsula, says Measey. When current taxonomic classifications have been completed, as many as five species may be recognised as being endemic to the peninsula, meaning they occur naturally nowhere else on Earth.
One that is found in the Cape Point area is the endangered Cape Platanna, at risk partly because it hybridises with the plentiful Common Platanna that is roughly twice or even three times as large.
Another is Rose’s Mountain Toadlet, a “very interesting” species, says Measey. This is partly because it’s the only South African frog that is entirely silent, and also because it breeds in random stormwater puddles than may be just a centimetre or two deep. Originally thought to have enjoyed a peninsula-wide distribution, it is now known from just two tiny areas – one at Cape Point and the other in the Muizenberg mountains. So this frog has very high conservation needs and is being subjected to intensive research, says Measey.
Justin Buchmann, senior section ranger of the southern part of the Table Mountain National Park, says they need to understand why frogs’ breeding sites are diminishing and what the current status of the various species is. “And we also want everyone to know the management challenges that we face in trying to protect them.”
For example, the park is under huge pressure to increase tourism and ecotourism opportunities that could include night activities, he says. But migrating frogs – some of them tiny and difficult to see – choose easy routes between breeding sites, such as roads that have few obstacles, and these amphibians will be particularly vulnerable to vehicles, bikes and trampling during their short breeding season.
“We’re under pressure to open up the park to other activities, but we don’t necessarily have a handle on the impacts on animals that you can’t see,” says Buchmann. “Rose’s Mountain Toadlet is the size of your little finger and it makes no sound – so how on arth do you monitor a species like that? And it could move (to start its breeding cycle) on any night of the year. We simply don’t know.”
What’s in a name? Toad or frog, frog or toad…
Actually, nothing of scientific significance. It’s all to do with language and the relative paucity of amphibian species in England, explains Stellenbosch University herpetologist Dr John Measey.
In terms of taxonomic classification, all frogs and toads belong to the order Anura.
The more specialised taxonomic grouping below order is family, and in Britain there are just two “frog” families that look very different from one another. Species of one family, Ranidae (this has the widest global distribution of any frog family) all look like what are now traditionally considered frogs, while those in the other all look like what most people would now call toads, from the family Bufonidae.
Because the two families look so very different in Britain, there are different English words for these two groups, says Measey.
“But in South Africa, we have 12 families, each of which look as different from one another as the two English families do, and we don’t have words for all our different groups. And there are no members of the family Ranidae in South Africa.”
I use the word ‘frog’ for all Anura, so that ‘toads’ are a subset of these in a similar way that ‘owls’ are a subset of ‘birds’.
“The beauty of the scientific classification system has enabled us to appreciate their full diversity. Sadly, the English language has not managed to catch up!”
Cape Argus