Unexpected Inhabitants of the Namib

When exploring the vast Namib Sand Sea, one may come across the occasional small rock, as seemingly lifeless as the surrounding area. Upon lifting the rock, a pseudoscorpion or two may be found – kilometres away from other visible life forms, let alone civilisation. Pseudoscorpions are tiny creatures, several millimetres long, resembling scorpions yet lacking the tail or stinger. Occasionally found perching on flowers, they can wait for flies, bees, or butterflies in order to catch a ride by clinging to a leg and then detaching themselves whenever it is deemed suitable, hence these tiny terrestrial arthropods show up in distant and remote places. In 1969 biologist Peter Weygoldt wrote in his aptly named academic book The Biology of Pseudoscorpions, “Sometimes I am asked why I study animals so unimportant to human life and economy as pseudoscorpions. There is one simple answer: every aspect of nature that interests the human mind is worthy of study whether or not it is of direct importance to man”.

Why are small forms of life important or worthy of study? A perpetual question that often troubles biologists and taxonomists. The world over we are losing species by the day, more often than not due to anthropogenic causes; yet life persists regardless of diversity loss, filling gaps in any available niches. The problem is, however, that we simply do not know of all species that are vital to the sustained functioning of an ecosystem, or the long-term implications of such rapid species loss.

To serve as an example: there is a small, green species of fly known as the !nara fly, of which science knows very little. The fly is thought to be found only on the !nara plant in the Namib Desert. !Nara is of fundamental anthropological, biological, commercial and historical importance. !Nara has provided a valuable source of food for indigenous peoples for thousands of years. The ≠Aonin Topnaar, current indigenous inhabitants of the Namib-Naukluft and Dorob national parks, still harvest !nara, crucial to their cultural identity and lifestyle. !Nara demonstrates its growing commercial success with products such as !nara soap, oils, lotions and seeds. !Nara also serves as a critical fortress and source of food for many organisms; its thorny stems protect small animals from predation and provide stability in sandy soil, enabling many creatures to create burrows. In 2013 scientists produced evidence showing that, among other tiny insects, the !nara fly is a pollinator of the plant. We do not know the full impact the fly has upon the plant, but its potential significance as a pollinator is huge, regardless of its physical size. If the fly were to suddenly disappear, the decrease in !nara pollination would result in a drastic reduction of fruit. Modern biodiversity loss has resulted in a global concern for pollinator conservation since food supplies worldwide are reliant on tiny insects such as the !nara fly.Traversing the desiccated terrain of the Namib Desert, one could be forgiven for believing that one had been transported to another planet. The Namib Sand Sea, a majestic yet inhospitable body of dunes, flowing over some three million hectares, engulfs the land with its parched grasp. What decades of research, documentation and observation on the Namib have told us, however, is that it is anything but inhospitable – at least for the countless desert-adapted organisms that grace its scenic grandeur.

The diverse array of specially adapted organisms found in the Namib never fails to impress. Countless creatures have evolved to contently inhabit this otherworldly environment, such as burrow-digging geckos, scorpions and spiders, or the beetles, which conjure up inventive ways to exploit the regular fog to obtain necessary moisture. These organisms and many others have captivated generations of curious minds. Often one can physically see and therefore logically understand the extraordinary evolutionary adaptations bestowed upon these creatures, which enable them to survive in hyper-arid conditions. While one may be able to deduce that many of these desert-dwelling inhabitants belong to this environment, merely by observing physical traits, beneath the surface lie some rather unexpected, logic-defying residents – snails.

Terrestrial snails are present in many of the world’s deserts, and the Namib is no exception. Snails are often associated with wet areas; to learn that they exist here may therefore come as a surprise. Parts of the Namib seldom see rainfall and some years may go by without any rain at all. Incredibly some snails have evolved to exploit infrequent rainfall, lying dormant for months or even years at a time and then surfacing shortly after heavy rainfall or on damp, foggy nights and mornings at certain times of the year.

Certain snails have been observed to bury themselves several metres below ground, entering a state of dormancy. When the snails are dormant, water loss is dramatically reduced to the point where some species can survive for several years without moisture. Upon rare desert rainfall seeping into the sandy soil, snails can emerge for a limited time to feed and reproduce before cosily burying themselves beneath the surface once again.

There have been reports of snails emerging from their subterranean dwellings in droves – making it impossible to walk across the surface without crushing their shells – only for all of them to completely disappear ten minutes later at sunrise. Even digging does not reveal the slightest evidence of the prior mass-congregation. Once a snail from an arid region of northern Africa, thought dead, was glued to a plaque in the British Natural History Museum, where it emerged from its shell four years later after water had been applied to the plaque. For creatures that are often overlooked or disregarded, they are certainly capable of some truly incredible feats.

At Gobabeb, a scientific research station in the central Namib Desert, several snail shells have been lying in and around a small fenced-off enclosure on a remote interdune area for many years. The shells have baffled many a scientist, their origin is a mystery. Several of these shells were recently sent to an expert in South Africa, Dr Willem Sirgel, who identified them as Trigonephrus haughtoni, a relatively large terrestrial species of snail, which has been previously found and studied in the southern Namib but never in the Gobabeb area. “The fact that no living snails have been seen [at Gobabeb] is not so strange”, explains Dr Sirgel. “Trigonephrus spends most of its life underground [and] I can only come to the conclusion that if there are shells, there must be some snails at least nearby”. Dr Sirgel proposes that the snail shells in and around the enclosure plot may be a result of birds preying on them and carrying them there to perch on the fence, the only elevated point on the otherwise barren interdune, and discarding the shells after consuming the contents. Has the mysterious origin of snail shells around Gobabeb’s enclosure plot finally been solved?

This article first appeared in the Spring 2017 edition of TNN.