Miniature but Mighty
by Charlotte Overby

Shrews, Missouri's smallest mammals, have Godzilla-sized appetites.

"The thing I like most about shrews," says Mark McGimsey, a biologist who studied shrews in graduate school, "is that they have huge appetites. I read an account of a shrew that attacked a rabbit, and another case where a shrew tried to eat a ribbon snake."

Not bad for Missouri's smallest mammal, the shortest species of which, fully grown, is only about 3 inches long. Rabbits and snakes are not part of a shrew's everyday diet, but for their size, shrews often try to eat surprisingly large objects. Bulk is important; shrews have to eat at least two-thirds their own weight in food every day to survive. Some eat even more.

There are four species of shrews in Missouri: masked, southeastern, short-tailed and least shrew. They share similar characteristics and habits, and southeastern shrews weigh the least, coming in at just 2 to 2.5 grams, or about 1/10 ounce.

Shrews are dark brown to brownish gray, have long pointed noses, tiny black eyes, and thin tails. Their front and back limbs are quite small, and each foot has five toes with claws.

Their ears are flat against their heads and concealed by soft fur. They appear to have good hearing. Like bats, shrews make use of echolocation-finding objects by bouncing high-pitched sounds off them. Bats use echolocation to find insects to eat and to "see" larger objects when they fly; shrews make high-pitched, ultrasonic calls to explore tunnels, but probably not to find food.

About the size of a finger, shrews are the "mighty mites" of mammals, often ferociously attacking animals much larger than themselves.

Shrews dig their own tunnels in open grassy or brushy areas, but they also use tunnels made by mice and moles. Some tunnels are shallow while others may be 8 inches under the surface. Sometimes shrews cooperate and build tunnels together. They do not have good eyesight and rely, instead, on their well-developed sense of touch to find food. They also spend a lot of time above ground. Shrews are active throughout the year at all times of the day and night, and they rest or sleep on and off, often sleeping together in piles to keep warm.

In tunnels and above ground, shrews search for insects, snails, slugs, earthworms, centipedes, spiders, small rodents and the dead bodies of small animals to eat. Shrews also attack frogs and crickets, crippling them by biting their hind legs before eating them. They hardly touch their vegetables-plant matter, that is. They are mainly carnivores-or meat eaters-and seldom eat plants.

Least Shrew

Shrews are tough, cranky, somewhat nervous bullies of the small mammal world. They take on creatures larger themselves and make clicking, twittering and chirping sounds. Chris Montgomery, photo specialist at the State Historical Society, says she encountered a shrew while picnicking near the banks of the Missouri River.

"It sure was trying to look ferocious," she says of the tiny mammal. "It made all kinds of sputtering noises and moved quickly. It was small, but I wasn't going to pick a fight with it," she jokes. If food is scarce, shrews think nothing of fighting with each other and sometimes kill and eat one another.

Shrews give birth to litters of three to seven young. Newborn shrews have no fur, closed eyes and ears, no visible teeth and weigh just 1/100 of an ounce! When they are 1 week old, their fur grows in. At 2 weeks of age their eyes and ears open, and at 3 weeks they have teeth. By the ripe old age of 1 month, a young shrew looks like it is fully grown.

Orin Mock, professor at Kirksville College of Osteopathic Medicine, has maintained a colony of captive shrews since 1966. Missouri shrews have been the focus of Dr. Mock's research, particularly what shrews can teach us about toxins.

"I became interested in shrews years ago because one of my professors was doing research on them." he explains. "Until the 1960s, we didn't know the southeastern shrew even lived in Missouri. One was found in Barry County, then we discovered they were living in northeast Missouri, too."

Southeastern Shrew

Dr. Mock's research also contributes to the over-all body of knowledge about shrews, which are an important food source for many other animals, including owls, hawks, snakes and weasels. House cats sometimes hunt shrews, too. Shrews are also important because they work the soil and eat pesky insects. Understanding the behavior of Missouri's smallest mammals helps us learn more about the bigger picture of Missouri's wild animals and habitats.

A Few Shrew(ed) Facts

• Shrews have amazing appetites. Masked shrews eat up to three times their own weight in food every 24 hours. That means to keep pace with a masked shrew, a kid weighing 75 pounds would have to eat 225 pounds of food per day!
  
  
• A least shrew has 30 teeth contained within tiny jawbones. Kids start out with 20 primary teeth and as adults, usually end up with around 28.
  
  
• A least shrew's heart beats about 400 times per minute and can even go as high as 1,000 beats per minute. Human hearts beat an average of 70 times per minute. An elephant's heart rate is just about 25.
  
  
• In 1894, two biologists observed least shrews sometimes climbing into bee hives. The shrews nested in the hives and ate the bees. They called this species the "bee shrew."
  
  
• Archaeologists discovered mummified shrews in a ceremonial animal tomb near Thebes, Egypt. Shrews are believed to have played an important part in the religion of ancient Egyptians.
  

Masked Shrew

Short-tailed Shrew

SHREW PREYING ON RIBBON SNAKE

Journal of Mammology, Vol. 30, No. 3. August 1949

"On October 10, 1948, I encountered a ribbon snake about 22 inches long engaged in a relatively violent struggle with a shrew . . . A shrew had emerged from the grass and leaves and began moving over the coils of the snake, biting it rapidly in many places. . . . the shrew seemed determined to bite every part of the snake. It had succeeded in biting off the last 2 inches of the snake's tail and inflicting a noticeable wound on the head. All of the snake's efforts were directed toward escape . . . The shrew was extremely aggressive and seemed to be trying to pull the snake under the leaves, possibly into a hole.

By this time the snake was becoming dazed . . . but managed to draw itself up on a cross member [of a table leg] about 9 inches off the ground. The shrew had kept hold of the snake's tail and . . . kept tugging on it for some time. For some reason the shrew suddenly abandoned the fight and moved off under the leaves. It returned twice within the next 10 minutes, passing under the snake and raising its nose up through the leaves. Although the snake's tail was hanging within easy reach, the shrew apparently did not see it and moved on.

I had hoped to see this struggle concluded [and I ] returned to the sight every few minutes for the next hour until the snake eventually disappeared. I felt certain that the shrew could easily have killed the snake had it not been disturbed. Two weeks later I found the chewed-up remains of possibly the same ribbon snake at a spot 20 feet from the location of the fight. This find raised the interesting conjecture that the battle had been resumed and concluded after I lost track of the participants." -R.A. Riley, Jr., Davisburg, Mich.

The Shrew (-ist's) Site

Voted "Coolest Science Site" by Science Magazine, this website was launched by an Austrian mammalogist. It contains articles about shrews, photos, drawings, literature, updates about recent research, folklore, a place to post questions and a list of shrew biologists working around the world. It even tells you how to say the word "shrew" in 55 different languages. Check it out at < http://members.vienna.at/shrew>