30 Years Of Live-Trapping Data Show Mammal Species Moving Steadily North In Michigan - Mongabay

A new study shows that mammals in the state of Michigan are moving north because of climate change, pushing out other species on the way. Researchers studied the distribution and population of nine small mammals from live-trapping data over 30 years and notes from research museums covering the past hundred years. They utilized over 14,000 records covering the nine species.

"We're talking about the commonest mammals there, mammals that have considerable ecological impact," said lead author Philip Myers, professor of ecology and evolutionary biology at University of Michigan. "They disperse seeds, they eat seeds, they eat the insects that kill trees, they disperse the fungus that grows in tree roots that is necessary for trees to grow, and they're the prey base for a huge number of carnivorous birds, mammals and snakes. But we don't know enough about their natural history to know whether replacing a northern species with a southern equivalent is going to pass unnoticed or is going to be catastrophic. It could work either way.”

The study, published in Global Change Biology, found that the four species with the more southern range—white-footed mice, southern flying squirrels, eastern chipmunks and common opossums—were increasing in population, while the northern species—woodland deer mice, southern red-backed voles, northern flying squirrels, woodland jumping mice, and least chipmunks—faced declines.

After compiling and studying 14,000 records, the researchers looked for an explanation. "There's a lot more forest now than in the late 1800s and early 1900s, when logging and fires almost completely destroyed the forests of the northern Great Lakes region," Myers said. "But that doesn't work as an explanation for the patterns we see, because the species that are moving in and becoming more common are actually ones that do very well when forests are cut over."

EDIT

http://news.mongabay.com/2009/0513-hance_michigan.html

I don't think there were ever very many possums in Minnesota and all of a sudden they seem common. I was recently in Nashville (actually Franklin), TN and someone there mentioned that they're starting to see armadillos. -- Mostly dead in the middle of the road just like Jim Hightower said, but they never used to see them, at least in that part of Tennessee.