Monday, March 10, 2014
By Ken Allen
Observant folks can always amuse themselves with something to gawk at in nature, even in our winter yards, and a perfect example occurred not long ago on an early morning after a late December snow dusting.
While standing inside our garage, I lifted the sliding door and noted small rodent tracks in the driveway, leading to a small crack on the bottom corner between the doorjamb and concrete sill. The tiny opening looked too small for a cricket to squeeze through, but no tracks led away from the door – just to it. Clearly, the mouse had entered the building – mousetrap time.
I assumed my visitor was a house mouse (Mus musculum), a good guess. A white-footed mouse (Peromyscus leucopus) leaves the same size tracks with four toes on the front feet, two straight forward and two lateral, and five toes on the back feet, three pointed forward and one at each side. However, house mice are far more common at our home than white-foots.
The next day, while watching a technician repair my snowblower in the garage, I noticed a dead house mouse in the very center of the floor. I mentioned it but gave no details about species, thinking the guy would stereotype me as a geek.
The dead rodent gave me pause for thought, though. This species is indigenous to Asia, and many centuries ago, it migrated to Europe before hitching a ride west on early ships, carrying settlers to North America.
This introduced species established itself in the New World in the early 1600s and eventually expanded all over the continent, even to Alaska. I wondered why a member of this successful species had died of no apparent reason in my semi-heated garage.
My curiosity about rodents began in my early 20s while sitting on deer crossings. The scratching, rustling sound of Maine’s small rodents beneath dry leaves often caught my ear, but not my eye.
In those days as now, much to my annoyance, little rodents in the wild seldom showed themselves. They stay under leaves, ground plants or fallen trunks to hide from avian predators, so my hunting vigils back then taught me nothing about identifying rodents.
However, my house cats brought these critters home to show off on doorsteps or in driveways, offering me a chance to scrutinize them. Many species carry diseases, so it was an eyeballing exercise. The topic fascinated me, though, so curiosity spurred my observations.
Most people call small rodents “mice,” but in Maine, we also have voles, lemmings, shrews and moles. Folks can often identify moles and shrews by their pointy noses and squinty eyes, but voles and lemmings take more scrutiny for casual observers to ID.
This is an unscientific rule of thumb, but mice species normally have long tails, while voles, lemmings, shrews and moles have short tails. Certainly, a long-tailed shrew (Sorex dispar) is a common exception, hence the name.
One Maine rodent intrigues me because it remains quite active in winter and ranks as one of the most abundant mammals in the state – meadow voles (Microtus pennsylvanicus). They live around my shrubs in winter, and often at dusk or days with low storm clouds, they offer me a brief glimpse – cute as rodents go – like a Disney cartoon.
Northern short-tailed shrews (Blarina brevicauda) have five toes on each foot and intrigue nature types – a rare mammal with a poisonous bite. A venom secretion from glands between the bottom incisor teeth runs into the fresh bite of tiny animals and invertebrates – often insects and earthworms.
This evolutionary quirk allows short-tails to kill larger rodents for food, and in “Wild Mammals of New England” (DeLorme Publishing – 1977), Alfred J. Godin claimed this shrew’s poison can kill a rabbit.
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