Mammals of Indiana: A Field Guide

Order SORICOMORPHA—Shrews and Moles

63 Order SORICOMORPHA—Shrews and Moles Family Soricidae Sorex cinereus / Masked Shrew Sorex fumeus / Smoky Shrew Sorex hoyi / Pygmy Shrew Sorex longirostris / Southeastern Shrew Blarina brevicauda / Northern Short-tailed Shrew Cryptotis parva / Least Shrew Family Talpidae Scalopus aquaticus / Eastern Mole Condylura cristata / Star-nosed Mole Order Soricomorpha The moles and shrews were previously classed as order Insectivora but are now in the order Soricomorpha. Only two families occur in North America: the shrews, Soricidae, and the moles, Talpidae. North Americansoricomorphshavefivetoesonfrontandrearfeet,smalleyes and ears, a long, tapering snout extending considerably beyond the jaw, and a wedge-shaped skull. The zygomatic arch is complete but reduced in size in moles and is lacking in shrews. Moles have white teeth, and North American shrews have chestnut-colored enamel on their teeth. There are six species of shrews and two species of moles in Indiana. Family Soricidae Shrews include about 312 species of small mammals with soft fur that will lie either forward or backward. The first upper incisors, which protrude forward, are efficient in gathering the tiny prey on which shrews feed. They are enlarged and pincer- or sicklelike but have a posterior cusp as well. Behind these enlarged teeth are a series of 4 or 5 small teeth called the “unicuspids.” The number and size of the unicuspids have been much used in shrew identification. We have not included standard tooth formulas for shrews, since it is not clear, in this case, how “unicuspids” might relate to the incisors, canines, and premolars of the standard formula. In North American shrews, all of which belong to the subfamily Soricinae, the “red-toothed shrews,” the teeth have chestnut-colored tips. Shrews are seldom seen but are exceedingly active, constantly running about, squeaking, wriggling their noses, and sniffing this way and that. They also have exceedingly high metabolic rates. The heart rate may reach 1,200 beats per minute, and respiration rates run from 168 breaths per minute when at rest to 750 per minute when undergoing Mammals.indb 63 3/31/10 3:09 PM 64   Species Accounts Listed by Family “average” activity. Few individuals live much over a year. Shrews are among the smallest of mammals, and our pygmy shrew is the smallest of the shrews. Shrews are often numerous. They consume great quantities of worms, insects and other invertebrates, and some vegetation. Shrews, Blarina, often feed on the minute subterranean fungus Endogone and related genera. Shrews have a number of glands that may impart an odor to the shrew, and many of them probably function to bring the sexes together. One might think these glands would deter predators, but predators often eat shrews. At least some shrews are known to use echolocation for navigational purposes. Shrews have an interesting distribution in the state. As is often the case, shrews in the same area generally are of different sizes, eat different foods, and divide up the habitat in some way, thus avoiding competition . The six shrews of Indiana have evolved in this way. Blarina brevicauda and Cryptotis parva occur throughout the state, although Cryptotis is increasingly uncommon to the north. Sorex cinereus occursthroughoutthestateexceptinthesouthcentralhillcountry .Sorex longirostris occurs in the southern part of the state. In the southwest it occurs in the uplands, S. cinereus in the bottoms. In the southeast it occurs in uplands and bottoms. In the south central unglaciated hill country, S. cinereus is absent, S. longirostris occurs in the bottoms, and S. hoyi and S. fumeus inhabit the uplands. Masked Shrew Sorex cinereus Kerr Distinguishing Features and Measurements: The masked shrew, the pygmy shrew (Sorex hoyi), and the southeastern shrew (Sorex longirostris ) are the smallest Indiana mammals. All are long-tailed, brownish in color, and have pointed snouts and tiny beady eyes. The smoky shrew, Sorex fumeus, also occurs in Indiana, but it is somewhat larger and is usually gray or grayish. The ears in these species are small and nearly concealed in the fur, which is fine, soft, and dense. The pygmy shrew is the smallest of these species (averaging 2.2 grams) and is somewhat more grayish. However, the best character for identifying it is by the third and fifth unicuspid teeth, which are reduced in size and hidden, making it appear as though they number only 3. The masked and southeastern shrews have 4 large, followed by 1 smaller unicuspid tooth. Coloration and measurements of the masked shrew and the southeastern shrew are similar. Both have pale, silvery colored undersides. The masked shrew tends to have a longer...