Snoozing Bats Tune Out Traffic Noise

For an easily crushed animal that rests during the day, a highway seems like maybe the worst possible home. Yet some bats pick roosts that are under bridges, or in other spots booming with human noise. Why subject themselves to that? For bats of at least one species, the sound of traffic is easy to doze through. And the more they hear it, the more they ignore it.

The greater mouse-eared bat, Myotis myotis, often turns up under bridges in Europe. Jinhong Luo, a PhD student at the Max Planck Institute for Ornithology, wanted to know how they can tolerate the noise. He and his colleagues trapped male bats from a cave in Bulgaria and brought them back to the laboratory for a hearing test, which was really a sleeping test.

Well, not sleeping exactly. Like many other bat species, the greater mouse-eared bat goes into "torpor" during the day, which is like a mini-hibernation. Its metabolism and body temperature drop sharply, letting the animal conserve energy. In the evening, the bats start to stir. After waking up gradually, they head out from their caves (or under-bridge roosts) to hunt.

The researchers created several different sound recordings that they would play to roosting bats to try to wake them up. There was a recording of the bats' own colony, another of local bird sounds, and one of trees rustling in the wind. The authors also created recordings that mimicked highway traffic passing 25 meters, 50 meters, and 100 meters away.

Each bat was housed by itself for the sound tests. Over the course of two roosting days, the bats heard each recording twice for five minutes. By monitoring temperature sensors on the animals' skin, the scientists could see whether bats started to wake up—that is, warm themselves—after hearing each sound.

Luo and the others tested a dozen bats. (They started with 15, but two weren't snoozing deeply enough to run all the tests, and one somehow pulled the temperature logger off the middle of its back.) The bats were most likely to wake up after hearing the recording of their colony, or the sound of rustling trees. But traffic sounds were least likely to wake them. Bats responded more strongly to all sounds later in the day, as it got closer to their normal waking time.

It's not too surprising that bats respond to the squeaks and shuffles of their own colony, which might hold useful information. But why the windblown trees? A likely answer is that Myotis myotis doesn't hunt by echolocation. Instead, it listens for the sounds of beetles walking through the grass. Since the bats are already attuned to the noise of swishing vegetation, it may make a good alarm clock.

As for the sound of cars passing, Luo points out that most rumbling traffic is at a lower frequency than the sounds of a bat colony or rustling leaves. Since bats hear better at higher frequencies, this means traffic noise is "basically out of the best hearing frequencies for nearly all bat species."

However, Luo is quick to add, "We would never claim that traffic noise is not disturbing to roosting bats or even to torpid bats." The bats in his study did respond slightly to traffic noise, raising their body temperatures compared to when there was silence. And bats might react differently to highway sounds when they're awake, or when they're roosting but not in a state of torpor.

Whatever sound they heard, bats responded less on the second playback, or when it was played continuously for an hour. They were especially quick to adjust to traffic sounds. Like a teenager sleeping through an alarm clock, bats can tune out a familiar noise more easily. But that doesn't mean they're immune to harm from their noisy human neighbors. We just don't know all the ways that living with our roads and other rackets might influence them.

"To be honest, we are in the very beginning of understanding the potential effects," Luo says. "Answers are not always straightforward."


Image: USFWS/Ann Froschauer

Luo J, Clarin BM, Borissov IM, & Siemers BM (2013). Are torpid bats immune to anthropogenic noise? The Journal of experimental biology PMID: 24311817

Cooler Than Your Environmental Club: An Interview with My Little Sister about the Adirondack Youth Climate Summit

Teenagers who want to cause a disruption don't have to ride a skateboard anymore; these days they can do it on a bike generator. Earlier this November a crowd of students came together in Upstate New York to share ideas about greening their schools and addressing climate change on a small and large scale.  My youngest sister, Leigh, is a senior in high school and was at the conference for her second year. I asked her what they did there, and she told me about energy efficiency, celeriac soup, and how her generation is going to do things differently. (I never did get a straight answer about some Facebook photos, though.)

*****************

Hi Leigh! So who attends the Adirondack Youth Climate Summit?

There were about 150 students representing 27 colleges and high schools around New York, mostly from the Adirondack region. Each school could send 5 to 6 students along with a teacher chaperone. Students at my school had to write an essay explaining why they wanted to go to the summit and what interest they had in climate change. (Most students I talked to were shocked that my school had been so selective because their schools just brought their entire environmental club.)

By the way, I hope email is OK. Would I have more generational cred with you right now if I were conducting this interview via SnapChat or something?

I have to say, I much prefer the transfer of information through text bubbles containing less than 140 characters attached to a picture I can only view for 10 seconds on a 4-inch screen...but I guess this will do.

What kinds of workshops did you go to?

I got to attend three different workshops of my choice on the first day, splitting up with my school group so that we could cover more ground. I attended the three that were geared towards successfully sustaining a school garden and implementing younger students into climate action, because that's what I've been focused on at school the past couple years. The rest of my team attended workshops about composting, green teams, energy efficiency, biofuels, and recycling.

I hear the food was a highlight.

The food was absolutely delicious! All the meals and snacks were provided by local farms and vendors. They had vegetarian, vegan and gluten-free options, and Ben & Jerry's (a major sponsor of the summit) provided ice cream the second day. I caught myself enjoying kale chips and even tried parsnip and celeriac for the first time in a delicious soup that a Culinary Arts professor from Paul Smith's College made. (See recipe below.)

As weird as it sounds, I think the presence of wholesome, fresh, unprocessed food really boosted everyone's brain power for a few days.

And there were speakers too?

Brian Stillwell of Alliance for Climate Education kicked off the summit with a catchy, motivating presentation about climate change and the science behind it, followed by Brother Yusef Burgess of Youth Ed-Venture and the Children & Nature Network, who spoke about using the power of nature to transform and educate youth. Later in the afternoon Dr. Susan Powers, the Associate Director for Sustainability at Clarkson University, presented to us the outcomes of climate change in both our best and worst case scenarios.

Mark and Kristin Kimball, who own Essex Farm in the Adirondacks, hosted the dance party, fed us freshly harvested carrots, and encouraged our generation to be the driving force of the climate movement—and, more importantly, to have fun doing it. They made the point that these days, things like smoking cigarettes or dumping gasoline into a lake are considered "socially unacceptable," but that took time. Now, it is our time to make not caring about the environment be socially unacceptable.

Was it valuable just interacting with the other kids there, from different kinds of schools? Were you learning and getting ideas from each other?

YES. The second day, there was a 2-hour poster session where all the schools displayed posters of their current "green" efforts and plans for the future. I had a chance to talk to so many different schools and share ideas about outdoors clubs, gardening problems, recycling efforts and cafeteria food. I had conversations with a high school that was having trouble even starting an environmental club due to the lack of support from administration, and on the other end of the spectrum, I talked to a school that had livestock and taught all their science classes on a farm.

