coastal Washington, particularly on the Olympic Peninsula Description Mountain beavers are gray or brown, but their fur can range from slightly more reddish to more blackish depending on subspecies, with a light patch under each ear. The animals have distinctively short tails. Adults weigh about , with a few specimens topping . Total length is about , with a tail length of . Their superficial similarity with true beavers reflects only their relatively large size (for rodents), strong odor, preference for living in extremely watery / moist habitats, and propensity to consume tree seedlings as food. Mountain beavers do not fell adult trees (though such trees may be killed by "girdling"), build dams, live in lodges, or communicate by tail slappings. They are predominantly nocturnal in above ground activities. They are known to climb trees a few meters to acquire food in the form of branches and leaves, but otherwise their diet consists mostly of ferns, especially species that are toxic to other animals. The skull is protrogomorphous; it has no specialized attachments for the masseter muscles as seen in other rodents. It is flattened and lacks a postorbital process. The baculum is thin and distinctly forked. The penis is about in length. The male does not have a true scrotum, but the testes move into a position called semiscrotal during the breeding season. Mountain beavers have an unusual projection on each molar and premolar tooth, which is unique among mammals and allows for easy identification of teeth. This projection points toward the cheek on the upper tooth row, but points toward the tongue on the lower. The cheek teeth lack the complex folds of other rodents and instead consist of single basins. They are hypsodont and ever-growing. Two upper and one lower premolars are present, along with all the molars, giving a dental formula of Mountain beavers cannot produce concentrated urine. They are thought to be physiologically restricted to the temperate rain forest regions of the North American Pacific coast and moist microenvironments inland due to their inability to obtain sufficient water in more arid environments. It is thought that Aplodontia prefer vegetation high in water content due to their poor ability to concentrate urine which makes it necessary to consume large amounts of water daily. Habitat and distribution Mountain beavers are found in the Cascade Mountains of British Columbia and southward including the rest of the Cascade Range