Saturday, October 17, 2009

A Look at the Shrews of the Adirondacks

On Wednesday I promised you a future with shrews it in, so we’ll take a look at shrews today. Shrews are another member of the Order of mammals known as Insectivora, which is a reflection of their diet: they eat a lot of insects. Much like their mole cousins, shrews spend a good portion of their lives underground, and as such, like moles, they have no (or nearly no) external ear flaps, weeny little eyes, and non-directional fur. Their bodies are also rather long and cylindrical, which helps them move easily through tunnels.

Six species of shrews call the Adirondacks home: the masked shrew (Sorex cinereus), the water shrew (S. palustris), the smoky shrew (S. fumeus), the long-tailed or rock shrew (S. dispar), the pygmy shrew (S. hoyi), and the short-tailed shrew (Blarina brevicauda). Most of these you will never see, for they are rather secretive animals, but one, the short-tailed shrew, is quite common and frequently found in houses, so we’ll start with that one.

As you might have guessed, the short-tailed shrew has a short tail, as compared to the relative lengths of its brethren shrews. In fact, its species name, brevicauda, means exactly that: short (brevi) tail (cauda). Despite its abbreviated appendage, however, it is our largest shrew, coming in between 15 and 35 grams (less than an ounce). It’s a chunky animal, and compared to other shrews it has a rather blunt snout. But the thing that stands out most about this animal is not something you will see or hear, smell or taste. This shrew is most noted for being venomous. Yes, that’s right – venomous. In fact, I think it is the only mammal in North America that has venom. But fear not, for unless you really pester a short-tailed shrew, you will not be on its hit list, and even if you were, you probably wouldn’t suffer much. You see, the venomous saliva is reserved for subduing the shrew’s prey. It is a neurotoxin, and when the shrew bites into its prey, say a mouse, which is significantly larger than it is, the prey soon becomes paralyzed, allowing the shrew to cart it off home for dinner. Scientists estimate that the “poison glands” of a single shrew contain enough toxin to do in about 200 mice. It might even be enough to kill off a small house cat. And if you are bitten, you might have a localized reaction, and you might even feel ill (depending on your sensitivity), but the likelihood of your demise from the bite is slim to none.

Our next largest shrew is the water shrew (seen in photo above), which is also the longest shrew living in the Adirondack Park. The perceptive reader has probably already deduced that this shrew likes the water. In fact, it has special foot features (feetures?) adapted for its semi-aquatic life: rather wide hind feet that are partially webbed, and stiff hairs lining the edges of its toes. These adaptations help the shrew navigate with relative ease through its watery habitats. If you find yourself in a bog, marsh, or shrub swamp, or wandering along the edge of a lake, river, pond or stream, you will be in water shrew habitat.

The rock, or long-tailed shrew has an exceptionally long tail and likes to live in rocky habitats. Perhaps this is why no one can agree on a common name – both these features stand out as characteristic of the species. And not just any rocky abode will do; oh, no. The rock shrew prefers lots of rocks and boulders that are covered with mosses. Mosses tend to prefer cool, moist sites. So, if you have mossy boulders and rocks in great deep piles, you might very well have rock shrews. It seems, however, that as interesting as this shrew is, there isn’t really a whole lot of information out there about it, so we’ll move on to the next shrew on our list.

And since we are going by weight class, the next shrew we come to is the smoky shrew, so named because of the color of its winter coat. You can tell you have a smoky shrew if its tail is bicolored: grey-brown above and yellowish below. None-the-less, it seems that in the summer smoky shrews can be mistaken for masked shrews if one isn’t paying attention. Some features to look for are a stockier build, larger ears and feet, and a relatively shorter tail. The smoky comes across as a bit lazy, though, for it prefers to use the tunnels made by other animals rather than digging its own. It also rarely digs burrows. Smokies are considered rather vocal animals, twittering as they forage and crying out with high-pitched noises when alarmed.

Masked shrews, like the other shrews, are semi-fossorial, spending a good part of their lives below ground. As such, they sport non-directional fur, long skinny bodies, long skinny snouts, little legs, tiny eyes, and nearly non-existent ear flaps. Like the short-tailed shrew, the masked shrew is found in most terrestrial habitats, and is fairly common. And like most shrews it must eat constantly. That’s the drawback of being a tiny mammal – you have to eat constantly to keep your speedy metabolism fed. Although insects and other invertebrates make up most of its diet, this shrew also eats soft seeds, salamanders and even baby birds.

And finally we come to our smallest shrew, the appropriately named pygmy shrew. Not only is the pygmy shrew one of the world’s smallest mammals (the smallest being the bumblebee bat), but it is also one of the rarest in the Adirondacks, based on the number of specimens captured. Despite its small size, it is often confused with masked shrews. Although a rather boreal species, the pygmy has been found as far south as North Carolina. It has a massive appetite, and its diet includes just about anything it can get its hungry jaws around.

While I have encountered my share of live shrews, both inside my house and out, most of my shrew findings have been in owl pellets. Every year we dissect owl pellets with school groups, and while most of the bones we find come from mice, shrews are probably the next most commonly found bones in the pellets. Two things make shrew skulls stand out immediately from mouse skulls: they are long and narrow, and they have tiny, pointy red-black teeth.

If you are interested in learning more about the shrews that live in the Adirondacks, I recommend D. Andrew Saunders’ book Adirondack Mammals.


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Ellen Rathbone is by her own admission a "certified nature nut." She began contributing to the Adirondack Almanack while living in Newcomb, when she was an environmental educator for the Adirondack Park Agency's Visitor Interpretive Centers for nearly ten years.

Ellen graduated from SUNY ESF in 1988 with a BS in forestry and biology and has worked as a naturalist in New York, New Jersey, and Vermont.

In 2010 her work took her to Michigan, where she currently resides and serves as Education Director of the Dahlem Conservancy just outside Jackson, Michigan.

She also writes her own blog about her Michigan adventures.

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