The desmans, in which there are two species, lead a somewhat different way of life. The Pyrenees desman Galemys pyrenaicus is restricted to permanent, swift-flowing streams in the Pyrenees mountain range and parts of northern Iberia, while the Russian desman Galemys pyrenaicus is found in Russia. Desmana moschata is restricted to slower-moving waters and lakes in western and central Soviet Union. Just as moles are exceptionally well suited to a fossorial lifestyle, desmans are similarly well adapted to water.
The Pyrenean desman's streamlined body enables it to glide quickly through the water, powered by powerful webbed hindlimbs and partially driven by a long, wide tail.
Nutrition and maintaining body heat are paramount concerns for any animal living in snow-fed mountain streams. Unlike hedgehogs or tenrecs, desmans do not go into hibernation or torpor during the winter months when prey is scarce. They must therefore live in optimal environments to ensure their survival during these months.
What Food Do Desmans Consume?
Desmans feed on aquatic insect larvae such as the stone fly and caddis fly, as well as small crustaceans that they find by probing their proboscis-like snouts under small rocks and removing debris from the stream bed with their sharp elongated claws. Prey is ingested at the surface, where a thorough body grooming routine is performed after each dive. This is a critical operation because it not only keeps the fur clean and in good health, but also preserves its water-repellent properties by distributing oil from sebaceous glands across the body.
How Do They Build Nests?
Desmans nest in the banks of streams. The Russian desman excavates a complex burrow, which it can share with other desmans, while the Pyrenean desman lives in a purely solitary nest, which is normally formed by enlarging an existing tunnel or crevice. Nests are constructed entirely of leaves and dried grasses and are often built above the water's surface.
Season of Reproduction
Desmans' breeding activity is poorly understood. Mating occurs in the spring (March to April) in the Pyrenean desman, and since these animals typically form a stable pair bond, competition for mates by solitary males is often very fierce. At this time of year, each pair of animals experiences an interesting phenomenon: males become significantly more territorial, spending the majority of their active time on the upper and lower reaches of their riverine territories. Thus, energy is expended defending the territory's feeding resources and, more importantly, the girl. In comparison, females spend the majority of their active time feeding, surveying for an appropriate nest location, and collecting nesting materials.
Young are born approximately four weeks after gestation and are solely cared for by the female. Juveniles leave the nest for the first time at about seven weeks, when they are already proficient swimmers. Juveniles remain within their parents' territory until they are approximately two and a half months old, at which point they depart in search of a mate and breeding territory for the following year.