Wildlife

Strange and Unbelievable Facts About Shrews

Young shrews (crocidura, most likely c. russula) near their nest. Picture taken at a compost heap in Germany. Photo © Holger Casselmann / Wikimedia Commons through a CC BY-SA 3.0 license

You’re walking along some bushes in a park, and suddenly see a tiny gray creature skittering into the fallen leaves. At first you might think it’s a rodent, but this frenetic ball of energy is actually a shrew.

While it may appear small and gray, shrews are one of the most voracious mammalian predators on the planet. And they’re abundant and widespread, found on five continents in a variety of habitats. In the United Kingdom, there are an estimated 50 shrews per hectare in woodlands, with a country-wide population of more than 40 million shrews. The northern short-tailed shrew may be the most common mammal of the eastern United States.

Soricidae, the shrew family, contains more than 385 species. Superficially, many of these species look similar, with most having pointy snouts, a streamlined body and a grayish coloration. But they exhibit a diversity of behaviors. Even though they’re common and widespread, few people see them and fewer know their crazy habits and adaptations.

Let’s take a look at just some of the many reasons to marvel at shrews.

  1. Life in the Fast Lane

    If you’re lucky enough to see a shrew, you’ll notice that it’s moving rapidly, with rapid, jerky movements. This isn’t because you scared it; shrews just live life fast and furious. Your most highly caffeinated, Type A colleague will appear downright slothful compared to a shrew.

    While this varies among species, a shrew’s heart rate beats 800 to 1000 times per minute. The Etruscan shrew, the smallest terrestrial mammal on earth, has a heart rate that can reach 1500 beats per minute, more than any other mammal and more even than the hummingbird.

    Shrews have been recorded making 12 body movements per second. (Go ahead and try to duplicate this feat). They’re in constant motion, rarely stopping to sleep. They have a high metabolism, which means they have to eat. A lot.

    A shrew’s life is a constant search for prey. Many species must eat their body weight’s worth of food each day. (I advise you not to attempt this one). If a shrew doesn’t eat within a few hours, it dies. This constant need for food has led to some truly bizarre and even disturbing adaptations.

  2. Watch Those Whiskers

    Northern Short-tailed Shrew. Photo © Gilles Gonthier / Flickr through a CC BY 2.0 license

    Shrews must find and subdue prey fast. They have poor eyesight and often live in thick cover filled with obstacles. How do they manage?

    Many sources mention that some shrews use echolocation: they emit sounds producing sonar that helps them navigate their world (much like bats). Shrews emit a sound described as a “twitter” and it is often assumed this is used in echo-location. However, much of the evidence appears anecdotal.  An article in the journal Biology Letters found “shrew-like calls can indeed yield echo scenes useful for habitat assessment at close range.”

    There isn’t evidence that this echolocation is used to find prey. Instead, shrews rely on their long, highly sensitive whiskers, also known as vibrissae. According to a study published in Philosophical Transactions B, the Etruscan shrew hunts in an environment where crickets are particularly abundant. It moves its whiskers constantly –  a motion called, appropriately enough, whisking – until it brushes its prey. Then it strikes quickly and with great precision.

    Of course, wasting time attacking non-prey items that the whiskers brush against would burn precious energy. The researchers conducted an intriguing test:

    “Experiments with dummy prey objects showed that shrews attacked a plastic replica of a cricket but not other plastic objects of similar size. Altering the shape of crickets by gluing on additional body parts from donor animals revealed that the jumping legs but not the head are key features in prey recognition.”

  3. Shrew Venom, A Horror Story

    You can spend way too much time on YouTube watching videos of shrews attacking mice, scorpions, snakes and other larger creatures. Spoiler alert: the shrew wins.

    This is because many shrew species are venomous. Research has found that an individual shrew stores enough venom to kill 200 mice. Some shrews also use this venom for something called live hoarding.

