WEBVTT - How Do Squirrels Organize Their Hoards?

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<v Speaker 1>Welcome to brain Stuff production of iHeartRadio. Hey brain Stuff,

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<v Speaker 1>Lauren Vogelbaum Here. Tree squirrels are pretty common in cities, neighborhoods,

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<v Speaker 1>and wooded spaces around the world. But how much do

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<v Speaker 1>you really know about them? I'm not saying that they're

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<v Speaker 1>planning something big. There's a misconception that tree squirrels hibernate

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<v Speaker 1>during the winter. Trust me from looking out my kitchen window,

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<v Speaker 1>they are plenty active. Hibernation is an evolutionary trick some

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<v Speaker 1>animals use to conserve energy when food is scarce. Tree

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<v Speaker 1>squirrels don't need it because they store enough away to

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<v Speaker 1>keep themselves fed. However, their cousins, the ground squirrels, which

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<v Speaker 1>have a less bushy tail, burrow underground and are common

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<v Speaker 1>in the American West, do hibernate during colder months. Another

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<v Speaker 1>misconception is that tree squirrels store that food they've collected

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<v Speaker 1>during the summer and fall, like for example, acorns directly

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<v Speaker 1>in their nests are dens for easy access during the winter.

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<v Speaker 1>But the process by which tree squirrels keep themselves fed

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<v Speaker 1>during the lean months turns out to be way more

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<v Speaker 1>complex and active than stalking a pantry at home. Researchers

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<v Speaker 1>are learning that it suggests some advanced memory skills. A

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<v Speaker 1>group out of the Department of Psychology at UC Berkeley

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<v Speaker 1>published a study about this back in twenty seventeen. In it,

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<v Speaker 1>they lay out how tree squirrels use a mnemonic technique

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<v Speaker 1>called spatial chunking to sort out and hide their nuts

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<v Speaker 1>scores by size, type, and perhaps even nutritional value and taste.

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<v Speaker 1>When they're hungry later, it's theorized they can remember where

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<v Speaker 1>to find what they want. But let's back up a little.

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<v Speaker 1>The tree squirrels are a diverse group of squirrels that

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<v Speaker 1>live primarily in trees instead of burrowing in the ground.

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<v Speaker 1>They'll eat pretty much anything seeds, nuts, tree buds, berries, leaves,

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<v Speaker 1>parts of pine cones, bird eggs, nestlings, and the occasional

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<v Speaker 1>slice of found pizza. Some of that stuff they eat

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<v Speaker 1>right away and the rest they well squirrel away for later.

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<v Speaker 1>But as winter approaches, squirrels are faced with a challenge.

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<v Speaker 1>They know instinctively that food sources will soon be scarce,

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<v Speaker 1>so they gather all the food they'll need for a

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<v Speaker 1>few months while also keeping themselves fed day to day.

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<v Speaker 1>That's why they're so busy in the fall, when nuts

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<v Speaker 1>like acorns have all fallen from their trees. Some squirrels,

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<v Speaker 1>like red squirrels, tend to hide their food in a

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<v Speaker 1>single stash, but others are what's known as scatter hoarders,

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<v Speaker 1>which means pretty much what it sounds like. They hoard

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<v Speaker 1>their food and scatter it in several different locations where

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<v Speaker 1>they can easily access it. That's usually close to the

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<v Speaker 1>tree holding their nest or done, but they often expand

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<v Speaker 1>into areas of around seven acres or three hectors. Rather

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<v Speaker 1>than leaving their goods above ground where other squirrels might

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<v Speaker 1>steal them, they bury them. This is called caching about

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<v Speaker 1>an inch under the soil that's around two to three centimeters.

