Desmana moschata (Linnaeus, 1758)
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publication ID |
https://doi.org/ 10.5281/zenodo.6678191 |
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DOI |
https://doi.org/10.5281/zenodo.6671952 |
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persistent identifier |
https://treatment.plazi.org/id/0380B547-B656-FF85-9F96-FD89F652C18B |
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treatment provided by |
Valdenar |
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scientific name |
Desmana moschata |
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Russian Desman
French: Desman de Russie / German: Russischer Desman / Spanish: Desmaén ruso
Other common names: Desman, Water Mole
Taxonomy. Castor moschatus Linnaeus, 1758 ,
“Russia.”
Desmana moschata View in CoL is the only extant species
of Desmana View in CoL . Monotypic.
Distribution. Watersheds of Dnieper, Don, Volga, and Kama rivers, and middle and lower reaches of Ural River in European Russia, E Ukraine, and NW Kazakhstan. Introduced to the upper reaches of Ob River in W Siberia. View Figure
Descriptive notes. Head-body 200-225 mm (males) and 193-240 mm (females), tail 185-203 mm (males) and 180-210 mm (females), hindfoot 51-58 mm; weight 390-450 g (males) and 370-447 g (females). Sexes are about the same size. Body of the Russian Desman is chunky; head is conical, with long snout that is dorso-ventrally flattened and grooved on lower side. Whiskers are short, and dorsally situated nostrils can be closed underwater. Eyes are small, and pinna is absent. Tail is 90-95% of head-body length, laterally compressed, and more massive at base where scent glands are located. Rings of horny scales cover tail, with scarce hairs in between. Hindfoot is much larger that forefoot; each has five fingers with strong claws. Palms and soles are webbed and fringed with stiff hairs. Skin is thicker on chest (0-43 mm) than on back (0-28 mm). Pelage consists of short, dense underfur and longer, coarser guard hair. Fur is denser on venter (20,300 hairs/cm?) than dorsum (15,800 hairs/cm?). Fur is deep reddish brown to almost blackish above and ash-gray below. Skin is characteristically silvery. Young are duller. Albinos are rare; one was found among 5000-6000 skins. Females have four pairs of nipples. Skull is robust and powerful. When seen from above, massive rostrum has parallel edges. Braincase is deep, wide, and well ridged for insertion of powerful masseters. Mandible is deep and robust, with high coronoid process and massive angular process. Dental formula is usually given as I 3/3, C1/1,P4/4,M 3/3 (x2) = 44. Because premaxilla bears only two teeth, formula can be equally well interpreted as 12/2, C1/1,P5/5,M 3/3 (x2) = 44. I' is much enlarged and dagger-like;it is separated from I? by diastema. Molars are rather large, but crowns are low. Karyotype consists of 32 chromosomes; all autosomes are biarmed.
Habitat. Mainly floodplains with water at all times. Russian Desmans preferred densely vegetated lakes and still rivers, with muddy bottoms and high abundance of invertebrates. Smallest bodies of waterstill populated by Russian Desmans are 60-100 m?. Water must be deep enough (usually 2-3 m) not to freeze to the bottom. Banks have to be suitable for burrowing (i.e. steep enough and high). Woody vegetation makes habitat more suitable because it buffers climatic extremes and floods. Water reservoirs, extensive lakes, and larger rivers with strong currents are usually not suitable for Russian Desmans, but beaver ponds are suitable.
Food and Feeding. The Russian Desman obtains most food on the bottom of water bodies. Main prey includes Gordian worms (Gordius), earthworms ( Lumbricus ), various leeches (Hirudinea), crustaceans (Asellus and Potamobius), spiders (Aranea), insects and their larvae, mollusks (Viviparus, Limnaea, Planorbis, Bithynia, Valvata, Sphaerium, Anodonta, and Unio), frogs (Anura), and various fishes: pike (Esox lucius), common roach (Rutilus rutilus), daces (Leuciscus), European weather loach (Misgurnus fossilis), and redfin perch (Perca fluviatilis). Various plants is also eaten: horsetail ( Equisetum , Equisetaceae ); water plantain ( Alisma plantago-aquatica) and arrowhead ( Sagittaria ), both Alismataceae ; floating pondweed ( Potamogeton natans, Potamogetonaceae ); bulrush ( Typha ) and burreed ( Sparganium ), both Typhaceae ; bog arum ( Calla palustris, Araceae ); reeds ( Phragmites communis, Poaceae ); sedges ( Carex ) and club-rush ( Scirpus lacustris), both Cyperaceae ; dwarf waterlily ( Nymphaea candida) and yellow water-lily ( Nuphar luteum), both Nymphaeaceae ; comfrey ( Symphytum officinale, Boraginaceae ); and sorrels ( Rumex , Polygonaceae ). Smallsized aquatic invertebrates (leeches, mollusks, and insects) form the bulk in a diet regardless of season. Plants are more often eaten in spring and autumn, and fish are eaten more frequently in winter. Mean weight of stomach content is 1-7 g (maximum 7 g). Captive Russian Desmans were not selective regarding food; they readily accepted meat, fish, potatoes, bread, porridge, eggs, annelids, mollusks, and young mice.
