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Birds Steer Clear of Invisible Roads

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Forget about whether the chicken crossed the road or not. The question for some scientists is why other birds won’t even come near a roadway. 

Wherever wildlife and automobile traffic meet, it’s usually bad news for the animals. More than just making roadkill, roads use up land, create noise and pollution, and act as barriers that cut animals off from resources, mates, and territory. Because of all these problems, bird populations tend to decline sharply within a kilometer of a road or other human infrastructure, and mammals begin declining within five kilometers. 

You’re within about a kilometer away from a road in more than 80 percent of the USA. That’s a whole lot of country covered in things that bug birds. But what bothers them most? The trash? Close calls with windshields? A lot of research has suggested that it's the level of noise around a busy roadway, but most of these studies have been done along actual roads. When all the potential bird-deterring effects are there at the same time, it’s hard to pin down the strength of any single one. 

To isolate the noise factor and see how much it matters to birds, biologists from Boise State University in Idaho wanted a way to create traffic noise without actual traffic. They decided to hide speakers in the trees of a southern Idaho forest that migrating birds use as a rest stop. When they piped recordings of traffic sounds through the speakers, they had a half-kilometer-long “phantom road” that wouldn’t bother the birds any way but through their ears. 

The Road Not Taken

Alternating between four days of noise and four days of quiet throughout the fall migration season, the researchers recorded visits of more than 8000 individual birds from 59 species to their phantom road and a noise-less control site. Whenever they turned the speakers on, the total bird abundance at the phantom road declined by more than a quarter. Some species avoided the area in even greater proportions, and a few, like the cedar waxwing, avoided it almost entirely.

Scaring away that many birds with only traffic noise is a startling demonstration of how man-made noise can alter the way animals use space. Because of the sheer amount of land that roads cover in the U.S., particularly noise-sensitive species like the waxwings and yellow warblers are pushed away from a whole lot of otherwise useable habitat because it’s too loud for them. 

Even within national parks and other protected areas, the researchers say, roads can produce noise levels similar to their phantom road, and man-made noise needs to be taken into account when preserving and managing land and wildlife. The next step is figuring out why noise is such a big deterrent for birds. It could be that noise masks birds’ songs and calls and keeps them from finding or communicating with one another. Other scientists have found that birds with high-frequency songs aren’t as bothered by roads and certain industrial sites because these low-frequency noises don’t drown out their songs as much as they do some other species. 

Road noise might also turn birds away because it keeps them from hearing predators. Some birds, like chaffinches, and other animals are more vigilant in noisy areas so other animals don’t get the drop on them, often at the expense of eating or other normal behaviors. If more noise means less eating, then roads are especially lousy places to be when a bird is migrating and needs fuel to keep going. 

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Big Questions
Do Cats Fart?
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Certain philosophical questions can invade even the most disciplined of minds. Do aliens exist? Can a soul ever be measured? Do cats fart?

While the latter may not have weighed heavily on some of history’s great brains, it’s certainly no less deserving of an answer. And in contrast to existential queries, there’s a pretty definitive response: Yes, they do. We just don’t really hear it.

According to veterinarians who have realized their job sometimes involves answering inane questions about animals passing gas, cats have all the biological hardware necessary for a fart: a gastrointestinal system and an anus. When excess air builds up as a result of gulping breaths or gut bacteria, a pungent cloud will be released from their rear ends. Smell a kitten’s butt sometime and you’ll walk away convinced that cats fart.

The discretion, or lack of audible farts, is probably due to the fact that cats don’t gulp their food like dogs do, leading to less air accumulating in their digestive tract.

So, yes, cats do fart. But they do it with the same grace and stealth they use to approach everything else. Think about that the next time you blame the dog.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Animals
Squirrels Are Probably More Organized Than You, Study Finds
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Despite having a brain that's slightly bigger than the size of a peanut M&M, squirrels have a fascinating, razor-sharp instinct when it comes to survival. They know that acorns that are high in fat and sprout late are perfect for long-term storage, so they salvage them for winter and eat the less nutritionally dense white-oak acorns right away. They also tend to remember where they put their acorn stash rather than relying solely on smell. Like nature's perfect stunt performer, they can even fall out of trees in a way that minimizes physical damage. Now, researchers at the University of California, Berkeley have unveiled a newly discovered part of a squirrel's hoarding strategy, Atlas Obscura reports.

The researchers tracked 45 wild fox squirrels on the UC-Berkeley campus for nearly two years. They made available to the squirrels four different types of nuts—walnuts, pecans, almonds, and hazelnuts. Sometimes the animals were given a single type of nut, and other times the nuts were mixed. Either way, the squirrels promptly sorted and stored their food according to type—walnuts went in one hiding place, almonds in another, and so on.

This type of behavior is known as "chunking" and makes it easier to retrieve data in memory. In doing this, a squirrel won't have to visit several different places looking for pecans: They know just where the main supply is. Squirrels can stockpile up to 10,000 nuts a year, so it's essential for them to know which type of nut is where.

The study, published in Royal Society Open Science, also indicated that squirrels seem to understand nuts have weight, choosing to carry heavier acquisitions to a different location than lighter nuts.

Squirrels being squirrels, they were happy to be gifted an assortment of nuts during the experiment, but there was one wrinkle: Rather than stash them away, sometimes they'd just eat them on the spot.

[h/t Atlas Obscura]

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