Perception Channels: tactile ; chemical
A darkly colored shrew with a white underside. Coloration on dorsal and ventral sides are sharply demarcated. A fringe of bristles runs along the ventral surface of the tail and on the paws which are thought to serve as a swimming aid. Teeth have red tips. Females have five pairs of mammae.
Other Physical Features: endothermic ; bilateral symmetry
Average mass: 15 g.
Average basal metabolic rate: 0.328 W.
Average lifespan
Status: wild: 3.0 years.
Average lifespan
Status: captivity: 1.6 years.
Found on the banks of both standing or flowing fresh water and adjacent areas.
Terrestrial Biomes: forest
Aquatic Biomes: lakes and ponds; rivers and streams
Neomys fodiens occurs throughout Eurasia, to western Siberia, northern Asia Minor, the Pacific coast of Siberia, and North Korea.
Biogeographic Regions: palearctic (Native )
These shrews forage almost exclusively underwater, efficiently preying on aquatic invertebrates such as snails, mollusks, freshwater insects, and also small vertebrates such as fish, amphibians and frogs. Prey are weakened by a poisonous secretion from the submaxillary gland. They generally forage by taking a dive that can last up to 20 seconds. After coming onto land, water shrews quickly run into their burrows and emerge a moment later almost dry, after coming through the tight squeeze of the tunnel where the water is absorbed by the soil. The process is then repeated a few meters away along the stream bank. Water shrews are also known to eat some terrestrial insects as well, such as dipteran larvae.
These shrews eat the larvae of insects which some humans find bothersome.
No negative impacts known.
Quite common within its geographical range.
IUCN Red List of Threatened Species: least concern
During dives, air remains trapped between the outer hairs of the thick coat of water shrews. This greatly increases the bouyancy of this shrew. In a laboratory experiment, a few tenths of a mg of the neurotoxic saliva killed a vole very quickly.
The breeding season in England occurs fom April to September, with multiple litters per season. Litter size can be between 3 and 12, more commonly 5 or 6. Gestation lasts approximately 20 days, and lactation twice that. Sexual maturity is reached between 6 and 8 months.
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual
Average birth mass: 0.78 g.
Average gestation period: 20 days.
Average number of offspring: 5.
Average age at sexual or reproductive maturity (male)
Sex: male: 106 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 106 days.
The Eurasian water shrew (Neomys fodiens), known in the United Kingdom as the water shrew, is a relatively large shrew, up to 10 cm (4 in) long, with a tail up to three-quarters as long again. It has short, dark fur, often with a few white tufts, a white belly, and a few stiff hairs around the feet and tail. It lives close to fresh water, hunting aquatic prey in the water and nearby. Its fur traps bubbles of air in the water which greatly aids its buoyancy, but requires it to anchor itself to remain underwater for more than the briefest of dives.
Like many shrews, the water shrew has venomous saliva, making it one of the few venomous mammals, although it is not able to puncture the skin of large animals, nor that of humans. Highly territorial, it lives a solitary life and is found throughout the northern part of Europe and Asia, from Britain to Korea.
