As a dozen students from the University of Michigan’s Biological Station in Pellston laid traps in the forest, they speculated about what their mammal census would reveal. Previous trappings had captured chipmunks, voles, and mice. This time around, the students—many of whom were first time trappers—would be happy to catch anything at all.
But Phillip Myers, a professor at the Biological Station and organizer of the census, was eager to capture one species in particular. When Myers began trapping surveys in 1989, he regularly caught woodland deer mice. Not long after, though, the number of deer mice captured dropped sharply, and in recent years not one has been caught. The species has apparently vanished from the forest.
The most likely cause for the decline of the deer mouse is climate change. Historically, northern Michigan has been common ground for both the deer mouse and the white-footed mouse, a closely related species. The deer mouse, a cold weather specialist, would dominate the forest floor in years with harsh winters, while the white-footed mouse would thrive in mild years. Myers speculates that as the area’s climate warms, white-footed mice are permanently replacing deer mice.
Myers’s suspicions were confirmed by the results of the trapping; of the 27 live traps that had captured a rodent, every one contained a white-footed mouse. It is uncertain what ecological consequences this evident change in species will bring.
Although disappointed that no deer mice were captured, the trappers made the best of their catch, and students enthusiastically posed for photos with the frisky beasts after Myers had weighed and measured them. Upon release, the mice demonstrated their ability to lay claim to new habitat as they scampered onto heads and up pant legs in their quest for shelter.
By Kyle Anderson