Unusual Overwintering Behavior of Squirrels and Chipmunks

Autumn usually brings big changes in the life of wild animals. Many birds migrate to warmer places, insects and other arthropods normally try to find shelters to overwinter either as adults, pupae, larvae or eggs. Mammals also have all kinds of strategies to pass the cold winter season in the northern parts of the globe. Many of them work tirelessly to prepare for the long winter. Gray squirrels get ready for the cold season by storing acorn and nuts typically in shallow holes. They bury thousands of nuts to make sure there’s enough food for the winter. However, some eastern gray squirrels (Sciurus carolinensis) in our backyard did something unusual this fall. There’s a huge cavity high in the old oak tree in our backyard and the squirrels started collecting food inside of it. We have never seen them using it this way nor to brood newborns here during the summer, but they have always liked to shelter inside the hole when the weather is really bad, especially when it’s cold and windy. I took this photo of a gray squirrel just before entering the burrow in January 2022 when we had some snow in Connecticut.

Gray Squirrel

The following photo was taken last January on a windy day, when this squirrel took refuge in the hole from the cold breeze. It’s common for them to use it as a den in the winter and sometimes even in the summer.

Gray Squirrel

However, in the last two months, we noticed the squirrels bringing nuts in the hole. They are currently very busy building their food cache as winter approaching and they thought this cavity will be a good place for that purpose too. Gray squirrels are scatter hoarders, so they usually store individual acorns or seeds in different areas. Storing nuts in hollow trees is an uncommon behavior for them. Although, this is not the most interesting part of the story. We also have eastern chipmunks (Tamias striatus) in our backyard. They are one the busiest gatherers in North America. Chipmunks sleep for long periods during winter, but they are not true hibernators. They occasionally wake up to eat nuts from their cache, so they need to build lots of storage to help them through the cold months. Since they are ground squirrels, they spend most of their time on the ground searching for and collecting food. They store their food in the chambers of their underground tunnels. Sometimes they climb to trees but normally not too high. Anyhow, the chipmunks in our backyard discovered the gray squirrels’ cache in the oak tree and they decided to regularly rob this store.

Eastern Chipmunk

These little striped thieves are brave enough not only to climb that high up the tree, but to frequently pull off risky heists from their much larger tree-dwelling cousins. When a naughty chipmunk is inside the hole, it looks like he tries to eat as much nut as possible while regularly looking around to see if there’s danger. I’ve never seen them coming out with full cheek pouches. Maybe the gray squirrels chose this high burrow to store some oily food that would easily get spoiled in the ground and chipmunks don’t cache such food either, but they still like munching on them to build some fat for winter. Anyway, it was nice observing such a unique behavior and it’s mind-boggling to think about how many interesting or funny stories unfold in nature every day where most of the time nobody sees them.

The first image was shot with my Canon EOS 1 camera using Kodak Portra 400 film. For the rest of the images, I used my Canon EOS 5Ds camera. All images were taken with my 500mm f/4 lens + 1.4x extender on a Gitzo tripod and RRS ballhead.

Eastern Chipmunk

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