    Live hoarding sounds innocuous enough, but in reality it shares numerous plot points with that terrifying movie Hostel. Here’s how it works.

    The shrew lacks hollow fangs (as in venomous snakes) but instead has a gland that allows saliva to flow with the venom. When the shrew encounters its prey – often an invertebrate, but it can also be a mouse or other vertebrate – it begins biting it, allowing the venomous saliva to flow into the wound.

    For the prey, this is the beginning of a very bad day. The venom paralyzes the creature, but keeps it very much alive. The shrew can then move it to a cache, available for whenever hunting is not going so great. For an animal that has to eat constantly, this keeps a fresh if unsavory meal always at the ready.

    The American Chemical Society reports that a mealworm can be kept, paralyzed but alive, for 15 days.

    Shrew bites on humans are reportedly painful but fade in a few days. Be very, very glad these animals are not larger.

  4. Following the Herd

    Mormon crickets in Nevada, 2006. Photo © katie madonia / Wikimedia Commons through a CC BY 2.5 license

    In the sagebrush country of the western United States, one species of shrews may follow the thundering herds … of Mormon crickets. Mormon crickets (actually a species of katydid) are prone to periodically have population explosions resulting in large swarms.

    Vladimir Dinets, in the Peterson Field Guide to Finding Mammals, includes this intriguing description: “On arid plains these shrews follow swarms of Mormon crickets the same way Gray Wolves follow migrating Caribou herds. If you encounter a swarm, look for shrews scurrying along its tail edge.”

    Dinets’ book, by the way, is like a shrew spotter’s bible, including tips on where and how to seek all the North American species.

  5. Walking on Water

    Water shrew on Pebble Creek. Photo by NPS/April Henderson on Flickr in the Public Domain

    You can find a shrew species in just about any habitat. Several species of water shrews even take to streams. The water shrew has stiff hairs on its feet that allow it to scamper across the surface of the water. Its stiff fur also traps air bubbles, allowing it to stay underwater for short bursts. It must stay in constant motion underwater, or it pops back up to the surface. It hunts caddis larvae and other small aquatic prey.

    Theodore Roosevelt (yes, the president) observed a water shrew catching a minnow in North Idaho. He described it in his book The Wilderness Hunter: “It was less in size than a mouse, and as it paddled rapidly underneath the water its body seemed flattened like a disk, and was spangled by tiny bubbles, like flecks of silver.”

    As a side note, Theodore Roosevelt also kept a shrew in captivity (he fed it a mouse and garter snake) and observed, wrote about and collected shrew species on his lengthy African safari. He even has a shrew species named after him. I’m not surprised that he had a love of shrews, given his accomplishments as a conservationist, naturalist and outdoors enthusiast. I wish for another politician like him nearly every day.

  6. The Incredible Shrinking Brain

    Common shrew (Sorex araneus). Photo © Dr Mary Gillham Archive Project / Flickr through a CC BY 2.0 license

    Many wildlife species feast and bulk up for the cold winter months. With the shrew’s metabolism, weight gain is not an option. And so at least one shrew species shrinks. A recent study, published in the journal Nature, found that in common shrews in Germany, “Their spines also got shorter, and major organs, including the heart, lungs and spleen, shrank. Even their brain mass dropped by 20–30%.”

    Researcher Javier Lazaro hypothesized that “reducing their body mass during winter might increase their chances of survival, because they wouldn’t need so much food.” The brain in particular has high energy requirements, but the study could not determine if shrews experienced decreased cognitive functions.

  7. Foxes Hate Them, Trout Love Them

    The shrew-eating trout of Togiak National Wildlife Refuge. Photo: U.S. Fish and Wildlife Service.

    Shrews may be fierce predators, but they’re small, which means they in turn become prey. Many mammalian predators, including red foxes, raccoons and cats, will attack them but rarely actually eat them. That’s because shrews emit an unpleasant musk that some liken to the smell of skunk.

