Africa's Twin Veldts

Africa has suffered immensely to the cold. With little humidity to help retain heat over much of the continent, when the Sun’s shine shrank away, the temperature crashed with deadly rapidity. Even the advantage of montane life was not enough, for Africa’s cool, high-elevation areas are simply too small and spread apart. As such, the question of who survived and who died is dominated significantly by random chance, favoring organisms with large ranges that included considerable temperature and biome variations. After the world stabilized, the very thin strip of habitable land that now connects Africa and Arabia to India provides enough resistance to newcomers that Africa has maintained a unique host of creatures.

Separated only by a narrow belt of forest, Africa’s northern and southern veldts have considerable interchange between them and are thus essentially one grassland; combined, they are by far the largest in the world. Perhaps oddly in this age of decreased rainfall, some of the Sahara is wetter than it was in its dry periods before the extinction. This is because of two competing factors caused by the decrease in insolation: First, the global temperature fell and average humidity decreased, of course, but second, many complex meteorological phenomena collapsed from the lack of energy to maintain them. This included the cycle that transitioned the Sahara Desert from wet to dry and back again every few thousand years. As such, the Sahara collapsed into a middle state, which then continued to suffer decreases in humidity, pushing the desert northward into cooler areas. Now the grasslands have expanded northward while much of the Sahara is a cool desert bordering the tundra and ice sheet in the Mediterranean area.

Africa’s twin veldts are at least as dry as they were before the extinction, though now they are temperate instead of tropical. Grasses obviously dominate this continent, often tracing their decent from South Africa or the Ethiopian highlands. Shrubs and trees are a similar miscellany, including descendants of Cistus monspeliensis, the Montpellier cistus, from Morocco, and various Olea species, containing the olive and its relatives, from all over the Old World. Beside rivers and lakes, the African cherry, Prunus africana, has diversified into a wide array of trees and shrubs thanks to its slight frost tolerance early on. As is common worldwide, coniferous plants are very well represented.

To an even greater extent than the plants, the animal survivors are lucky and miscellaneous. Birds of prey, as expected, have weathered through rather well and are common denizens, as are the immense swarms of locusts that send waves through the grasslands every so often. Pierid butterflies follow the rains loosely, pursuing the smell of freshly opened flowers. Larger animals of several sorts are present as well, unaware of how fortunate their kinds are to have survived. The most prolific of these are descendants of the klipspringer.

Klipspringers’ survival is no coincidence. They were small, but not too small, and their range took up much of Africa, occurring at nearly every possible latitude. Their hollow, coarse hairs protected them from both high and low temperatures, as necessary for their high-elevation lifestyle. Their most notable progeny are the veldlopers which share many of these traits despite their increased size.

Veldlopers have kept their ancestors’ rough, hollow hair, as well as a strange tiptoed gait atop elongated hooves which klipspringers once used to grip rocky crags. Unlike their ancestors, veldlopers are diurnal, wandering about in herds many hundreds strong, and are much larger, weighing up to 90 kg (198 lb). Their social lives are little changed, however. For example, both sexes have black glands near their eyes which produce a smelly fluid often rubbed on nearby rocks and trees. These serve to stake out temporary territory when the herd is not moving. The males and females bond for several years at a time, staying near each other and raising young every breeding season. There is little sexual dimorphism, other than the small horns of males used to fend off rivals.

Alongside the veldlopers are myriad medium-sized mammals descended from the rock hyrax (Procavia capensis). Rock hyraxes squeezed by the extinction in a similar way klipspringers did, with their large ranges, perfect size, and ability to take extreme temperatures in their high-elevation homes. Their descendants now climb trees, burrow in the dirt for tubers, and munch away in the underbrush, each to their own niche.

These prey items don’t typically flee from mammalian hunters. Instead, most of the large terrestrial predators here are secretary bird descendants. Unlike their mammalian competition, these relatively small predators fled from the cooler areas of their range just quickly enough thanks to their retained flight. With much of the continent clear for the taking, they now dominate the larger carnivorous niches. Unlike their ancestors which would use strong kicks to dispatch most prey and use their beaks only for very small items, the largest of the descendants rely almost entirely on their beaks. These heftier predators' bills act like sharpened clamps, holding the neck and yanking around as the prey animal dies. The sharp, curved tip of their bill aids in severing blood vessels in this process. Smaller ones will instead bludgeon and puncture their prey with stomps and kicks. In most species, the wings find use as airfoils for quick turns.

