In last month’s phenology report we talked about small mammals in the order Rodentia, this month we are going to consider three common members of the order Insectivora. These are the masked shrew, the short tailed shrew, and the water shrew. Other members of the order include the pygmy shrew, the arctic shrew, and the star nosed mole. Setting those aside for another time let’s get to know these members of this unusual group.
Masked shrew. (c) James Parnell. Source: NPS.gov
The masked shrew is one of Minnesota’s smallest mammals and certainly the smallest common mammal. It can be found statewide and in almost every habitat type. It has a long pointed nose and its teeth are tipped with brown. The masked shrew is not quite 4 inches in length and nearly half that is the tail. The body might be two inches long. It would take a hundred or so to make a pound.
Don’t let its small size fool you, they are constantly on the go looking for high-energy foods. Think of the shrew as a land based hummingbird. They are of similar size and both must feed almost continually to maintain body temperature. A masked shrew must eat every few hours or starve to death. They probably eat their body weight in food each day. Insects, both adult and larval, comprise most of their diet but they will attack and kill mice or voles that are nearly twice their size. They are not averse to any carrion they might stumble upon as well.
In one grisly episode I recovered a sticky trap with a mouse caught in it. A shrew had waded into the goo to eat the mouse. The shrew became caught in the mess too, but undeterred ate all of the mouse it could reach. I took the trap outside cleaned the shrew as best I could and released it in hope that it would continue to attack the mouse populations near my house.
Short tailed shew. CC-licensed Flickr photo by Gilles Gonthier.
The short tailed shrew is the other common shrew of Minnesota. At nearly five inches in length it is seldom confused with the masked shrew. The short tailed shrew is just that, short tailed. The tail is about one inch long leaving the body at near four inches again making confusion with the masked shrew difficult. I have seen masked shrews in my house but never a short tailed shrew.
The short tailed shrew is markedly different from the other shrews found in Minnesota. It is large and therefore doesn’t need to feed as often as the smaller shrews. Some kept in captivity have survived for more than twenty-four hours without eating, something that is not possible for its smaller relatives. And strikingly, the short tailed shrew is venomous. Glands in the mouth produce a poison that will quickly kill a mouse when bitten. With the exception of a single large shrew-like Insectivore found in Cuba and Hispaniola, this is the only venomous mammal in the North America. Naturally when dealing with the short tailed shrew care should be taken since a bite might be painful at the least, and could be temporarily incapacitating in sensitive individuals.
Water shrew. CC-licensed Flickr photo by wildlifewanderer.
The water shrew is not often encountered by the average outdoors person. They are found in the northeastern part of the state and are seldom seen on land. They are larger than the masked shrews, have a longer tail than the short tailed shrews, and are distinctly bicolor with dark brown fur above and silvery fur on the belly. Their hind feet are quite large, nearly three quarters of an inch, on a body that is roughly three inches long.
These large feet are uniquely developed to aid in swimming. There are stiff hairs protruding around the edge of the foot that increase the surface area. Water shrews are strong swimmers well adapted to find prey underwater. They swim up to potential meals, exhale a small bubble of air from their lungs up against the side of their intended dinner, quickly inhale the bubble and if it smells like supper they attack.
Shrews have many enemies but their strong musky odor often keeps their predators from eating them. My dogs have killed a few and I have found the bodies uneaten. Fox often do the same. Anyone who keeps an outdoors cat has more than likely encountered shrews. Hawks and owls, whose sense of smell is often diminished are not as particular and will eat them whenever they get the chance. These tiny little bundles of menace are of little consequence to humans but they are busy controlling insect populations and limiting the success of mice and voles. For that alone we should be glad to share the world with them.
John Latimer is well known throughout northern Minnesota for his phenology work. John will deliver the keynote presentation at the March 2012 Minnesota Family Woodlands Conference and appears weekly on KAXE radio in Grand Rapids, and audio and twitter archives are available here. We hope his work will be a frequent feature on MyMinnesotaWoods. This article also appeared in the Duluth Senior Journal. It is printed with the author’s permission.