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<v Speaker 1>Squirrels are even known to crack open nuts before burying

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<v Speaker 1>them to prevent them from germinating, though not always and

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<v Speaker 1>actually squirrels accidentally plant a lot of trees trease. Anyway,

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<v Speaker 1>when it comes time to eat, they forage for the

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<v Speaker 1>nuts they buried. Squirrels do possess a strong sense of smell,

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<v Speaker 1>which allows them to sniff out nuts from under a

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<v Speaker 1>blanket of dirt, especially if the squirrels marked its nuts

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<v Speaker 1>with their own scent, usually from glands on their face,

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<v Speaker 1>but researchers have long noticed evidence of strategic intelligence in

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<v Speaker 1>the placement of their food. For instance, one study in

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<v Speaker 1>two thousand and eight reported that Eastern gray squirrels engage

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<v Speaker 1>in deceptive caching, That is, they dig a hole, pretend

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<v Speaker 1>to throw in an acorn while holding it in their mouth,

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<v Speaker 1>cover up the empty hole, and then run off to

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<v Speaker 1>another secret stash place. They do this, it was suggested,

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<v Speaker 1>to fool other squirrels who might be watching, and the

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<v Speaker 1>study from twenty seventeen indicates even more complex thinking behind

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<v Speaker 1>the caching. In field experiments conducted over nineteen months from

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<v Speaker 1>twenty twelve to twenty fourteen, researchers fed forty five marked

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<v Speaker 1>free ranging Eastern fox squirrels one nut at a time,

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<v Speaker 1>as sixteen total for each squirrel, varying the type of

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<v Speaker 1>nut almonds, hazelnuts, pecans, and walnuts. If the squirrels didn't

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<v Speaker 1>eat the nuts right away, the researchers tracked through GPS

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<v Speaker 1>where the squirrels subsequently buried their prizes. What they found

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<v Speaker 1>showed evidence of spatial chunking, meaning that the squirrels put

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<v Speaker 1>specific nuts in similar places to apparently help them remember

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<v Speaker 1>which nuts were ware, So for example, a given animal

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<v Speaker 1>would place almonds in one general area and hazel nuts

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<v Speaker 1>in another. We can only assume that had pizza been involved,

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<v Speaker 1>it would have gotten its own location too. This mneumonic

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<v Speaker 1>strategy has also been seen in rats. The researchers explained

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<v Speaker 1>that the strategy could make it easier for squirrels to

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<v Speaker 1>find not just any stash, but the specific type of

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<v Speaker 1>stash they're looking for, and use less brain space to

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<v Speaker 1>do it. For the article this Episodes based on How

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<v Speaker 1>Stuff Works, spoke via email with Michael A. Steel, a

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<v Speaker 1>biology professor at Wilkes University in Pennsylvania and the guy

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<v Speaker 1>who first described the deceptive cas us mentioned above. He said,

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<v Speaker 1>I find the results consistent with some of my studies

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<v Speaker 1>and those of others in which we are learning how

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<v Speaker 1>involved the scatter hoarding process is for tree squirrels. Squirrels

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<v Speaker 1>are certainly well adapted to solve foraging and caching problems,

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<v Speaker 1>well beyond most people's greatest expectations. We know that gray

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<v Speaker 1>squirrels selectively move more valuable seeds or nuts to sites

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<v Speaker 1>in the open where predation risks are higher, but pilfridge

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<v Speaker 1>risks from other squirrels are lower. This means squirrels cess

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<v Speaker 1>seed and nut quality and trade off some risk of

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<v Speaker 1>predation to secure seeds and sights. The twenty seventeen study

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<v Speaker 1>took into account, among other variables, the sex of the

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<v Speaker 1>squirrels in the experiment, the order in which the nuts

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<v Speaker 1>were received by the squirrels, and the weight and nutritional

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<v Speaker 1>value of each nut. They appeared to be organizing nuts

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<v Speaker 1>by size in addition to type, so the next time

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<v Speaker 1>you see a squirrel digging up a nut, know that

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<v Speaker 1>she might have found the exact one she was looking for.

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<v Speaker 1>Today's episode is based on the article squirrels actually organize

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<v Speaker 1>their net hoard Here's Why on HowStuffWorks dot Com, written

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<v Speaker 1>by Jamie Allen. Green Stuff is production of by Heart

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<v Speaker 1>Radio in partnership with how stuffworks dot Com, and it

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<v Speaker 1>is produced by Tyler Klang. Four more podcasts from my

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<v Speaker 1>heart Radio, visit the iHeartRadio app, Apple Podcasts, or wherever

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