Colours of Wildlife: Common Caco
Created | Updated Jul 9, 2017
Common Caco
Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"
It's high time I featured a cold-blooded critter again! This is a Common Caco, or Boettger's Dainty Frog, Cacosternum boettgeri. It's a tiny froggy, 20-25 mm/0.8"-1" in length – it would easily sit on the first joint of your index finger. Yet, it makes quite a huge noise. Actually, from a distance it just sounds like short 'clicks', such as tapping the rear end of a tin can with a tin spoon. Indeed, in Afrikaans, we call it a 'blikslanertjie' ('little-tin-can-tapper'). But up close, this can become a deafening noise, especially if many individuals are calling together. The little caco has a vocal sac that almost doubles the size of its body when it expands! Perhaps the name 'caco' comes from 'cacophony'… I'm not entirely sure, though. I don't know why it's coupled to 'sternum' in the Latin genus name, unless it signifies the chest-based vocal sac. The name 'dainty frog', though, should be self-evident.
Great in Variety
Tiny as it is, this species is big in diversity of appearance. It's almost a case of no two looking alike. The painting I've made, shows an individual that is mostly green above, apart from some black markings and a bronze stripe down its back. In the field, some are entirely green above; some have the green marked with black spots or stripes; some have additional brown markings – both reddish or bronze-brown, or a duller greyish brown; some are entirely brown. Markings can be small or faint black spots or stripes. In most, there is a blackish patch over the eyes and stretching to the ears. This occurs in many frogs, and is a way to disguise the otherwise strikingly coloured eye, making them harder to spot by predators. Below, they're whitish with grey markings, except for the underside of the throat, which is orange. The variety of caco colorations nevertheless are all quite effective in camouflaging these little things on brown soil surfaces with scattered patches of green from moss or leaves. This, in addition to their small size, make them very hard to spot.
Cacos include a few different species in Africa. This one is quite common in most of South Africa, stretching northward into tropical Africa. Its favoured environment for breeding is seasonal wetland – in other words, regions dry for much of the year and then moist as the rain comes and water floods in. It also prefers shallow water. Such water, only there for part of the year, and only shallow, is less likely to be hosting large fish that can eat the tiny tadpoles. There are still many other threats, even from other frogs sharing the same environment, as well as from wetland birds and mammals.
Cacos do things quickly to minimize their exposure to danger. As soon as the thunderstorms so typical of the South African interior start, the cacos move in towards the shallow marshes and pans as they become inundated. The males congregate amidst the stalks of reeds or flooded grass stems, and start sounding their tinny calls at dusk. The female chooses her favourite tin-tapper and they unite in amplexus. Remember that for amphibians, this is as intimate as it gets: there's a passionate embrace, but nothing deeper. The female sheds the eggs which the male fertilizes as they emerge. The tiny tadpoles emerge, feed and rapidly transform into froglets even tinier than the adults, which hop away into the much safer grass. Cacos are highly successful, one of the most abundant frog species in southern Africa, in spite of being so rarely seen. At present, they're not considered to be endangered. But amphibians as a whole are suffering, globally, from a fungal disease as well as from pollution, habitat destruction, and climate change (the environments of some rare, localized species becoming too hot and/or dry for them). So please spare a thought for all the frogs of the world! They're not only pretty and fascinating, they're also vital for the global ecology.
