By Ian Foote of State University of New York College of Environmental Science and Forestry
The Okavango Delta is often known for two things: its mammals and its birds. The Delta is home to the highest density of elephants, large herbivores and predators in Africa, and hosts an assemblage of over 440 species of birds. While distracted by charismatic megafauna, it is easy to ignore other, less flashy, organisms who equally contribute to the ecosystem’s integrity.
Arthropods, reptiles, amphibians and other ‘background fauna’ are often overlooked but are spectacular in their own way. In addition to seeing some magnificent megafauna like wild dogs (Lycan pictus), sable antelope (Hippotragus niger), cheetahs (Acinonyx jubatus) and bateleur eagles (Terathopius ecaudatus), each week we have the privilege of observing the little guys, some of whom I’ll introduce here.
The granulated-thick tailed scorpion (Parabuthus granulatus) and burrowing scorpion (Opistophthalmus walbergii) are vivacious predators common in sandy, well drained soils (which conveniently, is also where we like to place our tents…). Known for packing a nasty punch, the granulated-thick tail scorpion is a rather unassuming individual; equipped with small claws, a scrawny abdomen and a powerful tail loaded with neurotoxins designed to immobilize prey. Unlike the burrowing scorpion who is an ambush predator, P. granulatus actively hunts its prey, chasing down other moderately sized arthropods and piercing them into submission. Their brown coloration blends well in fallen mopane tree leaves, and they are notoriously difficult to spot. Under a blacklight, however, they emit a bright green fluorescence. This phenomenon is not scientifically understood but makes walking to our tents at night slightly less stressful.
Growing up to 5 meters in length, the black mamba (Dendroaspis polylepis) is a powerful and often deadly snake, widely considered the most venomous in Africa. In the past week we spotted two along dense transects of mopane woodland. Neither was fully grown (one with a length of 1.5m, and the other 2m) but their presence was no less powerful. The first day we spotted a black mamba, we drove up slowly in our car, to witness the mamba spring its head nearly a meter off the ground while rotating backwards, a common tactic used to avoid and intimidate predators. Its avoidance tactic worked; we quickly rolled up our windows and watched as it disappeared into the foliage of a nearby tree. Contrary to popular belief, these dangerous predators often want nothing to do with humans, preferring to save their venom and energy for prey.
The leopard tortoise (Sigmochelys pardalis), a less notorious cousin of the mamba, possesses a docile persona, preferring to bask in roadside sunlight while browsing on fresh vegetation and hyena dung. We have spotted multiple along the sandy border of Moremi Game Reserve, slowly dragging their heavy ovular bodies away from our loud cars. The slow-moving individuals have thick, brown, spotted shells weighing up to 40kg. Living over 100 years, many grandfather tortoises have been present since long before the country’s independence in 1966.
Sand
frogs (Tomopterna spp.) are the final modest species we often see,
prowling their small territory in the late hours of night. As dusk approaches,
these stocky amphibians exit their daytime refugia underground and wander the
sandy ground in search of prey. They commonly snatch up crickets, beetles and other
small insects, digesting all but their hard exoskeletons. Unintentionally, we
captured multiple in “the pit,” a hole we dug, just for the fun of it.
While we all get excited each time we see one of the big flashy species – the elephants, top predators, or giraffes – these small species have brought much to our experience in Botswana and to our understanding of the local ecology.
