Swirling Sirenhorn

Evolution is not linear, working toward a goal. The huge, decorative  crests of early hothouse sirenhorns seemed posed to only become more lavish. But this is not the case for most. For now there are more predators, more rivals, and more danger in general. The swirling sirenhorn, with modest, slightly spiraled crests, appears far less extreme or dramatic than its ancestor, but it is now one of the most numerous herbivores in the world.

Over 30 million swirling sirenhorns live across Serinarcta, covering a very wide range that includes most of Serinarcta save for the northeastern quadrant, which is too wet and forested for these plains-adapted grazers to survive. Swirling sirenhorns occur in vast herds throughout the southern savannah woodlands, west along the upland plain of the continent and north to the arctic plateau as far as the open woodlands south of the nightforest. By range, they are the single widest-ranging thorngrazer, and by population, they are Serinarcta's most abundant megafauna.

Weighing up to 300 pounds and standing around six foot high with their crests, swirling sirenhorns are mid-sized herbivores that have reduced in size significantly, yet they are so abundant they have wide-reaching ecological effects related to their herd's constant feeding. Sirenhorns are strongly nomadic and crop grasses neatly just above the soil level, so that in a week's time, tender new blades will have grown in their place, by which time the herd will have moved on. This, in addition to the plowing of their hooves into the earth and the deposition of their droppings, regenerates the plains, and though it may initially appear devastated, an area visited by these sirenhorns quickly returns to greater health than before it was grazed. Certain other grazers, particularly trunkos which can only consume softer, newer grass, follow behind sirenhorn herds in their march to feed on the greener pastures always left behind. Sirenhorns are a major limiting factor to the growth of dancing trees and other non-cementree flora, as they graze away many seedlings. Thorns, though they have evolved abundantly as a deterrent in other mature plants to discourage large browsers, have little effect against thorngrazer teeth, and so some plains vegetation has evolved to become extremely poisonous, and even to advertise its toxicity with warning colors so that such grazers stay away. This is about the only way any grassland plant that cannot grow quickly enough to recover from damage can now survive.

Swirling sirenhorns are so numerous not just because they can find abundant food on the evergreen grasslands, but because among animals their size, they have very effective anti-predator defenses. They use their fur patterns as disruptive camouflage, making it harder to single out one individual in a herd; this is most apparent when they are threatened and group together in a tight formation, moving flank to flank. Though they are fast-runners and able to travel very long distances, this species is difficult for many predators to hunt because when frightened it is reluctant to break rank and run. By grouping together in their vast numbers and facing their enemies defensively, sirenhorns confuse predator's instincts to chase a moving target and worry them with their coordinated confidence. They also have evolved behaviors that collectively produce a disorientating effect to enemies, whole herds bunching up and walking all together in a vast circle so that their patterns become a swirling, dazzling visual sight (from which they gain their common name,) and they synchronize harsh, loud, reverberating calls that, together, become loud enough to damage the hearing of predators and even to vibrate the ground itself disconcertingly. Very large herds of wailing, swirling sirenhorns have even been known to produce such intense vibrations in their bellowing that they register as small earthquakes, and the stresses produces on the land nearby can shatter cementrees and send them crumbling to the ground. Sirenhorn mobs will kill smaller predators, those which would normally hunt animals their size, by surrounding and trampling them with their sheer numbers. As a result of these behaviors, they are only threatened to any real degree by far larger subjugator sawjaws and by cyngosaur herds, each too large to be killed underfoot. Cygnosaurs, though only infrequent predators, are their most important limiting-factor as they prevent the sirenhorn from spending more than brief visits to any one site by constantly chasing them away. This protects seedling cementrees, which though well-defended from singular grazers would be trampled and destroyed by herds so large as these if they stuck around.