River Bunnies

(to reiterate, this was a commission for a species of foot-propelled aquatic rabbits, with the details below based on those given by the commissioner)

---

Living in the river systems of a tidally-locked world orbiting a red dwarf star. The meltwater of massive glacial mountains flowing down the slopes and into the continental lowlands creates massive tributaries spanning thousands of miles. These are the basis for complex aquatic ecosystems similar to marine reefs, with kelp and seaweed-like algaes of both green and purples colours, and photosynthetic annelids which grow like coral from the riverbeds. The abundance of underwater vegetation has prompted the evolution of swimming adaptations in formerly terrestrial animals eager to exploit these vast untamed pastures.

These are a relatively primitive species from a branch of aquatic rabbits seeded upon this world. Their powerful back legs, once used for bounding hops across dry land, are now tools of underwater propulsion, similar to that which evolved in Earth's frogs and waterbirds, such as cormorants and loons. Its large webbed feet easily propel the lagomorphs through the water searching for tasty aquatic macroalgaes. Lower-growing algaes are ripped up are packed into their cheeks, while taller species are gnawed off at the roots or trunk and pulled up to the surface, where they can be eaten more leisurely while floating. The front legs have been reduced in size, limiting their terrestrial mobility, so they do not stray far from a river as to avoid being caught by a predator on land. A last resort defence, they may lash out with kicks from their powerful back legs, clawing with the nails on their back feet.

Unlike many aquatic mammals, the rabbits retain their ears, which are covered in a watertight cuticle derived from earwax to limit heat loss while underwater. Its ears are stiffened by rings of cartilage, allowing them to be used like rudders while swimming underwater, but they can also be pressed against the body during faster bursts of speed for greater hydrodynamic movement. Both the ears and nostrils are closed off underwater, and they can remain underwater for up to five minutes at a time, although they usually do not stay underwater that long. Their under fur is very short, but very dense, with roughly one-hundred hairs per follicle, and has an outer guard layer of stiffer hairs, which traps a layer of air against their skin, helping them maintain buoyancy and, along with a layer of blubbery fat, keeping them warm in cooler water.

If pursued by an underwater predator and about to be caught, they are able to release an unusual defensive measure, excreting a very oily and foul-tasting substance from the base of their ears like how a squid will shoot ink. This substance sticks to the skin of the attacker, and can be extremely detrimental to those with waterproof oils or protective mucous films over their skin, as this substance interferes with the functions of such layers and is very difficult to wash off thanks to its oily properties. If it gets into the mouth, it provides a nauseating experience which a hunter is sure to keep in mind for next time it encounters these rabbits.