The Eurasian water shrew grows to a length of about 10 cm (4 in) long with a tail length of 8 cm (3 in) and weight of 15 to 19 grams (0.53 to 0.67 oz). The dense short fur on the head, back and sides is greyish-black. The underparts are dirty white and are sharply demarcated from the dorsal surface. Sometimes they are tinged with rusty brown or occasionally are entirely dark grey. There is a white spot just behind the eye and often another near the small, rounded ear which is nearly hidden in the fur. The nose is black and the snout long and tapering.[4] The sharp, mostly white teeth are tipped with red, typical of the shrew subfamily Soricinae. The rusty colour comes from deposits of iron which serve to harden the enamel and which are concentrated in the tips of the teeth, particularly the molars which are the teeth most subject to wear.[5] The female has five pairs of nipples. The legs are short and the hind feet are powerful, with a fringe of short, stiff hairs on the outer edge, both of which features assist while it is driving its body through the water. The tail is slender and has a keel of short white hairs on the underside.[4] This shrew often utters shrill cries as it scurries about.[4]
Its karyotype has 2n = 52 and FN = 98.[1]
The Eurasian water shrew is found throughout Europe with the exception of Iceland, Ireland, certain Mediterranean islands and the Balkans.[4] In Asia, its range extends from western Siberia and Asia Minor to North Korea and the Pacific coast of Siberia.[6] It rarely strays far from water and is found in and around ditches, streams, ponds, watercress beds, fish ponds, damp meadows and rough bushy ground adjoining water.[4]
Outside the breeding season, both male and female Eurasian water shrews maintain a territory but during the breeding season, only the females do so. At this time the males wander about visiting various female territories which indicates a promiscuous mating system without pair bonding.[7] On the whole they are solitary animals that seem to mutually avoid each other and there is no social hierarchy.[6]
The breeding season extends from April to September and much of the courtship takes place in the water. It either uses pre-existing burrows or digs its own. The nesting chamber is lined with moss, dry grass and leaves. Litters of four to eight or more young are born after a twenty-four-day gestation period. The young are tiny and helpless at birth. Their eyes open at fifteen to eighteen days and they are fully weaned at about seven weeks. Females can produce two or three litters a year.[4] The juveniles disperse after weaning, setting up their own territories.[7] They are sexually mature at six to eight months and their life expectancy is about three years.[6]
The Eurasian water shrew is active both night and day and is thoroughly at home in the water. Its short fur holds air and the skin does not get wet when it swims. When it emerges from the water it enters one of its many burrows and any moisture adhering to the fur is absorbed by the earth walls. It mostly feeds on aquatic organisms which are caught while it is swimming. It can remain underwater for twenty seconds before it has to surface to breathe. Larger prey items can be subdued by the toxic secretions from its submaxillary glands. They feed on crayfish, water snails, small fish, aquatic larvae, insects, spiders, amphibians, especially newts and small rodents are also eaten. It also feeds on land on such things as insect larvae.[6]
The Eurasian water shrew has a pair of glands under its jaw which produce venom, and this has been shown to be potent against the field vole (Microtus agrestis), and lethal at a minimum dose of fifteen milligrams per kilogram body weight.[8] The venom consists of a paralytic peptide which has been patented for use in neuromuscular therapy.[9] Overall, the Eurasian water shrew venom has stronger paralytic properties and lower cardioinhibitory activity. Thus acting as an immobilizing agent towards their prey or to organisms that may threathen them.[10]
Their behavior in captivity is described in Konrad Lorenz's book King Solomon's Ring.
The International Union for Conservation of Nature lists the Eurasian water shrew as being of "Least concern" in its Red List of Threatened Species. This is because it has a large population distributed across a wide range and its population seems fairly stable. In some areas habitat degradation is occurring and wetlands are being drained but not to such an extent as to increase the status to "Vulnerable". Other possible threats include agricultural products and sewage which may pollute waterways and reduce the availability of food. In western Spain, a separate subspecies (N. f. niethammeri) has a very limited range and may be declining in numbers.[11]
{{cite journal}}: CS1 maint: multiple names: authors list (link) The Eurasian water shrew (Neomys fodiens), known in the United Kingdom as the water shrew, is a relatively large shrew, up to 10 cm (4 in) long, with a tail up to three-quarters as long again. It has short, dark fur, often with a few white tufts, a white belly, and a few stiff hairs around the feet and tail. It lives close to fresh water, hunting aquatic prey in the water and nearby. Its fur traps bubbles of air in the water which greatly aids its buoyancy, but requires it to anchor itself to remain underwater for more than the briefest of dives.
Like many shrews, the water shrew has venomous saliva, making it one of the few venomous mammals, although it is not able to puncture the skin of large animals, nor that of humans. Highly territorial, it lives a solitary life and is found throughout the northern part of Europe and Asia, from Britain to Korea.