We also had the amazing opportunity to Skype with Finland, where they were holding a similar youth climate summit modeled after ours in the Adirondacks. Despite the sound lag and language barrier, it was still inspiring to see that kids our age halfway around the globe are facing the same problems we are.

It looks like you guys had a lot of fun at this dance party. In your Facebook photos I observed electric guitar, someone crowdsurfing, a guy in a sailor hat juggling fire, and what appeared to be people using ropes to move a large rock. Are these the elements of a good party for the young environmentalist crowd?

I think these are the elements of any good party, actually. Moving the rock could have been a metaphor for how teamwork can move the world or something, but it was really just for the fun of moving a rock. We were told that our generation will make it through this difficult time in climate change only if we have fun in the process.

What sorts of ideas or projects did you bring back from the summit to use at school?

The second day of the summit, all the teams were given 2 hours to create their school's "Climate Action Plan" and a detailed timeline to present to the rest of the schools at the end of the day. Our team decided to focus on 4 major projects in the coming year: improving the school garden, building a bike generator for the lobby, holding a bi-annual school-wide locker clean-out to donate gently used school supplies and teach proper recycling, and finding places to cut the school's phantom energy usage (a.k.a. the wattage used by electronics when they're turned off but still plugged in).

You may not know this, but back when I was at your school I belonged to an "environmental club" too. This meant that a couple of us would go to all the classrooms after school and pull trash out of the blue bins, because otherwise the maintenance guys refused to recycle. Is it fair to say things have come a long way?

Simply put, yes. We have a recycling bin in every classroom, our cafeteria serves vegetables from a number of local farms, quarterly grades and comments are now only available online, our drinking fountains are now water-bottle filling stations, and we have a garden that brings vegetables to the salad bar. We have solar panels on one building and another LEED-qualified building, with another one in the construction phase.

I think we're also a little cooler than your environmental club, because now we are the "Green Avengers," equipped with a logo and a Facebook page.

Are you optimistic about climate change? Do you come back from an event like this feeling like you're part of a group of people who will actually make a difference, whether it's through school-level projects now, or after college as policy makers? Or are we pretty much screwed?

Both times going to the summit I came back incredibly high in motivation, but I knew if I didn't write down all my ideas and get acting quickly, I would lose my energy. Spending time around so many like-minded people definitely makes me excited to get out there and make change.

It also reminds me we have to be able to work on our own and not rely on the work of others because that's part of the attitude that brought us to this predicament in the first place. As Dr. Powers told us, even in the earth's "best-case scenario," we'll still experience rising global temperatures. It's just up to my generation to slow the acceleration of carbon dioxide emissions and provide the optimistic attitude.

Celeriac and Parsnip Soup
Yields 18-24 servings (reduce if you're not feeding a youth summit)

Ingredients:
5 pounds cubed celeriac root
5 pounds chopped parsnip
6 tablespoons olive oil
15 cups vegetable stock
1 bundle thyme
1/2 teaspoon salt
1/2 teaspoon ground black pepper

Preparation:
Preheat the over to 400°F. Toss the celeriac and parsnip with the olive oil. Arrange the vegetables in a single layer on a foil-covered baking sheet. Roast them 35-45 minutes, flipping once, until they are tender and golden brown. Combine the caramelized vegetables with the stock and other ingredients in a pot over medium-high heat. After bringing to a boil, let the soup simmer for 15 minutes. Put all the food through a blender or food processor until smooth and serve hot.

Images: The Wild Center (top); Leigh Preston (bottom).

Elusive Marine Mammal Uses Interspecies Buddy System

What ocean mammal is a rare bird but not a lone wolf? Meet the false killer whale. You're not likely to ever spot one in the wild, but if you do, it won't be alone. These animals prefer to travel with a crowd—not just of their own species, but also including their closest companion, the bottlenose dolphin.

False killer whales are so named because the look a little like killer whales, or orcas.* Yet unlike their showy namesake, false killer whales are rarely encountered by humans. In most places where we know they live, it's only because they've turned up stranded on the shores. We don't even know whether they migrate with the seasons.

We do know that the whales are social, and that they sometimes pal around with other species. Jochen Zaeschmar, a master's student at Massey University in New Zealand, has been rescuing and studying false killer whales and other species since 2000. This summer he published a paper reporting that false killer whales sometimes partner with bottlenose dolphins to hunt. On two occasions, researchers had come across large groups of the whales and dolphins apparently working together to round up fish. They blew bursts of bubbles to herd their prey into one helpless crowd, then feasted.

For Zaeschmar's latest study, he and other researchers gathered up records of false killer whale sightings along the northeast coast of New Zealand between 1995 and 2012. It was a total of just 47 encounters—on one whale-watch boat, false killer whale sightings happened on less than half of one percent of trips.

The observations of whales and dolphins hunting together had been no (ahem) fluke. When false killer whales were seen, bottlenose dolphins were by their side "virtually all the time," Zaeschmar says—in 43 out of the 47 sightings.

"Increasing the size of your group...increases the chances of finding food," Zaeschmar explains. The prey fish hunted by these mammals are plentiful, but spread out. Working together could help the hunters find their prey, he says, and "once they do find it there won't be any competition, because there is enough for everyone."

It's also possible, Zaeschmar notes, that one species is just taking advantage of the other's superior hunting skill. The dolphins and whales seem to be working in a true partnership. But "it's difficult to really prove it."

Either way, hunting was happening during less than half of the mixed-species encounters. Yet the animals—anywhere from dozens to hundreds of them at a time—behaved like a single group. There must be some other reason they seek each other's company. "Social factors might play a role," the authors write. Staying in large groups might also help the animals keep an eye out for their own predators, which include (real) killer whales.

The researchers were able to identify some individual animals using distinctive marks and scars on their bodies, such as bites from cookie-cutter sharks (named for the shape of the bite they take out of their victims). Spotting certain animals over and over, the scientists could build a rough map of the animals' social structure. They found that "long-term associations exist between the two species," Zaeschmar says, "with some of the same dolphins observed together with the same whales [over] at least 5 years and 650 kilometers."

"These associations appear to be stable," he says. The two species stick together, whether they're ruthlessly rounding up prey or surprising a boatful of very lucky humans.

*Technically, both the false killer whale and the real killer whale are types of dolphins. But just because marine biologists like to make their lives difficult doesn't mean we have to, so I refer to the false killer whale here as a "whale."

Images: (top) Mazdak Radjainia, (bottom) David Hall.

