1 00:00:01,960 --> 00:00:07,280 Speaker 1: Welcome to brain Stuff production of iHeartRadio. Hey brain Stuff, 2 00:00:07,320 --> 00:00:12,320 Speaker 1: Lauren Vogelbaum Here. Tree squirrels are pretty common in cities, neighborhoods, 3 00:00:12,320 --> 00:00:15,360 Speaker 1: and wooded spaces around the world. But how much do 4 00:00:15,400 --> 00:00:18,439 Speaker 1: you really know about them? I'm not saying that they're 5 00:00:18,560 --> 00:00:23,120 Speaker 1: planning something big. There's a misconception that tree squirrels hibernate 6 00:00:23,200 --> 00:00:26,560 Speaker 1: during the winter. Trust me from looking out my kitchen window, 7 00:00:26,760 --> 00:00:30,760 Speaker 1: they are plenty active. Hibernation is an evolutionary trick some 8 00:00:30,840 --> 00:00:34,280 Speaker 1: animals use to conserve energy when food is scarce. Tree 9 00:00:34,320 --> 00:00:36,800 Speaker 1: squirrels don't need it because they store enough away to 10 00:00:36,920 --> 00:00:40,800 Speaker 1: keep themselves fed. However, their cousins, the ground squirrels, which 11 00:00:40,840 --> 00:00:43,800 Speaker 1: have a less bushy tail, burrow underground and are common 12 00:00:43,840 --> 00:00:47,800 Speaker 1: in the American West, do hibernate during colder months. Another 13 00:00:47,880 --> 00:00:51,239 Speaker 1: misconception is that tree squirrels store that food they've collected 14 00:00:51,320 --> 00:00:54,760 Speaker 1: during the summer and fall, like for example, acorns directly 15 00:00:54,800 --> 00:00:57,880 Speaker 1: in their nests are dens for easy access during the winter. 16 00:00:58,720 --> 00:01:01,800 Speaker 1: But the process by which tree squirrels keep themselves fed 17 00:01:01,880 --> 00:01:04,200 Speaker 1: during the lean months turns out to be way more 18 00:01:04,240 --> 00:01:08,680 Speaker 1: complex and active than stalking a pantry at home. Researchers 19 00:01:08,680 --> 00:01:12,920 Speaker 1: are learning that it suggests some advanced memory skills. A 20 00:01:12,959 --> 00:01:15,520 Speaker 1: group out of the Department of Psychology at UC Berkeley 21 00:01:15,560 --> 00:01:19,120 Speaker 1: published a study about this back in twenty seventeen. In it, 22 00:01:19,200 --> 00:01:22,320 Speaker 1: they lay out how tree squirrels use a mnemonic technique 23 00:01:22,319 --> 00:01:25,520 Speaker 1: called spatial chunking to sort out and hide their nuts 24 00:01:25,520 --> 00:01:29,960 Speaker 1: scores by size, type, and perhaps even nutritional value and taste. 25 00:01:30,959 --> 00:01:34,119 Speaker 1: When they're hungry later, it's theorized they can remember where 26 00:01:34,120 --> 00:01:37,520 Speaker 1: to find what they want. But let's back up a little. 27 00:01:37,920 --> 00:01:40,640 Speaker 1: The tree squirrels are a diverse group of squirrels that 28 00:01:40,720 --> 00:01:43,600 Speaker 1: live primarily in trees instead of burrowing in the ground. 29 00:01:44,040 --> 00:01:48,280 Speaker 1: They'll eat pretty much anything seeds, nuts, tree buds, berries, leaves, 30 00:01:48,400 --> 00:01:51,800 Speaker 1: parts of pine cones, bird eggs, nestlings, and the occasional 31 00:01:51,840 --> 00:01:55,200 Speaker 1: slice of found pizza. Some of that stuff they eat 32 00:01:55,280 --> 00:01:58,760 Speaker 1: right away and the rest they well squirrel away for later. 33 00:02:00,440 --> 00:02:03,760 Speaker 1: But as winter approaches, squirrels are faced with a challenge. 