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Backyard Chipmunks Living the Good Life

Chipmunk_cheeks.jpg
Illustration by Adelaide Tyrol

Each fall day he appears with a skinny face and leaves with ballooned cheeks. Over and over, he fills his cheeks and runs away to empty them. Our eastern chipmunk, it seems, is living in a good neighborhood. Our bird feeders provide him with an endless supply of sunflower seeds.

Impossible to count as he gathers them, the seeds make me wonder how many he carries on each trip. University of Vermont biology professor Bernd Heinrich pondered the same question. While examining a road-killed specimen, he found that he could stuff 60 sunflower seeds in one cheek, about a heaping tablespoon.

Chipmunks can hoard up to 8 pounds of seeds for the winter. So how many trips would the chipmunk have to take to fill up his storehouse? I weighed 120 sunflower seeds on a kitchen scale. At 2 ounces a mouthful, it would take him just 64 trips.

Sometime in November, I noticed that our resident chipmunk was no longer making trips to the seed market. And now standing on frozen ground and a bit of snow, I imagine him lying curled asleep in his nesting chamber. The main tunnel is perhaps 20 to 30 feet long with several full granaries, sleeping quarters, and separate escape tunnels. But what is it actually doing down there in the dark for five months?

Eastern chipmunks are restless hibernators. They don’t just sleep away the winter months. Chipmunks live off their seed hoard. Unlike other mammals such as bats, chipmunks don’t lay on fat for winter. Instead, they rely on good food stored in the pantry. All winter long, chipmunks eat and chill out, eat and chill out. And not just “chill out” in the sense of kicking back. They really do chill out by falling into torpor for stretches of up to eight days. Torpor is characterized by reduced body temperature, oxygen consumption, heart rate, and breathing, which all lead to much lower energy use. It makes a mouthful of sunflower seeds go a long way.

Many animals enter torpor during times of resource scarcity. When things get tough, they shut the system down and wait for better times. But torpor can have serious physiological costs. It’s not easy on the body in the long run, but it does allow for short-term survival. Individuals that have good energy reserves may not enter torpor as much as those that may need to stretch their food stores a bit more.

Each arousal from torpor is also energetically costly. Arousals can account for 80 to 90 percent of total energy expenditure each winter. But they can’t be avoided: long bouts of torpor can depress the immune system, cause dehydration, memory loss, and damage to tissues through oxidation. As an animal cools down, the circulation of antioxidant enzymes and vitamins are slowed, resulting in oxidative damage to tissues over time.

Daniel Monroe and his colleagues from Sherbrook University in Quebec thought that chipmunks might be faced with a cost/benefit trade-off. They can benefit in the short-term by going into deep and prolonged torpor to allow for energy savings in lean times, but they risk long-term physiological damage to their bodies from staying in torpor for too long if conditions stay rough.

They set out to test this with free-ranging, wild chipmunks using miniature data loggers that measured skin temperature mounted on tiny collars that the chipmunks wore around their necks, a proxy for internal body temperature. Chipmunks in the summer had skin temperatures that averaged about 99 degrees F. In midwinter, they averaged 97 degrees F when not in torpor, in a chamber that was usually below 50 degrees F. Those on a natural diet spent a total of 104 days in torpor with an average skin temperature of just 48 degrees F, while those fed on a diet of black sunflower seeds and peanuts only spent 13 days in torpor with a skin temperature of 72 degrees F. Clear evidence that chipmunks could adjust the depth and duration of torpor according to the size and composition of their food cache.

They also found that male chipmunks are more responsive than females to food supplementation. Males probably use more food during the winter to ensure that they have maximum reproductive capacity for early spring mating. Females, meanwhile, maintain deeper, more prolonged torpor to conserve their food cache for pregnancy and lactation during the early spring before fresh food is available.

The chipmunk in my backyard feeding on sunflower seeds has a diet far higher in fatty acids than those in the woods eating acorns and beechnuts. And because nut crops wax and wane over the years, woodland chipmunks may also have a smaller hoard most years. My backyard chipmunk is guaranteed a steady supply of sunflower seeds that contain 30 to 50 percent fat. With the pile of seeds that our backyard friend has, he’s surely living the good life right now, underground.

Discussion *

Oct 03, 2021

I’m baffled. The last two years I’ve gotten a chipmunk (the same one?) use to me. Last year it even took nuts from my hand. This year I just left them. It recognized the sounds of the doors when I went in and came out and it popped out waiting for the almonds. But I didn’t try to get it to get closer like the year before. More skittish than last year. It clearly knew I was providing, but took off after stuffing its jaws. It’d come back like that over and over. I haven’t seen hide nor hare of it in over a month. It’s October now. There were two of them that’d come out a few times. I think they were a couple! Anyway, does anyone have an idea why they would suddenly stop showing up? Carl.

Carl
May 11, 2020

Somewhere I read chipmunk love apples so I set some pieces out “pouch” size. Notakers.. I then set same apples combined with sunflower seeds. They cleaned out the seeds and left the apples untouched..Now we have verified field data!

Bob Burns
Aug 15, 2019

I have 3 or 4 that visit my yard 2 that actually come on the porch and beg for peanuts ( prefer) as they also store sunflower and safflower seeds they are very territorial I have one that comes up on the porch all the time and he runs everyone else off and I’m pretty sure his cachet is pretty extensive I just love the little guys they’re so cute I do find that they are smarter than squirrels I’ve seen them run birds off squirrels off all I have to do is open the 10 to my bird seed container and he comes running up the stairs one of the other ones caught on to that trick too but he seems to run him off all the time they are funny to watch I’m pretty sure my little guys will have a good winter.

Cheryl Teaver
Jun 12, 2018

Nice if you want them otherwise they are very destructive.I do not agree with feeding them they end up dependent of humans. No thanks.

Charles Walker
Oct 10, 2017

Sandra, if you’re in an area where bears pass through, I recommend against leaving food around outside. However, from a chipmunk perspective, they would be delighted to add your shelled seeds to their winter larders. See: http://northernwoodlands.org/outside_story/article/chipmunk

Elise Tillinghast
Oct 10, 2017

Hell-0, We are wondering if it is ok to be putting out black oil sunflower seeds with the shells on for the chipmunks.

Sandra Blomberg
Sep 07, 2017

My wife and I have three chipmunks that we feed…thought it might be nice to share comments with others that do the same…

Chuck Boyce
May 19, 2016

Is it bad to give chipmunks hulled black oil seed in the spring? Do they start storing right away or eat most everything in the sporting? Don’t want their stored seeds to go bad due to no shell.
David

David Denton

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