Shrews are mouselike animals, but they are not mice, and they do not have the chisel-like front teeth that characterize mice, beaver, and other rodents. Instead, they have sharp, spiky teeth, used for hunting prey instead of gnawing on plant material. Shrews are more closely related to moles than to any other Missouri mammals.
Shrews, like moles, are small mammals with an elongated head, often with a movable snout projecting well over the mouth; small to no external ears; very small eyes; teeth that are not well differentiated into incisors, canines, and premolars; 5 toes on each foot; and a primitive brain.
Members of the shrew family have the first or central incisors of both upper and lower jaws greatly enlarged and specialized into grasping pincers. The front and hind feet are about equal in size. Small external ears, or flaps, may be present. The eyes are tiny and probably provide very limited vision. The fur has a plushlike quality and will lie either forward or backward.
Six species of shrews occur in Missouri
Specialists use details of the skull and teeth to identify Missouri’s six species of shrews, but the following descriptions are useful for the rest of us:
1. The North American least shrew (Cryptotis parva), sometimes called simply the "least shrew" or the "bee shrew," is one of the smallest mammals in Missouri, measuring only about 3 inches from the tip of the nose to the tip of the tail. It has a long, pointed snout that extends considerably beyond the mouth and contains the nostrils at the end; tiny, black eyes; large ear openings hidden in the velvety fur; a distinct neck; moderately slender body; small front and hind limbs with 5 claw-bearing toes each; and an extremely short tail. The fur is soft and short and is not differentiated into underfur and overhair. The back is dark brown to brownish gray while the belly is gray. The upper surface of the tail is colored like the back and the undersurface like the belly.
The least shrew is distinguished from cinereus and southeastern shrews by the shorter tail and from short-tailed shrews by its smaller size, brown to brownish-gray color on the upperparts, and fewer number of teeth.
The least shrew has a large range in North America. They are generally abundant and probably occur statewide. Their preferred habitats include sites with open grass, brush, and dry, fallow fields, with marshy or timbered areas to a lesser extent.
2–4. Short-tailed shrews (genus Blarina) have an exceedingly pugnacious and energetic nature. For a long time, they were considered a single, widespread species (called the short-tailed shrew, B. brevicauda). Now, four species are recognized, with three occurring in Missouri. Specialists use cranial measurements and DNA sequencing to ID the different species.
- Northern short-tailed shrew (Blarina brevicauda)
- Southern short-tailed shrew (Blarina carolinensis)
- Elliot’s short-tailed shrew (Blarina hylophaga)
Because the three species look so similar, we treat them together here. All have a pointed head; distinct neck; cylindrical body; short, slender legs with 5 clawed toes on each foot; and a short, furred tail. The flexible, sensitive snout, which contains the nostrils, projects slightly over and beyond the mouth. The tiny black eyes are capable of light perception, but overall their vision is poor. The external ear opening is large but concealed in the fur. The senses of touch and hearing are well developed; that of smell is poorly developed. The velvety fur is short and brushes equally well in any direction. A microscopic examination shows whiplike tips on the hairs, similar to the hairs of moles but unlike those of any other mammal.
While short-tailed shrews are generally gray in color, they are darker on the back and lighter on the underparts, feet, undersurface of the tail, and around the mouth.
Short-tailed shrews are distinguished from the cinereus and southeastern shrews by their grayer color and shorter tails, and from the least shrew by their larger size and dark gray color on the upperparts. Specialists will note that short-tailed shrews have 32 teeth while least shrews have only 30 (sometimes 28) teeth.
Short-tailed shrews occur statewide, but each species’ range is imperfectly known. Their populations can fluctuate violently from year to year. They live in dark, damp, or wet localities in flooded areas or fields covered with heavy, weedy growth. They occur less often in grassy cover.
5. The cinereus shrew (or masked shrew) (Sorex cinereus) is distinguished from short-tailed and least shrews by a longer tail (the tail is more than one-half the length of head and body) and from the southeastern shrew by the grayish brown color on the upperparts and slightly longer tail with an obvious constriction at the base.
Usually scarce throughout its North American range, in some places and times it can be very abundant. In Missouri, it occurs in low, damp areas along streams and in floodplains (usually not in grasslands) in the northern half of the state. Our Missouri population seems to represent a southward range expansion from Iowa that occurred since the 1970s.
6. The southeastern shrew (Sorex longirostris) is distinguished from short-tailed and least shrews by a longer tail (the tail is more than one-half the length of head and body) and from the cinereus shrew by the reddish-brown color on the upperparts and a slightly shorter tail without an obvious constriction at the base.
Uncommon across Missouri, the southeastern shrew probably occurs in all but the northwest corner of the state. In most of its North American range, it is associated with marshy or swampy areas, or wooded places with dense ground cover. In Missouri, it is known mostly from dry upland sites with some woods.