Shrew

The shrew (Sorex) is a small insectivorous animal from the shrew family. They live on all continents in the northern hemisphere, mainly in forests and tundra. This genus includes winners in the categories “smallest” and “most voracious” among mammals. Challenging Bergman's law and demonstrating the Danel effect. In total, there are about 70 species in the genus, of which in Russia – 15 — 17 kinds.

View origin and description

Photo: Shrew

Photo: Shrew

The genus name comes from a Latin word meaning “whisper, twitter, buzz”. These are the sounds that animals make during collisions with each other. The Russian name of the genus is given for the reddish-brown color of the tops of the teeth.

The species are distinguished by the structure of the teeth, which is quite difficult for a non-specialist. The taxonomy is poorly developed, today there are different classifications, according to one of them there are three subgroups.

Video: Shrew

But according to another — four:

  • species of unclear origin, including the tiny shrew (Sorex minutissimus) – indeed, the smallest mammal in Russia and the second in the world, smaller than only the pygmy shrew (multitooth) from the same shrews;
  • subgenus Sorex, to which the common shrew belongs, it is also a shrew (Sorex araneus) – the most common and typical representative of the genus and the most numerous mammal of northern Europe;
  • subgenus Ognevia with the only, but the largest representative — giant shrew (Sorex mirabilis);
  • subgenus Otisorex includes mainly North American species and the smallest native mammal — the American pygmy shrew (Sorex hoyi).

The fossils date back to the Upper Eocene, the time when modern orders of mammals appeared.

Appearance and Features

Photo: What a shrew looks like

Photo: What a shrew looks like

The animals at first glance look like mice, but they belong to a completely different order – insectivores. The structure of the body upon closer examination differs markedly from that of the mouse. First of all, a relatively large head with a muzzle extended into a flexible proboscis is striking. The animal constantly moves it, sniffing and looking for prey. The ears are tiny, practically do not protrude from the fur. The eyes are microscopic, completely inexpressive.

If we consider them a mirror of the soul, then the shrew has almost no soul – all the thoughts of the animal are only about daily bread. But such small animals cannot do otherwise, they lose too much heat compared to large ones, they constantly need energy replenishment of the metabolic processes that go on at a frantic speed. “The less weight — the more food” — This is a general rule for all warm-blooded animals. The babies have 32 teeth, like a person, but the incisors, especially the lower ones, are very long. Milk teeth are replaced by permanent ones still in the embryo, so that the animal is born already fully equipped with all teeth.

Body length (without tail) in different species can be from 4 cm in a tiny shrew, up to 10 cm in a giant one; weight ranges from 1.2 — 4 g to 14 g respectively. The average size, for example, of an ordinary shrew is 6–9 cm plus a tail of 3–5.5 cm. The color of the fur on the upper side is reddish, brownish or grayish and well masks the animal on the soil, on the underside the body is light gray.

The tail can be either very short or almost equal to the body, covered with sparse hairs. On the sides and at the base of the tail, there are usually glands that secrete a sharp-smelling musky secret that protects the shrew from predators. Females have 6 to 10 nipples. In males, the testes are located inside the body, and the copulatory organ can reach 2/3 of the body length.

Interesting fact: The skull of a shrew is like an elongated triangle – it has a greatly expanded brain section and is narrowed towards the nose, so that the jaws look like tweezers. By winter, the skull decreases, reducing the volume of the brain region, and increases in summer (the so-called “Denel effect”). The brain makes up 10% of the weight of the entire animal and this ratio is greater than that of a human or even a dolphin. Apparently, the constant need to solve food problems contributes to the development of the brain.

Where does the shrew live?

Photo: Shrew in Russia

Photo: Shrew in Russia

The range of the genus covers mainly subarctic and temperate zones of all continents of the northern hemisphere. In more southern regions, such as Central America or Central Asia, shrews are found in the highlands.

A typical — The common shrew is the most versatile and adapted to life in a variety of natural zones from the northern tundra to the flat steppes, where it chooses river floodplains and tall grass meadows for settlement. Animals do not like open places, they cannot stand direct sunlight – their favorite habitats are always shady and damp. In winter, they live under a layer of snow, practically without leaving the surface.

In central Russia, common shrews are found everywhere in forests and parks, especially cluttered ones, with dense undergrowth and a thick layer of forest litter. They live along the banks of stagnant reservoirs in thickets of coastal vegetation, near swamps. But they are not uncommon in cultivated summer cottages, which is confirmed by cats that bring them as prey. They are especially attracted to human habitation in anticipation of winter, when they can even climb into houses.

