If you go down to the dam today, you could be in for a big surprise.
Particularly if you hear what sounds like the loud whistling of a finch, because it might well turn out to be the “non-croak” of a tiny frog no bigger than the top joint of your thumb.
And if you think you have heard the painted reed frog – sightings are difficult because it’s so small and because it’s so mobile it can even climb trees, so it takes a practised eye to locate them – please let Stellenbosch University frog researcher Sarah Davies know as soon as possible.
Davies, who is also research manager at the university’s Centre for Invasion Biology, is studying this species (Hyperolius marmoratus) for her PhD in zoology, and is trying to determine whether increasing numbers in the Western Cape may threaten endemic frogs.
Painted reed frogs used to occur only in the eastern parts of South Africa, such as Limpopo, Mpumalanga, the KwaZulu-Natal coastal regions and the Eastern Cape as far as Mossel Bay, she explains.
“However, in surveys for the SA Frog Atlas Project between 1997 and 2003, the first painted reed frogs were also observed in the western parts of the Western Cape.
“Since then, all three colour forms of this frog, each with its own body pattern, have been observed as far as the Cape.”
Davies says painted reed frogs normally live and breed near pans and dams in subtropical environments, but that they do sometimes find their way into houses and even vehicles.
She speculates that it’s these frogs’ tendency to climb into nursery plants and vehicles, combined with the increasing number of vehicles on the roads, that are responsible for their increasing southward migration.
“The occurrence of farm dams in the Western Cape also makes it attractive for these frogs to survive here and even to flourish,” she adds.
The painted reed frog does not necessarily pose a threat to the Western Cape’s endemic frog species, Davies points out.
But, as all good invasion biologists know, timely research on such a possibility is of extreme importance, she explains.
This obviates the need to make a plan to eradicate undesirable invaders once they’ve become established, which sometimes proves near-impossible.
“Because they do tend to congregate in large numbers, painted reed frogs could impact on certain ecosystems and could, among other things, place our indigenous arum lily frogs under pressure,” she suggests.
Only about 3cm long, painted reed-frogs are difficult to spot. But during mating time in the summer months, the males are very noisy, which makes it considerably easier for Davies with her finely-tuned ear to track them down in vleis and dams.
This species does not croak, as such, she explains: “The painted reed frog’s definitive whistle sounds almost like that of a finch.”
She would like all nature-lovers to help her establish how far this species might have spread in the province.
“If you see or hear one, please send me information on the day, time and place, and a photo or sound recording to accompany this would be fantastic.”
Although GPS co-ordinates would be a bonus, a complete street address or farm name and the area in which the frog was seen or heard would already be a great help, she adds.
* Information can be sent to her at 021 808 3922 or [email protected].
* To listen to the sound of the painted reed frog, see http://academic.sun.ac.za/cib/team/staff/sarah/paintedreed frog.htm - Cape Argus