JOCHEN R. ZAESCHMAR, INGRID N. VISSER, DAGMAR FERTL, SARAH L. DWYER, ANNA M. MEISSNER, JOANNE HALLIDAY, JO BERGHAN, DAVID DONNELLY, & KAREN A. STOCKIN (2013). Occurrence of false killer whales (Pseudorca crassidens) and their association with common bottlenose dolphins (Tursiops truncatus) off northeastern New Zealand. Marine Mammal Science DOI: 10.1111/mms.12065

Jochen R. Zaeschmar, Sarah L. Dwyer, & Karen A. Stockin (2013). Rare observations of false killer whales (Pseudorca crassidens) cooperatively feeding with common bottlenose dolphins (Tursiops truncatus) in the Hauraki Gulf, New Zealand. Marine Mammal Science DOI: 10.1111/j.1748-7692.2012.00582.x

Fish Grow Big Fake Eyes When Predators Are Near

If you're a young, edible animal, a little flexibility about how you develop can save your behind. Or, if you're a damselfish, it can get a few bites taken out of your behind but ultimately save your life.

The damselfish Pomacentrus amboinensis lives on coral reefs in the western Pacific, where it spends its days nibbling algae and trying to avoid being swallowed. As juveniles, these small fish have a pronounced eyespot toward the back of their bodies—a cartoonish false eye drawn on the body, like you might see on a butterfly's wing. Normally, the eyespot fades as the fish matures.

Researchers from James Cook University in Australia and the University of Saskatchewan in Canada asked just how flexible damselfish are while those false eyes are fading away. Can fish opt to keep their false eyes in certain situations? And if they do, does this not-very-subtle disguise actually do anything to protect them?

The scientists raised damselfish in tanks divided into compartments. Some damselfish lived alongside a natural predator of theirs: Pseudochromis fuscus, the "dusky dottyback." Thanks to the special tanks' clear windows and shared water, the young damselfish could see and smell the predator all the time. Other damselfish were raised on their own, or in tanks shared with a harmless vegetarian fish.

After maturing for six weeks in their respective tanks, the fish showed some clear differences. Compared to the other fish, damselfish that had lived near predators had larger false eyes. And their real eyes—startlingly to the scientists—were actually smaller.

"I was very surprised by the result," says lead author Oona Lonnstedt, a PhD student at James Cook University. "It just goes to show the lengths small prey will go to minimize predator attention on their front end."

This assumes that the point of all this camouflaging—growing a big fake eye near your tail and minimizing the actual eyes on your face—is to focus predators' attention on the wrong end of your body. The researchers didn't test predatory fish to see which part of a damselfish they chomped down on. But they did put the damselfish from their experiment onto isolated reef patches in the wild to see how they fared.

Within two days, up to half of the control fish (those raised alone or with non-predators) had disappeared from the reefs, and were presumed eaten. Damselfish that had grown up in a tank with predators, though, radically outperformed the others. Four days after being released onto the reefs, 90% of them were still alive and well.

Their large eyespots and minimized eyes may have made predators chase their back end, where a bite isn't as fatal as one to the head. These fish had also grown up taller in the spine-to-belly dimension, which gives an added challenge to hunters limited by the size of their mouths (and may give the damselfish better bursts of speed too). In the lab, these fish were less active and spent more time hiding; their reticence may also have helped them survive in the wild.

There's a trade-off happening, Lonnstedt says. Damselfish that live with predators and grow large false eyes also have stunted eye growth, which probably impairs their vision. It's not bad enough, though, to keep them from avoiding predators on the reef. In the end, being flexible about how their bodies develop allows them to survive and swim another day.

Image: Lonnstedt et al. (The fish on top grew up in the predator tank.)

Lönnstedt OM, McCormick MI, & Chivers DP (2013). Predator-induced changes in the growth of eyes and false eyespots. Scientific reports, 3 PMID: 23887772

Why a Lost Baby Seal May Soon Be at Your Doorstep

Every host knows when you run out of ice, the party's over. For young seals surviving on ice floes, the festivities are breaking up sooner than they used to. That sends vulnerable youngsters into the ocean before they're ready—maybe to end up stranded on a beach near you.

To keep their young from becoming drifting bait in a predator-filled ocean, female harp seals give birth on top of winter sea ice. The pups stay on the ice, undercover in a coat of white fur, until they're old enough to survive in the ocean. Then they shed their white coats, dive in, and begin migrating with the rest of their population.

Harp seals live in two main populations, one on either side of the northern Atlantic. From the population on this side of the pond, increasing numbers of seals have been showing up stranded along the U.S. coast, from Maine all the way down to North Carolina. Researchers at Duke University looked for patterns in these strandings—more than 3,000 over the past two decades.

Not too surprisingly, there was a clear relationship between strandings and the amount of sea ice. Years with more ice had fewer strandings. In years with less ice, when melting floes might force pups into the water before they're ready, strandings went up.

The same trend didn't apply to adults, however. Strandings of adult harp seals weren't linked to the amount of sea ice in that year. But in all years, the majority of stranded seals were pups. That means fluctuations in sea ice have the strongest effect on young harp seals.

The researchers also saw that males were more likely to strand than females. This may be due to what they call a "tendency to wander" among males. Brianne Soulen, one of the paper's lead authors, adds that because adult females need to spend more energy on things like pregnancy, they're less likely to stray from safe feeding grounds.

Genetic factors may also be at work. Soulen says they found slightly less genetic diversity among males, which in theory could make them more susceptible to disease or other factors. No matter the reason, if a harp seal does wind up on the shore of your local beach, it's likely to be a baby boy. Get blue balloons.

In the most recent years included in the study, 2009 and 2010, the usual pattern didn't hold up. The year 2010 was bad for ice, but didn't have a lot of strandings. However, Soulen doesn't see this as reason for optimism. An earlier study saw harp seals changing their migratory behavior in response to shifting ice cover; they may simply be stranding someplace else now, where they're not counted. Or the population as a whole may have dropped dramatically.

It matters, of course, because the ice is running out everywhere. Despite year-to-year fluctuation, the authors write, ice cover in the North Atlantic is disappearing at up to 6% per decade. And Soulen says what's happening with the harp seals provides a big hint about the state of other marine mammals. "Harp seals are a good representative species of the effects of ice changes." The hooded seal population in the western North Atlantic, for example, has declined by 90% since the 1940s, as ice there has steadily disappeared.

When sea ice is gone, there's no one who can dash out for more. The party may not be over quite yet, but it's getting pretty lame.


Image: courtesy of the International Fund for Animal Welfare

Brianne K. Soulen, Kristina Cammen, Thomas F. Schultz, & David W. Johnston (2013). Factors Affecting Harp Seal (Pagophilus groenlandicus) Strandings in the Northwest Atlantic PLOS ONE DOI: 10.1371/journal.pone.0068779

Compost Program Could Bring Dangerous Fungus into NYC Homes

If Mayor Bloomberg's wildest decay-related fantasies are realized, New Yorkers will soon be sparing their food scraps from the garbage. A new composting program would encourage (or possibly require) people in the city to collect their food waste in a separate container. Yet Bloomberg may want to consider whether a Manhattan apartment has the square footage to fit both its residents and their potentially harmful compost fungi.