An interesting fact: The smallest species live in the tundra and highlands, endure the fierce frosts of central Siberia, although, it would seem, they should strive for warmer places. Moreover, studies of the American ash shrew (Sorex cinereus) have shown that the size of the body of the animals is the smaller, the further north they live. This contradicts the well-known Bergman's rule, according to which the size of individuals in cold areas of the range should increase.

Now you know where the shrew is found. Let's see what this animal eats.

What does the shrew eat?

Photo: Shrew from the Red Book

Photo: Shrew from the Red Book

When searching for food, shrews are guided by a keen sense of smell and keen hearing, some species use echolocation. Animal food, as the most high-calorie, is the basis of the diet. The shrew eats anything it can catch and gnaw on with its exceptionally sharp teeth — needles.

These can be:

  • any insects at all stages of development, beetles, dipterans and lepidoptera, more larvae are eaten;
  • spiders;
  • earthworms;
  • mollusks, including slugs, to which shrews owe worms;
  • other invertebrates; for example, nods eaten by the giant shrew;
  • babies of mouse-like rodents;
  • small amphibians;
  • carrion, such as a bird or a mouse;
  • in extreme cases, cannibalizes, eating even their own children;
  • consumes plant foods in winter, in particular coniferous seeds, which can be up to half of the diet;
  • it also eats mushrooms and droppings.

In search of food, it makes narrow branched passages in the snow. The amount of food eaten per day is 2-4 times more than the weight of the animal itself.

Character and Lifestyle Features

Photo: Common shrew

Photo: Common shrew

The most studied is our closest neighbor in the natural world — common shrew. Using her example, consider how these animals live and what they are doing. The shrew is agile and mobile. Despite her weak paws, she cheerfully makes her way through the grass and loose forest litter, snoops under fallen bark and brushwood, can climb on the butts of trees, swim and jump. She does not dig holes, but uses other people's underground passages, not being interested in the opinion of the owner. The greedy baby is driven by the demand of the stomach and death from starvation is more real for her than from the teeth of a predator. Without food, she dies after 7 – 9 hours, and smaller species – after 5.

More than half of the time, 66.5%, the animal spends in motion and continuous search for food. After eating, he sleeps, and after sleeping, he goes in search of food, and such cycles during the day can be from 9 to 15, the slightest delay in this cycle will cost him his life. During the search, it travels up to 2.5 km per day. When food is depleted, it moves to other places.

In autumn, and especially in winter, the shrew reduces activity, but does not hibernate. The baby simply cannot accumulate enough reserves for wintering and is forced to spin even in cold weather. It's amazing that she even survives until spring. Shedding occurs in April — May and September — October, like all inhabitants of places with a seasonal climate. In winter, the skin becomes lighter. Sounds can be defined as squeaks, chirps, or subtle chirps. They are issued mainly at the meeting and the fight that follows it.

An interesting fact: the tiny shrew eats 120 times every 10 to 50 minutes during the day. However, it lives in a colder zone of Eurasia than the common shrew.

Social structure and reproduction

Photo: Baby shrew

Photo: Baby shrew

Shrews do not live together and when they meet, they show aggressiveness, attacking each other with a cry and emitting their signature smell. Male and female unite only for a short moment for mating, which in the common shrew can occur 3 or 4 times from April to October.

After the meeting, the female finds an old stump, tussock, trunk, empty hole or a pile of brushwood and makes a nest from hay, moss or leaves. The nest is round with a cavity 8-10 cm in diameter. After about three weeks, the female gives birth to (3) 6 – 8 (11) babies. The weight of the cub is about 0.5 g, the length is less than 2 cm, it does not see, it is devoid of hair and even a proboscis. But after 22 – 25 days, the new generation is quite ready for independent life, and the female is ready for new reproduction.

The young become sexually mature the next year, although the first spring litter is able to breed in three or four months. The rush is justified – superactive little animals live no more than 2 years. Which is common to all members of the genus.

An interesting fact: If the nest is in danger, the mother and young cubs of some species (common shrew, ashy shrew) form the so-called “caravans” & # 8212; the first child grabs the mother by the base of the tail, the rest cling to each other in the same way. So they move in search of a safe shelter. There is another opinion that they study the surroundings, conduct “excursions in nature”, so to speak.

