On January 18th, 2018 we learned about

Survey of species parses the prerequisites for a wielding a weaponized tail

It’s hard to fight with your rear end. Aside from a creature like a horse chasing away flies with its tail, few creatures can be said to be more intimidating from behind. There are exceptions to this rule, and they’re unusual enough that researchers have studied every tail-swinging tough-guy to see why those species evolved to fight with their rears instead of their claws or faces. Even though using one’s head or limbs would seem perilous in its own way, the number of anatomical requirements needed to make a tail weapon functional may have curtailed (ahem) their popularity in both living and extinct animals.

There’s obviously some variety to how a weaponized tail can operate. Dinosaurs like Stegosaurus carried spiked thagomizers, while some ankylosaurs ended up with bludgeoning clubs. Living species are generally a tad less ornamented, but the quills on a porcupine or the speedy snap of a monitor lizard’s tail can still make a foe think twice about attacking. Once a list of 286 species was assembled, researchers categorized them by an array of traits, from diet to size to the presence of bone or spikes on the tail’s tip. At that point, the data could be sorted and sifted to find what common threads united the reptiles, mammals and dinosaurs that have ever purposely backed into a fight.

Two traits proved to be universal among all the tail-swingers. Every animal that did battle with its rump was an herbivore, and as such these weapons weren’t being used for hunting. Most living species with dangerous derrieres only use them defensively, although exceptions, like rainbow agama lizard, pick fights to compete for mates. Still, it seems that teeth and claws have an edge (sorry) for predatory activities, beating out clubbed behinds as the anatomy of choice for predators around the world.

Other traits that were tied to tail weapons weren’t quite as obvious. Creatures with enlarged tail tips, like Ankylosaurus, Glyptodon or Shunosaurus, were all huge, with specially formed vertebrae in their tails. Stiff tails seem to require a smaller minimum body size, but shared a likelihood for osteoderms, or bony skin armor. Tail spikes, such as those found on a Stegosaurus or meiolaniid turtles, were tied to more head ornamentation, wide hips and some kind of bony but discontinuous armor on the torso. All the extinct species were also found to share osteoderms enveloping their tail tips, as well as an unusually stiff trunk, possibly to provide better leverage for lateral tail-swings. Living backside-battlers still follow many of these rules, although the minimum size requirements have shrunk down to around three feet in length since the age of dinosaurs.

Putting these parts in perspective

This may seem like a very roundabout way to describe animals we already know of, but organizing these traits helps bring a few things into focus. Requirements like stiff bodies and protective skin covering had to evolve before tails were weaponized, since a tail club or spike is the less common feature, and there’s evidence that anatomy like osteoderms actually fused together to create those weapons in the first place. However, most large herbivores found other ways to protect themselves before actually developing a rear-mounted defense mechanism. This isn’t to say that tail weapons were ineffective at their jobs, but that they require so many other anatomical conditions first, they’re very unlikely to evolve in the first place.

It also seems that, as cool as a tail bludgeon or thagomizer may have been, the complete package of bulk, armor and bone didn’t necessarily out-compete other forms of defense once they were assembled. Instead, brawling with one’s butt remains a bit of a niche adaptation that evolution keeps playing with, but rarely fully commits to.

Source: Where did all the tail clubs go? by Victoria Arbour, Pseudoplocephalus

On January 18th, 2018 we learned about

Updating our spotty, rat-filled understanding of the 14th century plague epidemics

If there’s one thing we can learn from the Black Death in the 14th century, it’s the importance of record keeping in times of crisis. Granted, it was probably hard to focus on documenting what was going on when tens of millions of people were dropping dead for no obvious reason. However, piecing together exactly how the plague spread with the speed it did has been an ongoing question, even long after we’ve come to understand and successfully treat the Yersinia pestis bacteria that actually causes bubonic plague. While rats have long been thought to have carried fleas that carried the bacteria, new investigations are starting to cast doubt on what we thought we knew about these horrifying epidemics.

