Speaker 1: Welcome to brain Stuff production of iHeartRadio. Hey brain Stuff,
Speaker 1: Lauren Vogelbaum Here. Tree squirrels are pretty common in cities, neighborhoods,
Speaker 1: and wooded spaces around the world. But how much do
Speaker 1: you really know about them? I'm not saying that they're
Speaker 1: planning something big. There's a misconception that tree squirrels hibernate
Speaker 1: during the winter. Trust me from looking out my kitchen window,
Speaker 1: they are plenty active. Hibernation is an evolutionary trick some
Speaker 1: animals use to conserve energy when food is scarce. Tree
Speaker 1: squirrels don't need it because they store enough away to
Speaker 1: keep themselves fed. However, their cousins, the ground squirrels, which
Speaker 1: have a less bushy tail, burrow underground and are common
Speaker 1: in the American West, do hibernate during colder months. Another
Speaker 1: misconception is that tree squirrels store that food they've collected
Speaker 1: during the summer and fall, like for example, acorns directly
Speaker 1: in their nests are dens for easy access during the winter.
Speaker 1: But the process by which tree squirrels keep themselves fed
Speaker 1: during the lean months turns out to be way more
Speaker 1: complex and active than stalking a pantry at home. Researchers
Speaker 1: are learning that it suggests some advanced memory skills. A
Speaker 1: group out of the Department of Psychology at UC Berkeley
Speaker 1: published a study about this back in twenty seventeen. In it,
Speaker 1: they lay out how tree squirrels use a mnemonic technique
Speaker 1: called spatial chunking to sort out and hide their nuts
Speaker 1: scores by size, type, and perhaps even nutritional value and taste.
Speaker 1: When they're hungry later, it's theorized they can remember where
Speaker 1: to find what they want. But let's back up a little.
Speaker 1: The tree squirrels are a diverse group of squirrels that
Speaker 1: live primarily in trees instead of burrowing in the ground.
Speaker 1: They'll eat pretty much anything seeds, nuts, tree buds, berries, leaves,
Speaker 1: parts of pine cones, bird eggs, nestlings, and the occasional
Speaker 1: slice of found pizza. Some of that stuff they eat
Speaker 1: right away and the rest they well squirrel away for later.
Speaker 1: But as winter approaches, squirrels are faced with a challenge.
Speaker 1: They know instinctively that food sources will soon be scarce,
Speaker 1: so they gather all the food they'll need for a
Speaker 1: few months while also keeping themselves fed day to day.
Speaker 1: That's why they're so busy in the fall, when nuts
Speaker 1: like acorns have all fallen from their trees. Some squirrels,
Speaker 1: like red squirrels, tend to hide their food in a
Speaker 1: single stash, but others are what's known as scatter hoarders,
Speaker 1: which means pretty much what it sounds like. They hoard
Speaker 1: their food and scatter it in several different locations where
Speaker 1: they can easily access it. That's usually close to the
Speaker 1: tree holding their nest or done, but they often expand
Speaker 1: into areas of around seven acres or three hectors. Rather
Speaker 1: than leaving their goods above ground where other squirrels might
Speaker 1: steal them, they bury them. This is called caching about
Speaker 1: an inch under the soil that's around two to three centimeters.
Speaker 1: Squirrels are even known to crack open nuts before burying
Speaker 1: them to prevent them from germinating, though not always and
Speaker 1: actually squirrels accidentally plant a lot of trees trease. Anyway,
Speaker 1: when it comes time to eat, they forage for the
Speaker 1: nuts they buried. Squirrels do possess a strong sense of smell,
Speaker 1: which allows them to sniff out nuts from under a
Speaker 1: blanket of dirt, especially if the squirrels marked its nuts
Speaker 1: with their own scent, usually from glands on their face,
Speaker 1: but researchers have long noticed evidence of strategic intelligence in
Speaker 1: the placement of their food. For instance, one study in
Speaker 1: two thousand and eight reported that Eastern gray squirrels engage
Speaker 1: in deceptive caching, That is, they dig a hole, pretend
Speaker 1: to throw in an acorn while holding it in their mouth,
Speaker 1: cover up the empty hole, and then run off to
Speaker 1: another secret stash place. They do this, it was suggested,
Speaker 1: to fool other squirrels who might be watching, and the
Speaker 1: study from twenty seventeen indicates even more complex thinking behind
Speaker 1: the caching. In field experiments conducted over nineteen months from
Speaker 1: twenty twelve to twenty fourteen, researchers fed forty five marked
Speaker 1: free ranging Eastern fox squirrels one nut at a time,
Speaker 1: as sixteen total for each squirrel, varying the type of
Speaker 1: nut almonds, hazelnuts, pecans, and walnuts. If the squirrels didn't
Speaker 1: eat the nuts right away, the researchers tracked through GPS
Speaker 1: where the squirrels subsequently buried their prizes. What they found
Speaker 1: showed evidence of spatial chunking, meaning that the squirrels put
Speaker 1: specific nuts in similar places to apparently help them remember
Speaker 1: which nuts were ware, So for example, a given animal
Speaker 1: would place almonds in one general area and hazel nuts
Speaker 1: in another. We can only assume that had pizza been involved,
Speaker 1: it would have gotten its own location too. This mneumonic
Speaker 1: strategy has also been seen in rats. The researchers explained
Speaker 1: that the strategy could make it easier for squirrels to
Speaker 1: find not just any stash, but the specific type of
Speaker 1: stash they're looking for, and use less brain space to
Speaker 1: do it. For the article this Episodes based on How
Speaker 1: Stuff Works, spoke via email with Michael A. Steel, a
Speaker 1: biology professor at Wilkes University in Pennsylvania and the guy
Speaker 1: who first described the deceptive cas us mentioned above. He said,
Speaker 1: I find the results consistent with some of my studies
Speaker 1: and those of others in which we are learning how
Speaker 1: involved the scatter hoarding process is for tree squirrels. Squirrels
Speaker 1: are certainly well adapted to solve foraging and caching problems,
Speaker 1: well beyond most people's greatest expectations. We know that gray
Speaker 1: squirrels selectively move more valuable seeds or nuts to sites
Speaker 1: in the open where predation risks are higher, but pilfridge
Speaker 1: risks from other squirrels are lower. This means squirrels cess
Speaker 1: seed and nut quality and trade off some risk of
Speaker 1: predation to secure seeds and sights. The twenty seventeen study
Speaker 1: took into account, among other variables, the sex of the
Speaker 1: squirrels in the experiment, the order in which the nuts
Speaker 1: were received by the squirrels, and the weight and nutritional
Speaker 1: value of each nut. They appeared to be organizing nuts
Speaker 1: by size in addition to type, so the next time
Speaker 1: you see a squirrel digging up a nut, know that
Speaker 1: she might have found the exact one she was looking for.
Speaker 1: Today's episode is based on the article squirrels actually organize
Speaker 1: their net hoard Here's Why on HowStuffWorks dot Com, written
Speaker 1: by Jamie Allen. Green Stuff is production of by Heart
Speaker 1: Radio in partnership with how stuffworks dot Com, and it
Speaker 1: is produced by Tyler Klang. Four more podcasts from my
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