The New York City recycling plan, as described in the New York Times this week, would start out on a voluntary basis. Participants would gather their food waste in "containers the size of picnic baskets in their homes," then dump the compost in curbside bins for regular collection. Instead of going into landfills, that waste might be turned into biogas for electricity. Eventually, the program could become mandatory.

Vidya De Gannes, a graduate student at the University of the West Indies, St. Augustine campus, in Trinidad and Tobago, has been composting too. She made three kinds of compost, each based on one type of dried plant material (agricultural wastes from the processing of rice, sugar cane, or coffee) mixed with cow or sheep manure. De Gannes and William Hickey, a soil microbiologist at the University of Wisconsin, Madison, who's the senior author of the new study, say these composts are most similar to a homeowner's compost mix of grass and yard waste.

To study the biodiversity of species living in compost, De Gannes collected fungal DNA from her compost containers and sequenced it. In total, she found 120 different species of fungus. Each kind of compost had a unique mix of species living inside it.

She also turned up 15 fungus species that can cause disease in humans. These were present in every kind of compost and ranged from Aspergillus fumigatus, a common fungus that can cause lung infections in people with compromised immune systems, to other species that can infect the skin or eyes.

Although the composts De Gannes studied weren't quite what New Yorkers would be collecting in their kitchens—unless they're keeping pet sheep too—some of the potentially dangerous fungi she found have also turned up in studies of all-plant compost.

Keeping a compost bucket in an enclosed space is "potentially risky," Hickey and De Gannes wrote in an email. Fungal spores floating on the air can cause infections, especially in people with weakened immune systems. "Compost kept in an enclosed area like a small apartment would probably not have adequate ventilation."

To get some fresh air, composters might have to leave their apartments and go around the corner for an extra-extra-large soda.


Image: Waldo Jaquith (not, as far as I know, a dangerous fungus)

De Gannes, V., Eudoxie, G., & Hickey, W. (2013). Insights into fungal communities in composts revealed by 454-pyrosequencing: implications for human health and safety Frontiers in Microbiology, 4 DOI: 10.3389/fmicb.2013.00164

Whale Turns Down Its Hearing When Expecting Loud Sounds

We can knit sweaters for oiled penguins, but it's harder to protect whales and dolphins from the harm of having us as neighbors. Loud underwater sounds from activities like sonar and drilling may damage these animals' hearing and even lead to mass strandings. Though we can't chase cetaceans around with homemade earmuffs, we might be able to teach them to tune us out.

Like squinting or letting one's pupil shrink in bright light, some animals can adjust how sensitive their ears are. When we're making loud noises, humans reflexively squeeze the muscles of the middle ear to dampen our hearing. Some bats do the same thing while echolocating.

"Generally speaking, mammals have evolved mechanisms to protect their auditory systems from self-produced intense sounds," write Paul Nachtigall of the University of Hawaii and Alexander Supin of the Russian Academy of Sciences. In 2008, the pair showed that a false killer whale (Pseudorca crassidens) could adjust its hearing while it echolocated. So they set out to see whether the species could also dial down its hearing in response to sounds made by someone else.

They taught their whale (a female, originally caught in the wild and now thought to be 30 or 40 years old) that hearing a quiet warning sound meant a louder sound was coming soon. The subject wore suction-cup electrodes on her head during the experiment. Waiting at an underwater listening station, she first heard a series of tones while the electrodes measured which ones her ears responded to. Then, a variable amount of time later, she heard a sudden loud sound (170 decibels).

Over hundreds of trials,* the researchers saw that the whale learned to anticipate the loud sound. If it came within 35 seconds of the warning sound starting, the whale was able to desensitize her ears before it played. (With a longer delay, her response wasn't as strong.) The authors report their results in the Journal of Experimental Biology.

Nachtigall can't say how a whale turns down its hearing. "No one knows for sure how the cetacean middle ear works," he says. Whales don't have eardrums like humans or other land animals, he says, because the sounds they hear must travel through tissue instead of air. So his whale subject probably doesn't squeeze her ear muscles to dampen sound, as a human or bat would. He speculates that it's more likely a top-down control from the brain.

However she does it, the whale can make her ears less sensitive when she knows a loud sound is coming soon. The biggest decrease in her hearing sensitivity was about 13 decibels. That's "about what your hearing changes if you stick your fingers in your ears," Nachtigall says. If you—or the whale—are trying to protect your hearing from a loud noise, he says, "That helps. This would help."

When humans must make a racket underwater, it's possible that we could help whales and other animals by making quieter warning sounds beforehand. This could teach the animals to anticipate the sound and "plug" their ears.

Since he's only studied one animal so far, Nachtigall doesn't know how the abilities of other marine mammals to desensitize their ears compare. "To ask whether [warning sounds] would prevent whale hearing damage is sort of like asking whether ear plugs would prevent deafness in people who work next to jet engines," he says. "I believe the possibility is great, but there are more questions to be answered."

Image: by MichiKimmig (Flickr)

Nachtigall, P., & Supin, A. (2013). A false killer whale reduces its hearing sensitivity when a loud sound is preceded by a warning Journal of Experimental Biology DOI: 10.1242/​jeb.085068

*If you're wondering how one convinces a whale to participate in so many trials, the answer is "fish reinforcement."

New Journal Celebrates Animal Stalking

Christmas arrived early this year for people who love animals carrying transmitters around. A new open-access journal called Animal Biotelemetry launched this week, and it promises to bring new tales of mind-blowing bird migrations and seals that study climate change (without exactly having volunteered for the job). Also, sharks.

Published by BioMed Central, the journal will include all kinds of research having to do with biological data gathered by instruments attached to animals. This is a field that's been expanding as the technologies themselves shrink. A few decades ago, scientists were limited to studying the movements of giant land animals such as bears or elk—because transmitters and battery packs were too bulky to comfortably attach to other creatures. Now, miniaturized electronics (aided by GPS satellites) mean that even lightweight birds can carry tracking devices.

Editor A. Peter Klimley describes the history of the field in an introduction to the journal. Klimley himself is a professor and shark guy at the University of California, Davis. His biography claims that he "is known to have held his breath while diving up to 100m deep in order to hand-tag hammerhead sharks with a dart gun." In case "biotelemetry" didn't sound exciting to you.

To mark the occasion, here are some earlier posts involving animals carrying transmitters around, since I am one of the aforementioned people who love them.