34 00:02:03,920 --> 00:02:06,960 Speaker 1: They know instinctively that food sources will soon be scarce, 35 00:02:07,120 --> 00:02:09,040 Speaker 1: so they gather all the food they'll need for a 36 00:02:09,040 --> 00:02:11,959 Speaker 1: few months while also keeping themselves fed day to day. 37 00:02:12,760 --> 00:02:14,959 Speaker 1: That's why they're so busy in the fall, when nuts 38 00:02:15,000 --> 00:02:19,239 Speaker 1: like acorns have all fallen from their trees. Some squirrels, 39 00:02:19,400 --> 00:02:21,640 Speaker 1: like red squirrels, tend to hide their food in a 40 00:02:21,639 --> 00:02:25,359 Speaker 1: single stash, but others are what's known as scatter hoarders, 41 00:02:25,720 --> 00:02:28,440 Speaker 1: which means pretty much what it sounds like. They hoard 42 00:02:28,480 --> 00:02:31,440 Speaker 1: their food and scatter it in several different locations where 43 00:02:31,480 --> 00:02:34,920 Speaker 1: they can easily access it. That's usually close to the 44 00:02:34,960 --> 00:02:37,720 Speaker 1: tree holding their nest or done, but they often expand 45 00:02:37,720 --> 00:02:41,560 Speaker 1: into areas of around seven acres or three hectors. Rather 46 00:02:41,600 --> 00:02:44,240 Speaker 1: than leaving their goods above ground where other squirrels might 47 00:02:44,280 --> 00:02:47,600 Speaker 1: steal them, they bury them. This is called caching about 48 00:02:47,600 --> 00:02:50,160 Speaker 1: an inch under the soil that's around two to three centimeters. 49 00:02:50,880 --> 00:02:53,720 Speaker 1: Squirrels are even known to crack open nuts before burying 50 00:02:53,720 --> 00:02:57,160 Speaker 1: them to prevent them from germinating, though not always and 51 00:02:57,360 --> 00:03:01,560 Speaker 1: actually squirrels accidentally plant a lot of trees trease. Anyway, 52 00:03:01,840 --> 00:03:04,120 Speaker 1: when it comes time to eat, they forage for the 53 00:03:04,200 --> 00:03:07,880 Speaker 1: nuts they buried. Squirrels do possess a strong sense of smell, 54 00:03:08,040 --> 00:03:10,440 Speaker 1: which allows them to sniff out nuts from under a 55 00:03:10,440 --> 00:03:12,960 Speaker 1: blanket of dirt, especially if the squirrels marked its nuts 56 00:03:12,960 --> 00:03:15,480 Speaker 1: with their own scent, usually from glands on their face, 57 00:03:15,960 --> 00:03:20,040 Speaker 1: but researchers have long noticed evidence of strategic intelligence in 58 00:03:20,080 --> 00:03:23,840 Speaker 1: the placement of their food. For instance, one study in 59 00:03:23,880 --> 00:03:27,200 Speaker 1: two thousand and eight reported that Eastern gray squirrels engage 60 00:03:27,240 --> 00:03:31,000 Speaker 1: in deceptive caching, That is, they dig a hole, pretend 61 00:03:31,160 --> 00:03:33,480 Speaker 1: to throw in an acorn while holding it in their mouth, 62 00:03:33,840 --> 00:03:35,760 Speaker 1: cover up the empty hole, and then run off to 63 00:03:35,800 --> 00:03:39,640 Speaker 1: another secret stash place. They do this, it was suggested, 64 00:03:39,680 --> 00:03:43,120 Speaker 1: to fool other squirrels who might be watching, and the 65 00:03:43,120 --> 00:03:46,960 Speaker 1: study from twenty seventeen indicates even more complex thinking behind 66 00:03:46,960 --> 00:03:50,840 Speaker 1: the caching. In field experiments conducted over nineteen months from 67 00:03:50,920 --> 00:03:55,040 Speaker 1: twenty twelve to twenty fourteen, researchers fed forty five marked 68 00:03:55,160 --> 00:03:58,120 Speaker 1: free ranging Eastern fox squirrels one nut at a time, 69 00:03:58,240 --> 00:04:01,240 Speaker 1: as sixteen total for each squirrel, varying the type of 70 00:04:01,320 --> 00:04:05,440 Speaker 1: nut almonds, hazelnuts, pecans, and walnuts. If the squirrels didn't 71 00:04:05,440 --> 00:04:08,760 Speaker 1: eat the nuts right away, the researchers tracked through GPS 72 00:04:08,880 --> 00:04:12,720 Speaker 1: where the squirrels subsequently buried their prizes. What they found 73 00:04:12,760 --> 00:04:16,760 Speaker 1: showed evidence of spatial chunking, meaning