Connecticut’s white-footed mouse population amount divides experts

I unlidded the galvanized can where I store my birdfeeder’s sunflower seeds and two sets of bright black eyes were staring at me piteously, two sets of quivering ears, then two white-footed mice scrambling like mad to escape.

Luckily, the can was nearly empty. I lugged it to the door, tipped it on its side and the two scurried away. Whether they reentered the place and risked death by peanut butter-laden mouse traps was up to them.

It has been, at my house, a mighty mouse year.

I get them every fall and winter, trap a few and that’s that. This year, the trapping hasn’t stopped. I’ve lost count of the kills thrown on my compost pile.

There are two lines of thought here. One is the white-footed mouse population is on the high side of a boom-and-bust cycle. The other is that my old home and its old foundation hath many rooms for mice.

On the boom side of the argument is the research done by Chris Floyd, a teaching professor at the University of Rhode Island in Kingston R.I.

Floyd’s mammalogy class sets 50 outdoor traps a year to study whitefooted mice. Ordinarily, they catch a few — two, three, no more than six.

This year, they caught 24 in one night.

“There were so many that after a while, I told the students, ‘Just let them go,’ ” Floyd said. “We couldn’t ear-tag them all.”

There are stories, too — what’s called anecdotal evidence. Floyd said he saw two white-footed mice run right by him while walking his dog. Whitefooted mice are nocturnal. They generally do not scamper by day.

“To see two out is incredible,” Floyd said.

Jenny Dickson, director of the wildlife division of the state Department of Energy and Environmental Protection, takes the boom side of the discussion as well.

“Yes,” she said. “Anecdotally, they’re in my house. It seems to be a good year for them.”

Bob Scribner, the owner of Scribner Pest and Wildlife Control in Danbury, said he ordinarily gets calls from people complaining about mice in winter as soon as it starts getting cold.. This year, he said, he’s gotten more.

“The answer is, relatively, yes,” he said.

There are reasons why this might be. We’ve had two mild winters in a row, allowing more mice to survive and breed, which they do with abandon. A female can have 3 to 4 litters a year, with 4 to 8 pups — or pinkies — a litter

The DEEP’s Dickson also said the rainy summer allowed plants to produce a lot of seed and berries and fruit, all of which mice prosper on.

“Everything had a great growing season,” she said.

Lots of white-footed mice means, in turn, a good year for the predators that feed on them.

White-footed mice are extremely common in most of North America. That means they supply food for foxes, coyotes, owls and hawks. They also spread seeds and fungi. They make the landscape healthier.

Unfortunately, they make humans sick. They’re one of the main reservoirs for the bacteria that causes Lyme disease. Black-legged ticks feed on white-footed mice for one blood meal, pick up the bacteria. When they bite humans for another meal, they spread it to us.

Their droppings can also carry Hantavirus, a rare but serious flu-like illness that humans get by breathing dust contaminated by mouse droppings and urine.

Dan Schwarzbeck, owner of Got Wildlife?, a pest and wildlife control company serving the tri-state area, said people should always spray mouse droppings with bleach or disinfectant before removing them.

“Never sweep them up,” he said.

There’s also the alternative answer. There’s been no mouse explosion. People have mice in their homes because they always do in winter

Richard Ostfeld, a disease ecologist at the Cary Institute of Ecosystems Studies in Millbrook, N.Y., has studied the ecological connections between mice, ticks, deer and forest systems for years.

In an email, Ostfeld said mouse populations in the institute’s study areas in Dutchess County were “extremely low” May through November, largely because there was a poor acorn crop in 2020.

“Mice do start to enter homes, sheds, garages etc., when the weather turns quite cold,” Ostfeld said in the email. “So this might be what folks have been seeing lately, but it isn’t necessarily an accurate indicator of overall population size.”

Which is what Schwarzbeck sees.

“Once it gets cold,” he said, “We get calls.”

Contributed photo A white-footed mouse.