Last year's mild winter and a bumper crop of nuts have caused an apparent explosion in the squirrel population in patches of the country, bewildering fruit growers with their ravenous appetites, littering highway shoulders as roadkill, and keeping homeowners and pest control experts busy.
In southern Vermont, Clarence Boston said he hasn't seen such an infestation of pests in the 33 years he has been an orchardist on 60 farms in five states.
The squirrels wait until his apple crop is nearly ripe to swarm into the trees from nearby forests, sometimes eating half a tree's fruit in two or three hours. Sometimes, the squirrels will take only one bite, but the teeth marks make the apples worthless for retail sale.
"It's leaving me reeling. I'm sort of used to getting kicked around; I'm a farmer," said Boston, who estimates squirrels destroyed about half of his most profitable variety of apples following a season already made tough by the weather. "I was not expecting the next plague to be red squirrels."
Biologists know squirrel populations have rare but periodic "eruptions," when conditions coincide to produce abundant foods that fuel the fast-reproducing animals. This year's squirrel boom in parts of Vermont followed two seasons of bountiful acorn and beechnut crops and last year's mild winter.
In addition to eating up cash crops, squirrels can also prevent future harvests by "girdling" trees — eating away a band of bark around the trunk, causing it to die.
At South Carolina's Clemson University, gray squirrels have been so abundant in the past several years that they have killed more than 100 mature trees, said Greg Yarrow, chairman of the school's division of natural resources.
The school has experimented with non-lethal squirrel-control methods, including capturing and then injecting them with birth control chemicals. Another, less labor-intensive method has involves leaving chemical-laced bait that inhibits reproduction.
"In this state we are getting increased calls of problems," Yarrow said. "I know it's similar in other states. ... It's all food-related."
The same conditions are contributing to increases in other rodents, such as red squirrels and certain species of mice, experts say.
Experts noting an increase in squirrel populations include Paul Curtis, an associate professor at Cornell University's Department of Natural Resources and a pest management expert. Such eruptions are rare but noted in historical literature, he said.
"This is the first one I've heard of," Curtis said. "I've been here in New York state for 20 years."
Trying to get a precise measurement of the scope of the infestation is difficult. The population booms appear to be happening in some places, but not others.
Curtis said he has heard of problems in New York's Hudson Valley, north of New York City, but not in western New York. Similar booms have been reported in New Mexico, and squirrel hunters in Indiana and Ohio are expecting banner seasons. But hunters in Pennsylvania are being told it could be a tough season.
In Vermont, at least, the plague is expected to end this winter. After two good nut seasons, this year saw poor acorn and beechnut crops. That could be contributing to high activity as many squirrels look for food elsewhere, Hammond said.
For farmers, the beginning of the end is of little consolation in the here and now.
Before this year, John Barber never had a problem with squirrels at his 25-acre Apple Hill Orchard in Whitehall, N.Y. Now the animals are building nests in his trees and sampling different varieties of apples as the fruit matures, staying one step ahead of his pickers.
He estimates, conservatively, that he is going to lose 15 to 20 percent of his crop.
"Usually your best fruit is the fruit that's fully exposed to the sun; it gets the best color to it," Barber said. "Your size is usually out on the upper canopy of the tree. That's what they're doing; they're climbing up into the upper canopy."
Farmers aren't the only ones reporting problems.
Drivers are dodging squirrels that dart across roads or skirting ones that are killed while crossing. Hammond said he has seen carcasses on roadsides from Vermont to Connecticut.
Squirrels can also move into attics and build nests, creating a mess with droppings and urine. People commonly complain they can hear the pests scurrying through their attics at 4 a.m. They'll chew through wires, which can cause fires, said Dan Schwarzbeck, owner of the pest control company Got Wildlife? in Newburgh, N.Y.
His business, which does both commercial and residential pest control, has been getting about 60 to 120 calls a week about squirrel problems ranging from New York's Dutchess County to central New Jersey, by far the most in the 10 years he has been in business.
He sees all kinds of squirrels — gray, red and even flying squirrels, which don't really fly but have a flap of skin that helps them glide from tree to tree.
"The gray is the most destructive and the widely spread. We get the flyers, but it's in select areas," he said. "The gray, you can get them in urban, you can get them in cities, rural it doesn't matter."
Boston, the Vermont orchardist, is also a pest control consultant for orchards.
"I am somewhat stunned. You get used to looking at disasters," he said. "It just happens, but this one is new. It's different."