The tramplerat-trenchcrawler combo
The landscape of the Follia Plateau would resemble a trample steppe from 10 million years ago if not for the significant size changes in its inhabitants. In this cold prairie, we can still find descendants of two typical trample steppe residents: tramplerats and trenchcrawlers. But oh, how the tables have turned! While trenchcrawlers were once tiny compared to tramplerats, the sole surviving trenchcrawler species, the poop trenchcrawler (Copropollus relictus), now stands as tall as a man. Conversely, the only surviving tramplerat, known as the muskox tramplerat (Nanitherium relictus), has shrunk from the size of a rhino to that of a small cow.
The Past
Tramplerats and trenchcrawlers managed to survive due to extremely fortuitous events. About 86 million years AP, as suitable habitats dwindled, the last large predator in Antarctica died out without descendants, leaving behind a degraded trophic chain that eventually collapsed. Tramplerat descendants, already halved in size compared to their ancestors, were on the brink of extinction in their continental environment. However, a single population managed to reach a large insular environment in the far north, which forced these animals to drastically reduce their size even further. By 89 million years AP, a rapid and brutal cooling event wiped out the continental tramplerats, leading to what is known as the Continental Crisis, which resulted in the extinction of many other species.
The sea regression allowed the insular tramplerats to expand back to the mainland via a land bridge; these insular tramplerats reached the mainland just before the total extinction of their continental counterparts. This gradual substitution may have saved some trample steppe-adapted species from extinction. but, despite this, the few survivors were severely impacted, including the ancestor of the poop trenchcrawler. It's believed that only 500 trenchcrawlers survived the Continental Crisis, resulting in some metabolic issues. However, rostrids have shown resilience to bottlenecks in the past, and trenchcrawlers began to flourish again, increasing their size to cope with less nutritious food.
The lack of large predators created a significant shift in the Antarctic ecosystem, transitioning from a top-down to a bottom-up system, allowing the remaining herbivores to reach optimal population densities. Megafauna biomass increased from a mere 1 ton per km² to the current 4 tons per km², still less than half of what it was 10 million years ago but sufficient to restore some potential niches in the Follia Plateau. By 89.3 million years AP, the balance of the Follia Plateau environment was more or less restored, despite significant species loss.
The Ecology
Muskox tramplerats and poop trenchcrawlers are connected by a strong symbiotic relationship. Muskox tramplerats are hindgut fermenters focusing on food quantity over quality, feeding on almost any plant matter found in their habitat. In contrast, poop trenchcrawlers are stomach-fermenting species, similar to ruminants, that prefer highly nutritious food for the best energy intake. The presence of trenchcrawlers maintains more palatable food, benefiting the tramplerat, while the stronger trampling action of the latter favors a more mixed vegetation that significantly increase trenchcrawlers' density. It turns out then that tramplerats are highly dependent on poop trenchcrawlers, while poop trenchcrawlers can still survive relatively well in areas without tramplerats, which can be found even outside the Follia Plateau, even in the harsh Greenrock region. These populations, however, are genetically dependent on the core population in the Follia Plateau, the only ecologically productive region on the continent.
Unlike their ancestors, poop trenchcrawlers are no longer pioneer species and have become more selective in their diet. Nevertheless, they have an important ecological role by feeding on young sprouts of doorpeas, a thermogenic shrub that could threaten the Plateau's rich environment. While doorpeas' leaves become toxic when fully formed, their buds contain fewer alkaloids and are edible to trenchcrawlers, who can tolerate small amounts of toxins. Poop trenchcrawlers' name come from their habit of feeding on feces (of their own and, recently, even the tramplerat ones!), which helps them integrate vitamins and buffer the toxic effects of doorpeas. They often feed on the feces of other herbivores, including their tramplerat colleagues, though this adaptation increases the risk of disease transmission and harmful bacteria ingestion. Poop trenchcrawlers are largely solitary but interact with others seasonally, either cheerfully or aggressively.
Muskox tramplerats, on the other hand, are social herbivores that primarily feed on herbs and tubers, which they excavate with their strong front legs. Their heads are relatively bulky like their ancestors, but they have lost their defensive role. Muskox tramplerats have become very tame, typical of insular species where large predators lacks: some carnivores occasionally hunt young individuals, but adult tramplerats become unassailable after one year. When their cubs (litters rarely exceed one individual) are threatened, female tramplerats sometimes stand their ground by aggressively biting the predator, but this behavior decreases significantly after weaning, which lasts three months. It's not uncommon to see a predator attacking a young tramplerat while the mother watches passively.
Despite the ongoing challenges, the muskox tramplerats and poop trenchcrawlers continue to persist, a testament to their resilience in the face of a changing environment. But how long will luck be merciful?
Head of a tramplerat. Its horizontal eyes inherited by its ancestors enhance the amount of light entering the eye in the forward and backward directions, while decreasing the amount of light entering the eye from above. A perferct adaptation for foraging while keeping an eye on surroundings.