    This does not deter other predators, like owls and snakes. But my favorite incidence of shrew predation is a rainbow trout caught at Alaska’s Togiak National Wildlife Refuge that had 19 shrews in its stomach. These were not water shrews, but other species that fell into the water and became prey. You can read the full account in my previous blog.

  8. Shakespeare and Shrews

    Petruchio (Kevin Black) and Katherina (Emily Jordan) from the 2003 Carmel Shakespeare Festival production at the Forest Theater. Photo © Smatprt / Wikimedia Commons through a CC BY-SA 3.0 license

    And then there’s the literary work, Shakespeare’s Taming of the Shrew. During my Shakespearean literature class in college, my professor stated that the Bard did not refer to the literal shrew, as such a benign, inconsequential mammal wouldn’t fit the theme of the play.

    As a lifelong mammal nerd, this amounted to heresy. I decided to make my final paper for the class a detailed comparison of the real shrew with the literary one. This, in retrospect, was a bit of a gamble. I relied on a store of shrew facts, many of which now appear in this blog.

    As I read my professor’s comments on the paper, I could sense that she was initially annoyed at my topic, then became increasingly alarmed as she realized I was quite serious. The paper received an “A”, along with the pointed suggestion that I pursue a career in nature writing as opposed to academia.

    And here I am, still sharing shrew facts.

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52 comments

  1. Thank you! Fascinating stuff. Yay for Nature’s students always learning from Her.

  2. Long ago I worked in an arboretum in upstate New York. One week my job was to clean up a poorly maintained slope covered with various evergreen species. Under a low growing spruce I found a whiskey bottle containing the skeletons of five shrews. My guess is that one shrew entered the bottle followed by another. One ate the other and could not get out. Subsequently three more shrews entered the bottle and one ate the other. Repeat – until five were trapped and either eaten or unable to get out because they had eaten. Not too shrewed – or maybe too shrewed.

  3. Matthew wrote that foxes don’t eat shrews, and hypothesized, “ That’s because shrews emit an unpleasant musk that some liken to the smell of skunk.”

    This was the subject of my MS work. At least for red foxes and the northern short-tailed shrew, avoidance is probably because of the poison glands.

  4. When I was a kid, I saw a movie theater trailer for an upcoming sci-fi feature, Killer Shrews, about some mutated variety of shrew the size of German Shepherds, and what they could do. The trailer alone was scary. I never did see the movie.

  5. That was a good read. I learned a few new behaviors of a Shrew that I wasn’t aware of.

  6. I live about 20 miles south of Dallas. Texas. Moved out here in 1982 & had never seen one of these shrews before. The land we are on is old farmland & use to be hay pastures. We see them quite often when we catch the feral cats playing with them. They do not however eat them like they do a mouse or rat.

  7. Glad that you indeed took up nature writing. I enjoyed this quick, highly informative – and amusing – read about shrews.

    1. Thank you very much, Michael, and thanks for reading Cool Green Science!

  8. I loved all of the details you shared about shrews, and particularly your anecdote about the Shakespeare paper! I take children on nature walks in Northern Virginia, and with the first cold snaps of fall we often see dead shrews on the trail. Do you know if they die from the cold, the sudden absence of insects for food or other causes?

    1. Hi Sarah,
      Thanks for reading the blog. I have noticed dead shrews along the greenbelt path near my home in Boise. I suspect it is a combination of factors — some could die of cold, and I also believe some are probably killed by foxes, cats, etc and left dead on the path (for reasons described above). Shrews seem to live fast and die hard…

  9. Thank you so much for this! I am a conservation biologist working on species at risk in southwest BC and we have the endangered Pacific Water Shrew here (Sorex bendirii). Shrews can be a hard sell in conservation (especially water shrews like our “Benny”) because they are rarely seen by people, are often mistaken for rats or mice and don’t garner the cute and cuddly attention that some of our charismatic fauna like caribou or spotted owls do. But I love them and having these sorts of articles may help others love them too!

