Etruscan shrew

Genomics

A chromosome-level genome assembly of Suncus etruscus was published in 2024. The primary genome assembly is approximately 2.5 Gb, organized into 22 chromosomes. It has a BUSCO completeness of 94.9% and contains 19,819 predicted protein-coding genes.

Activity

Etruscan shrews live alone except during mating periods. Their lifespan is estimated at typically around two years, but with a large uncertainty. They protect their territories by making chirping noises and signs of aggressiveness. 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. Clicking sounds are heard when these shrews are moving, which cease when they rest. 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. They reach their maximum level of activity at dawn.

Due to its small size and consequent high surface-area-to-volume ratio, the Etruscan shrew is at a constant risk of hypothermia, and would quickly die of hypothermia if not for its extremely rapid metabolism. Its skeletal muscles contract at a rate of about 13 contractions/sec during respiration alone. In cold seasons and during shortages of food, the shrews lower their body temperatures down to about 12 °C (54 °F) and enter a state of temporary hibernation to reduce energy consumption. Recovery from this state is accompanied by shivering at a frequency of 58 muscle contractions/sec. This induces heating at a rate of up to 0.83 °C/min, which is among the highest values recorded in mammals; the heart rate increases with time from 100 to 800–1200 beats/min, and the respiratory rate rises linearly from 50 to 600–800 breaths/min.

Etruscan shrews mate primarily from March to October, though they can be pregnant at any time of the year. Pairs usually form in the spring and may tolerate each other and their young for some time at the nest. The gestation period is 27–28 days, and they have 2–6 cubs per litter. Cubs are born naked and blind, weighing only 0.2 g (0.0071 oz). After their eyes open at 14 to 16 days old, they mature quickly. The mother usually moves the young when they are 9 to 10 days old, and if disturbed, she relocates them by leading them with her tail in a train-like formation, a behaviour known as caravanning, with each cub biting the tail of the one in front. The young Etruscan shrews are weaned at 20 days old. By three to four weeks of age, the young are independent and are soon sexually mature.

Distribution

The Etruscan shrew inhabits a belt extending between 10° and 40°N latitude across Eurasia. In Southern Europe, it has been found in Albania, Bosnia and Herzegovina, Bulgaria, Croatia, Cyprus, France, North 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 Mallorca and the Canary Islands.

The shrew also occurs in North Africa (Algeria, Egypt, Libya, Morocco, Tunisia) and around the Arabian Peninsula (Bahrain, Israel, Jordan, Lebanon, Oman, Syria, and Yemen including Socotra). In Asia, it was observed in Afghanistan, Azerbaijan, Bhutan, China (Gengma County only), Myanmar, Georgia, 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.

Overall the species is widespread and not threatened, but its density is generally lower than of the other shrews living in the area. In some regions it is rare, especially in Azerbaijan, Georgia, Jordan and Kazakhstan (included into the Red Book).

Habitat

The Etruscan shrew favors warm and damp habitats covered with shrubs, which it uses to hide from predators. Areas where open terrain such as grasslands and scrub meet deciduous forests are usually inhabited. It can be found at sea level but is usually confined to the foothills and lower belts of mountain ranges, though has been found up to 3,000 m (9,800 ft) 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 and edges of fields). The shrew, however, avoids intensively cultivated areas, as well as dense forests and sand dunes. It is poorly adapted to digging burrows, so it arranges its nests in various natural shelters, crevices and others' uninhabited burrows. They frequent rocks, boulders, stone walls and ruins, darting quickly in and out between them.

Hunting and feeding

Because of its high ratio of surface area to body volume, the Etruscan shrew has an extremely fast metabolism and must eat 1.5–2.0 times its body weight in food per day. It feeds mostly on various invertebrates, including insects, larvae and earthworms, as well as the young of amphibians, lizards and rodents, and can hunt prey of nearly the same body size as itself. It prefers species with a soft, thin exoskeleton, so it avoids ants when given a choice. Grasshoppers, where common, are often regular prey. It kills large prey by a bite to the head and eats it immediately, but takes small insects back to its nest. If it eats nothing for only four hours, it starves to death. When hunting, it relies mostly on its sense of touch rather than vision, and may even run into its food at night.

Predators and threats

The largest threat to Etruscan shrews originates from human activities, particularly destruction of their nesting grounds and habitats as a result of farming. Etruscan shrews are also sensitive to weather changes, such as cold winters and dry periods. Major predators are birds of prey.