Monitoring from Space Shows Even This Giant Crab Can Navigate Better than You

Climate-Studying Seals Bring Back Happy News

This Penguin: An Unexpected Journey


Klimley, A. (2013). Why publish Animal Biotelemetry? Animal Biotelemetry, 1 (1) DOI: 10.1186/2050-3385-1-1

Image: by MEOP Norway North

Bats, like Batman, Thrive in a Post-Apocalyptic Environment

Without plagues, earthquakes, and unhinged criminal masterminds, the residents of Gotham might never need to put up the bat signal. Real bats, of course, are less concerned with responding to emergencies than with eating bugs. But like Batman, they do just fine—if not better than ever—in recently devastated environments. Specifically, forests that have burned down.

For five weeks in the summer of 2002, a wildfire tore through national forests in the Sierra Nevada mountains. The McNally Fire was started by a careless human, and ended with over 150,000 acres burned. A year later, scientists came by to see how the bats were doing.

"Bat ecologists have known for a while now that bats respond favorably to controlled, low intensity fires," says Michael Buchalski of Western Michigan University, one of the study's authors. "We were more interested in the effects of large, natural fires." These blazes can completely destroy the forest canopy, leaving an area unrecognizable.

Researchers visited 14 sites in the woods, half in burned areas and half in areas that were untouched. They left devices that recorded the ultrasonic cries of echolocating bats at night. Since tallying up all the bat activity they heard could be misleading—one flourishing species of bats might mask the disappearance of another—they divided the recordings into groups of similar-sounding calls, representing groups of bat species.

The researchers estimated how plentiful each type of bat was based on how often they heard its calls. Comparing burned and unburned areas, they found that no bat group was bothered by the fire. Instead, every group of bats was at least as plentiful in the fire-scorched areas—and some were doing even better than usual.

Despite the absence of costumed criminals, a few factors might account for bats' increased activity in a scorched landscape. Bats hunt by swooping through the air and searching for insects below. With much of the vegetation cleared out by fire, insects have fewer places to hide, and hunting bats have a clearer view for their echolocation.

Additionally, the first plant regrowth after a fire leads to a boom in insect species. This means there's more prey than ever available for hungry bats. "One-stop shopping!" says coauthor Joseph Fontaine of Murdoch University. Those bats may find new places to roost—or, if you prefer, build their secret lairs—inside dead trees.

Buchalski and Fontaine say bats probably need a mix of landscapes to thrive, including areas that have recently burned. Carefully allowing forests to burn more like they did in the past could lead to "healthier forests and healthier wildlife populations," Buchalski says. "However, this is a very contentious issue within the field of forestry management."

"We have spent the majority of the last century suppressing and excluding fire," Fontaine adds. "More fire right now is probably not a bad thing whatsoever." (For non-human animals, anyway.) With climate change increasing the potential for drought and wildfire, the authors say that understanding how different species deal with fire is becoming more important.

Bats aren't the only animals that appreciate a fire. Fontaine says deer mice and other short-lived rodents respond very well to fire, and deer and elk like to chew on the soft new shrubs that have regrown a few years later. Several types of woodpeckers, he adds, rely on fires. Many bird species that forage in the open and don't need living trees to make their nests have a similar response to the bats.

Although forest fires are a boon for many species, the robin doesn't seem to be among them.


Buchalski, M., Fontaine, J., Heady, P., Hayes, J., & Frick, W. (2013). Bat Response to Differing Fire Severity in Mixed-Conifer Forest California, USA PLoS ONE, 8 (3) DOI: 10.1371/journal.pone.0057884

Image from public domain files at Wikia.

Sneaky Kids Teach Parents to be Environmentally Responsible

Don't trust your kids. Like a miniature, juice-fueled army with subliminal messaging tactics, they can get inside your mind and make you do things. You won't realize what's happening until you step out of your low-flow shower one morning, turn the calendar page, and see a smug endangered trout looking back at you.

Though we usually think of education flowing down from parents and teachers to children, some people would prefer it to go upstream too. Environmental educators, for example, may hope when they teach groups of children about recycling or saving energy that they'll go home and impose new habits on their parents.

In the Seychelles, an archipelago nation in the Indian Ocean, preserving the wetlands is a major concern. An NGO called Wildlife Clubs Seychelles runs extracurricular "wildlife clubs" in the schools; these groups organize projects and go on field trips to learn about the environment. Researchers from Imperial College London took advantage of the widespread clubs to find out whether environmental education can travel against the current.

During the year before the study, certain wildlife clubs had taught a unit on wetlands while others studied something else. Lead author Peter Damerell and his colleagues studied 7 wildlife clubs that had done the wetlands unit and 8 that hadn't, with kids in the groups ranging from age 7 to 15.

The researchers distributed a questionnaire for kids to fill out in school. A second set of questionnaires went home to the kids' parents. The forms included questions to test wetland knowledge as well as questions about how people used water in their homes.

When the questionnaires came back, there were 137 complete parent-child pairs in the batch. Kids who had participated in a wetland unit scored better on questions about wetland knowledge (what kinds of species live in local wetlands, what threatens these habitats, and so on). More surprisingly, the authors report in Environmental Research Letters, the kids' knowledge had rubbed off on their parents. Moms and dads of wetland-educated kids outscored parents of kids who hadn't studied wetlands.

The questionnaires also asked parents point-blank whether they'd learned anything about wetlands from their children. Their answers, it turned out, were totally unrelated to their actual scores. Even when kids had taught their parents something, parents didn't necessarily know it.

On questions about people's water use in their homes—whether they made choices that use less water, in light of water shortages in the Seychelles—families whose children had studied wetlands with their wildlife clubs again scored significantly better. (It's also possible, the researchers note, that these families just knew the "right" answers to water-use questions. It would take more research to find out whether they actually used less water.)

Since scores didn't increase with children's ages, Damerell and his coauthors don't think regular classroom time did the trick. The wildlife clubs' field trips and outdoor projects may have been just exciting enough to make a real impression on kids—and to get them talking about their fun swamp adventures with their parents. Er, indoctrinating them.

Damerell, P., Howe, C., & Milner-Gulland, E. (2013). Child-orientated environmental education influences adult knowledge and household behaviour Environmental Research Letters, 8 (1) DOI: 10.1088/1748-9326/8/1/015016

Image: jmb_craftypickle (Flickr)

Captive Animals Act Smarter

In the Kenyan wilderness, hyenas facing a meat-stuffed puzzle box performed impressively—impressively badly, that is. Researchers expected the animals to be up to the challenge, but few of them ever got the box open. Now, repeating the experiment with captive hyenas, they've discovered that there's no contest: the captive animals are better problem solvers.

Out of 62 wild hyenas in last year's study, less than 15 percent ever managed to slide the latch and swing open the door of the barred metal box. Despite multiple chances, most of the animals were losers in this game.