Africa's great veldt has produced an unusual vacuum: Flying predatory insects. The lack of eusocial wasps is a major factor here as much as it is anywhere else, but the veldt's dryness and size also makes life as a water-dependent insect more difficult. This means that dragonflies and damselflies, key predators of flying insects, find it more difficult to live here, for they are pressured to migrate back to a wetter place to breed. In response, several lineages have stood up to the plate. One example is the jailer fly, a species of robber fly.

Robber flies in general are large quick-flying flies and, despite their name, do not actually steal anything. They pursue and catch flying insects, piercing them with their specialized mouthparts and sucking them dry. These same mouthparts serve as a painful bite against predators. In particular, the jailer fly is a descendant of the genus Laphria. These are often Müllerian mimics of bees, since Laphria can deliver a painful bite just like bees can deliver a painful sting, so the shared patterning protects both insects. Crucially, their larvae are terrestrial, not aquatic, living in leaf litter or rotten wood as predators and occasionally detritivores. Thus these creatures were in the perfect position to diversify when their eusocial competition disappeared and their water-dependent competition waned.

Jailer flies are fairly large, at about 4 cm (1.6 in) long and 5 cm (2 in) in wingspan. They have retained their bee-like appearance from their ancestors, with their dense coating of hair and bright black and yellow coloration. Their hairs are more than just for show, however; their real use is in predation. Take their overgrown mystax, for example. A mystax is a dense tuft of bristles around the mouthparts that helps protect the head from struggling prey and is a common feature in robber flies. In the jailer flies, the stiff bristles that make the mystax are so long that they make the head appear two times as tall as it actually is. Their proboscis, almost twice the length of their ancestor's, seems to barely protrude from the hair. Even more striking than their mystax, however, is the patch of bristles on the thorax, so long and dense that their gangly legs appear to attach to its edge. In truth, the long coxa, or first segment, of each leg reaches deep into the hair to attach to the thorax buried deep below.

The purpose of this overgrown forest of bristles is the same as that for the long proboscis and lanky legs: this insect hunts big, dangerous prey. Stinging bees and solitary wasps, armored beetles, migrating dragonflies and damselflies, and even its larger robber fly relatives. In search of these the jailer fly will usually find a choice spot to sit in, scanning all around it with its bulbous eyes. When it targets a prey item, often several times the fly's own weight, it will take off and pursue the target at high speed. It approaches from behind, and when the time is right its legs open and snap shut around the prey, encasing the larger animal in a cage that gives the jailer fly its name. The thick legs, lined with barbs, hold the prey as still as possible and as far as possible from the body while the two fight for control in the air. With its long proboscis the jailer fly injects the prey with its powerful venom, then lands to eat as the prey's movements grow weak. All in all the jailer fly is an effective predator, with no flying insect off its menu, even those over ten times its size. The fly may even take down small fledgling birds, engulfing them in its now-undersized cage and, with luck, eating them just the same. The fly may be so swollen after its meal that it can hardly take off, but even then do not often finish their food. Jailer fly leftovers are an important food source for many small scavengers of the veldt.

Male jailer flies are slightly smaller than females, though both are capable predators. While the female can produce thousands of eggs in her adult life and needs all the protein she can get for this purpose, male jailer flies have little need for it other than to keep themselves going. Thus, male jailer flies are habitual gift-givers. When he wishes to mate, the male will carry a prey item until he finds a female. If she accepts the gift, he will pass the meal to her — an entertaining process as they fumble the giant prey from one set of lanky legs to the other — and he will mate with her as she eats. Females have grown dependent on these gifts and will rarely mate without one. These gifts free the male from having to guard their mates from other males, since females will not likely mate when they are full, so she herself will turn down other males' gifts for as long as her meal fuels her.

Jailer fly eggs are laid in rotting wood and leaf litter, hatching into maggots which live as detritivores and predators of minute animals for two years. Jailer flies live one, sometimes two years as adults, for although most robber flies overwinter only as larvae, the cold temperatures have selected for jailer flies that can at least occasionally do the same as adults. Males, however, never live past their first year as imagoes.