Natural enemies of shrews

Photo: Common Shrew

Photo: Common Shrew

Everyone has enemies, even in such angry and foul-smelling babies. Some simply kill them, while others may eat them if they do not have a good sense of smell.

These are:

  • mammalian predators, including domestic cats, who usually leave their victims without eating;
  • owls that eat them despite the smell;
  • hawks and other diurnal predators;
  • storks;
  • vipers and other snakes;
  • predatory fish grab swimming animals;
  • the shrews themselves are dangerous to each other;
  • parasites (helminths, fleas, etc.) do a lot of harm to health.

Shrews usually peacefully coexist with people, although of course they can fall under the distribution during terrorist attacks against mice and rats. Nevertheless, people cause the greatest harm indirectly – by changing the habitat by deforestation and urban development, using pesticides.

Interesting fact: When studying one of the populations of the common shrew, 15 species of helminths were found in crumbs belonging to round and flatworms. One individual contained 497 different worms. Here is a typical example of harmony in nature!

Population and species status

Photo: What a shrew looks like

Photo: What a shrew looks like

The population sizes of different species vary greatly. The most numerous and common species of Eurasia – the common shrew can have a population of 200 & # 8212; 600 copies per hectare. The more food and hidden places for shelter, the greater the population density. Similar Eurasian ranges are found in the lesser shrew, tiny shrew, even-toothed shrew, and many others. Large and densely populated areas covering the tundra and forest zones are characteristic of many American species.

Some species are more local, such as the Caucasian shrew inhabiting the forests of the Caucasus and Transcaucasia, or the Kamchatka shrew from Kamchatka and the coast of the Sea of ​​u200bu200bOkhotsk. But very rare, few and found in a small area, not so frequent. Different countries have their own rarities.

The regional Red Data Books of Russia include:

  • the tiny shrew (S. minutissimus) is protected in the Moscow, Ryazan, Tver, Kaluga regions;
  • the clawed shrew (S. unguiculatus) and the slender-nosed shrew (Sorex gracillimus) were included in the Red Data Book of the Amur Region;
  • Rade's shrew (S. raddei) in the Red Book of a number of North Caucasian republics;
  • the lesser shrew (S. minutus) is a Crimean rarity. Just in case, it is also included in the Red Book of Moscow as an indicator of forests that have been preserved in an undisturbed state. Although, in general, nothing threatens the species;
  • the even-toothed shrew (S. isodon) is protected in the Moscow region and Karelia. The range covers the forest zone of Eurasia from Scandinavia to the Pacific Ocean.

Protection of shrews

Photo: Shrew from the Red Book

Photo: Shrew from the Red Book

В The Red Book of Russia has only one species: the giant shrew. Indeed, the largest representative of the genus. Category 3 – a rare species with low abundance and a limited range. It is classified as low risk by the IUCN. An inhabitant of broad-leaved and mixed forests of Southern Primorye, found in only three places: in the Lazovsky and Kedrovaya Pad reserves, as well as near Lake. Hanka.

The IUCN International Red Data Book lists:

  • The great-toothed shrew (S. macrodon) is a vulnerable species with a declining range. Several localities are known in the mountains of Mexico in forests at altitudes from 1200 to 2600 m. Occurs on an area of ​​6400 km², the proposed range is 33627 km²;
  • Carmen shrew (S. milleri) — vulnerable look. It occurs in the mountain forests of Mexico at altitudes of 2400 – 3700 m. The estimated range is 11703 km²;
  • pribilofensis shrew (S. pribilofensis) — an endangered species that occurs in coastal meadows only on one of the Pribylov Islands (USA) in the Bering Sea. The area of ​​the island is 90 km². The number of the species is 10,000 – 19,000 pieces;
  • Sclater's shrew (S. sclateri) — species on the brink of extinction. 2-3 localities are known in Mexico. Lives in forests, the area of ​​u200bu200bwhich is declining. Nothing is known about abundance;
  • San Cristobal shrew (S. stizodon) — species on the brink of extinction. Lives in damp mountain forests. One locality is known in Mexico, fortunately in a protected area.

The conservation measures are not original: the preservation of undisturbed territories where the animals could live in numbers sufficient for reproduction. Nature does not tolerate emptiness. Any ecological niche must be occupied, and even such ephemeral creatures that exist on the verge of warm-blooded capabilities find a place for themselves. Let not under the sun, but in the shade of other organisms – the main thing is that the shrew can survive.

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