It’s not your imagination: there really are more squirrels scampering around Maine this summer.

Skeeter, an adult eastern gray squirrel, chomps down on a snack Tuesday. Maine and other states in the Northeast are experiencing an “irruption,” or boom, in the resident population of eastern gray squirrels.

And a lot of them are ending up dead on the sides of the state’s roads.

Drivers in the southern Maine have found themselves dodging the small rodents as they dart across streets and steering around squashed squirrels that didn’t make it to the other side. There have been so many squirrels, in fact, that motorists have taken to social media to ponder whether some unseen force of nature is at work.

The explanation, it turns out, is not all that mysterious.

A bumper crop of acorns, pine cones and other staples last year led to a bit of a population boom for small rodents, including squirrels. And it’s that time of year when the young mammals are setting out on their own in search of new territory and food.

Sarah Haggerty, a conservation biologist at Maine Audubon, admits she probably notices squirrels more than the average driver, but even she has been surprised by the number she’s seen this year. A few weeks ago, the booming population was evident as she drove from upstate New York to Maine – especially in New Hampshire, where it seems the squirrel population is doing particularly well.

“I was dodging them on the highway,” she said. “It was crazy.”

Haggerty said squirrels and other animals do have these “population irruptions,” which means a population spike associated with favorable environmental conditions. In the case of the squirrels, it seems plentiful food sources and protective snow cover over the winter are contributing to the irruption, she said. During the past two to three weeks, young squirrels have been venturing out in their habitats, which are often bisected by roads.

An adult eastern gray squirrel peaks out of a box Tuesday at the Center for Wildlife as Libby Peck brings it food. The squirrel was found injured in a road and brought to the shelter in Cape Neddick, which treats injured and orphaned wildlife, including squirrels that have been found after being hit by cars.

There are more than 350 species of squirrels worldwide, but the eastern gray squirrel is the most common in Maine. The rodents known for their bushy tails are diurnal, which means they are active during the day. That daytime activity is rare among wild mammals and makes them much more visible to people who spot them raiding bird feeders and darting across roads.

EXTRA ACORNS – AND A FOOD CHAIN THRIVES

Scott Lindsay, a wildlife biologist with Inland Fisheries and Wildlife, said there are likely two factors leading to the noticeable increase in squirrels in the southern half of the state: an abundance of acorns last fall and the arrival of the peak season for animal populations. This is the time of year when the first litter of squirrels are out on their own and the newest litters will be headed out soon, he said.

Last fall, Lindsay noticed the large number of acorns in southern and central Maine, which happens every five or six years.

“If that happens in the fall, any animal that feeds on or stores them for winter is at a real advantage,” Lindsay said.

A juvenile eastern gray squirrel is fed at the Center for Wildlife on Tuesday. Many young squirrels are found and brought in after leaving their nests when their parents get killed on the roads.

Rodents such as chipmunks, mice and squirrels benefit from the extra acorns, but animals higher up on the food chain such as foxes and raptors also benefit and could have stronger populations next year, Lindsay said.

“Any of the predators that feed on those rodents, and there are many, they’re all in very good condition right now,” he said. “It’s going to be a time of plenty for many mammals. Those small mammals, their pantries are going to be chock full of acorns.”

Curiosity about the squirrel population has been so high that the Center for Wildlife in Cape Neddick has been fielding extra phone calls from people wondering what is going on. The nonprofit center treats injured and orphaned wildlife, including squirrels that have been found after being hit by cars or babies whose mothers have died.

‘EXTRAORDINARY NUMBERS OF SQUIRRELS’

Executive Director Kristen Lamb last week filmed a Facebook live video to try to answer some of the questions posed by wildlife lovers concerned about the squirrels. The video was filmed inside the center’s baby mammal room as an employee hand-fed a tiny squirrel that had been brought in days before.

“We’ve seen extraordinary numbers of squirrels in the road,” Lamb said.

Lamb said the visible increase in squirrels this year is likely from a cyclical population boom that happens every one to three years depending on species. But the development of their habitat also is likely a factor, she said.

Kim Andre feeds a juvenile eastern gray squirrel at the Center for Wildlife on Tuesday.

“When we have a new road built, a new plaza, new housing, that cuts into their habitat,” she said.

For the past six years, Maine Audubon has used a network of citizen scientists to track animals – both dead and alive – on or near the state’s roads. The data is used to map places with high concentrations of animal road crossings and determine where things like fencing and under-road culverts can be installed to help give animals safe passage. Haggerty said it is too soon to see roadkill data reflecting a population spike.

The Maine Department of Transportation doesn’t track roadkill, but crews out on the roads have certainly noticed more of it this year, department spokesman Ted Talbot said. Crews clean up roadkill as they come across it or when someone asks, but there’s not much else they can do.

“They say there are more raccoon, porcupine, foxes, deer and gray squirrels showing up dead on or beside our roadways,” he said. “We’ll just keep cleaning them up.”

Gillian Graham can be contacted at 791-6315 or at:

ggraham@pressherald.com

Twitter: grahamgillian