    Pamela Zevit RPBio
    South Coast Conservation Program
    BC, Canada

    1. Thank you Pamela for loving these little creatures. Your job sounds wonderful! May I suggest reading “ “Kinship with all Life” written by J Allen Boone to your students? If you haven’t already🙂

  10. So, that explains why I had so many shrews in my yard the years I had foxes living under my barn. No mice, though. (Wish the foxes would come back, but unfortunately neighbors removed the wooded corridor behind my property.)

    I like shrews– interesting creatures- and enjoyed learning some more interesting things about them. Loved the film- both hilarious and a bit frightening! The Teddy Roosevelt quote was very much like something one of my daughters, age 5, said after watching a water shrew go downstream during one of our camping trips. Very observant kid. (She is currently studying for her PhD in biology.)

    Glad your teacher steered you toward nature writing, too, but somehow suspect that’s where you were going, anyway. Gift to all of us nature nerds.

    1. Thanks Annie, much appreciate. And yes, by the time that teacher made that suggestion, I was already firmly committed to my desired career path!

  11. Theodore Roosevelt is considered to have been a conservationist, but he was a tremendous persecutor of large predators, notably mountain lions. While I realize that this negative attitude towards large predators was common in Roosevelt’s time, I would certainly prefer politicians who are true conservationists and see the value of all species.

    1. Thanks for your comment. And I understand your point of view. But attitudes and values change, and I’ve never found it fruitful to apply today’s attitudes and values to times past. Even Aldo Leopold persecuted wolves (although he had a change of heart). And I should note that I know several accomplished and eloquent conservationists today who hunt mountain lions.

      Regarding Roosevelt, he was critical in establishing national parks, the national wildlife refuge system and so much more. I continue to wish for more like him, every day.

  12. Amazing creature. Thanks for the article. I learn so much from this site.

  13. Great article…fascinating……..ounce for ounce a pretty tough customer……I am guessing their life expectancy is comparatively short.

  14. I used to regularly find dead shrews,usually a foot above the water line near ponds after rainstorms,any clue why this happens?
    My theory is they get wet and it supercharges there metabolism and there poor little bodies can’t take it?

  15. Just found a shrew in my back yard. My dogs have been barking at something and driving us crazy fo r the past week. Now we saw the shrew tonight and managed to get the dogs away from it with a hose. We have cats as well. Now what do we do with this animal. Its driving us nuts. Which reminds me we do feed the jay birds with nuts during the day. So maybe that is why this creature has appeared. We live in Beaverton, Oregon. Can anyone help.

  16. I had to relocate a shrew that lived in our garden, to both protect her from feral cats, and to reduce the insectivorus competition for the local hedgehog that still likes to live here (it’s incredible how many insects a single shrew eats per day!). So after having scouted a new suitable habitat, I installed a live trap, watched it constantly, and as soon as it snapped shut, I covered it with a cloth to reduce stress, and took it to the new location. I had te be quick, due to the fast metabolism. After opening the trap door, the shrew gingerly got out, looked back at me, shouted angrily something in shrewanese, and ran away. I sure hope she got many offsprings.

    Oh, btw, shrews are said to be far cousins of hedgehogs.

  17. I caught a shrew today by the entry of a grocery store. I saw it running and it stopped sometimes and I picked it up..I had gloves on. It nestled right down in my glove..I put it in a little box with high sides, put the glove in the box and it hid under it. Took it to the humane society, talked with guy there, left it with them….really kind of wanted to take it home. Called them later, but those people were gone, I’ll call them tomorrow. I’ve read a lot about them and think I could keep it decently. Am I crazy??? I’m not fond of the fact they paralyze something and then eat it alive!!!! But that’s nature I guess. They probably wouldn’t let me have it back anyway….Maybe it died. It was a very cute little critter.

