Animals of the Skeleton Coast

No other sand dune system in the world has an animal life comparable to that of the dunes of the Namib Desert. An established pattern of food and water chains revolves around the all-important fog moisture generated by the Benguela Current and the detritus consisting of dried-out animal and plant material. This organic matter on which the dune creatures feed is blown into the dune areas from the hinterland, or from the plains and corridors between the dunes where grass springs up after the occasional rain shower. Here it is stored indefinitely in a vast open-air pantry for the many primary dune dwellers such as termites, beetles, fish moths and ants, which in turn are preyed on by lizards, snakes, spiders, scorpions and wasps.

Sentinels of the dunes

Most striking and relatively well known is the colorful translucent web-footed gecko, Palmatogecko rangei. This strictly nocturnal gecko can run at considerable speeds, holding itself high above the surface of the ground, leaving fig leaf-like imprints with its specialized webbed feet. Its thin, virtually transparent skin gives the Palmatogecko an ethereal appearance. Its body is a delicate salmon pink, with white markings along the belly and on the feet, while the eyes are large, dark and protruding, with white lids and turquoise blue spots directly behind them. It feeds on smaller insects and arachnids and is preyed on by dancing white lady spiders, hunting spiders and the sidewinding adder.

Two sand-diving lizards found in the dunes of the Skeleton Coast are the dune-plated lizard, Angolosaurus skoogi, and the slip-face lizard, Aporosaura anchietae. The former is a heavy-bodied vegetarian lizard which grows up to 30 centimeters (one foot) long. Its body scales are creamy yellow with orange spots and have an almost wet appearance, the male being distinguished by its shiny black chin and throat. This lizard's distribution is restricted to the northern Namib dune fields.

The slip-face lizard occurs commonly throughout the dune fields. Aporosaura is considerably smaller than Angolosaurus, an average specimen being about 10 cm in length, and is an attractive creature with a delicate pearlgold sheen that brightens up its mottled light and dark-brown dorsal pattern.

When disturbed these dune-dwelling lizards dive beneath the sand with a rapid wriggling movement. To keep cool they perform a thermoregulatory footlifting dance, holding the tail high above the surface of the sand.

Legless lizards are occasionally seen at the Skeleton Coast, but only briefly, as they are strictly nocturnal. Their spoor is, however, often seen on dune slipfaces.

The tenebrionid beetles of the northern Namib

Unique to the Namib are the unusually colored"white" Onymacris tenebrionid beetles, of which the white O. bicolor, the white and yellow O. Iangi and the yellow O. marginipennis occur in the Skeleton Coast dunes. Researchers have found that the abdominal white or yellow topside or elytra of these beetles, which covers most of their upper surface, reduces their body temperatures by up to 5 degrees C, which means that they are able to remain active on the dune surface after their black relatives have had to dive into the sand to avoid overheating. In the cooler zones of the northern Namib the colored beetles are able to function in the heat of the day, and are thus ideally suited for optimum existence on the Skeleton Coast.

Of the same genus and also seen at the Skeleton Coast is the shiny black longlegged O. unguicularis. This beetle, which has been termed "a living condensation unit", is active during the warmer parts of the day. On mornings when fog has penetrated the dune area and enveloped the dune slipfaces where the beetles have buried themselves for the night, they surface and make their way to the crest of the dune. Here, turning towards the wind, they let the fog condense on their bodies. They then lift themselves up by their back legs into a head-standing position so that the drops run forwards towards their mouths, enabling them to drink their fill.

Snakes and spiders

An interesting snake found among the dunes is the sidewinding or Peringuey's adder, Bitis peringueyi, which drinks by sucking droplets of condensed moisture from its body. During the daytime it takes refuge in the sand, lying with only its eyes, situated conveniently on top of its head, showing above the surface. Its eyes and skin closely resemble the quartz sand grains and so provide an excellent camouflage. The sidewinder's tracks, a diagonal series of broken transverse lines, are distinctive.

Various sand snakes (Psammophis spp. ) are active in the dune areas during the heat of the day. These snakes and the sidewinding adder give bites that, although lethal to lizards, are painful but not dangerous to humans.

Conspicuous spiders which occur in the dunes are the white lady trapdoor spiders, Leucorchestris spp. , also called dancing white ladies. These spiders construct their homes by digging holes in the sand and covering the walls with a cobweb lining to prevent the loose sand from filling it in. A kind of trapdoor, which is closed when the spider is inside, is constructed over the hole. Black dune wasps prey on these spiders. Paralyzing the spider with its sting, the wasp places it in a burrow in the sand and lays an egg on its body. The larval wasp eventually feeds on the living body of the spider.

Closely related to the dancing white ladies are the Namib wheeling spiders (Carparachne spp. ), which have a peculiar mechanism when threatened. In an attempt to evade its predators, this spider forms itself into a tight ball and rolls rapidly down a dune slope.

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