To most people living in the mountains, any small fuzzy animal less than three inches long is a mouse. Rarely do these tiny invaders of home and tent warrant any further attention. Their role in life is to frustrate us as we awake from the sounds of them scurrying atop our nylon sleeping bags. Despite their diversity, they've been lumped under the name "mouse", a nickname which covers an amazing diversity of creatures.
House mice are the most well known and least admired of this group. Their ability to get into just about any structure is something to be both admired and abhorred. A night spent in one of the many mountain hostels or huts will often reintroduce you to these little guys--that is if you have been away from their presence for too long. House mice are a social animal and often live in colonies, usually indoors to avoid the harsh weather that we occasionally seem to get.
Along with their relative, the deer mouse, the true mice form one of the least popular groups of rodents. Most of us have had the opportunity to forcibly evict one of these tiny rodents out of our humble abodes at one time or another.
Similar to the mice, and often unceremoniously lumped together with them, are the voles. They can be distinguished from mice by their much smaller ears and eyes and shorter tails. These small animals prefer more natural settings to the formal decor within your home. They manage to deal with winters assault by building tunnels beneath the snow to provide them easy movement while insulating them from the unpleasant cold above the snows. Often, I've come across them as they scurry across the snow for a short distance during their constant search for more and more food. They eat plants of all kinds, from flowers to all manner of shrub. They are also quite agile in their culinary pursuits and will climb all around in a shrub to find the most succulent morsels.
In this area, the two most common voles are the red-backed and the meadow vole. The red-backed has been named for the obvious reddish band along its back. Keep an eye out for them while out ski touring and you may catch a glimpse of them as they scurry across the snow. At such times they seem remarkably fearless and will even run right over your ski boot if it happens to fall within their chosen path.
Perhaps the most voracious of our tiny residents are the shrews. Looking like a small mouse with a long pointed nose, shrews stay active year round and are constantly on the hunt for insects to eat. Unlike the mice and voles, shrews are not interested in munching on a flower or getting into your cupboards, they are ardent hunters and spend most of their waking hours trying to fill their ever hungry belly's. Since they have an incredibly high metabolism--their tiny hearts beat at over 1,000 beats per minute--they have to eat their weight in food every day simply to survive. Needless to say this leaves very little time to relax.
While some of these small residents may be unpopular in your kitchen, they form a vital link in the areas food chain. Eaten by just about any other animal that eats meat, they reproduce rapidly and as a result their populations tend to boom and bust. However, without them, we may not have some of the more exciting local hunters like the coyote. They may be small, but they sure are tasty to a hungry hunter.
To survive long periods of winter, small animals need to utilize strategies that differ from those of their larger mamalian cousins. Their small size can function as both an advantage and a liability. For instance, small animals lose heat more readily than do large animals. As a result, they must develop strategies to compensate for this increased heat loss. One ideal strategy is to avoid the cold temperatures as much as possible. This is accomplished through their leaving the world above the snows during the winter months and retiring to tunnels created beneath the snowpack.
Near the ground, the temperature is much warmer than above the snow and this allows mice and their relatives to insulate themselves from the extremes found only a few feet above their tiny heads. Within these tunnels, they are able to do all the foraging they need, and only occasionally do they (particularly voles) pop their heads above the snows and scurry a short distance to some unknown destination. These above ground wanderings are kept to a minimum as they not only expose them to the potentially nasty weather, but to the eyes and ears of hungry predators.
Many species of mice become much more social during the winter months. Species that would normally guard their territory jealously during the mating season, will tend towards large groupings in the winter in order to reduce heat loss. Deer mice are one of the most antisocial of creatures during the summer, but in winter will not only allow other deer mice into their den, but will even allow other types of mice to huddle together with them to stay warm. Shrews don't follow this strategy and still remain solitary hunters of quality insects.
During the cold months these subnivian, as animals living beneath the snow are known, animals also restrict their daily activities. Watching a mouse in the warm summer sun can be quite interesting as they wander, seemingly without reason, for long periods. When the snow flies, these wanderings are reduced to an absolute minimum. All expenditures of energy must be necessary. The building of tunnels also helps to reduce the amount of energy needed to forage beneath the snows.
While these strategies would seem to insulate mice and voles not only from the cold, but from predators, it's surprising to witness the ease with which many predators find these seemingly safe animals. Finely tuned ears can detect the slightest motion beneath quite a bit of snow and so coyotes and owls still find themselves with an ample supply of tiny treats to aid in their winter survival strategies. As one animal develops a strategy to ensure it's survival through the vagaries of mountain life, those animals that survive by hunting them develop counter-strategies. This co-evolution is integral in the maintenance of the many, highly developed predator-prey interactions that take place on a daily basis throughout the bow valley.