Pygmy Shrew, Lesser Shrew

Observations: Not much is known about the longevity of these animals, but they are likely short-lived. One captive specimen lived 1.3 years (Richard Weigl 2005). They have been estimated to live up to 2 years in the wild (Bernhard Grzimek 1990). Maximum longevity is considered unknown.

Sorex minutus is abundant throughout its range and is listed as a species of "least concern" on the IUCN Red List of Threatened Species.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

The scent glands of Sorex minutus may serve as a deterrent to some predators. The major predators of S. minutus are tawny owls (Strix aluco), barn owls (Tyco alba), raptors, stoats and weasels (Mustelidae), foxes (Canidae), and domestic cats (Felis catus).

Known Predators:

• Barn owl (Tyco alba)
• Stoats (Mustelidae)
• Weasel (Mustelidae)
• Fox (Canidae)
• Domestic cat (Felis catus)

The coat of Sorex minutus is sleek, short, and dense with dorsal coloration ranging from grey-brown to brown and ventral coloration that is grayish-white. Occasionally, individuals have white tipped tails, and although rare, albinism occurs as well. It moults both in autumn (August to November, from tail to snout) and in spring (March to June, from snout to tail).

As with other Sorex species, the teeth of Sorex minutus are red, which is due to the deposition of iron that helps protect the teeth against wear. It has an extremely high metabolic rate (9.62 cm^3 oxygen/hour), which is typical of Sorex species as well.

Sorex minutus is the smallest native British shrew. Adult body length ranges from 39 to 60 mm, tail length ranges from 32 to 46 mm, and adult weight ranges from 2.4 to 6.1 g (decreasing by 28% in the winter). It can easily be confused with the Eurasian shrew (Sorex araneus), but can be distinguished by its slightly paler coat color and a distinctly bi-colored tail that is longer and hairier than that of the Eurasian shrew. Sorex minutus has small eyes and short, rounded ears and complex lobes in the ear conch. The snout is narrow, long, and slender (i.e., pointed) with large whiskers at the end. It has short legs and plantigrade posture. Each foot has five digits, and the length of the hindfeet measures from 10 to 11 mm. Sexual dimorphism in S. minutus is minimal, with adult females having three pairs of visible teat spots and adult males having visible testicles. Both males and females have scent glands located on the flanks.

Range mass: 2.4 to 6.1 g.

Average mass: 3.0 ± 0.13 g.

Range length: 71 to 106 mm.

Average basal metabolic rate: 9.62 cm3.O2/g/hr.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike

Sorex minutus is able to survive up to 16 months in captivity and anywhere from 1.5 to 2 years in the wild. Peak mortality occurs in the first 2 to 4 months of life, which is when the young are naïve to predators and are learning which insects are edible.

Typical lifespan
Status: wild: 1.5 to 2 years.

Typical lifespan
Status: captivity: 16 (high) months.

Sorex minutus is a terrestrial mammal, preferring to live in areas with dense vegetation, which serve as protective cover. Since such conditions are easily met in many plant community types, S. minutus can be found in forests (boreal, temperate, and montane), woodland edge, shrubland (boreal and temperate), heathland, grasslands (temperate), wetlands (bogs, marshes, swamps, fens, peatlands), coastal sand dunes, and rocky areas. Though not natural, due to the dense ground cover, S. minutus also thrives in pastureland and hedgerows. It can also be found across a wide range of elevations, from sea level to 2260 m.

Range elevation: 0 to 2,260 m.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: taiga ; desert or dune ; savanna or grassland ; chaparral ; forest ; mountains

Aquatic Biomes: coastal

Wetlands: marsh ; swamp ; bog

Other Habitat Features: agricultural

Sorex minutus, more commonly known as the Eurasian pygmy shrew, is a small mammal that is native to the Palearctic region. It is the most widespread Eurasian shrew, and is found in northern Iberia and the British Isles as well as continental Europe, European Russia and Siberia. Although commonly found throughout Eurasia, S. minutus is absent from many islands, including the Shetland Isles, the Channel Isles, the Isles of Scilly and some of the smaller islands in the Stockholm archipelago.

Rangemap of Sorex minutus

Biogeographic Regions: palearctic (Native )

Sorex minutus is an insectivorous mammal, eating both insects and other terrestrial arthropods (spiders, mites, scorpions, isopods, etc.). It is an opportunistic predator, using ultrasound as a primitive form of echolocation to help it locate food up to 12 cm deep in soil. It also hunts by probing into soil with its snout, smelling and feeling for potential prey. When a prey item is located, S. minutus attacks the head first to immobilize it and avoids the unpalatable parts (legs, large wings, etc.) while eating.

The diet of Sorex minutus depends on the availability of prey, which can be affected by seasonality, weather, and habitat. With the possible exception of some millipede species, it is a non-specific insectivore and readily consumes most arthropods. Its diet consists of prey that are less than 6 mm long, including beetles (Coleoptera), woodlice, adult flies, insect larvae (e.g., winter moth, Operophtera brumata), and spiders (Nemastomatoidea spp. and Linyphiidae spp.). It has also been known to eat small slugs and snails, and small amounts of plant material, none of which are preferred food items.

