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SALT LAKE CITY — Warming temperatures are luring the common house mouse and its wild relatives out from their dens and turning hordes of them into maurading trespassers.
"You could say they are invading," said Terry Messmer, a wildlife specialist with the Utah State University Extension Service. "There seems to be an eruption over the last couple of weeks. I've had a half-dozen calls in just the last week or so from people panicking that these mice have made it into their home."
Culprits include the common house mouse and the deer mouse, or field mouse, which typically stays out in the wild and "dens" up until it gets warm.
But Messmer said the temperate January days have opened doors — literally — to these creatures seeking food and shelter.
"There's been doors left open, screens left open and mice don't need that kind of invitation. If you have any kind of gap or opening that is a quarter- to a half-inch, they are pretty good at gnawing their way in. If they can find an opening, they are pretty inquisitive."
Once a mouse or two has maneuvered its way into a house, there can soon be a mischief of mice about — that is, mice are fast reproducers and soon there will be babies. Lots of them, Messmer warned.
There's been doors left open, screens left open and mice don't need that kind of invitation. If you have any kind of gap or opening that is a quarter- to a half-inch, they are pretty good and gnawing their way in. If they can find an opening, they are pretty inquisitive.
–Terry Mesmer, Utah State University wildlife specialist
“If you start seeing them around in the daytime, this could indicate you have several mice in the house,” he said. “And mice have a very high reproductive rate. Within a matter of months, a pair of mice can produce several litters. These litters can also start producing mice within two months of birth.”
Messmer said the best way to control mice is to keep them from getting in by sealing all openings larger than a quarter-inch. Homeowners should use heavy materials like concrete mortar, sheet metal or heavy gauge hardware cloth.
Food should also be protected, and leaving dog or cat food out will encourage mice as well.
Mice carry diseases and are destructive, so they should be safely removed as soon as possible, he warned.
As it turns out, no one has really come up with a better way to build a mouse trap than the simple, wooden, old-fashioned kind. Bait it with something like peanut butter, and line the traps along the wall, where mice tend to roam.
"Mice have terrible eyesight but a great sense of smell."
Those simple traps baited with peanut butter or bacon work better than poison because the mouse is trapped on site, rather than going off to die (and decay) somewhere undetected in the house, Messmer added.
The extension service has also put together a pamphlet with homeowner tips on mice, how to detect damage from mice and ways to control them.