Breeding. Russian Desmans are monogamous. Pregnant females were recorded in all months of the year. Peak of reproduction is probably in spring when Russian Desmans are most active and noisy. Family groups of 3-7 individuals remain together until autumn when young disperse, and parents separate. A female supposedly has a single litter each year; possibility of the second litter is disputed. Most young (89%) are born in June-August. Numbers of embryos are 1-5/female (means 2:5-3-7), depending on the region. Numbers of young perlitter are usually lower, with means of 1:5-3-9. Spring and summer litters tend to be larger. Gestation lasts 40-45 days, and lactating females were observed in March—October. A motherstays with young for 5-10 days but moves afterward to another nest within the same burrow system from where she regularly visits her litter. Males participate in rearing young. Neonates are naked, blind, and toothless; they are 75 mm long and weigh 16 g. At 5-7 days old, dorsum is covered with gray silky hair,
and venterisstill pink. At c.10 days, young are 110 mm in length; they are hairy except on feet and snout. Ears open at 18 days old, and young start leaving the nest and swimming at ¢.23 days old. Solid food is eaten after 27 days. Postnatal mortality is estimated to be 40%. Young steadily gain weight throughout their first year oflife from mean of 196 g at 1-5-2 months old to more than 300 g at 3-5 months old and 333 g at 7-10 months old. Males achieve sexual maturity at 4-6 months old and females at 9-11 months. Russian Desmans do not reproduce in captivity. Survival, regardless of age, is heavily affected by environmental extremes, particularly rapid and extreme fluctuations in water levels that are triggered by rains and snow melt. Sudden unseasonal flooding can drown Russian Desmans in their burrows or push them out where they are exposed to predators. Low water levels reduce availability of prey and lower reproductive success. Population size fluctuates widely between years;it tends to be higher in years with sufficient precipitation and moderate oscillations in water levels. During two decades, the population of Russian Desmans on the Oka River oscillated between 69 individuals and 207 individuals. Maximum life expectancy is c.4 years, perhaps more.
Activity patterns. Russian Desmans swim well using their tails and hindfeet to propel them through water. When underwater, they remain submerged and keep tips of snouts just above the water for breathing. For orientation, they rely on hearing, smell, and touch, but they have poor vision. In danger, they always escape into water; however, postnatal dispersion is mainly over land. Circadian activity is primarily nocturnal, mostly at dusk and down. Underice, activity is diurnal with three peaks at 05:30-07:30 h, 12:30— 14:30 h, and 19:30-21:30 h. Russian Desmans can be seen during the day during floods or after rapid snow melt when they have been expelled from their nests by high water. They sleep in their nests with heads hidden under their stomachs. Body temperatures vary depending on ambient temperature, being 34-5°C at air temperature of —12-6°C and 37-2°C at 26°C. At high ambient temperatures and in the absence of water, Russian Desmansrisk overheating. They excavate burrows into steep banks. Entrance, with diameter of c.14 cm,is always below the water surface, usually at such a depth to remain useable when water is frozen. Each family has a single nesting burrow, which is nearly always close to the surface (20-30 cm underground). Nesting burrows are the most complex, with 2-3 entrances and several nest chambers that are frequently sheltered by tree roots or some other dense vegetation. Oval chamberis 17-35 cm in diameter and lined with dry plant material. Captive Russian Desmans built nest with mosses. One to three tunnels with dead ends, each 20-30 cm long, lead from the nest. Nest is usually above the highest level reached by water in summer. A family of Russian Desmans also excavates 3-5 simple feeding chambers for eating prey and resting. These chambers are frequentlylittered with food remnants. During spring floods, Russian Desmans shelter in temporary burrows, each with up to four exits. During an emergency, they even construct rudimentary nests in hollow trees and floating hollow trunks. Galleries can spread out more than 10 m from the bank. As a rule, a Russian Desman will dig until it reaches a tree that will shelter the nest. Burrows tend to be more extensive (up to 22 m of tunnels) in gently sloped banks than in steep banks (up to 5 m). Russian Desmans also use burrows dug by Eurasian Beavers (Castorfiber) or introduced Muskrats (Ondatra zibethicus).