No rats required

To be clear, Y. pestis is still the cause of death that killed millions of Europeans on more than one occasion. The question is how big a role rats played in transmitting the bacteria to humans. Part of our evidence against the rodents is that they have often play a role in plague outbreaks today, which understandably makes a strong case for their guilt in the 14th century. However, there are some holes in the story of past epidemics, such as no reporting on dead rats turning up in large numbers (as the rodents can be killed by the plague just as we can.) Researchers have also questioned if the flow of infections that we do know about really required rats’ presence in the first place, so they ran some tests to find out.

These experiments obviously didn’t involve risking any human or rat lives. They were conducted as simulations in a computer, allowing changes in different variables to be run over and over, eventually revealing the likelihood of one scenario over another. Obviously, long-shots can still happen, but these simulations showed that fleas biting humans could be passed around quite efficiently with no help from furry friends. In fact, in seven out of nine cities’ virtual infections, the human-flea-human model was a better match for mortality records than scenarios that depended on the movement of rodents.

Looking at leprosy

While these simulations have tried to consider an array of data sources to build a more accurate picture of how the plague spread, some historical gaps have been filled erroneously. Many images that are now archived as contemporary depictions of plague victims are actually pictures of other diseases entirely, such as leprosy. This kind of mistake has become common enough that it’s likely reshaping people’s understanding of what symptoms the bubonic plague actually produces.

Medieval images of leprosy, later labeled as the plague, often include eye-catching lesions on the victims’ skin. It’s dramatic and easily understood as a sign of disease, making these mislabeled images all the more convince to audiences lucky enough to never encounter an actual bubo- the real calling card of the bubonic plague. While some victims could occasionally end up with dark red spots under their skin, most people would end up with a single swollen lymph node in the armpit or neck, depending on where the bacteria-carrying flea bit them. However, these buboes don’t turn up in any drawings or paintings from the 14th century outbreaks. Instead of showing the medical reality of the plague, the few contemporary images directly related to the epidemic focus on its effect on societies, such as a drawing of people burying coffins from 1349, or Jews being burned alive in the 1340s after they were blamed for the disease.

Seeing patterns in the symptoms

Even after the dramatic epidemic of the 14th century, the plague revisited Europe every few decades. Bit by bit, people started to put the pieces together, even making a point to record what an actual plague victim looked like. Images of swollen lymph nodes are directly connected to the plague in imagery from the 15th century, both in artwork and medical documents, some of which suggested lancing buboes to save infected patients.

It’s understandable that people didn’t know what to keep track of before they even knew what was making them sick. But it’s interesting to consider how much information about a curable disease is still hard to be sure of. As someone who was preemptively treated for bubonic plague once as a toddler, I guess I’m just grateful that someone around me knew what to look for at a time when it counted. For what it’s worth, in that case people blamed a flea-bitten cat.

Source: Maybe Rats Aren't to Blame for the Black Death by Michael Greshko, National Geographic

On January 17th, 2018 we learned about

Identifying the brain cells that mammals use to make mental maps of where their peers are moving

You can, presumably, walk through your house without needing to concentrate on where you are. You’ll probably make a note of a chair out of place, or shoes left on the floor, but you won’t have to think much about your relationship to the space around you thanks to your hippocampus. This small structure in the center of your brain has been found to use neurons known as “place cells” to essentially build a map of wherever you are. In addition to keeping track of your position in your immediate surroundings, researchers are now finding that the hippocampus is also tracking where social peers are moving, as well as the trajectories of other objects.

To see these varying layers of functionality in action, researchers monitored the brain activity of both rats and Egyptian fruit bats while they moved through a closed environment. They compared which neurons in the hippocampus were active when the primary animal was moving to when they watched a peer moving through the same space. For rats, this was easier, as the primary rat could watch from a closed space while their peer explored a simple T-shaped maze. The bats initially wanted to fly right alongside their peers though, so researchers had to rely on social hierarchies a bit. They allowed an alpha male in the group to fly between designated waypoints first as a “teacher,” while monitoring the brain activity in a subservient “student” bat who had to wait its turn.

Brain cells for spatial awareness

With lightweight “neural loggers” in place, researchers were able to precisely observe which neurons in the hippocampus were needed for each phase of each experiment. With both rats and bats, the place cells seemed to be sorted into a few general groupings. Some were active only when the primary animal was traveling through the maze, or flying to the designated perches. Other place cells seemed to be designated for tracking the peer animals’ travel, although there was some overlap in these groups, possibly for when the primary animal arrived in a location previously occupied by its peer.

