Hide, seek and go

The Namaqua dwarf adder (Bitis schneideri) is one of the many species of reptiles unique to the Namaqualand coastal strip.

Namaqua National Park covers a remarkable diversity of habitats, ranging from arid uplands famous for spectacular wildflower blooms, to rolling coastal dunes and rugged coastline. At first glance the landscape appears devoid of wildlife.

However, a remarkable diversity of smaller animal species such as rodents, tortoises, lizards, snakes, chameleons, and even frogs abound here, and most occur only in this part of the world. In fact, the Succulent Karoo Biome, of which Namaqua National Park is part, is one of only two arid biodiversity hot spots in the world.

The Namaqua dwarf adder (Bitis schneideri) is one of the many species of reptiles unique to the Namaqualand coastal strip.
At birth these diminutive snakes measure only 100mm and weigh in at less than 3g, while adults reach a grand length of just over 200mm, making them the world’s smallest viper. Namaqua dwarf adders are also masters of disguise – until recently few specimens had been recorded and little was known about their biology.

They spend most of their time buried just beneath the surface in loose sand, usually with only their eyes exposed. This behaviour allows them to avoid the prying eyes of predators (and humans) and simultaneously allows them to regulate their body temperature effectively while they lie in wait to ambush passing prey. With such a secretive lifestyle it is little wonder that these amazing creatures often go unnoticed, even by keen wildlife observers. This adder was classified as “vulnerable” (VU) by the IUCN owing to loss of its habitat, mainly strip-mining for diamonds, and the threat of illegal collection for the pet trade. However, a much clearer picture of the adder’s biology was recently gained during a five-year study by researchers of the University of the Witwatersrand. The study revealed many interesting and surprising facts and resulted in a change to its conservation status, recently-published in the Reptile Atlas (Atlas and Red List of the Reptiles of South Africa, Lesotho and Swaziland).

The adder has been downgraded to the category of “least concern” because it is no longer considered a threatened species. This is truly good news. Once researchers gained a window into the animal’s biology, it turned out to be much more common than previously thought. In fact, densities of up to nearly 20 individuals per hectare were measured – one of the highest densities known for any snake species in southern Africa. Using miniature radio transmitters glued to the adders’ backs, and nearly 600 hours of observation, the Namaqua dwarf adders were shown to not only be abundant in suitable habitat, but individuals tend to occupy small home ranges.

The fact that they do not usually stray from their home turf mean that they must be capable of remembering landmarks around them. They are also not fussy eaters and will consume any suitably-sized animal that they can ambush. Various lizards, rain frogs that emerge from beneath the sand when it rains, and small shrews are included on the menu. The study also showed that the adders suffer high rates of predation, mostly by birds and mongooses, and that populations are maintained only through frequent reproduction.

In most viper species, females produce litters only once every second or third year when they have managed to build up sufficient fat reserves. Female Namaqua dwarf adders generally breed every year, a feat that is only possible because of the stable climate that characterises the Namaqualand coastal strip.
Source: Bates, M.F., Branch, W.R., et al.  (eds). Atlas and Red List of the Reptiles of South Africa, Lesotho and Swaziland.




Bryann Maritz and Graham Alexander - Animal, Plant and Environmental Sciences, University of the Witwatersrand

Latest News