The Tegzander

Varpikes, those predatory tribtiles which evolved in the Pangeacene, have not done well at clade level with the cooling climate at the start of the middle Ultimocene. Dropping global temperatures and the rapid loss of tropical forest communities that took tens of millions of years to evolve has meant that almost the entire group of these unusual tribbets have gone extinct... all that is, save for one.

Continuing to eke out a living in the cool forests along and just north of the equator, perhaps the most unique of any of them can still be found. Small, only a little bigger than a common squirrel, with a small, floppy dorsal sail apparently no longer of any use, yet not yet fully lost, the tegzander is the last living varpike and one totally unlike any of its ancestors. Shaped by a very different climate to that they originally evolved in, to survive in a harsh environment has required these former cannibals to cooperate if they want to survive.

Whilst most varpikes relied entirely on the heat of the sun to stay active, the tegzander now remains active even in temperatures approaching freezing., yet they are not any more able to maintain a body temperate above the ambient than any other varpike could do on its own. They are very arboreal, spending most of their time in the branches of trees, and are always found in large groups. The trick to their survival in a climate that would kill most other ectotherms that tried to stay active the year-round indeed lies in these large family units; tegzanders colonize hollow trees and here form tightly-clustered aggregations known as huddles, where many individuals effectively hug one another in a ball-like formation, and shiver their muscles to collectively generate a substantial amount of body heat which is shared between them and maintained in the huddle far better than it could be by any one individual. These huddles are more efficient the more individuals they are comprised of and so there is absolutely no territorial behavior among this species; not even males fight over breeding rights, with females quite promiscuous and males simply waiting their turn to mate after their neighbors - survival in this environment, for a cold-blooded animal, is simply too reliant on cooperation for there to be any room for conflict.

The tegzander's huddling behavior allows the entire group to function effectively like a single warm-blooded animal. The huddle never breaks entirely if the temperature is below a certain threshold, around fifty degrees Fahrenheit, which means they remain in formation through almost all nights and occasionally through the entire day as well. During "huddling weather" below this threshold, only a few individuals ever leave the nest at one time, taking short ten to fifteen minute forays outside the huddle to gather food and bring it back to the nest before returning to the group. The huddle can be up to thirty-five degrees warmer than the surrounding air temperature, and so chilled individuals returning into its center are rapidly revitalized, while individuals which had returned earlier move toward the outer edge as new arrivals return until eventually they shift to the edge and then are ready to leave on another foraging trip of their own.

The food the tegzander takes also differs from its now bygone fellows; unlike most varpikes they are omnivores and consume more plant matter - primarily fruit and seeds - than meat or insect prey, since these foods are far more easily collected in the cold than most animal foods. Tegzanders even store such food in their nests and so can rely on food saved during warm and mild weather to endure the coldest spells without having to break their huddle and leave the nest. What little animal prey they do take is only found opportunistically; molodont nestlings left unattended, snails or insects found under tree bark, or occasionally another small ectotherm animal, caught alone and too cold to quickly escape their gnashing jaws.

The tegzander might seem a perfect example of a species adapting to the harsh, coming days of cold, yet the beginning of the mid-Ultimocene ice age has come much too rapidly for the tegzander to have evolved its suite of behavioral and physiological adaptations specifically in response. It has so far persisted in this last refuge because unlike any of its fellows before it, its ancestors had already adapted to survive in a similar climate to that which now dominates sea-level land at the equator long before the current ice age brought winters' chill so far south, changes that occurred over not thousands but millions of years. They had evolved, an aberrant and isolated branch of their family, to live high on a few isolated mountains, the high peaks of which were similar to the currently widespread equatorial climate back when the lower elevations were still balmy and tropical. They are thus refugees of a colder climate now brought down to lower elevations by increasing glaciation, rather than hold-outs from the tropics.

A widespread cooling of the equator has allowed the tegzander, once marooned on the few cold mountain habitats they had specialized to exploit, to spread wide across the equator and beyond in the past few thousands of years. For a time, at least, the ice age has benefited this unique species. Unfortunately, the land is still cooling and may well soon become too harsh even for this most adaptable little tribbet to endure; tegzanders can endure temperatures hovering around freezing, but not prolonged spells below it as occur in the far north - conditions set to spread further south in coming millenia. it remains to be seen whether these cold-blooded creatures can continue to cheat evolution, using cooperation to stay warm in conditions that would shortly kill any one of them caught alone.