Movements, Home range and Social organization. Russian Desmans are semi-nomadic, a consequence offluctuating environmental conditions in its habitat. Mature individuals can migrate up to 7 km downstream (13 km in years with high water) and 2-3-5 km upstream. The longest recorded movement was 15 km in 69 days. Movements in response to droughts are invariably short (90-450 m). Densities in the late 1930s were 0-16-29:6 ind/10 km of riverbank, 0-3-0-8 ind/ha of lake surface, or 10-20 burrow entrances/ 100 m of a river course. In both habitats, densities depended on habitat quality. Current densities are 0-5—15-2 burrows/km, but sites with more than several individuals per kilometer are rare. The Russian Desman is social and non-territorial. In captivity, males and females coexisted without aggressive interactions. In the wild, however, only 1-2 adult females reproduce in the same lake. Males live in groups and are less aggressive to each other than are females. Russian Desmans rub their burrow substrate with glands under theirtails. A very strong scent might havelittle or no importance in social communication but helps in orientation. Russian Desmans are acoustic, emitting loud squeals and trills during social contacts.
Status and Conservation. Classified as Endangered on The IUCN Red List. Thisclassification of the Russian Desman is justified by the fragmented distribution and population decline of more than 50% between 2001 and 2010-2013. Itislisted in The Red Book ofRussian Federation in category 2 (declining), but there are arguments for upgrading to category 1 (under threat of extinction). In The Red Book ofKazakhstan, the Russian Desman is listed as category 2 (vulnerable). It is a Red Book species in Ukraine where it has been on the verge of extinction since the early 1990s;it is already extinct in Belarus. Numbers were in decline throughout the 20" century. A population of 600,000-800,000 Russian Desmans in 1930 dropped to 70,900 individuals in 1970 and further declined to 40,800 in 1985. Global population was estimated to be 28,000 in 2000-2001 and 25,000 in 2005. There are perhaps as few as 13,320 Russian Desmansleft in Russia. Habitat change and degradation were the main threats in the previous century, but since 1990, the key problem is bycatch from fishing. The introduced Muskrat was also blamed for excluding the Russian Desman from its habitat, although this is tenuous. A number of actions have been tried to stabilize declining populations, some dating back to the first decades of the 20™ century. The Russian Desman is strictly protected and intensively monitored. In the 1920s, an extensive program of translocations started. Russian Desmans were restocked in many places in their historical distribution (e.g. Dnieper River, Belarus, Bashkiria) and beyond in Lithuania in 1948 and western Siberia (Ob and Tobol watersheds) since 1940. From 1929 to 1970, close to 10,000 Russian Desmans were released in 36 administrative districts of the former Soviet Union. Although failures outnumbered successes, these activities supposedly slowed down the decline. Introduced Russian Desmans established a viable population in western Siberia. Main drawbacks with reintroductions
were a consequence of habitat change and decline of prey availability. Captive breeding has not been effective despite numerous attempts. In the past, Russian Desmans have been trapped for fur. During the 19" and early 20" centuries, up to 50,000-100,000 skins were harvested each year. Protection has been enforced in 1920, but trapping was reestablished in the 1930s until it was banned for good in 1956. During the final decade of trapping, an average yearly harvest in the former Soviet Union was 15,500 skins. Scale of decline can be fully understood by comparing this numberto the 60,000 skins that were harvest in 1913 in just the area of Voronezh.
Bibliography. Bakka et al. (2018), Bobrov et al. (2008), Borodin (1963), Emelyanova & Nasyrova (1996), Kawada, Koyasu et al. (2002), Khakhin & Ivanov (1990), Kiris (1973), Kryzhanovsky (1996), Migulin (1938), Mishta & Merzlikin (2009), Ognev (1928), Pavlov et al. (1973), Popov (1960), Queiroz et al. (1996), Rozhdestvenskaya & Sidorovich (1996), Rutovskaya (1996), Rutovskaya et al. (2017), Skoptsov (1966), Zaitsev et al. (2014).
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