Meadow Vole Tracks & Tunnels
Tracking animals can be an elusive endeavor because so many things can alter the condition of the tracks. Have recent flurries erased the details of an imprint? Has the sun melted and enlarged a track? Was every toe registering? Did wind-blown snow cause the tracks to vanish into thin air? Was the animal walking, loping or tunneling or a combination of all three?
The reason you use more than just one track to gather information, such as the stride of the animal and the width of its trail, is that sometimes the individual tracks defy the hard and fast rules of some tracking guides. A commonly accepted generality is that Deer and White-footed Mouse tails leave drag marks, and Meadow Voles’ shorter tails don’t. However, in the right conditions, even a vole’s one-inch tail can drag (see photo), though not creating as long a line as a mouse’s tail would. The Meadow Vole whose tracks are in this photograph was loping along when it suddenly decided to seek cover under the snow and began to (try to) tunnel. Perhaps a predator instigated this behavior.
Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.
Tunnel Vents
Frequently you find a hole about an inch wide in the snow in the middle of a field, with no tracks going in or coming out of it. Logic tells you it leads to the subnivean layer – where the snow, warmed by the ground, sublimates into water vapor, creating a small space between the surface of the ground and the snow where the temperatures is relatively stable at 32 F. It is here that small rodents such as mice and voles create a maze of tunnels through which they travel from their sleeping quarters to feeding stations, undetected by many predators.
However, the lack of tracks into and out of this hole indicates that it is not an exit or entrance to the subnivean layer, but rather, it is a vent leading from the subnivean tunnels to the surface of the snow. Carbon dioxide from animal respiration as well as carbon dioxide released from the ground builds up to an unhealthy level in these tunnels. The holes we see in the snow are ventilation shafts, allowing the carbon dioxide to escape from the tunnels. The formation of crystals around the edge of the pictured vent indicates that warm, moist air from rodent lungs is rising up out of it.
Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.
Meadow Voles Soon To Begin Breeding
Under perfect conditions, with no predators, no deaths and abundant food, a pair of meadow voles (Microtus pennsylvanicus) could produce a million descendants in a single year. Because they are prey for nearly every meat-eating animal that exists, however, their population, while large, is nowhere near this.
Even though the number of meadow voles is relatively high and they are active day and night, year round, it is unusual to actually set eyes on one. What we do find, especially this time of year, are meadow vole signs in the snow: mazes of runways on the surface of the ground that are exposed as snow starts to melt, air-exchange holes originating in their tunnels and extending to the surface of the snow, tracks and entrance/exit holes to their tunnels.
The social behavior of meadow voles is about to undergo a seasonal change. During the winter, when they are not breeding, meadow voles are more social and commonly share their nests, probably to conserve heat. In another month, however, as breeding begins, females become fiercely territorial towards other females, and males are aggressively establishing dominance over each other. The peaceable subnivean meadow vole kingdom is about to come to an end. (Thanks to Susan and Dean Greenberg for photo op.)
Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.
Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.
Meadow Vole Nests
Meadow voles (Microtus pennsylvanicus), tiny mouse-like rodents, spend a majority of their time on the surface of the ground, particularly in moist fields filled with grasses and sedges. They have elaborate runways through the vegetation – well-worn trails about the width of a garden hose which they keep mowed down with their incisors. Latrines of small brownish-green pellets can be found intermittently along the trails.
Most meadow vole nests are constructed out of dried grasses, also on the surface of the ground, although they are sometimes built at the end of shallow burrows. When above ground, the nests are often located in the center of a grass tussock, where they are less apt to be flooded. When there is snow on the ground they are a bit easier to find, as the heat of the voles inside the nest melts away the snow, forming a chimney that sometimes reveals the nest below.
Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.
Mice vs. Voles
Mice and voles are commonly lumped together, probably because the differences between them are so slight. Both are small, furry rodents, but mice generally have large eyes, large ears and long tails (close to or greater than the length of their bodies). Voles have smaller eyes, smaller ears (often concealed in their fur), and shorter tails. Voles tend to be active day and night, whereas mice are mainly nocturnal. ( Meadow voles are commonly referred to as “field mice,” which tends to add to the confusion regarding these two groups of mammals!) There are five species of mice in New England (white-footed, deer, house, meadow jumping and woodland jumping), and four species of voles (meadow, southern red-backed, rock and woodland).
Meadow Vole Trail
Thanks to a dusting of snow we are suddenly privy to the comings and goings of the creatures we live amongst. Some animals are small enough to remain hidden once winter snows arrive, because they live in the subnivean layer between the surface of the ground and the snow. But when the snow is too shallow for them to create this network of tunnels, their movements are easily discernible. The pictured meadow vole trail shows where the vole initially tried (unsuccessfully) to tunnel under the snow (it wasn’t deep enough), at the bottom of the photograph. It then scampered over the grass until it stopped to rest for a moment, leaving a whole body imprint, including its short tail. It’s fairly unusual to see the entire body print of small rodents such as voles and mice, for they are so vulnerable out in the open that they rarely stop long enough to leave one.
Meadow Vole Tunnels
The melting snow has revealed a labyrinth of vole tunnels, which these little rodents excavate in the snow next to the ground in what is referred to as the subnivean layer. The tunnels are advantageous in several ways – they provide protection from the wind and cold, and keep the voles hidden from predators. Voles stay in these tunnels as long as the snow is deep enough, finding food in the form of seeds as they dig through the snow. Every once in a while you’ll find a dining area (close-up photo) where seeds, in this case, white ash, have been eaten. If you look closely enough you’ll also see some vole scat.
What Other Naturally Curious People Are Saying