CHICAGO — Brittney Allen was walking her dog, Darla, in Avondale when a squirrel leaped over her head onto a low-hanging tree branch.
“I screamed, and Darla was looking at me like, ‘What is going on?’” Allen said. “Recently, I’ve noticed tons of squirrels darting around, doing weird parkour moves. They ricochet off fences and into the trees. I’ve never seen anything like it.”
It turns out squirrels are doing backflips to celebrate the fact that oak trees have surprised them with a huge influx of acorns this fall.
Oak trees are masting right now, which means they’re dropping more acorns than usual, said Jalene LaMontagne, a biology researcher and professor at DePaul University.
“There’s a big oak tree near the fence where [the squirrels] all hang out and there’s acorns littered all over the ground,” Allen said. “It’s like their little hotspot where they find all their stuff.”
Masting events usually happen about every three to six years, but oak trees avoid settling into a predictable routine so that they can keep squirrels on their toes, LaMontagne said.
“The time that masting occurs varies so that animals can’t figure out trees’ timeline and eat all the acorns,” LaMontagne said. “If the squirrels could predict when trees typically mast, they probably would have evolved to have their babies around that time. If they ate all those acorns, there’d be no more oak trees.”
Squirrels are active year-round, so their survival throughout the winter depends on how many supplies they can store away before the cold weather eliminates some of their food sources, LaMontagne said.
From a squirrel’s perspective, a random surge of their favorite food has miraculously appeared just in time for them to stock up before it gets cold, LaMontagne said.
The plethora of acorns seems to have made squirrels more confident, said Tim Rosado who’s noticed droves of squirrels foraging in Riis Park, 6100 W. Fullerton Ave.
“The squirrels have gone wild,” said Rosado, who lives in Belmont Cragin. “It’s like they’re not afraid of humans anymore. They used to be more skittish, but now they’re just hanging out, eating acorns or gathering them and they’re not bothered by anything else.
“They’re like, ‘Well, we have an abundance of acorns so we don’t care about you,’” Rosado continued.
Even Darla noticed that something weird has been going on, Allen said.
“My dog won’t walk over the parts of the sidewalk where the acorns are because there’s so many and I think they hurt her little feet,” Allen said. “She doesn’t go after the squirrels, but she’s definitely more interested in seeing what’s going on with them.
“I feel like she’s probably wondering, ‘Why are there so many?’”
There’s such a surplus of acorns because the oak trees have been preparing to release them for years. Oak trees are pollinated by the wind. So, after a few particularly windy seasons, the trees have stored up enough resources to drop a plethora of seeds, LaMontagne said.
“The weather in previous years will cue trees that it’s time to reproduce,” LaMontagne said. “If a tree drops a lot of acorns this year, they won’t have the resources to do it again next year.”
Squirrels, birds and insects eat most acorns in normal years, LaMontagne said. The main point of masting events is to increase the chance acorns settle somewhere to grow into new trees.
“During masting, there are so many acorns that they can’t possibly eat them all,” LaMontagne said.
So many, in fact, the acorns are piling up on the sidewalks and against bus stops, Rosado said. Plus, there are tons of little scraps left behind by feasting squirrels who can’t be bothered.
“It makes sense the squirrels are busy running around and trying to gather everything,” Rosado said. “I find it interesting that the acorn situation has given them a lot of supplies for this year. That’s good for them, I guess.”
Luckily for oak trees, squirrels are terrible at remembering where they’ve hidden their acorns, LaMontagne said.
“Sometimes squirrels will store acorns in the ground and cover them up with some leaves, then forget about them,” LaMontagne said. “So they’re actually helping out the trees by dispersing their seeds.”
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