Finally, there were cells that were activated by watching non-animals in the space. The bats, for instance, were shown bat-sized balls that were moved through the same course they’d flown through themselves. This movement was still mapped to place cells in the bat’s hippocampus, but they didn’t show the same overlap as before. There seemed to be a bigger distinction being made for the ball, although at this point it’s hard to be sure if this was because the bat recognized that the ball wasn’t alive, or if it was simply not a bat.

More than a simple map

While the bundles of place cells weren’t described identically in both studies, they both point to similar categorization in rat and bat hippocampuses. The place cells for the primary animal partially overlapped with the cells activated by watching a peer, and these were separate from inanimate objects on the same map. Researchers suspect that the overlap with living peers may be informed by their social relationship to the primary bat or rat. This would mean that the hippocampus isn’t only charting the physical world, but also the animal’s social relationships as well. If this is true, a bat watching a rat would map the rat’s location more like it mapped the ball- as a discrete group, instead of overlapping with the bat’s own location.

The functionality of these animals’ hippocampuses isn’t only relevant to how a rat finds its way through burrow. The similarity between these two species’ brains is very likely to originate from a common mammal ancestor, which means that our own hippocampus is mapping the world in the same way. Even if we don’t normally need to consciously think about these relationships when walking through our house, knowing how our brains deal with the world will help us work with these functions break down due to aging, disease or other damage.

Source: ‘Bat-nav’ reveals how the brain tracks other animals by Alison Abbott, Nature

On January 17th, 2018 we learned about

Science scrutinizes what factors make for a superior smile

My third-grader has mastered her publicity smile. While she isn’t posting selfies anywhere yet, she’s apparently put some work into making sure she has a camera-ready grin. I realize that, as her parent, I probably carry some biases about her appearance, but fortunately scientists around the world have been working to figure out what a truly optimal smile looks like. Crafting a smile isn’t risk-free though, as research has also found a few downsides in even the most beaming grin.

Perfect mouth position

As many of us have found out the hard way, not all smiles are created equal. How much a person opens their mouth or exposes their teeth can make greatly change how that smile is received by onlookers. To really parse which combination of mouth-shapes matter, researchers from the University of Minnesota surveyed people with images of an artificial head so that the other features could remain consistent while the smile was tweaked and adjusted in small ways. What they found was that a wide smile is judged as attractive if the teeth don’t show, a more open smile looks good if the mouth isn’t stretched wide, and a “medium” smile is pretty safe with teeth, no teeth, or something in between. To be more specific, the best-rated grins had a mouth angled between 13 and 17 degrees at the corners, with a width between 55 and 62 percent the distance between the eyes.

Before you worry about pulling out a ruler the next time you see a camera, it should be noted that these measurements don’t tell the full story. Cultural differences, asymmetrical features and the expression in your eyes can all influence how a smile will be received. The context of your smile counts too, since what’s a great smile on vacation might not be so winning at work.

Friendly but flakey?

A second study looked at how prospective clients view smiles of an agent they’d like to hire for different tasks. Overall, broader smiles were judged as being warmer, which may be great for someone working as a customer service agent. People with jobs that involved potential risk, like surgeons or investment advisers, were penalized if they had a large smile. They were still seen as warm, but also less competent than competition who looked more reserved.

The appearance of age

That broad, warm smile may also misrepresent your age. A third study found that participants all felt positively about images of smiling people, but they surprisingly also expected them to be older than they were. Despite what participants expected of how a facial expression might affect appearances, looking surprised was apparently the best way to look younger, probably because a wide-eyed gasp helps hide wrinkles, while a solid smile adds some friendly crinkles around the eyes and mouth.

Smiling after stealing

This may seem like a lot of pressure for something as simple as a photo, but the highest stakes for your smile may be tied to social competition. Researchers at the USC Institute for Creative Technologies had test participants play a simple game, where they could either compete or cooperate with a partner to win money. For each round of the game, players chose to either split the money or steal it. If both agreed to split the money, they did exactly that. If one chose steal, they got all the money, and if both chose steal, both players received nothing.

