Tiny terrors: Two toothy rodents with bloodthirsty reputation
“A spiteful, nagging, and ill-tempered person” is one definition of a shrew. Two species of shrews, of the animal nature, occur in our area and this name association hasn’t improved their images.
Indeed, some distinctive characteristics of the Least Shrew and Desert Shrew contribute to their perception as bloodthirsty, insatiable predators. However, if we examine the lifestyles of these shrews, we may find that they don’t deserve reputations for shrew-like behavior.
Built with bite
The Least Shrew and Desert Shrew are three inches or less in length from the tip of their noses to the end of their tails; with the Least Shrew being the smallest. Both have short, grayish dorsal fur and lighter, white to light gray bellies. Their legs and feet are short and small, respectively and both have elongated, pointed snouts with prominent, sensitive whiskers. Ears and eyes of the Least Shrew are almost completely hidden in its fur; whereas, the Desert Shrew has more prominent ears and larger eyes. Also, the tail of the Desert Shrew is almost twice as long as the Least Shrew’s tail. The jaws of both shrews contain many teeth and enlarged, procumbent (projecting forward) first incisors. These incisors are pointed, sharp, and used to deliver rapid, initial bites to prey and as tweezer-like tools to help manipulate and carry prey and other objects.
'Blood'-stained teeth!
Shrews are born with permanent, dilambdodont teeth (= shaped like a “W”) with sharp, pointy, outer cusps and another feature giving shrews part of their reputation as bloodthirsty killers. The teeth cusps are a dark, rusty red color and appear bloodstained! The red color is caused by iron containing pigments in the tooth enamel. The pigments help reinforce areas of the shrew’s teeth subjected to stress during biting and chewing.
Both species occur throughout North Texas and Southwestern Oklahoma. The Least Shrew is more common in our eastern counties; whereas the Desert Shrew is more at home in the region’s drier western counties. Both occur in habitats ranging from mesquite and oak woodlands, riparian areas, grassy fields and washes, cactus patches, and human dwellings and structures. Shrews often use trails and runways of mice, cotton rats, woodrats, and other animals for foraging and travel. Small, golf ball-sized nests are constructed of leaves, grasses, moth and spider silk, and other materials in appropriate, mesic (moist) microhabitats, such as shallow burrows (usually excavated by the shews) and spaces underneath leaf litter, rocks, natural and human debris, and, notably, within woodrat nests. Shrews seem to live peacefully with woodrats and several researchers have observed groups of shrews (sometimes as large as 30 individuals) inhabiting the same nest or nesting complex: especially during winter. Also, multiple shrews have been observed peacefully co-existing in captive conditions. These examples of the social natures of Least and Desert Shrews are contrary to the belief in their bad tempers.
Only a threat to insects
Both shrews are insectivores and feed upon a wide variety of invertebrates and occasionally upon small vertebrates and carrion. Diet items include crickets, grasshoppers, insect larvae, earthworms, cutworms, beetles, scorpions, spiders, and centipedes. Shrews can subdue animals larger than themselves and hunt with quick striking and biting movements usually aimed at the prey’s head and/or neck. Shrews often immobilize crickets and grasshoppers by removing or biting through their legs. In addition, the Least Shrew is known to produce a paralyzing venom in its salivary glands and there is some evidence for a similar type of venom production by the Desert Shrew. The venom is effective upon insect prey but harmless to humans. Shrews are one of the few mammalian species known to produce venom and the venom doubtless increases the shrew’s predatory efficiency. This is essential because of the amount of food a shrew must consume on a daily basis. Because of their small size, shrews have very high metabolisms and must consume a daily volume of food items approximately equal to or exceeding their body weights; thus, shrews spend a lot of time searching for food.
Hearing with their snouts?
Shrews are usually solitary hunters and will often obtain and store extra prey items in a larder area within their burrows and/or nesting areas. Shrews hunt with noses and snouts raised and they may also utilize a form of echolocation to navigate within burrows and tunnels. Hearing and olfaction aid in locating prey and, although their eyes are small, vision must be important for targeting where to bite prey animals. Nests are kept scrupulously clean and shrews defecate in a specific area outside the nest (referred to as a midden area): often depositing their feces on leaves and other raised objects. Foraging occurs at any hour and during all seasons of the year and, although shrews are not know to hibernate, they enter periods of very deep sleep and/or torpor-like daily resting conditions.
The Least Shrew and Desert Shrew produce several litters (averaging four to five young) per year. Reproduction may occur throughout the year but has not been observed during winter months in our region. Newborn shrews mature rapidly and usually leave their nests 20 to 40 days after birth. The lifespan of shrews is relatively short and most shrews probably survive less than one year. The most effective predators of shrews are Great-horned Owls and Barn Owls; followed by a few species of snakes and, possibly, domestic cats (although cats don’t seem to consume shrews). Perhaps because of strong odors and/or blood and body fluid composition, shrews are distasteful to most predators.
Hunt or starve motivates tireless beasts
As we have discussed, shrews are almost tireless hunters; but they must either hunt or starve because of their high metabolic demands. Their teeth aren’t bloodstained but, instead, are reinforced with iron to prevent excessive wear and, instead of being bad tempered, shrews are at least moderately social and also co-exist peacefully with other animals. Therefore, our little insectivores may be “shrews” but they don’t really behave in a “shrew-like” manner!
This article originally appeared on Wichita Falls Times Record News: Tiny terrors: Two toothy rodents with bloodthirsty reputation
