Vertebrate Zoology - V. M. Konstantinov 2011

Chordates
Terrestrial, or Four-Legged, Vertebrates — Vertebrates with Embryonic Membranes
Class Mammalia, or Mammals — Subclass Theria — Infraclass Placentalia, or Eutheria — Order Insectivora

Insectivores are the most ancient and primitive order of placental mammals, known as far back as the Late Cretaceous. The cerebral hemispheres are small and unconvulsed. The braincase is relatively small, and the Teeth are weakly differentiated. The canines are small and conical. In most species, the anterior part of the snout is elongated into a mobile proboscis. Many species possess scent glands. Insectivores are small- to medium-sized animals (Fig. 190). The body length of the least shrew (Sorex minutissimus) and the Etruscan shrew (Suncus etruscus) is about 4 cm, making them the smallest mammals in the world. Insectivores are distributed worldwide, except for Australia and most of South America. The order includes terrestrial, subterranean, aquatic, and arboreal species. The fauna of Russia comprises species from four families: Moles, Desmans, Hedgehogs, and Shrews.

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Fig. 190. Insectivores:

1 — African elephant shrew; 2 — shrew; 3 — tenrec; 4 — mole; 5 — Russian desman

The family Soricidae (shrews) comprises small mammals that externally resemble mice. They inhabit a variety of environments, but most frequently forests with thick leaf litter. As a rule, they do not dig their own burrows, instead utilizing natural cavities in the soil, forest litter, under tree roots, or abandoned rodent burrows. They feed on insects, worms, and occasionally small mouse-like rodents and conifer seeds. They are beneficial due to their destruction of harmful insects and their larvae. Common species in Russia include the common shrew (Sorex araneus) and the Eurasian Water shrew (Neomys fodiens). One of the largest insectivores, the giant musk shrew (Praesorex goliath), lives in the tropical forests of West Africa, reaching a body length of 15–18 cm and a tail length of 11 cm.

The family Talpidae (moles) includes the most specialized species of the order. Moles, including the European mole (Talpa europaea), are typical inhabitants of the upper soil horizons. Virtually their entire lives are spent underground; moles come to the surface very rarely, such as when their burrows are flooded with water. The mole is remarkably adapted to subterranean life. Its body is elongated, its HEAD is conical, and its neck is externally indistinct. The fur is short and velvety, an adaptation for moving through narrow tunnels. The short forelimbs are armed with powerful claws, which the mole uses to dig through the earth, pushing the excavated soil upward with the top of its head. The eyes are vestigial and, in some subspecies, concealed beneath the Skin. The Senses of Touch and smell are well developed. Moles have excellent Hearing, despite having vestigial pinnae.

Moles excavate complex systems of underground tunnels, most of which do not serve as living quarters, but are instead dug while foraging for food (Fig. 191).

When constructing deep tunnels, moles push the soil to the surface through vertical shafts, forming characteristic mounds of earth known as molehills. However, the majority of mole tunnels are typically shallow. In such cases, the animal barely digs the earth, instead pushing it aside and upward, leaving no molehills behind.

Fig. 191. Layout of a mole's foraging tunnels in a forest clearing. Numbers indicate the depth of the tunnels in cm.

The most favorable habitats for the mole are deciduous forests with humus-rich soils. Moles avoid sandy and waterlogged soils. They feed on earthworms and insect larvae. They reproduce once, rarely twice a year, in the middle latitudes during May and June. Litter size ranges from 2 to 8 young. Gestation lasts approximately 40 days. Moles undergo a complex molt three times a year. The molting process is clearly visible on the flesh side of the pelt as dark patches in areas where Hair replacement is taking place. These patches are caused by pigment accumulation at the base of growing hairs.

Moles are distributed throughout the forest and forest-steppe zones of Europe, the Caucasus, and the Siberian taiga eastward to the Lena River. THE ECOLOGICAL AND economic significance of moles is substantial. They destroy agricultural and forestry insect pests. Any Damage caused by the destruction of earthworms and the creation of soil heaps in meadows and gardens is local in nature and far outweighed by the benefits they provide. Moles are also trapped for the fur trade.

The family Desmanidae comprises two species. One of them, the Pyrenean desman (Galemys pyrenaicus), is native to the Iberian Peninsula and is small in size, measuring 12–15 cm with a tail of equal length. The other species, the Russian desman (Desmana moschata), is a typical semi-aquatic mammal inhabiting standing or slow-flowing water bodies within the Don, Volga, and Ural river basins. Its body length is 18–20 cm, with a tail of the same length, and its body weight reaches up to 520 g. It leads a highly secretive lifestyle, foraging for food underwater. It feeds on Mollusks, insects and their larvae, certain plants, and occasionally fish. Females reproduce once a year, constructing nests in burrows with underwater entrances (Fig. 192). The breeding season is extended from May to November, with litter sizes ranging from one to five young.

The desman is a valuable fur-bearing animal with exceptionally fine fur. The musk glands located at the Base of the tail are also utilized. Due to overhunting, the desman population was severely depleted. Conservation efforts involving reintroduction into historical habitats and artificial translocation to new areas have helped increase its numbers. Hunting the desman is strictly prohibited. Because their population levels remain low, desmans are listed in the Red Data Books of Russia and the IUCN Red List.

Fig. 192. Desman burrows on high and low banks. A and C — horizontal projections; B and D — vertical projections

The family Erinaceidae (hedgehogs) comprises distinctive animals covered in spines that can roll into a tight ball when threatened. In Russia, they are distributed across forest, steppe, and desert zones. Unlike other insectivores, they hibernate during the winter. They feed on insects, mollusks, reptiles, and occasionally bird eggs and nestlings. These animals are highly beneficial.

Elephant shrews (Macroscelidae) are widespread in Africa. Like many other small desert mammals, they have elongated hind legs and shortened forelimbs, bearing a strong external resemblance to desert rodents such as jerboas. Golden moles (Chrysochloridae), which superficially resemble European moles, inhabit the deserts of South Africa. Two additional families feature relict distribution ranges: Solenodontidae (solenodons), found in Cuba and Hispaniola, and Tenrecidae (tenrecs), distributed across Central Africa, Madagascar, and the Canary Islands.