When a shadow falls over the jungle on a cloudless day, a Yorennul is flying overhead. Yorennul are titanic Flying-types that rarely return to the ground once they take flight. They are built for a life in the sky, with hollow bones and an astounding wing-to-body surface ratio. Many specimens easily reach wingspans twenty meters in length and often exceed it, but their bodies are quite slender and measure five or six meters from snout to tail. They are a shade of bluish gray all over, assumed to be a form of camouflage against both clear and overcast skies.
Only a scant few individuals have been tagged in their sleep, but the trackers embedded in these tags have recorded their flight patterns. Their gliding prowess is nearly unmatched. The data shows these specimens flying for nearly three months without landing, and the pauses in certain regions, presumed to be feeding sessions, last for so little time that the prevailing hypothesis is that they swoop to catch their prey and quickly ascend again to continue their eternal migration.
Not much was known about their diet until quite recently, but researchers in the jungle have witnessed them snatching high-flying Buzzwole or Harvespik in midair very soon after the species' discovery. Their wide jaws and long fangs are adapted to gripping and draining the fluids from large prey with prominent liquid sacs. Buzzwole muscle fluid and Harvespik nectar are both incredibly nutritious sources of energy, keeping a Yorennul fed for weeks. Sometimes they will capture prey much smaller than normal, in which case they will swallow it whole. Their neck and jaw muscles are incredibly powerful, far more powerful than their lean appearance would suggest. They can carry Buzzwole in their mouth while only losing a small amount of altitude due to the weight. Some Yorennul have been seen taking advantage of volcanic updrafts in order to avoid crashing while carrying prey.
Only one Yorennul carcass has been recovered, apparently shot out of the sky by angry Metascal triggering a lava fountain or launching a large rock from their volcanic home. By the time researchers recovered the body, most of the wing membranes had been eaten away by Metascal and the main body had been reduced to a desiccated husk by vengeful Buzzwole. Fortunately, the skull remained intact, revealing the straw-like structure of the fangs, confirming their adaptation to draining the bodily fluids of their prey.
The only time Yorennul ever truly roost is when they mate and lay their eggs. Partners meet by chance on their long travels and follow each other to a suitable mountain or cliff, where they land on their spindly hind legs and mate. They both leave when they're finished, and the female carries the eggs in her body until she finds a suitable place to lay them. Once laid, they hatch quickly, and the mother will capture one large piece of prey for the chicks to feed on. This initial meal causes a massive growth spurt. After this point, they're on their own. They take off from their nest and must quickly learn to fly or else fall prey to hungry beasts below. As they grow, they target small game such as Kanopi and their nests and high-altitude juice caches belonging to Harvespik. Eventually, they grow large and strong enough to be considered adults, just as capable of capturing large prey.
Studying Yorennul in its natural environment is incredibly difficult. Until more powerful technology that doesn't harm Ultra Jungle's ecosystem can be produced, researchers should carry a supply of Beast Balls at all times in order to capture a specimen for study when the opportunity presents itself.