But lead author Sarah Benson-Amram observed certain behavioral traits shared by the winners. Hyenas that tried more techniques to get the box open (biting, dragging, flipping the darn thing over) had greater odds of success. And hyenas that were less "neophobic"—that is, less wary when approaching a new object in their environment—also did better.

Previous studies with primates and birds had suggested that captive animals are both less neophobic and better at problem solving than wild ones. So Benson-Amram repeated her experiment on a group of hyenas living very far from their homeland, in Berkeley, California.

This group was smaller than the wild hyena group, with only 19 animals tested. But three-quarters of them solved the puzzle, Benson-Amram reports in Animal Behaviour. And every successful captive hyena got the meat on its first try—unlike the wild animals, most of which needed more than one trial before they figured it out.

Although the wild and captive animals belonged to the same species, you would get very different impressions of hyenas' problem-solving smarts if you only looked at one group.

Benson-Amram ruled out a few possible explanations for that difference. Did well-fed animals have more energy for solving the puzzle? In the wild, high-ranking hyenas ate more but didn't do any better with the puzzle box. Were hungrier animals more motivated? Skinny hyenas had no advantage either, and captive hyenas didn't lose interest after eating.

Two explanations, though, held up. One was neophobia. In the wild, animals that were more cautious about approaching the manmade box were less likely to crack it open. Captive animals were overall less neophobic than wild ones. This isn't surprising, since they're used to living around humans and our metal objects.

The second notable difference was that captive hyenas tended to try more behaviors (biting, digging, pulling, and so on) than wild hyenas did. Benson-Amram thinks this has to do with distraction.

"It’s almost akin to giving a puzzle to a civilian in an active war zone versus giving one to a person in the comfort of their living room," she says. The wild hyena is busy watching out for predators, rather than wondering whether pushing and biting at the same time might get this box open. "The person in the war zone would likely give much less mental focus to the puzzle since they have to constantly look over their shoulder," Benson-Amram says.

Or maybe the comfortable home isn't the right analogy for the captive hyenas.

"Imagine giving a puzzle to a person in solitary confinement," Benson-Amram says. "That person may be much more excited about the puzzle and interested in solving it than the person in their living room who has TV, books, their family, and other fun diversions." She adds, "I am not trying to say that zoos are as bad as solitary confinement." But captive hyenas clearly live in a more predictable, less stimulating environment than the Kenyan savannah.

Not all the hyenas learned how to open the box. But scientists learned something that might be critical. When researchers are wondering about the "maximum cognitive abilities" of a species, Benson-Amram says, captive animals may be better subjects. When they want to know what a species is capable of in the wild, though, they should remember that it's a war zone out there.

Benson-Amram, S., Weldele, M., & Holekamp, K. (2012). A comparison of innovative problem-solving abilities between wild and captive spotted hyaenas, Crocuta crocuta Animal Behaviour DOI: 10.1016/j.anbehav.2012.11.003

Image and video courtesy of MSU.

12 Days of Inkfish, Day 9: Airport Worms

While you were vacationing on New Year's Day, nearly two million worms were working hard at Charlotte Douglas International Airport. The airport installed them in the fall of 2012 as part of its new recycling center. By munching through passengers' coffee grounds, used paper towels, and uneaten French fries, the worms are making garden fertilizer out of what used to be landfill fodder.

At the recycling center, employees first sort through the airport's 25 daily tons of trash. Recyclables such as cardboard, aluminum, and plastic are sold. (One airline, project director Bob Lucas said in November, discards entire sleeves of plastic cups even if only a few were used during a flight.) Clothing, which Lucas said panicked passengers dump in the trash when their bags are overweight, is collected by a "group of ladies" who clean and donate it.

As for the worm food itself, it gets heated and pre-composted before finally going to the red wigglers. The airport plans to use waste from the worms to fertilize its grounds. The slimy new employees are happy and—now that Lucas has figured out how to stop them fleeing during a thunderstorm—seem to plan on staying at their jobs.

Image: Sparrows' Friend (via Flickr). Thanks to Leigh for the tip!

Math Shows Penguins Only Care about Themselves

Don't let the adorable mini-orchestra-conductor look fool you: penguins aren't that nice. When emperor penguins huddle together during Antarctic storms, they act like they're all in it together. But a new mathematical model shows just how the clusters of birds keep warm, accounting for everything from their geometry to the speed of the wind. Concern for one's fellow bird, it turns out, isn't a factor.

Regardless of your motivations, huddling together in a group is a great way to wait out a frigid storm. Instead of burning up their own energy reserves trying to warm their bodies, emperor penguins can rely on the warmth of a bunch of big feathery animals pressed together. There may be ten or hundreds of bodies in the huddle. Inside, the temperature is between 20 and 37.5 degrees Celsius (a cozy 68 to 99.5 degrees Fahrenheit). In the chilliest storms, penguins squeeze as tight as 10 birds every square meter.

Those huddles aren't motionless, though. With a continuous slow shuffling, the penguins rotate through the formation. Birds with their backs exposed to the wind creep away from it, up the sides of the huddle, until they find some protection. Meanwhile, birds that were formerly on the warm interior find themselves on the outside.

Three applied mathematicians at the University of California, Merced, set out to create a computer model of penguin huddling. Aaron Waters, François Blanchette, and Arnold Kim wanted to find out how well the birds' strategy works—and whether any penguins are left out in the cold.

To pack their penguin huddle as tightly as possible, the mathematicians imagined the birds on a grid of hexagons. This is the best way for circles to squeeze into a plane (think of a honeycomb), and scientists in the field have observed that real penguins arrange themselves roughly this way. The researchers also assumed that "penguins in this huddle have uniform size and shape."

Next, they added wind to the model, which flowed around the huddle differently depending on its overall shape. Then they calculated the rate at which each computerized penguin was losing body heat. They sent the coldest penguin shuffling around the outside of the huddle until it found the warmest spot it could stand in, then started over with the new coldest penguin.

The simulated penguins constantly shifted positions within the huddle, just as real penguins do. Over time, the model huddle tended to take on the shape of a flat-sided oval and travel slowly downwind (as penguins on the windward side continuously moved away from it).

When they calculated the flock's heat loss, the authors discovered that their model huddle was very fair: every penguin lost approximately the same amount of body heat. But these model penguins were only programmed to maximize their own warmth, not to consider the warmth of other penguins or the group as a whole. This means that even if penguins are only looking out for themselves, the whole huddle stays warm, as the authors report in PLOS ONE.

Just because emperor penguins can be totally selfish doesn't mean they are, the authors point out. It's still possible that penguins are altruists, organizing their huddle by thinking about the group as a whole. But it's not necessary to explain how they behave in the wild.

There's one flaw in the penguins' strategy: the elliptical shape a huddle tends to take on isn't optimal. A less stretched-out formation would help the whole group stay a little warmer. Maybe the emperor penguins should consult with a mathematician.

