Plesioth Ecology

Disclaimer: This is merely a plausible explanation for the monster(s) in this article, and should not be considered canon.

In-Game Information
An enormous, flightless aquatic wyvern with wings that have evolved into fins for swimming. Although superficially fish-like, they can move on land as well. They love frogs.

Taxonomy
An extremely large Piscine Wyvern. It is closely related to its subspecies, Green Plesioth, but are more distantly related to other Piscines, including Cephadrome, Cephalos and Lavasioth.

Habitat Range
The Plesioth can only survive in large amounts of water. It can, however, live anywhere as long as there is a sufficient body of water. The Plesioth is able to survive on land, but only for a short periods of time and it must return to the water to keep its skin from drying out. Plesioth prefers to live in deep water areas, which it is well adapted to. The Plesioth is unable to live in volcanic areas as it is to hot for its survival, and is also unable to live in a subzero climate as it is both cold blooded and cannot survive in near frozen water. Plesioth can even withstand desert conditions, often living at an oasis or underground lake. Plesioth is also shown to inhabitat areas of Moga including the Deserted Island. At first, it was thought that the marine wyvern would be outcompeted by resident Leviathans, especially powerful Lagiacrus and even frog loving Gobul but it seems to have its ways of making a living with them around. Maybe it's because of the great abundance of food able to support so many large water wyverns or Plesioth may even feed off of the leftovers or even offspring of Leviathans. It may even follow a hunting Lagiacrus and attack any small prey fleeing before it similarly to African goshawks following hunting Honey Bagders. On the contrary, it could simply be that each is naturally wary of the other, for they are both deadly predators & each is easily capable of maiming the other.

Ecological Niche
Plesioth is a large ambush hunter. The creature can hunt both fish underwater and prey on the surface coming too close to the waters edge. Its defenses are somewhat poor, and it will try to avoid any kind of confrontation, be it on the surface or underwater. Plesioths are somewhat territorial, actively patrolling its turf until it finds a suitable meal. On land it is most likely high in the food chain, due to being so large many monsters would not attack it. However, due to their limited mobility out of water, they are at risk from attacks from other large, more agile monters, such as a fire wyvern or Tigrex, so they never venture far from their native rivers or lakes. In the water, Plesioth has fewer competitors and, therefore, is an apex predator there. As seen in the Plesioth's ecology video, it preys on herbivores that drink near the coastline.

Biological Adaptations
The Plesioth has adapted so well to the water areas that it has lost its ability to fly. The Plesioth seems to possess strong neck or stomach muscles in order to release highly pressurized water. Plesioth may also possess a sac where it stores water, so it may use its water beam on land. Plesioth have hard scales (which are blue in color, providing camouflage) on its back, that can repel most weapons. The Plesioth will mostly stay in the water until it is disturbed by loud noises, like the sound of a sonic bomb. Unlike the Cephadrome, whose wings have turned completely into fins, the Plesioth still retains its wing like features. The Plesioth is extremely sensitive to sound, which it uses to sense prey either swimming in the water or moving on land. The Plesioth is able to blast water at extremely high pressure, which is very effective on armors with low water resistance. Plesioths have great taste for King Lobsters and Frogs, but they have to ingest medium sized stones in order to digest the Lobster. Due to this behavior, Wyvern Stones can be formed from the stones ingested, infused with other minerals. There have been recent reports that older Plesioths have developed the ability to salivate a potent, tranquilizing fluid from its lower jaw gums, which apparently are used to bring down larger, more aggressive prey like young Daimyo Hermitaur and Apceros, injecting the fluid when it leaps out of the water and grazes the victim. The victim immediately falls into a comatose-like sleep, where the Plesioth can drag it back into the water and consume it at leisure.

Behavior
Plesioths will confront attackers from their aquatic home and will even come on land to fight hunters if they are angered enough. They dislike loud noises very much, and will flail about when audibly provoked, as their hearing is extremely sensitive.