Thanks to our friends at Minute Earth for supporting this episode of SciShow.

You can click the link in the description to check out their new book MinuteEarth Explains: How Did Whales Get So Big? And Other Curious Questions about Animals, Nature, Geology, and Planet Earth. [♪ INTRO] If you’ve seen animals stashing their food in hiding spots for the winter, you might wonder how they manage to remember where they put it months later.

Luckily for you, scientists have wondered the same thing and run several experiments to figure out what these hoarders are up to. They found that some animals’ brains change in preparation for this annual event. Other animals use similar tools to what you or I might use when remembering something important.

Each of us has adapted pretty impressive ways to make it through the year with food in our stomachs. Here are some of the coolest memory tools for the job. Lots of birds store food for the winter when fresh food is more scarce.

Nutcrackers, marsh tits, and black-capped chickadees all hide their food in spots scattered across a large area. This technique is called scatter hoarding. They’ll put one nut in one spot, another nut in another spot, and so on until they’ll hopefully have enough food to last through the winter.

Black-capped chickadees in particular are super-efficient and can store hundreds of morsels in a single day, all in different places. In total, they store thousands of them each year. But the number of food items stored also depends on where the bird lives.

Chickadees living in places with harsher winters will store more food than chickadees in friendlier climates. Researchers think this is because animals going through colder winters often need to rely on those stashes more to get through the season. And the sheer quantity of food that chickadees hide isn’t even the most impressive part of their food storage process.

When these birds store food in the Fall, the part of their brain most involved in remembering things, the hippocampus, grows. A 2010 study out of the University of Nevada-Reno found that memory exercises, like retrieving stored food, directly impact the number of new brain cells created in a chickadee’s hippocampus. Birds that were given the opportunity to store and retrieve food had more new brain cells in the hippocampus than birds that were not allowed to do so.

Some researchers suggest that this is because hippocampus cells are either already storing memories or available to store new memories. And that having more cells that are already storing memories triggers the brain to generate new cells. And they store more food in the fall than other times of the year, so chickadees have bigger hippocampi in October.

Researchers have found that the amount the hippocampus grows is proportional to the amount of food that the chickadee hides. On the other hand, in a 1989 study, researchers altered chickadees’ hippocampi to damage their cells, and as a result, the chickadees were less likely to find their caches. It was as if they were finding them by chance, or just guessing where to find food rather than remembering where they left it.

And a different study found that when chickadees retrieved their booty, they were three times more successful and over three times faster at finding their own caches than those of other animals. So they’re not just randomly lucky at finding snacks - they’re skilled at storing food and memories. In the end, it’s not like they can decide to make a part of their brain bigger.

But this next animal keeps their food storage techniques within the realm of what they can more easily control. Eastern fox squirrels also scatter hoard their food for the winter. But their hippocampi don’t change size with the seasons.

Instead, they use a mnemonic device called “chunking” to locate their food. You have probably used the same tool when remembering a long number. If you’re of a certain age, you might have used it to remember phone numbers.

Basically, you remember groups of numbers instead of each individual number so it becomes easier to remember more of them. This tool works because it reduces the load on your working memory. By mentally grouping objects together, there are fewer total objects to remember, so you can fit more things in your working memory at once.

Squirrels do this spatially. They’ll have a code for which type of nut goes where. These squirrels can tell different species of nuts apart and use that information to categorize them.

Then, they often hide all of the same type of nut in a certain area so each location has a different type of nut. A 1997 study in the journal Animal Behaviour tested how well grey squirrels could remember specific places after different lengths of time. They found that grey squirrels can remember a location well enough to retrieve their nuts with over 60% accuracy almost a month later.

And they can still remember where some of the food was stored several months later. Just think of all the phone numbers a squirrel could remember after the winter if they had phones. From growing their brains to using mnemonic devices, these tiny critters are more resilient than we usually give them credit for.

And many other animals have adapted their own ways of remembering their unique storage systems to help them survive the winter. Thank you for watching this SciShow video! I hope you’ll remember some of what you learned today.

If you know a kid who loves learning, they might love this book from our friends at Minute Earth! This book answers children’s most curious questions like Where Earth’s water came from and Why leaves change color in the fall. And it might answer a few questions you don’t know the answer to, or have never thought to ask, like Why are fish getting smaller or Why do some animals eat their babies?

Or, if this episode has got you wanting to learn more about how animals get ready for winter, you could learn why birds don’t migrate south via the shortest route. And, of course, all these answers are accompanied by the kind of gorgeous illustrations you expect from Minute Earth. If you like what you see and would like to snatch a copy of this book, you can head over to dftba.com/collections/minuteearth or click the link in the description. [♪ OUTRO]