| Etruscan shrew[1] | |
|---|---|
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Soricomorpha |
| Family: | Soricidae |
| Genus: | Suncus |
| Species: | S. etruscus |
| Binomial name | |
| Suncus etruscus (Savi, 1822) |
|
| Etruscan Shrew range (blue — native, black — probably extant origin uncertain) |
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The Etruscan shrew (Suncus etruscus), also known as the Etruscan pygmy shrew or the white-toothed pygmy shrew is the smallest known mammal by mass, weighing only about 1.8 grams on average[3][4][5][6][7] (the Bumblebee Bat is regarded as the smallest mammal by skull size).[3][8]
The Etruscan shrew has a body length of about 4 cm excluding the tail. It is characterized by very rapid movements and a fast metabolism, eating about 1.5–2 times its own body weight per day. It feeds on various small vertebrates and invertebrates, mostly insects, and can hunt individuals of the same size as itself. These shrews prefer warm and damp climates and are widely distributed in the belt between 10° and 30°N latitude stretching from Europe and North Africa up to Malaysia. They are relatively rare and are endangered in some countries.
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The Etruscan shrew has a slender (not truncated) body with a length between 3 and 4.5 cm excluding the tail. The tail is longer than half of the body. The body mass varies between 1.3[8] and 2.4 grams[4] and is usually about 1.8 grams.[3] The head is relatively large, with a long mobile proboscis, and the hind limbs are relatively small.[9] The Etruscan shrew has a very fast heart beating rate, up to 1511 beats/min (25 beats/s) and a relatively large heart muscle mass, 1.2% of body weight.[3] The fur color on the back and sides is pale brown, but is light gray on the stomach. The shrew usually has 30 teeth, but the 4th upper intermediate tooth is very small (rudimentary), and is absent in some individuals.[6] Near the mouth growth a dense array of short whiskers, which the shrew actively uses in searching for prey, especially in the night.[7] There is no clear difference in body features between males and females.[9]
The Etruscan shrew live alone, except during mating periods. Their lifetime is estimated as 2 years, but with a large uncertainty.[10] They protect their territory by making chirping noises and signs of aggressiveness.[11] They tend to groom themselves constantly when not eating and are always moving when awake and not hiding. The hiding periods are short and typically last less than half an hour. A clicking sound is heard when these shrews are moving, which ceases when they rest.[9] The shrews are more active during the night when they make long trips; during the day, they stay near the nest or in a hiding place.[6] They reach their maximum level of activity at dawn.[2]
The movements of the Etruscan shrew are rapid, with a rate of about 780 min−1 (13 s−1). In cold seasons and during shortages of food, the shrews lower the body temperature down to about 12 °C and enter a state of temporary hibernation to reduce energy consumption. The recovery from this state is accompanied by shivering with the frequency of about 3500 min−1 (58 s−1).[3] This induces heating with the rate up to 0.83 °C/min, which is among the highest values recorded in mammals; the heart rate increased exponentially with time from 100 to 800–1200 beats/min, and the respiratory rate rises linearly from 50 to 600–800 beats/min.[4]
The Etruscan shrew apparently breed all year round with gestation period of about 28 days and bring 2–6 cubs per litter. Most pregnancies occur between October and December.[2] Cubs are born naked and blind, but quickly develop, becoming independent and sexually mature at 3–4 weeks of age.[5][9]
The Etruscan shrew inhabits a belt extending between 10° and 40°N latitude across Eurasia.[3] In Southern Europe, it has been found in Albania, Bosnia and Herzegovina, Bulgaria, Croatia, Cyprus, France, Macedonia, Malta, Montenegro, Greece, Italy, Portugal, Slovenia, Spain, and Turkey, with unconfirmed reports in Andorra, Gibraltar and Monaco; it has been introduced by humans to some European islands, such as Canary Islands.[2]
The shrew also occurs in Northern Africa (Algeria, Egypt, Libya, Morocco, Tunisia) and around Arabian Peninsula (Bahrain, Israel, Jordan, Lebanon, Oman, Syria, and Yemen including Socotra). In Asia, it was observed in Afghanistan, Azerbaijan, Borneo, Bhutan, China (Gengma County only), Burma, Georgia, Guinea, India, Iran, Iraq, Kazakhstan, Laos, Malaysia (Malaysian part of Borneo island), Nepal, Pakistan, Philippines, Sri Lanka, Tajikistan, Thailand, Turkey, Turkmenistan and Vietnam. There are unconfirmed reports of the Etruscan shrew in West and East Africa (Guinea, Nigeria, Ethiopia) and in Armenia, Brunei, Indonesia, Kuwait and Uzbekistan.[1][5]
The shrew is relatively rare, especially in Azerbaijan, Georgia (included into the Red Book), Jordan and Kazakhstan (Red Book).[5] Even where not endangered, its density is always lower than of the other shrews living in the area.[2]
The Etruscan shrew favors warm and damp habitats covered with shrubs, which it uses to hide from predators. It is usually confined to the foothills and lower belts of mountain ranges, though has been found up to 3,000 m above sea level. It colonizes riparian thickets along the banks of lakes and rivers, as well as human-cultivated areas (abandoned gardens, orchards, vineyards, olive groves edges of fields). The shrew however avoids intensively cultivated areas, as well as dense forests sand dunes.[2] It is poorly adapted to digging burrows and therefore arranges its nests in various natural shelters, crevices and others uninhabited burrows.[5][6]
Because of their high ratio of surface area to body volume, the Etruscan shrew have an extremely fast metabolism and have to eat 1.5–2 times their body weight in food per day. They feed up to 25 times per day, mostly on various invertebrates (insects, their larvae, earthworms, etc.) as well as small vertebrates (young frogs, lizards and rodents), and can hunt prey of nearly the same body size as themselves. They prefer species with a soft and thin exoskeleton and for this reason avoid ants when given a choice. They kill large prey by a bite to the head and eat them immediately, whereas they take small insects back to their nest.[5][6][7] When hunting, the Etruscan shrew mostly rely on their sense of touch rather than vision and may even run into their food at night.[9] The Etruscan shrew might play important role in controlling the insect population.
The largest threat to the Etruscan shrew originates from human activities, particularly destruction of their nesting grounds and habitat as a result of farming. The Etruscan shrew is also sensitive to climate changes such as cold winters and dry periods.[5] Major predators are birds of prey, especially owls.[6][9]