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  • [♪ INTRO ]

  • Being attacked by a predator can be scary, but a new study in the journal Frontiers in

  • Ecology and Evolution helps us understand how some animals can keep cool under even

  • that most extreme pressure.

  • Even weirder, it turns out we can gain insight into how an animal would behave, even if we

  • can't watch it doing the thing.

  • Some animals areyucky.

  • They contain chemicals that make them toxic, nasty-tasting, or otherwise unpleasant to

  • be around, which is a great defense against predators.

  • It's so reliable that many of these animals are aposematic, meaning they have bright colors

  • or other signals that warn predators to keep away.

  • They don't hide, they advertise.

  • Aposematic animals tend to be relatively sluggish in their day-to-day movements.

  • After all, there's no need to rush if most predators won't mess with you.

  • But being under direct attack from a predator is a different story.

  • This study aimed to find out if animals with chemical defenses are able to remain relaxed

  • under predatory pressure.

  • To do so, the researchers tracked the behavior of 5 different species of tiger moths.

  • These moths have a remarkable ability to detect the echolocation of predatory bats.

  • If a moth hears a bat coming, it can take evasive maneuvers by spiraling or diving out

  • of the way.

  • But this comes with a cost: quick, panicky flight can make it easier to get yourself

  • lost, get stuck on a spider web, or draw the attention of other predators, not to mention

  • just uses their energy.

  • So if a moth has another line of defensesay, chemical grossnessit may be best for

  • them to stay relaxed when attacked.

  • To observe the moths' behavior, the researchers released a bunch of moths in an outdoor arena

  • where bats were known to hunt.

  • Over three years, they observed more than 300 bat-moth interactions.

  • Each time a moth was caught, the researchers observed whether the bat ate them or spat

  • them back out.

  • This data let them grade the moths on a spectrum of palatability, or tastiness.

  • The researchers also observed whether the moths tried to avoid the bats, or whether

  • they just kept flying pretty normally under attack.

  • That let them rank the moths according to nonchalance.

  • They found that the less palatable species were also cooler under pressure.

  • It seems those chemical defenses allow the moths to save energy on evasive maneuvers.

  • This is pretty exciting because it means we might be able to predict animals' behavior

  • from chemical traits.

  • Researchers could study a bug in a lab, or even a museum specimen, and based on its chemical

  • makeup, predict how it would act to avoid predators.

  • This is not only much easier than observing bugs under attack, but it could be done for

  • rare or even extinct species.

  • And it's not just tiger moths that do this.

  • Similar bat-avoiding behavior is seen in many species of beetles, mantises, lacewings, and

  • other moths and butterflies.

  • These findings could open up a whole new way to study aerial predator-prey interactions.

  • And while those researchers were exploring ecological dynamics in the air, another group

  • of scientists have presented findings on the importance of microbial ecosystems beneath

  • the soil.

  • Soil is obviously super important for life.

  • It not only provides a home for lots of living things, but also contains the nutrients necessary

  • for plants and other organisms to thrive.

  • A new study in the journal PNAS sheds new light on the ways bacteria are responsible

  • for creating that life-giving soil.

  • Soil is more than mere dirt.

  • It's a mixture of minerals, water, air, and organic matter, both alive and dead.

  • Beneath all that life-rich soil is a subsoil made of crumbly rocks, and beneath that is

  • tough bedrock.

  • Soil contains minerals that life needsthings like phosphorus and potassium.

  • Those are generally thought to come from down in the bedrock.

  • But plant roots and wind erosion can only break down rocks near the surface, and bedrock

  • can be several meters down.

  • So these scientists set out to explore how microbes deep underground might contribute

  • to the breakdown of bedrock.

  • To do so, they drilled a bunch of core samples from the soil and bedrock at the Luquillo

  • Critical Zone Observatory in Puerto Rico.

  • They ground up samples of the bedrock, added soil bacteria to some of the samples, and

  • then let all of the samples sit in the lab for 864 days.

  • After this extensive waiting period, they observed that the rocks had experienced some

  • chemical breakdown, but only if the bacteria were present.

  • What's more, the bacteria had increased in abundance.

  • Despite being in a dark room with no organic food sources, they were thriving.

  • The bacteria in question are chemolithotrophs, meaning they get their energy through chemical

  • reactions with inorganic materials in their environment.

  • Basically, they can feed on rocks.

  • Genetic analysis of these soil bacteria found that they produce special proteins on their

  • cell surface that allow them to swipe electrons from the iron in certain minerals, using those

  • electrons to power their own metabolism.

  • In the process, they accelerate the chemical weathering of the rock, breaking it down and

  • releasing all those wonderful nutrients that become part of the soil.

  • There are still some open questions.

  • For example, we don't how quickly this bacterial weathering occurs in nature, or how this microbial

  • action varies at different levels of soil.

  • But one thing is clear: these bacteria are a major player in the breakdown of rocks,

  • meaning we have them to thank for the abundance of minerals in soil that help give life to

  • the organisms on the surface.

  • It takes a long time to degrade bedrock into soil, but the time for holiday shopping is

  • almost up.

  • One quick way to check someone off your list is with a premium subscription to Brilliant.org.

  • If your loved ones are excited by science, math, and learning, they might really enjoy

  • the daily challenges and in-depth courses offered by Brilliant.

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  • [ ♪ OUTRO ]

Thanks to Brilliant for supporting this episode of SciShow.

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B2 中高級

這些飛蛾為什麼不躲避蝙蝠? (Why These Moths Don't Run Away from Bats)

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    林宜悉 發佈於 2021 年 01 月 14 日
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