This story by Liz Sauchelli was published by the Valley News on May 27, 2020.
Earlier this month, Sean Ogle discovered a chipmunk in the greenhouse at his Royalton home.
“It was in the trays, maybe eating the seeds,” said Ogle, who serves as the trail programs director for the Upper Valley Trails Alliance.
Ogle opened both doors of the greenhouse and chased the chipmunk back outside.
“There’s just more chipmunks than usual and not more squirrels,” he said, noting that he likely lost a few plants due the chipmunk’s intrusion. “I feel like I’ve seen them everywhere.”
Anecdotal evidence — and last year’s abundant acorn crop — indicate that it’s a strong year for the pint-sized rodents. Acorns are part of the mast family, which refers to the seeds, nuts, berries and buds that trees produce and wildlife eat, including beechnuts.
“This is actually one of the first years where I can remember that I saw chipmunks in every month of the year,” said Matthew D. Tarr, extension professor and wildlife specialist at the University of New Hampshire Cooperative Extension.
In addition to a good acorn crop, this winter’s mild temperatures likely played a role in their survival.
“Chipmunks had a really easygoing winter,” Tarr said. “I would say that anecdotally, I’m observing a fair number of chipmunks this year. That fluctuation year to year is pretty typical. It’s just a natural part of the cycle.”
It’s possible that chipmunks are making up their population numbers from years past.
In fall of 2017, the mast crop was plentiful, which meant that rodents were able to put away a lot of food to survive the winter, said Steve Faccio, a conservation biologist at the Vermont Center for Ecostudies. That led to a strong 2018 breeding season and an increase in their population numbers.
However, the 2018 mast crop wasn’t nearly as strong, which meant more rodents were competing for fewer resources, which led to more squirrels on the roadsides and more mice getting into homes. The rodent population was on the lower side going into 2019.
“Now those populations are slowly rebounding,” Faccio wrote in an email. “Whether or not there is a plentiful food supply this fall will determine if their populations will continue to grow, decline, or remain steady.”
Chipmunks breed twice a year: Once in the spring and once in late summer and have five to eight kits per litter. They work to store away food for the winter.
“Chipmunks aren’t true hibernators, but they go into periods where they’re not feeding. They do have to store food underground,” Faccio said in a phone interview. “The chipmunks are active right now because this is their spring season, but it could be because people are around their homes rather than their offices, they’re seeing them.”
Since chipmunks are mammals, they can be susceptible to rabies, but it’s quite rare, Tarr said. They can also be carriers of ticks and, with them, Lyme disease. Chipmunks are omnivores, meaning they primarily feed on nuts, seeds, fruit, plants and insects.
“One thing that is probably surprising to most folks is chipmunks are very important predators to songbird chicks when they’re in the nest,” Tarr said. “In years when the chipmunk population is high, nesting survival of songbirds is low.”
An influx of chipmunks can also have an impact on their predators, including red-tailed hawks, foxes and bobcats.
“They all will eat chipmunks so that’s an abundant food resource that many predators will benefit from,” Tarr said, adding that research has shown that a year after a rodent population boom, young hawks have better survival rates. “They’re able to provide their young with a decent amount of food so more food means a better chance for survival.”
The chipmunks create extensive underground burrow networks that allow them to store food in addition to escape from predators.
“I think they may help themselves to some produce on occasion if it’s available, but I don’t think they’re well-known to do as much damage as other rodents like meadow voles or a few others,” Faccio said. “I don’t think of chipmunks as getting into homes as much as mice or flying squirrels, which are really good at getting into attics.”
Danielle Allen, owner of Root 5 Farm, said that she has noticed more chipmunks around the Fairlee farm, as well as an abundance of acorns from the oak trees on the property.
“They don’t seem that interested in our crops. They’re just more up around the barn and the house,” Allen said. “We often will see squirrels too. But this year we’re not seeing the squirrels, we’re just seeing the chipmunks.”
By this time in previous springs, Catherine Greenleaf, owner of St. Francis Wild Bird Hospital in Lyme, has usually cared for a few chipmunks, but as of last Friday, she hadn’t taken any into her care, despite noticing the increase in their population.
“This year I have not had a single call for injured chipmunks or orphaned babies,” Greenleaf said. “In years past, I received a lot of chipmunks where they were nicked by a car tire. They usually do quite well if they’re treated right away. They’re not easy to catch even when they’re injured. They’re very fast. They have to be in really bad shape to be caught.”
One thing that has puzzled wildlife observers is the lack of squirrels, which also feast on acorns.
“There’s no real reason why we would expect a big abundance of squirrels and not chipmunks. They’re all sort of responding to the same types of factors,” Tarr said. “Chipmunks are part of the natural system and to the best that we can appreciate changes in their numbers and appreciate what they do, that’s how we can try to live in the balance with many of the wildlife species that call New Hampshire home.”