A Little Bit More
Despite the widespread distribution and large numbers of shrews, most people are totally unfamiliar with them. Part of this unfamiliarity is due to the shrew's secretiveness, but more often than not, when it is seen, a shrew is mistaken for some sort of "field mouse". Mice belong to the order Rodentia, along with rats, squirrels, Woodchucks, and Beavers. Shrews are members of a primitive order, Insectivora, with such creatures as moles, hedgehogs, and tenrecs.
Shrews are extremely active, nervous mammals that do most of their foraging at night but are known to be active at any hour, day or night. Their extremely high metabolism and activity level make it necessary for them to consume large amounts of food to avoid rapid starvation. Although shrews are reputed to eat more than their own body weight daily, studies have shown that they consume, on average, only one half of their weight in food each day. Even at that rate compared with humans, their food intake is prodigious.
Shrews have poor eyesight (it's hard to even see their tiny eyes) and sense of smell, relying on hearing and a highly developed sense of touch to navigate. Their long snout is covered with numerous vibrissae (whiskers); these tactile organs help them navigate. Furthermore, Short-tailed Shrews have been found to produce ultrasonic vocalizations that appear to help them interpret their environment in much the way bats echolocate.
Almost the entire diet of shrews consists of animal material. Although insects comprise the bulk of their diet, their food does include earthworms, snails, spiders, salamanders, snakes, birds, mice, and sometimes, even other shrews. Many stories have grown up around the shrew's fierce predatory nature. No doubt many are greatly exaggerated although on occasion shrews have been known to kill and eat animals larger than themselves. A reputable naturalist even tells of seeing a shrew successfully fight off an attack by a cat! Cats do often capture shrews; many cat owners have found dead shrews on their doorsteps. When a cat does kill a shrew, it's not likely to eat it, however. Shrews have a large gland on their belly that gives off a musky odor and is believed to discourage predation or maybe, better yet, consumption.
Shrews cache food in their tunnels during times of plenty, and move it from area to area to ensure that it remains as cool as possible. Apparently, the Short-tailed Shrew's salivary poison paralyzes its prey and makes it possible for it to cache live food items rather than dead ones that are subject to decomposition - sounds a little gruesome, but certainly a wonderful adaptation for survival.
Activities
Shrew Race
Objectives: Experience an important survival strategy
Materials: A variety of objects – you choose
Different animals have different "strategies" for survival. Shrews are particularly good at learning all of the twists and turns in the paths of their territory. By establishing these paths to memory, shrews are able to navigate much more quickly than would otherwise be possible. When danger threatens, a shrew knows exactly how to get to safety as fast as possible!
Here's an activity that should demonstrate my point:
Set up a course either outside or in a gym that has twists and turns from a starting point to finish line. The more twists and turns, overs and unders, the better, and the more hidden they are, the better too. You can use chairs, cardboard boxes, plastic jugs, even stuff from a garage to line a path that can be run, but nothing that has sharp edges or points. Divide your group into two teams. Group 1 will learn the path by practicing the course from beginning to end. Group 2 will not see it until you're ready to have your race.
Once group #1 is very familiar with the course, have those from group #1 and group #2 line up at the starting line out of sight of the course. Have members of the two teams line up every-other person so they can run the course alternately. On a signal, each should run as quickly as possible to the finish line - be sure to time each child and keep a record of group #1 times and group #2 times for comparison. It should become obvious very quickly that those familiar with the racing path are able to navigate the course much more quickly than those learning it for the first time. No wonder why shrews that are very familiar with their own territory and the paths to safety are much more likely to survive when pursued by a predator.
Key Concepts
Identification, Predator/Prey Relationships
Questions
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Posted by Morris Munns on May 01, 2005 at 06:44 PM
Q: We have a small inner-city (Battersea)garden but with a pond a good frog population & some mice. Today I heard a frog screaming & found it had a mouse (tho' I couldn't see clearly) fastened onto its back leg. I scared it off & rescued the frog.Is this a field mouse such as I have seen before, a different type of mouse or a shrew ? I'm fairly certain it wasn't a rat.Do mice eat frogs I thought they were seed eaters?
A: Believe it or not, mice will sometimes eat meat, however they're not very likely attacking live animals. Your thought that it might be a shrew is probably correct. Shrews are very active predators and I can easily see them attacking a frog. Although with really close inspection, you can see the difference between a shrew and a mouse, with just a quick look, they're very similar. Thanks for asking.
Posted by Dan on March 11, 2004 at 01:10 PM
Q: I wanted to know if you had any idea about how far shrews will travel in search of a home range. Specifically, I wanted to know about how close or far a shrew would set up its home range compared to that where it was reared. Are we talking tens of feet or miles.
Any help appreciated.
Dan
A: You've posed some interesting questions. My guess is, and it's only a guess, that they don't move very far from their birth site. Certainly, they would travel 100 or more feet if need be but I very much doubt they would travel as much as a mile. This would make an interesting research project although probably a difficult one. Keep in mind that a shrew would only have to travel to an area not already being defended by another shrew before it could settle in. Of course, it would also need to find suitable habitat as well so if its birthplace were surrounded by many acres of appropriate habitat, its search might be much easier. It is common for many young mammals to travel large distances from their birthplace in search for unoccupied habitat. I know that Muskrats, for example, are regularly killed on highways considerable distance from their preferred habitat as they travel to find new homes. Since shrews are so small, my guess is that their travels are much more limited than larger species.
Posted by Anonymous on August 25, 2003 at 11:46 AM
Q: I need a home remedy to get shrews out of my lawn.
A: I'm wondering if it's shrews in your lawn or field mice - I'm inclined to think mice. Shrews are mostly carnivores and should not be a problem to your plants. Field mice, on the other hand, can be a real problem, especially in the winter when they gnaw on the bark of many kinds of trees and shrubs.
I'd try to keep my lawn rather short and remove any other kinds of ground cover and this will reduce places they like to live in.
Keep in mind that populations of these animals often fluctuate quite a bit so one year you may be overrun while in another not even notice their presence.