*********

ADDENDUM: Francois Blanchette, who was traveling when I first contacted him, says that this research was inspired by (what else?) March of the Penguins. While watching the movie, he noticed that factors in the penguins' environment, such as wind flow and heat transfer, were relevant to his own field of fluid dynamics. "I figured there should be a problem I could address that had to do with penguins," he says. "I was looking to do something different than my usual line of research."

With penguins out of the way, Blanchette and his coauthors are now interested in modeling other groups of living things, such as bacterial colonies. "However, not being biologists," he says, "we are not very familiar with other biological systems where such a model could be useful." If you're a biologist with a clump of organisms you'd like to model, let him know.


Image: Emperor penguins, by Mtpaley (Wikimedia Commons)

Waters, A., Blanchette, F., & Kim, A. (2012). Modeling Huddling Penguins PLoS ONE, 7 (11) DOI: 10.1371/journal.pone.0050277

P.S. If you enjoy reading about math and self-interested animals, you may like my earlier post Geometry Proves Sheep Are Selfish Jerks.

City Birds Adapt to a New Enemy: Cats

Moving from a rural home into the city brings challenges like figuring out trains, maneuvering couches up staircases, and not being eaten. Birds that move into urban homes have to worry about a different set of predators than their relatives in the countryside do. Although they haven't learned how to avoid hungry truck grilles, urban birds have evolved some new tricks that help them dodge the claws of predatory house cats.

For a bird living in a rural habitat, the main threat is birds of prey. But when that same bird moves to a city, it's much less likely to get snatched from above by a swooping hawk or falcon. Instead, it has to contend with roaming cats. The American Bird Conservancy says that cats (both pets and strays) kill hundreds of millions of birds each year in the United States alone.

To find out whether urbanized birds have evolved in response to their new predators, a pair of researchers captured birds inside and outside of two cities: Brønderslev, Denmark, and Granada, Spain. The researchers are Juan Diego Ibáñez-Álamo, at the University of Granada, and Anders Pape Møller at Paris-Sud University. Using mist nets and traps, they collected 1132 birds.

Each time a bird was caught, a researcher immediately collected and tested it. By simply holding a bird in their hands briefly, the scientists could score all the ways it responded to capture. Did the bird scream out distress calls? Bite? Shed its feathers? When released, did it fly off right away or lie frozen in panic?

The researchers collected members of 15 bird species that lived in both the city and the country. For each of these species, they compared the behaviors of urban and rural birds to determine how the birds had adapted since moving into the city.

Like newly minted Manhattanites learning to keep their doors locked, urban birds have developed new safety habits, the authors report in Animal Behaviour. One such habit is screaming bloody murder. When researchers seized city birds and held them in their hands, the birds were much more likely to make alarm calls and "fear screams" than birds of the same species that lived in the country. Møller and Ibáñez-Álamo think this behavior has evolved because in the city, birds live close to their relatives instead of dispersing widely. Families that alert each other to predators keep their genes alive.

Other habits that may have helped birds escape from raptors when they lived in the country—namely, biting and wriggling around when caught—were less common in city birds. (I'm guessing biting was not as uncommon, however, as the researchers holding the birds would have liked.)

Urban birds also showed off a trick that was less common in their rural relatives: shedding feathers. This trait seems to help deter hungry cats. When finding yourself in the mouth of a house cat is a real danger, being able to shimmy away and leave that cat with a mouthful of feathers will help you survive.

Some of the bird species studied had lived in the city since the late 19th century, while others had only moved in during the 21st century (according to local bird experts who'd monitored their populations). For a couple of the escape behaviors they studied, the researchers were able to see changes increasing over time: birds that had spent a lot of generations in the city had changed more dramatically than recent immigrants had.

This suggests that as birds and other animals continue to reside and reproduce in the city, they'll keep evolving in response to their urban predators. If we give them long enough, maybe they'll even figure out how to escape cars.

Møller, A., & Ibáñez-Álamo, J. (2012). Escape behaviour of birds provides evidence of predation being involved in urbanization Animal Behaviour, 84 (2), 341-348 DOI: 10.1016/j.anbehav.2012.04.030

Image: Jody Sticca (Flickr)

Belly Button Safari: Who's Living in There?

"We are covered in an ecological wonderland," declares Rob Dunn, a man with a strange idea of a wonderland. In the wild bacterial jungle that is our skin, Dunn has been studying an especially dark cave: the belly button. He's found out which microorganisms are the big game, which are the rare birds, and which ones may take up residence in your navel if you stop bathing.

Dunn is a biologist at North Carolina State University who studies the tiny life forms that share our personal space, from insects in our yards and houses to microbes on our bodies. The organisms we live with can affect our health, for better or worse. Yet researchers are only beginning to explore the various ecosystems we carry on ourselves. From our intestines to our faces to the bottoms of our feet, each of us holds a planet's worth of different habitats.

Out of all these bacterial habitats, the belly button is especially convenient to study. Everyone has one. Its shape and size don't change dramatically from person to person (among innies, anyway). And it's hard to scrub clean, making it a relatively undisturbed environment on the body. A national park, if you will.

The belly button also has crowd appeal, which is important for Dunn's citizen-science approach. He's interested in projects that involve unsqueamish members of the public. For his belly button research, Dunn recruited crowds at two 2011 events: One was Darwin Day at the Museum of Natural Sciences in Raleigh, North Carolina, and the other was the annual Science Online conference in Raleigh.

In total, 60 volunteers had their navels swabbed. Researchers extracted the bacterial DNA from each sample, sequenced it, and searched it for matches to particular species.

What the team found was diversity, and lots of it, as they report today in PLOS ONE. With a median of 67 different bacterial species per person, Dunn says the navel is at least as diverse as the other skin areas studied so far. That diversity varied widely; some people housed more than 3 times as many species in their belly buttons as others.

Out of the thousands of bacterial species the researchers found overall, the vast majority showed up in only a few people, or in just one person. Even though this habitat looks similar from one person to the next, we all have very different collections of rare critters running around in the undergrowth. No one bacterial species appeared in every belly button.

But there are common belly button denizens, too. On our umbilical safari, these are big obvious trees and loud monkeys that show up in most people's jungles. Eight species of bacteria were present in more than 70% of subjects. And wherever these species show up, they do so in large numbers. If you could dump the bacteria from everyone's belly buttons into one pile, members of the 8 king-of-the-jungle species would make up nearly half the heap.

Extending this group to the 23 most common bacterial species, the researchers looked at how the group's DNA compared to rarer bacteria. They found that the ruling bacteria were more closely related to each other than randomly selected groups of bacteria were—sort of a royal family. This suggests that the most common belly button bacteria share evolved traits that help them thrive in this environment.