In the long grass and underbrush many animals run about, but this is only recently the case. In the early days the regenerating grassland had few small vertebrates calling it home. Most notable among the absentees were small mammals, as was often the case worldwide, though quite severe here. Rodents, shrews, moles, and others made it through, of course, but for some time they had very low populations and a much reduced diversity of species. This fact has been devastating to snakes. Snakes owe their modern diversity to mammals, for as mammals radiated in the Paleocene after the K-Pg extinction, so too did their reptilian predators. Deprived of their favored food source, made much worse by the fact that most snakes made their homes in tropical regions, snake diversity is only a fragment of what it once was. In particular, pit vipers and boas are gone, and with it the ability to detect heat with their specialized pits.

But as old innovations disappear, new ones rise in their place. Smaller, more generalist snakes, eating insects or lizards as the main parts of their diet, found their way into a world with few snake competitors but an increasing supply of food. Birds, having done much better overall than small mammals, were a precious source of food early on that only led to further specialization as things got better. In the African veldt, devoid of trees but filled with birds, snakes had to make ends meet.

One result of this is the jumpsnake. Jumpsnakes are a member of the largest family of snakes both before and after the extinction, the colubrids. As the grassland grew out and the ecosystem stabilized, the jumpsnake's ancestors shunned their old diets and reached for the small birds above. The problem is that the birds rarely approached the ground, and there were few trees for the snakes to ambush from, forcing them to ambush from below. But ambush they did, for competition was fierce as consumers battled for open niches. The pressure caused them to use the grass stalks in lieu of trees to support their bodies, closing the gap between them and their prey, leading to the evolution of the modern jumpsnake.

Jumpsnakes are extremely unusual. Standing almost vertically in the long grass like pillars, they seem almost to be balancing on end. Their bodies are well camouflaged, bearing longitudinal stripes like those of a tiger as well as keeled scales, blending their bodies into the shadows of the grass stalks. About one third down their bodies, the camouflage suddenly changes into large, muddled spots on a darker background. This blends in with the darker soil, spotted with dead leaves and clumps of dried dirt. However, the morphological changes go deeper than mere coloration.

The anterior third or so of a jumpviper’s spine is rigid and stiff, reinforced with thick ligaments that limit bending. The hind portion of their body, meanwhile, is broad and muscular, and its scales are very distinct. The ventral scales are reduced with anterior edges that protrude from the body like wedges, as well as having another wedge-shaped protrusion in their centers. They are surrounded by keeled scales which have evolved to stick out almost like blunt hooks on either side. These scales together act as cleats, giving the body extra grip against the ground. While these adaptations make them more awkward at slithering, jumpsnakes don’t need to venture far to acquire food. Instead, they find a patch of grass and stand their rigid portions up through it, leaning against a sturdy tuft. Here they wait, and they won’t have to wait long if their spot is a good one, for small, seed-eating birds will inevitably arrive. Upon seeing a nearby bird, the snake will begin rocking back and forth, imitating the wind blowing through the surrounding grass, working its head closer and farther from its target. Once within range, the snake will leap, driving its cleat-like scales against the earth, striking its target like a fanged javelin, often flying well above the tall grass and into the open air and sending other birds into flight. Like all colubrids, the jumpsnake is opisthoglyphous, or rear-fanged, meaning that its venom delivery system is relatively far back in its mouth. To envenomate its prey, it must manipulate its prey back toward its fangs, a fast process for its small quarry. Jumpsnakes have mild venom, as most colubrids that are venomous do.

Jumpsnakes have committed fully to their ground-living ways, from their clutches of eggs laid in hollows to their young, too small to be catching birds and instead hunting insects, to the adult that preys on its high-flying prey without need for a tree. Their tactic is not perfect, for their unusual posture is energy intensive even with a support, so their choice of location matters much. To maximize their chances, they prefer to hunt in plots of grass that are in seed to attract birds. This tradeoff has worked for them, for they are widespread and common in both veldts.

However, with success and omnipresence comes the opportunity for others to take advantage. Namely, several species of eagle and harrier have learned of the jumpsnake's ways. When a jumpsnake is spotted in hunting posture, the bird of prey will not kill and eat it outright. Instead, it perches nearby, perhaps in a small clearing or on a dead shrub, and waits. Inevitably the snake will shoot out of the grass, and if it nabs a prey item while doing so, the bird will follow the snake back to the parched earth, earning two meals for the price of one. Because the snake broadcasts its location loud and clear when it leaps, the opportunity for a two course meal sometimes shows itself by surprise.