Colours of Wildlife: Web-footed Gecko
Created | Updated Apr 3, 2016
Web-footed Gecko
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!"
Time for another reptile! This is a Web-footed Gecko, Pachydactylus rangei. Again the scientific name is inaccurate, meaning 'Range's thick-toe'. This gecko has very delicate toes, connected by thin webs. These are not used for swimming! Indeed, this gecko lives in one of the driest places on Earth – the Namib Desert. It uses its webbed feet to dig its burrows in the sand. They also give it great traction on the loose sand dunes. So why is it called a 'thick-toe' in science-speak? It used to be put in its own genus, Palmatogecko, 'palmate' indeed meaning 'webbed'. It turns out to be a close relative to other geckoes who do indeed have thick toes. Since they got described first, the web-footed gecko had to be sorted under the genus name already established for them. So it's just this single gecko of the large Pachydactylus genus who evolved aberrant feet as an adaptation for desert life.
A Delicate Desert Denizen
The Namib Desert lies along the entire coastline of the country of Namibia, as well as extending into southwestern Angola. The Richtersveld of north-western South Africa is a continuation of it. It is a very harsh and forbidding desert, in many places receiving hardly any rain ever. Yet, it supports many animals and plants, most species adapted to it being found nowhere else. The sparse plant growth often relies on moisture from the fogs rolling in from the ocean, the cold Benguella current drifting northwards from Antarctica along the Namibian coast. Other plants grow along riverbeds that only flow with water during years of exceptional rainfall further inland. A few plants even establish themselves in the loose sand of dunes, in optimal cases managing to 'fix' them in place so that other plants can also start to grow there. Rocky places also provide safe spots, the nooks and crannies around them helping to concentrate trickles of moisture which plant roots can gratefully absorb. Some animals in the desert feed on these tough plants, or on bits of vegetation and other matter blown in from the more temperate East. The few desert herbivores then serve as food for the even scarcer carnivores.
The web-footed gecko looks like an unlikely predator. It looks like an unlikely desert denizen, period. It is a tiny and exquisitely delicate creature: it reaches about 13 cm/5" in length, with very slender limbs and a head that looks too big for its body. Its skin and even much of its flesh is translucent, so that you can see its main veins and arteries, and even a dim glimpse of its inner organs, from the outside. How can such a delicate thing survive in this desert?
The answer is that this little gecko can dig! And there is so much sand in the desert to dig in! While the air above the sand is very dry, and prone to both extreme heat during the day and extreme cold during the night, the 'climate' just a short distance beneath the surface of the dunes is much more liveable. There is also a much higher humidity a short distance down, compared to on the surface. With its webbed feet, this gecko digs itself burrows in areas with sand not too loose or too firm. It shelters in these burrows during the day. It comes out at night when it is cooler, but can also retreat back underground if it becomes too cold. But like other geckoes, the web-footed gecko seems to do quite well in the cool or even cold night, when other reptiles have become too lethargic for any activity.
The webbed toes of this gecko are wonderful adaptations, being capable of fine muscular control. They also have myriads of tiny projections which, like in other geckoes, help its toes to 'stick' to surfaces, enabling it to clamber up rocks, though it mostly stays in the dunes.
Eye of Sauron
Like other geckoes, most of which are nocturnal, this gecko has huge eyes. Its eye indeed looks somewhat like the Eye of Sauron, with yellow to red 'flames' surrounding the slit pupil, against a black background. It is a saurian after all! This is more pronounced in some geckoes than in others. But generally, these geckoes' eyes are very impressive. The large eyes of course help them to see better in the dark. Another interesting feature is that geckoes don't have moveable eyelids! They therefore can't blink – so never try to engage one in a staring contest! So don't their eyes dry out? They solve that problem with a hard, transparent 'shell' that goes over the outside surface of their eyes, which is appropriately called a spectacle. They clean this, when it gets dirty from dust or sand, with their tongues! They also lick drops of dew off sand, pebbles, stones and plants, and also off their own bodies, as moisture condenses from the early morning mists. This covers their hydration needs adequately.
Their big eyes give these geckoes an advantage in the dark desert nights. They can't see very accurately, not being able to make out much detail, but able to see movements. They hunt mainly small invertebrates like crickets, beetles or spiders. In captivity you'll see they don't always target their prey effectively, not being remotely as accurate as chameleons for instance. But after several lunges they often do manage to grab their prey and gulp it down whole. Their advantage is they don't have many other competitors at night in the desert, although golden moles are also hunting at night, and might even make a meal of a gecko!
Loquacious Lizards
Most lizards are quite silent, but geckoes are an exception. Even here at home, the tropical house geckoes who share my house with me, utter their soft 'chuck-chuck-chuck-chuk' calls from behind the books and paintings in the night. Desert geckoes tend to be more vocal than most. This is vital because the overall scarcity of food means that gecko territories are large and individual animals can be far apart. But in the still desert night, any noises can carry quite far. The web-footed gecko has several kinds of call, varying from squeaks and clicks to croaks and barks. They serve various purposes, some to deter other geckoes or a predator, and others to attract females.
Reptile Reproduction
Males and females come together to breed during the autumn. After mating, the female lays eggs in a burrow, deep enough to be moist so the eggs don't dry out, but also in a warm spot, since they need a temperature of about 30 degrees Celsius in order to develop properly. As I've said, the underground situation evens out the heat as well as the cold, so the eggs maintain an even temperature. The eggs hatch in the spring to early summer, the baby geckoes digging themselves out and immediately scurrying off to lead independent lives.
Not Pets!
There is a current vogue for keeping geckoes (not to mention many other 'exotic' critters) as pets. These desert geckoes are often caught and sold to such enthusiasts. They're not affectionate pets like cats and dogs … they're pretty to look at, but they don't belong in captivity. What's the sense of such a superbly desert-adapted little critter living in a small glass box and being thrown crickets? And to fuel the trade, they're being caught in the desert and decimated in the place that's their real home. So please, people, don't do it! Even though this gecko can't at present be considered endangered, this is still not right.