that the squirrels put 74 00:04:16,800 --> 00:04:20,760 Speaker 1: specific nuts in similar places to apparently help them remember 75 00:04:20,880 --> 00:04:24,920 Speaker 1: which nuts were ware, So for example, a given animal 76 00:04:24,960 --> 00:04:28,240 Speaker 1: would place almonds in one general area and hazel nuts 77 00:04:28,240 --> 00:04:31,479 Speaker 1: in another. We can only assume that had pizza been involved, 78 00:04:31,480 --> 00:04:34,520 Speaker 1: it would have gotten its own location too. This mneumonic 79 00:04:34,560 --> 00:04:38,359 Speaker 1: strategy has also been seen in rats. The researchers explained 80 00:04:38,360 --> 00:04:40,800 Speaker 1: that the strategy could make it easier for squirrels to 81 00:04:40,960 --> 00:04:44,159 Speaker 1: find not just any stash, but the specific type of 82 00:04:44,160 --> 00:04:47,520 Speaker 1: stash they're looking for, and use less brain space to 83 00:04:47,560 --> 00:04:51,560 Speaker 1: do it. For the article this Episodes based on How 84 00:04:51,560 --> 00:04:54,440 Speaker 1: Stuff Works, spoke via email with Michael A. Steel, a 85 00:04:54,480 --> 00:04:58,240 Speaker 1: biology professor at Wilkes University in Pennsylvania and the guy 86 00:04:58,240 --> 00:05:02,679 Speaker 1: who first described the deceptive cas us mentioned above. He said, 87 00:05:03,360 --> 00:05:05,640 Speaker 1: I find the results consistent with some of my studies 88 00:05:05,680 --> 00:05:08,080 Speaker 1: and those of others in which we are learning how 89 00:05:08,160 --> 00:05:12,440 Speaker 1: involved the scatter hoarding process is for tree squirrels. Squirrels 90 00:05:12,440 --> 00:05:16,080 Speaker 1: are certainly well adapted to solve foraging and caching problems, 91 00:05:16,200 --> 00:05:20,360 Speaker 1: well beyond most people's greatest expectations. We know that gray 92 00:05:20,400 --> 00:05:23,960 Speaker 1: squirrels selectively move more valuable seeds or nuts to sites 93 00:05:24,000 --> 00:05:27,600 Speaker 1: in the open where predation risks are higher, but pilfridge 94 00:05:27,680 --> 00:05:31,600 Speaker 1: risks from other squirrels are lower. This means squirrels cess 95 00:05:31,640 --> 00:05:34,120 Speaker 1: seed and nut quality and trade off some risk of 96 00:05:34,160 --> 00:05:38,760 Speaker 1: predation to secure seeds and sights. The twenty seventeen study 97 00:05:38,800 --> 00:05:41,680 Speaker 1: took into account, among other variables, the sex of the 98 00:05:41,720 --> 00:05:44,120 Speaker 1: squirrels in the experiment, the order in which the nuts 99 00:05:44,160 --> 00:05:46,920 Speaker 1: were received by the squirrels, and the weight and nutritional 100 00:05:46,960 --> 00:05:50,479 Speaker 1: value of each nut. They appeared to be organizing nuts 101 00:05:50,520 --> 00:05:54,320 Speaker 1: by size in addition to type, so the next time 102 00:05:54,400 --> 00:05:57,039 Speaker 1: you see a squirrel digging up a nut, know that 103 00:05:57,080 --> 00:05:59,919 Speaker 1: she might have found the exact one she was looking for. 104 00:06:06,120 --> 00:06:09,320 Speaker 1: Today's episode is based on the article squirrels actually organize 105 00:06:09,320 --> 00:06:12,440 Speaker 1: their net hoard Here's Why on HowStuffWorks dot Com, written 106 00:06:12,440 --> 00:06:15,000 Speaker 1: by Jamie Allen. Green Stuff is production of by Heart 107 00:06:15,040 --> 00:06:17,160 Speaker 1: Radio in partnership with how stuffworks dot Com, and it 108 00:06:17,200 --> 00:06:19,920 Speaker 1: is produced by Tyler Klang. Four more podcasts from my 109 00:06:19,960 --> 00:06:23,239 Speaker 1: heart Radio, visit the iHeartRadio app, Apple Podcasts, or wherever 110 00:06:23,240 --> 00:06:24,640 Speaker 1: you listen to your favorite shows.