Boom in mouse population has implications for Lyme disease, basements, predators
By
Todd
McLeish
Christian
Floyd, a URI teaching professor who studies rodents and other small mammals,
said that his mammalogy class set 50 box traps in a forest to the north of the
Kingston campus this fall, and in one night they captured and released 24
white-footed mice. They typically capture no more than 6. The students also
captured many more images of white-footed mice on trail cameras than usual.
“Even
in down years, this mouse is the most abundant mammal in Rhode Island,” said
Floyd. “They’re everywhere – in fields, forests, farms, homes, everywhere.”
According to Floyd, mice typically live short lives because they are the primary prey for many common predators. But because females can reproduce just 30 days after being born, and they can produce 3 to 4 broods of 4 to 8 babies per year, their populations can grow rapidly if the conditions are right.
“A
white-footed mouse outbreak is all about survival,” he said. “They have a high
rate of being predated, but they seem to have survived better this year for
some reason. The predator populations don’t really change, but what does change
is their winter survival rates. The last couple winters haven’t been very
severe, and that’s one important factor.”
Floyd
said that the abundance of acorns in the last two years has also provided
plenty of food to carry the mice through the winter months.
“Acorns
are a major food source. They’ll eat seeds and other parts of plants, but it’s
mostly acorns, and acorns were abundant this year and last year,” Floyd said.
“That influences the size of their food cache for the winter.”
The
combination of high food availability, mild winters and their typically high
reproductive rate has led to a banner year for mice.
“What
that means is a higher risk for Lyme disease and babesiosis,” he said. “Both
are transmitted by black-legged ticks, but mice are the primary reservoir for
the bacteria that cause those diseases. Mice transmit Lyme and babesia to the
ticks.”
Floyd
said that homeowners should also expect a greater number of mice than usual in
their basements and garages this year.
“Since
the weather turned cool, I’ve been catching about one mouse a day in my
basement,” he said. “I’m up to 25 already. And that’s a problem, because they
chew the wiring, they make a nest out of the insulation, and they get inside
vehicles.”
An
abundant mouse population isn’t all bad news, however. Just as the abundance of
acorns probably contributed to the increase in the mouse population, the
abundance of mice will likely give a boost to wildlife populations that feed on
mice, like hawks, owls, foxes and weasels.
And
by burying seeds and mushroom spores, mice also play an important role in
supporting the regrowth of forests. So more mice could lead to healthier
forests. But a lot will depend on the weather this winter.
“It’s
already looking like we’re going to have another mild winter, and that’s a good
sign for white-footed mice.” Floyd said.