BOZEMAN, MT--Ask Rick Douglass, a man who has handled deer mice about 30,000 times, why the mouse goes into the house.
Douglass, a biologist at Montana Tech in Butte,Mont., wants to know what brings the rodents into Montana houses, barns and outbuildings, where the likelihood of spreading hantavirus to humans is far greater than in the field.
Hantavirus is a respiratory disease characterized by flu-like symptoms. Humans can catch the virus from deer mice urine, droppings, saliva or nesting materials. Ten Montanans have had the disease since it was first discovered in 1993. Three have died.
Most people see deer mice in the field or as road kill, but "you're not going to get the virus driving down the road," Douglass said during a recent lecture at Montana State University in Bozeman. "If you're going to get sick, you're going to get sick in a building."
That's why Douglass and MSU microbiologist Cliff Bond started the Mouse in the House study two years ago. In what he calls the "hotel experiment," Douglass set up three identical modular buildings at ranches near Butte and Cascade, Mont. The buildings have holes in each side, a grid on the floor and fluorescent dust at every entry. The dust coats the rodents so researchers can count the squares the mice visit.
One building is baited with peanut butter, one has cotton nesting material, and the third is empty.
"It's clear that they visit buildings for food, much more so than for bedding or shelter," Douglass said. The ones that go in the empty buildings may be drawn by the scent of a mate, a theory he plans to test in the future.
What's astounding, he added, is how quickly the mice find the buildings--within 15 minutes after dark.
"If you leave your deck door open, you're going to have deer mice going in and out and your cat's not going to see them," he said.