Hard microlife

In such a small place as the Sanctuary Peninsula, the smaller you are, the more abundant you become, and the less risk you face of dying out. However, being small in such a cold environment is energetically difficult, requiring significant food sources or designated micro-habitats for thermoregulation. It's no surprise that small vertebrates are very abundant in the ice-free regions of Antarctica, yet their range is often more localized and fragmented compared to larger animals. 

At the present time, a handful of cold-blooded species have been able to survive in small,  northern environments of Antarctica. Among all the past reptile species that radiated from those imported by Aves ex Machina, only two species of a single lineage have survived: lipidragons. These very derived lizards have adapted to the harsh climate of the continent through several pre-adaptations, including viviparity and the ability to rapidly store subcutaneous fat to insulate their bodies. Their metabolism is somewhat higher compared to standard reptiles, but it is still far from that of endothermic animals. Due to the harsh climate, lipidragons can remain active for just 3-4 months throughout the year, yet they can tolerate daily temperatures as low as 5°C by taking shelter in well-protected burrows or thermoregulating on dark rocks that absorb more heat.

The shrub lipidragon (Microcenosaurus relictus) is the smallest of the two surviving species, approximately the size of a human hand. This species inhabits the Seamount, where the presence of thermogenic plants at high density has created a relatively mild climate, allowing the species to thrive abundantly despite its limited range. They are generalist predators of insects and other terrestrial arthropods, often  hunted on shrubs and small trees thanks to their discrete scansorial adaptations. Like all lipidragons, their tails are proportionally shorter and more robust compared to an average lizard, in order to reduce heat loss.

While the shrub lipidragon is found in the warmest areas of the Sanctuary Peninsula and experiences few thermoregulation issues, the other species which is called robust lipidragons (Nicilacerta modestus) utilize microhabitats to thrive in much colder environments, specifically in the northern portion of the Follia Plateau. This reptile is as long as the Holocene green lizard but can weigh up to three times more due to its sturdy and compressed body, which reduces the volume/surface ratio as an adaptation to minimize heat loss. Compared to the shrub species, the robust lipidragon has a stronger bite force, allowing it to feed on larger arthropods such as orthopterans, beetles, and notably snails*, which can make up more than half of its summer diet. Bird's hatchlings can also account to a significant part of robust lipidragons' diet: while there are only 5 species of resident passerines in Antarctica, at least 20 species migrate to Antarctica for breeding during late spring.

Lipidragons often fall prey to larger birds, such as eggpouchers, which have gradually outcompeted the cosmopolitan ground tyrants, a group of poor flying adapted to dig and live on the ground. Thanks to their ovoviviparity, eggpouchers are much better adapted to the cold environments of Antarctica compared to the past ground tyrants, which suffered a significant decline at the start of the Biancocene and eventually disappeared around 83 million years AP. In contrast, eggpouchers' diversity rapidly increased at the beginning of the Biancocene, but they still struggled to withstand the immense habitat loss following the Continental Crisis. Although eggpouchers are abundant, their diversity is reaching a low point, with no more than four genera across the entire continent, excluding marine species (reefsurfers), which are much more diverse.

Among the most widespread eggpoucher genus is Criocuculus, found in the open lands of the Follia Plateau. They rank among the largest terrestrial eggpouchers after the banchisaraptor and are the largest flying eggpouchers. This genus is subdivided into two species, which have similar diets but different habitat preferences: the coastal eggpoucher and the cliff eggpoucher. Both species are primarily located in the western part of the Follia Plateau, where the oceanic microclimate is stronger, and habitat productivity is enhanced by the presence of larger amounts of megafauna. Coastal eggpouchers (Criocuculus litoralis) prefer to hunt for arthropods and small vertebrates in sandy areas, both marine and riparian, where they often create small dens to give birth and raise their chicks, which are born relatively precocial and can follow their parents a few days after birth. They can weigh up to 1,500 grams, compared to the smaller cliff eggpoucher (800 grams), making it one of the largest land eggpoucher currently present in Antarctica, second only to the banchisaraptor.

In contrast, the cliff eggpoucher (Criocuculus geomaritimus) is predominantly found in rocky microhabitats due to its habit of raising its chicks on large rocks (greater than 2 meters), which are unreachable by terrestrial species. These rocks are more frequently found as single reefs near the coast, justifying its specific name (geomaritimus = of the sea rock). Chicks are also born more precocial and can achieve short flights three days after birth, capable of following their parents almost immediately after being born. Some populations can also be found in the Seamount because of its rocky environment. The species also exhibit different social behaviors depending on their habitat: in the abundant coastal cliffs of the Follia Plateau, western populations tend to form small colonies or raise their chicks solitarily, while in the smaller rocky patches of the Seamount, they can form colonies of over 100 pairs. Both species are threatened by predators like the wandering pinpiercer, which preys on them. This nearly one-kilogram carnivorous bird specializes in feeding on small to medium-sized flying birds found both inland and along the coast, including these eggpouchers. Occasionally, even the plague pinpiercer can feed on these eggpochers, but it usually prefer larger prey. 

Although lipidragons and eggpouchers numbers are abundant, the ongoing cooling trend poses a serious long-term threat to these species. When invertebrate diversity will collapse due to permafrost, there will be no habitat left for any of these vertebrates, both cold-blooded and warm-blooded. However, until that time arrives, these species will continue to thrive. Until the very end.

*Land and freshwater snails have suffered from the Continental Crisis but remain widespread and diverse, with at least 18 known species (although 12 of these are found in insular environments and only 4 species are terrestrial). Among other ecologically important invertebrates, wormflies must also be mentioned. This long-lived group of worm-like dipterans can be found in every Antarctic environment, except for Greenrock and Land-no-Land.