| Common shrew[1] | |
|---|---|
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Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Eulipotyphla |
| Family: | Soricidae |
| Genus: | Sorex |
| Species: | S. araneus |
| Binomial name | |
| Sorex araneus | |
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| Common shrew range | |
| Synonyms | |
Sorex europaeus | |
Thecommon shrew (Sorex araneus), also known as theEurasian shrew, is the most commonshrew, and one of the most commonmammals, throughoutNorthern Europe, includingGreat Britain, but excludingIreland.[3] It is 55 to 82 millimetres (2.2 to 3.2 in) long and weighs 5 to 12 grams (0.2 to 0.4 oz), and has velvety dark brown fur with a pale underside. It is one of the rarevenomous mammals.[4] Juvenile shrews have lighter fur until their firstmoult. The common shrew has smalleyes, a pointed, mobile snout and red-tipped teeth. It has a life span of approximately 14 months.
Shrews are active day and night, taking short periods of rest between relatively long bursts of activity.[5]
Common shrews are found throughout thewoodlands,grasslands, and hedgelands of Britain,Scandinavia, andEastern Europe. Each shrew establishes a home range of 370 to 630 m2 (440 to 750 yd²). Males often extend the boundaries during the breeding season to find females. Shrews are extremelyterritorial and will aggressively defend their home ranges from other shrews. They make their nests underground or under dense vegetation.[6]
The common shrew'scarnivorous andinsectivorous diet consists ofinsects,slugs,spiders,worms,amphibians and smallrodents. Shrews need to consume 200% to 300% of their body weight in food each day in order to survive; to achieve this they must eat every 2 to 3 hours, and they will starve if they go without food much longer than that. They do not hibernate because their bodies are too small to store sufficient fat reserves and they have a short fasting duration.[5][7]
Common shrews have evolved adaptations to survive through the winter. Their skulls shrink by nearly 20% and their brains get smaller by as much as 30%. Their other organs also lose mass and their spines get shorter. As a result, total body mass drops by about 18%. When spring returns, they grow until they reach roughly their original size. Scientists believe that low temperatures trigger their bodies to break down bones and tissues and absorb them. As temperatures start to rise with the onset of spring, their bodies start to rebuild the lost bones and tissues. This ability to shrink their bodies significantly reduces their food requirements and increases their chances of survival in the winter.[8][9] Common shrews exhibit three distinct seasonal phenotypes; however, these phenotypes have the same relative oxygen consumption despite varying temperatures.[10]
Shrews have pooreyesight and instead use their excellent senses ofsmell andhearing to find food.
The common shrew breeding season lasts from April to September, but peaks during the summer months. After a gestation period of 24 to 25 days, a female gives birth to a litter of five to seven babies. A female rears two to four litters each year. The young are weaned and independent within 22 to 25 days.[11]
Young shrews often form a caravan behind their mother, each carrying the tail of its sibling in front with its mouth.
The chromosome number (karyotype) ofSorex araneus varies widely, with a number of distinct "chromosomal races" being present over the species' range.[2] One such race was described in 2002 as a new species,S. antinorii.[2] This is an example of chromosomalpolymorphism (chromosomal variability as a result of chromosome fusions or disassociations).[12][13]
These karyotypes have been known to naturally hybridize, such as in the Petchora race and the Naryan-Mar variant in Northeastern Russia.[14]
A study by Nanjing Normal University in 2019 found thatSorex araneus is capable of echolocation via high-frequency tittering and close-range spatial orientation. Comparison of genes involved in hearing betweenbats,bottlenose dolphins andSorex araneus suggests that this is a result of convergent evolution.[15]
The common shrew is not anendangered species, but inGreat Britain it, like other shrews, is protected from certain methods of killing by theWildlife and Countryside Act of 1981.[16]
In Britain, shrews can be found at densities of up to one per 200 m2 (240 yd²) in woodlands. The main predators of shrews areowls,cats,weasels,snakes,stoats, andred foxes.[6]
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