The Big Thaw ushers in spring

Steve Lekwa

Snow cover in the yard west of our house was undisturbed for weeks other than by a few passing squirrels, rabbits and deer. There’s a wet swale through the middle of that yard that funnels a lot of runoff to a culvert intake near the street. A portion of the swale was often too wet to mow. I followed nature’s suggestion and planted wet soil-tolerant flowers there. It’s kind of a rough and wild little area now, but something pretty is in bloom there most of the time from spring to early fall. 

I was looking out the window a couple of days into the Big Thaw. Amazing patterns were beginning to appear in the yard in what had been mostly trackless snow. It was as if someone had gently drawn long branching paths less than two inches wide on the snow surface radiating across the lawn from the wetland garden. The artist had left no apparent tracks of their own as they drew. In fact, the artist’s tracks were below the pattern instead of on top of it. I was seeing the collapsing snow tunnels of meadow mice, or voles, that live in the thicker, matted cover of the wetland garden. 

These common rodents are seldom seen since they never come indoors and live their entire lives in tunnels under matted vegetation and underground. They are quite different from the mice we are more familiar with – the pesky ones that like to join us in our homes and buildings. They’re dull brown above and gray below. Their eyes and ears are small, their noses are short and rounded and their short tails are moderately furred. They eat mostly plants that they harvest and stack in little haystacks about the size of a softball. There is little grass to feed on in the matted vegetation of the wetland garden. The tunnels radiating out into the yard were their paths to feed on haystacks that they made after the first snow. 

Snow offered cover and protection that mowed grass did not. Meadow mice are a prime food item for almost all of Iowa’s native predators. They try to stay out of sight as much as possible to avoid those predators. Owls, foxes and coyotes usually locate them by sound more than sight. Hawks working the day shift depend on detecting motion, if not the animal itself. Least weasels and short-tailed shrews hunt them down right in their own tunnels. 

As with most species that are heavily preyed upon, meadow mice are very prolific. They breed nearly year-round. Gestation is only 21 days and a female can be pregnant and nursing at the same time. Multiple litters of from one to seven young are produced per year with numbers of young and litters per year influenced by seasonal conditions and the availability of food. 

A captive meadow mouse female produced 17 litters in one year. Two-month-old young are ready to breed. It’s important that they produce lots of young quickly because they seldom live much past a year. Their phenomenal reproductive potential helps keep many species going, including their own.  

Early spring isn’t an easy time for some species. Food supplies are near the annual low point. Native Americans called this season “the hunger moon.” Snow was advantageous to animals like meadow mice and rabbits. Mice could hide more easily. Rabbits, being lighter with broad feet, could run on top of snow while a pursing fox or coyote had to plow through it. Snow depth also lifted rabbits higher where they could nibble more tender bark from young trees and shrubs. Worms aren’t within reach yet. Early migrant robins and other songbirds will have to fight for what dried fruits and berries are left. Squirrels and birds had eaten most of the crab apples from my tree weeks ago. 

I know some of my wild neighbors may not agree, but I’m going to enjoy what’s left of this wonderful late winter/early spring thaw before the pendulum swings back the other way as it so often does at this time of the year in Iowa.