  18. Shakespeare surely did mean a shrew in his WONDERFUL play. Take nothing away from that.
    But the Professor was surely thinking of a VOLE which is also a “wee timourous beestie” and can look very similar to literary folk ungiven to scientific thought. But the vole is a RODENT almost exclusively vegetarian whereas the shrew is a wild carnivore more related to a mole or a hedgehog.
    Compare their dentitions.

  19. I’m going to be late to work because I found your blog. WONDERFUL writing and thanks for the good laugh at the end….you just made my day. (I had looked up shrews to see why my barn cats ignored the trapped and killed shrew I offered them last night…..I get it now!)

  20. Dear Matthew Miller ….My hero is Theodore Roosevelt!! While reading Mornings on Horseback by David McCullough I came across the Great Shrew Incident……What the heck exactly is a shrew ….I googled…. wow did I get answers!!! Plus someone else on the planet knew my Teddy story!!!!!!!
    Sure am glad your teacher directed you to the world of nature AND gave you an A

  21. Until yesterday I had never seen a shrew. We caught three running through our living room! we live outside of Pgh. PA. We live in the country, and have had bats, mice and a squirrel come in but never a shrew! They looked like the ones at the top of your article. can you tell me what kind of shrews they are? my question is would they have had to be born in my house to have had three! Do they normally come into homes? Fascinating critters! thank you for your article!!!

  22. What’s your opinion on shrews being white and grey; my cat catches DOZENS of shrews in Pennsylvania. And he’s caught two that were identical to the grey ones, very small barely visible ears and eyes, longer snout, short tail, clawed smaller feet; but they were blocked colored grey and white like how some pet mice look! (Looked nothing like a mouse though) It was shocking because now I’ve been trying to research if it were even a shrew because I’ve never heard nor seen the coloring. Any thought? Thanks.

    1. I have not heard of this but shrews do have variation in their pelt coloration. I will look into it more. Thanks for your question.

      Matt

  23. I discovered six shrews in my compost bin during the turning process of producing usable material.
    On their exposure, they quickly scurried out of the bin through an entry hole at ground level. One was caught, photographed and then released through their escape hole. The shrews had formed a chamber at ground level which I am assuming was a breeding chamber. There is a meter of compost above ground level.
    The compost has a good supply of insects, worms, and woodlice, not sure about slugs or snails but in riddling the compost for use occasionally find empty snail shells.

  24. I really enjoyed reading and learning more about Shrews. I know if they don’t eat every 3 hours they will die. What I wanted to know is if they do eat every 3 hours. Do they have years they can live ?

    1. Shrews have short life spans, from 1.5 to 3 years depending on species. Most do not reach old age. Life in the fast lane is tough!

  25. So tickled to read all your fascinating facts about shrews. I’ve only seen one once, hunting in my yard, so tiny and busy and quick. T. Roosevelt just went up another notch in my estimation and second your wish for another. Thanks for the lead to Dinets.

  26. Loved the article and learning about shrews! I agree with your professor, you are a fantastic nature writer!

  27. Thank you, that was both informative and entertaining. I now recognize I’ve misidentified what was a shew for a mouse.

  28. We caught a shrew in a mouse trap under the kitchen sink. Reading your article makes me wiser! Last week I blamed my little chihuahua for chasing a skunk. Now I wonder if he had been chasing this shrew in our house or around it.

  29. I caught a northern short tailed shrew in my kitchen in Indianapolis today, and have enjoyed learning more about them. Might the presence of the shrew explain the absence of the annual ant invasion this year? We’ve had the house for 12 years and every spring until this one we have been invaded by ants from late February through about June. At any rate, I caught it in a live trap and released it in a nearby park. Hopefully I can find the hole it used to get in the house and seal it up.

  30. If they bit a small dog that weighs only 3to 5pounds or a cat can it kill them? How would you get rid of them if you have them in your house?

    1. They do not possess enough venom to kill a small dog or cat. Cats regularly kill shrews but don’t eat them, for reasons described in the story. I would contact a pest control company if you have problems with them in your home.

