The Terrible Tribulus

An animal that is small and shy alone, but becomes a terrible force together, the tribulus brutally overwhelms huge prey animals by calling backup and forming huge, temporary gangs. 

Dividopteran tribbats were one of the most successful surviving clades at the end of the Mid-Ultimocene ice age, with five species surviving, each representing a distinct sub-clade of their wider group. Along with the aeracudas, tribbfishers, moonbeasts and flapsnappers have persisted the nightbiters. Once small, solitary parasites of the boomsingers, they survived the harsh ice age that killed off their former prey by becoming more aggressive swarming predators that killed seabirds. When the world warmed, they quickly spread inland from the coasts, giving rise to new species worldwide. Most stayed small, becoming solitary hunters of small prey, while others returned to their roots and bit the newly abundant thorngrazers for sustenance.

The tribulus, though, has stayed a predator. It has evolved upon the insular archipelago of Ansteva, off the northwest coast of Serinaustra, which is notable for its more limited animal diversity than mainland Serinaustra. Sealumps reached this island continent just as they did mainland Serinaustra 5 million years ago, yet the burrowing burdle and the foxtrotter never came so far west; the currents they rode and ice bridges they crossed took them due south, missing the archipelago entirely. Their absence has allowed other more mobile lineages - flying creatures as well as the sealumps themselves - to fill roles they might otherwise fill in their absence.

The tribulus is a nocturnal, small dog-sized animal, standing about two feet high, with a lanky frame weighing less than ten pounds. On its own it is quite a shy animal, which is easily frightened and quick to take flight. Individuals roost in plant cover or rockwork by day and emerge singly to seek food at night. Though they can still fly, they are highly terrestrial and most often spend their time on the ground, where they scuttle quickly on long limbs with their wing membranes folded up along their arms. They still often scavenge seaside carrion near the ocean, gorging on washed up fish or snarks and occasional dead birds, and these food resources are small and most efficiently collected by solitary animals. But they are irregularly available, and these islands seem to host an awfully large population of this species, which crowd the beaches in the dark night, chattering and hissing as they bicker over these seemingly limited rations. The largest males exhibit horse-like manes of bristle-like hair, which they erect to show their size against other males and to impress females during courtship. The species prefers to stalk alone outside that time, their gatherings around these food sources purely competitive. When it is limited, they fight over it fiercely, and in times of scarcity any easy food will go to the biggest and strongest individuals with the most striking manes, at the expense of the smaller, old, or young. There simply isn't enough to eat on the beach for everyone all the time - and to get more food, some must travel inland.

Occasionally, when there is no easy carrion to take, a few of the hungriest tribulus will flutter off the beaches and over the trees to stalk the open woodlands and the meadows of the archipelago, where several types of large herbivorous sealumps, no longer associated with the ocean, make their home. Some of these animals will now weigh half a ton - much too big for a lone tribulus to kill outright. But these creeping creatures still follow them - at a safe distance - watching with blank, widely staring yellow eyes that betray no emotion, and analyzing each sealump's behavior. They seek to identify the weaker links; a clumsy calf, an ailing adult with an infected wound, or an elder too tired to keep up with its herd. These scouts don't just go up attack the sealumps though, no matter how unwell they might seem. Instead, once a target is identified, the scout will take flight and begin circling low over the herd, calling with a shrill, repetitive shriek. This is a rallying cry, to which any and all other tribulus within earshot will respond.

They join the scout one by one, joining the circle over the chosen prey, and the more that gather the more unnerved it becomes as a small and insignificant animal it would normally ignore becomes something increasingly deadly. As more arrive, and ten, then twenty, thirty or even more have soon gathered, they start to drop to the ground and close in around their victim. Alone, a tribulus is a nervous and flighty creature. As a gang, they are fearless and deadly. The gathering which forms around the weakened sealump is not a pack, or even a clan; the individuals have no social bonds, and may never interact again. Each one lives for its own sake alone and simply wants to eat, and it happens that the more of them which eat at once, the easier it becomes to do so when the meal at hand is very large. When so many have arrived that the prey cannot focus on any one of them, they move in, the boldest among them making the first tentative bites just seconds before they all rush in, simultaneously shearing mouthfuls of meat from its body while it is very much alive, taking bite anywhere they can get a grip. For a few minutes the sealump struggles, but it is like fighting a tidal wave of teeth. Flailing blindly, it may kill several - its herd may too try to fend off the plague - but the scent of spilled blood only draws in more, and the swarm grows ever bigger. Vastly outnumbered by a foe that is at its strongest in these darkest hours, the sealumps never win this fight. After a few fierce bites, those which can run soon do so, leaving the weakest to be engulfed. Over 150 of the tribbats may descend on a single sealump, skeletonizing it over the course of a single night. As its dying wails draw to a close with its final breaths, the forest falls silent around as all other creatures flee. Not even the tribulus make noises - with so much food, they have nothing to fight over, and so they feed without bickering.  Soon the only sounds left are the scissor-like shearing noises of teeth cutting together, scraping meat from inedible bone, and separating the energy accumulated in one large animal over years into many dozens of smaller animals in a matter of hours. When dawn breaks, a neatly articulated skeleton will lie picked clean where its owner died  - the swarm will have vanished, the gang members gone to roost in their own dens across the islands, solitary once more.

Until the next time the dinner bell rings.