Studies show direct resource competition between Sorex minutus and Sorex araneus (Eurasian shrew) where they occur sympatrically. However, to decrease the degree of competition, both participate in resource partitioning. Sorex minutus is a non-burrowing mammal and has more difficulty obtaining insect larvae. Sorex araneus is a burrowing mammal and therefore, has a much easier time accessing insect larvae and earthworms. In addition, both species forage on prey that is similar in size to themselves, with S. araneus feeding on larger prey than S. minutus. However, S. minutus may cache larger prey items when there is an overabundance of food, as their metabolic requirements are too great to go without food for longer than a few hours

Animal Foods: insects; terrestrial non-insect arthropods; mollusks; terrestrial worms

Other Foods: detritus

Foraging Behavior: stores or caches food

Primary Diet: carnivore (Insectivore )

As an insectivore, Sorex minutus may help control insect populations, and East (1974) noted that predation on winter moth larvae (Operophtera brumata) had a significant impact on their abundance. Because they are prey for many species, S. minutus may help support small carnivore populations throughout Eurasia. Finally, Sorex species are extremely vulnerable to environmental changes. As a result, they are good biological indicators of environmental change (e.g., habitat destruction, heavy metal pollution, pesticide pollution, and climate change).

Sorex minutus is an insectivore and requires large numbers insects due to its high metabolism. Thus, S. minutus may help control local insect populations, some of which may be significant agricultural pests. This species is also a good indicator of environment change.

Positive Impacts: controls pest population

There are no known adverse effects of Sorex minutus on humans.

Eurasian shrews communicate via chemical cues as well as vocally. Territories are demarcated via scent markings. It has been suggested that S. minutus uses high-frequency echolocation to locate conspecifics or individuals that are trespassing in its territory.

Communication Channels: acoustic ; chemical

Other Communication Modes: scent marks

Perception Channels: visual ; tactile ; acoustic ; ultrasound ; echolocation ; chemical

Little is known about mating in Sorex minutus. However, males expand their territories in search of females during breeding season.

Mating System: polygynous

Sorex minutus breeds from April to August (peaking in June) with a 19 to 25 day gestation period. Females either use abandoned nests made by other species or weave their own from dry grass. Females have two litters each season but can sometimes have as many as five. Lactation lasts for 22 to 30 days after birth and can sometimes cause anestrus (a period of sexual inactivity between breeding periods), causing a short break to occur between litters. Each litter consists of 4 to 12 altricial young, weighing 0.25 g on average, that are blind, naked, and toothless upon birth. Young often overwinter as immature pups and reach sexual maturity during their first spring; however, females born early in the year can mature prior to winter.

Breeding interval: Sorex minutus usually breeds twice per season, but have been recorded breeding up to five times per season.

Breeding season: Mating occurs from April to August.

Range number of offspring: 4 to 12.

Average number of offspring: 7.

Range gestation period: 19 to 25 days.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous

Little is known about parental investment in Sorex minutus; however, young are born essentially defenseless (blind, naked, and toothless). Lactation lasts for 22 to 30 days after birth and females are thought to provide most of the care.

Parental Investment: altricial ; female parental care ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female)

Pygmy shrews are active by day and night, interspersing bouts of activity with rest periods (5). They are typically solitary, and will defend their range against other pygmy shrews (2). They make surface tunnels through vegetation (2), and feed on invertebrates such as beetles, spiders and woodlice that can be found in the leaf-litter (5), but they very rarely tackle earthworms, possibly because they are too large for them to handle (4). Shrews are well known for their voracious appetites; due to their small size and high metabolic rate, they have to eat regularly, and consume about 125% of their own body weight in food each day in order to stay alive (4). They do not hibernate, as they are too small to store the fat reserves needed to sustain them, instead they have to remain active during winter (4). Births occur between April and August, peaking in June (5). Two litters are usually produced each year, each consisting of between 4 and 7 young (5). The young overwinter as immatures (2), reaching sexual maturity the following year, although some females born early in the year may even breed in the year of birth (5). Main predators of pygmy shrews are owls, raptors, mustelids, foxes and cats. The maximum life span is 16 months (5). Shrews belonging to the genus Sorex are known to produce ultrasound, which may be used in a primitive form of echolocation (6).

All shrews are protected under the Wildlife and Countryside Act, 1981 (3). This diminutive shrew will be likely to benefit from agri-environment schemes that encourage farmers to reduce the density of grazing livestock on their land, and to create conservation-friendly field boundaries (5).

As both the common and scientific names suggest (minutus means small), the pygmy shrew is tiny (2), in fact it is the smallest native British shrew (4). It has a pointed snout and greyish-brown fur that becomes paler on the underside (2). Compared to other species of British shrews, the pygmy shrew has a relatively longer, hairier tail (4). Like other shrews of the genus Sorex, this species has red-tipped teeth, formed by the deposition of iron, which toughens them against wear-and-tear (4).

Occurs in a very broad range of terrestrial habitats, wherever there is adequate ground cover (2).

This is a widespread and fairly abundant species throughout the British mainland; it also occurs on many offshore islands except Shetland, the Channel Isles and the Isles of Scilly (5). On continental Europe they are also widespread, although they are absent from some southern areas (5). It is the only shrew that occurs in Ireland (4).

Protected under Schedule 6 of the Wildlife and Countryside Act, 1981 (3).

The small size of the pygmy shrew makes it particularly susceptible to environmental unpredictability, such as adverse weather (5). Habitats loss, heavy grazing and the use of pesticides are also potential problems (5).

The pygmy shrew is the smallest mammal of Western Europe. Although it is found in many places on the mainland, it is only found on the Wadden Islands of Terschelling, Ameland, Borkum, Nordeney and Wangerooge. Pygmy shrews eat insects, spiders, insect larvae and sometimes carrion. They are constantly hungry and need to consume up to twice their own weight per day, due to their extremely high metabolism. Pygmy shrews are not eaten often by other animals, probably because they aren't very tasty.

The Eurasian pygmy shrew (Sorex minutus), often known simply as the pygmy shrew, is a widespread shrew of the northern Palearctic.