The most surprising thing about the belly button bacteria, Dunn says, is their ultimate predictability. Even though thousands of species turned up in his study, he now knows which ones are most likely to live in someone's navel. "I expected that the common species would be far more random," he says. "But the truth was otherwise." There are only a few bacteria ruling the belly button jungle, and a diverse throng of others that make up their subjects. Dunn thinks we might be able to study what goes on in our skin's ecosystem by focusing on these few common bacteria.

Dunn hopes that eventually he'll be able to predict the specific bacteria living in someone's belly button based on their age, gender, habits, and history. "But I'll admit we are having an interesting struggle," he says. The research shows that people can be sorted into two or three "bacteriotypes," like blood types, based on the clusters of bacteria that inhabit their navels. But as to why a person is one type or another? "So far we can't explain what causes those differences," Dunn says. "It is a real mystery."

He's getting a little help in this area from one Science Online participant who claimed not to have showered or bathed in "several years." This subject's belly button swab turned up two species of archaea—single-celled organisms, entirely separate from bacteria, that often live in extreme environments. Until now, no one had found archaea on human skin.

This social non-conformer might represent the kinds of bacteria that our ancestors carried around. "Historically, no one washed very often," Dunn says. "This colleague of yours may be far more representative of how our bodies were for thousands, or even millions, of years than are most folks."

He adds, "That isn't saying I'm encouraging everyone to abandon washing."

Dunn suspects that belly button depth, too, might influence what species live there. But he's had a hard time studying this. "No one really wants to answer a question about the depth of their innie, no matter how anonymous we make the process," he says. However, his group's next study will look at a larger group of people, including outies.

Future safaris into our bodies' ecosystems might help scientists understand skin allergies and other health issues. Although belly button sampling is over for now, Dunn encourages people who want to get involved to join the mailing list at yourwildlife.org. He's currently looking at camel crickets in basements, ants in yards, and bacteria in bedrooms and kitchens.

"Armpits," Dunn adds—or perhaps threatens—"are also on the horizon."


Jiri Hulcr, Andrew M. Latimer, Jessica B. Henley, Nina R. Rountree, Noah Fierer, Andrea Lucky, Margaret D. Lowman, & Robert R. Dunn (2012). A Jungle in There: Bacteria in Belly Buttons are Highly Diverse, but Predictable PLOS ONE : 10.1371/journal.pone.0047712

Images: Copyright Belly Button Biodiversity.

How Rice Plants Kick Out Party Crashers

To really sympathize with rice—and to understand why it's developed tricks for bossing insects around—I need you to imagine you're a plant throwing a party.

Have you got it? Let's say it's a sushi-making party, since, you know, you're a rice plant and you already have one ingredient.

So you're Oryza sativa and you're growing in a field somewhere in Asia, and you're enjoying your party with the other rice plants. But then a notorious moocher shows up: the brown planthopper, Nilaparavata lugens. And it brings a whole crowd of its friends.

Next thing you know, the moochers are stealing all your sushi and eating it. Which is to say, they're causing severe crop damage. Brown planthoppers are one of the world's biggest rice pests. They feed on sap from the stems, carry viruses that infect rice plants, and lay new generations of eggs on the leaves.

Since that kind of behavior can ruin a party, you (the rice plant) want to drive the freeloading insects out. You can't physically remove them, so instead you change the tone of your party to something that's not at all their taste. Let's say you switch off the classical music and crank up some heavy metal.

Really, the rice plant emits a chemical called S-linalool into the air when it senses the familiar chewing. Brown planthoppers don't care for the molecule. But if any of them stick around, they'll be sorry. That's because the loud music simultaneously attracts the rice plant's real friends, who love both heavy metal and laying their eggs inside the eggs of brown planthoppers.

These metal fans are the parasitic wasps Anagrus nilaparvatae. Their larvae grow inside the planthopper eggs where they're laid, consuming the unhatched planthoppers from the inside out. And the same chemical signal that hustles the mooching planthoppers out of the party summons the wasps to punish any that stay behind.

Yonggen Lou at the Zhejiang University in China, along with other researchers, found out what the rice plants were up to by spying on them both in the lab and in the field. They knew already that rice plants emit S-linalool when they're chewed on by planthoppers. In fact, all kinds of plants are known to release certain compounds in apparent self-defense. But to understand the crashed house party one step at a time, the scientists created genetically altered rice plants that couldn't make S-linalool at all.

Starting with regular, non-altered rice plants, the researchers showed that S-linalool (the heavy metal music) was turned on whenever brown planthoppers fed on the plants—or when humans repeatedly stabbed the rice stems with tiny needles, imitating planthoppers in search of sap.

Next the researchers released groups of brown planthoppers into cages holding the rice plants. They saw that females preferred to hang out and lay their eggs on the genetically altered plants that couldn't make S-linalool. This means regular, unaltered plants, which could crank up the music when they wanted to, ended up with fewer pest eggs.

To explore the tastes of the parasitic wasps, researchers didn't let them see the plants or the planthoppers at all. Instead, they put the wasps in tubes and gave them whiffs of chemicals previously released by  rice plants. The wasps followed the smell of regular plants that had been chewed by planthoppers—and released S-linalool—but weren't interested in the smell of genetically altered, non-heavy-metal-playing plants.

When the same genetically altered plants were growing in a field, scientists found more than twice as many female planthoppers on them (along with their eggs) than on the regular, S-linalool-producing plants. And the insects on the altered plants had significantly fewer parasitic wasps attacking them. There were also fewer predatory spiders on those plants. The rice plant, despite being stuck in one place and seeming pretty passive, is dictating in detail who's invited to its party. 

Not all compounds emitted by plants are for deterring pests, though. The researchers also studied a second chemical that comes from the rice plant called (E)-β-caryophyllene. Presumably it's helpful to the plants, because they make it all the time. But brown planthoppers are attracted to it—as are their parasitic wasps. At the sushi party, let's call it the beer.

Yonggen Lou thinks farmers might be able to take advantage of the compounds rice plants naturally emit. For example, they could grow rice around the outside of a field that's genetically engineered to produce only (E)-β-caryophyllene (the beer) but not S-linalool (the loud music). These plants would attract both brown planthoppers and their pests. The rest of the rice plants in the field would be engineered in the opposite way, cranking up the heavy metal without providing any beer. Since pests would gather at the edges of the field, where the more attractive molecules were in the air, farmers could reduce their pesticide use and protect their crop. They're the ones, after all, who would really like to be in charge of the guest list.

Xiao Y, Wang Q, Erb M, Turlings TC, Ge L, Hu L, Li J, Han X, Zhang T, Lu J, Zhang G, Lou Y, & Penuelas J (2012). Specific herbivore-induced volatiles defend plants and determine insect community composition in the field. Ecology letters, 15 (10), 1130-9 PMID: 22804824

Image: Brown planthoppers by IRRI Images (Flickr)