  31. I spotted three young shrews in my garden all busy running around about 5 hours later I went out in the garden saw a bit of movement under a few leaves. On closer inspection I found one eating another shrew and then spotted two more together dead, close together. Is this normal behaviour .

  32. I have a family of shrews in my kitchen and my three cats barely react to them. I think they live off the cat food. I had a baby one that wandered across the floor looking for water and I handled it before it ran off.

  33. I love to watch shrews. I have one that follows the same path every day at dusk. I put peanuts out for a couple of chipmunks every evening so that when they start foraging in the morning, they will find something. Yesterday, I saw my shrew friend take a peanut into the dense plant growth along my walkway. I had no idea that they ate anything other than small mammals and insects. I will make sure that I put some seed and peanuts out for him also. Thanks for the info.

  34. Have just discovered a pile of 7 dead shrews by a burrow , very strange. All in a neat little pile – any ideas?

  35. In the past week I caught 3 shrews in the mouse traps set in my garage. Never thought they were around! I had peanut butter on the traps and they probably were attracted to that. They were shrews because the nose was long and pointed, the tail was short, teeth were visible on the underside of the head and shorter legs. They were the same grey color as the mice living around here. Wisconsin.

  36. I enjoyed reading your article😬 I have been a fan of the often misidentified shrew. Years ago(precisely 38) I had spotted what I thought was a velvety brownish grey mouse. It was late at night, and I was taking advantage of the quiet alone time that late night would afford me the time to focus on my creative sewing projects. At the time, I was raising 2 little boys, ages 3 and 1 year. Late night was my escape into my own world of creative productivity.
    So on to the discovery of the shrew. I was at first startled by this bold little creature, coming out of hiding and leaning back on his hind legs, gave me a look of “oh, crap, you’re awake”. He didn’t seem very concerned about me, but rather scurried on to the kitchen, where I naturally assumed he was on the hunt for his next meal of tasty boxed cereal and then on to use my silverware drawer as his own personal restroom to relieve himself.
    I remember thinking that the following day would have to be my hunting day(this mouse would be pardoned for this night at least)
    I was not looking forward to sanitizing my dishwater, silverware, utensils ect.. Not to mention looking for any “chew holes”at the bottom of the boxes, bags or other containers in my pantry that housed the food that I prepared for my children. Wiping everything down with disinfectant was a daunting, time consuming task that I was not looking forward to. I hoped that my mouse hunting skills would be swift, but I knew deep in my heart that when you see “a” mouse, there are at least 10 more that you don’t see, keeping watch. Ugh! I really had better things to do with my time. On to the local hardware store to invest in some sort of contraption to catch these little critters that had so boldly taken up residence in my home. As much as I wanted them gone, I had no desire to kill them. My mother had read “Kinship with all life” to me as a child, and I have to admit, I did ask this mouse to leave the premises at once, or else! I figured he was going to stand his ground, so I would have to do the same. The guy at the hardware store said that it sounded more like a shrew and not a mouse. He then went on to tell me that I should be happy to share my home with this little critter, as they eat bugs and are not interested in any of the food in my pantry, except for maybe the cat and dog food. And as far as pooping on my silverware, had I actually identified any droppings? Not even one little poop, come to think of it, I hadn’t seen any sign at all that there were any mice in my home. Needless to say, I was eager to learn about this little critter that was feasting nightly on bugs and spiders, keeping my little boys safe from the possible poisonous bites of some of the common spiders found in the Midwest, which is where I live. I named our houseguest “Twinkles”. To this day my 2 boys remember our shrew as more of a pet than a pest. My husband told me yesterday that we have a mouse, a very strange looking one. I laughed and told him to leave it alone and be grateful for him living in our old farmhouse, that chances are he(the shrew) would most likely keep our home mouse free for the winter. I wonder what his name is….the shrew, that is😉