If one player successfully stole the money, the facial expressions of both players were found to greatly influence the next round of play. A smiling victor would almost certainly drive the loser to choose “steal” on next, apparently as a way get retribution for the previous loss. However, if the loser smiled, it would act as an instant peace treaty, and the both players would be more likely to “split” the next round of the game.

Nodding seems nice

With this many nuances and consequences being attached to a simple smile, it’s fair to be hoping for a tip on just feeling less self-conscious about your facial expressions. Fortunately, researchers in Japan may have a handy shortcut to boosting how likeable and approachable you look. Just nodding your head up and down, as when you’re agreeing to something, was found to improve a virtual human’s likability by 30 percent. Better yet, when the figure shook it’s head “no,” its likeability wasn’t penalized in viewers’ eyes, meaning you don’t even have to worry about saying “yes” to every question you encounter. These results were looking at a female face with Japanese viewers only, so they might not be shared by people around the world. But a friendly nod coupled with a moderate smile seems like practical enough formula to aim for the next time you need to make a good impression.

Source: A winning smile avoids showing too many teeth, researchers say by Nicola Davis, The Guardian

On January 16th, 2018 we learned about

The wolf, pirate and pelican spiders that prey upon their eight-legged peers

Going by the numbers, it may spiders seem to have a particular vendetta against insects. After all, eating up to 800 million tons of bugs every year takes some dedication, or at least some well-honed predatory adaptations. As it turns out, eating only bugs would leave a lot of other food on the table, such as spiders themselves, and so some species have diversified their diets. As great as spiders are at catching crickets and ants, it turns out that they’re great at hunting their fellow arachnids as well.

Speedy stalkers

On the generalist side of things, wolf spiders will eat just about anything they can get a hold of— even small vertebrates. Instead of waiting in a web, spiders in the Lycosidae family travel along the ground or in burrows to hunt for prey while trying to avoid being eaten themselves. Some wolf spiders can be slightly strategic in how they hide and ambush their food, but for the most part they get by on speed and a bit of stealth.

Home invaders

Cellar spiders, often known as daddy long-legs, use more traditionally “spidery” tactics to catch their food. Their messy, tangled webs can catch a variety of insects, but they’ll also venture into other spiders’ webs to attack its original occupant. Their long, spindly legs help them move quickly over both their own and other spiders’ silk, giving them an edge when they feel like dining on arachnid.

Pelican impalers

Eriauchenius and Madagascarchaea spiders are a bit more specialized for picking off other spiders. Known more commonly as pelican spiders, these unusual predators have long “necks” and even longer chelicerae, the fang-tipped mouthparts that are much more modestly sized on other species. The combination of an elevated mouth and long chelicerae lets these spiders impale and hoist their prey off the ground like a hungry forklift, trapping prey in the air until they finally die. Specimens found in amber show that this lineage has been using this immobilizing strategy for at least 50 million years. They can be found in South Africa, Australia, and Madagascar, with the latter location being home to half the species alive today.

Pirate raiders

Pirate spiders in the family Mimetidae don’t have any special hook or peg-leg anatomy, as their names comes from the range of behaviors they use to acquire food. Rather than build their own webs, they search for other species’ webs to raid, usually starting with orb or cobweb weaver themselves. The pirate spider will first pluck at different threads in the web to imitate trapped prey in an attempt to lure the original spider into danger. Once in range, the pirate spider will lunge at its target, where a bite to the leg will immediately paralyze it’s meal thanks to the hunter’s spider-specific venom. Once the host spider is dispatched, the pirate may make use of the web to catch a few bugs as well, even eating other spiders’ eggs if it finds them.

This is by no means the complete list of spider-on-spider predation. For every specialized nest or venom, there’s probably another spider waiting for its next chance to eat some of its kin, assuming it doesn’t fill up on insects first.

Source: Who eats spiders? by Ben Goren, Spiderbytes

On January 16th, 2018 we learned about

Future spacecraft will likely navigate by the light of distant pulsars

The universe is expanding, and accelerating, every day. More locally, the planets in our solar system are whipping around the Sun at up to 107,082 miles-per-hour. All this can make it hard for a spacecraft to pick a reference point, which is part of why our current probes have to call home for directions so often. While we obviously want to communicate with our spacecraft as they explore the galaxy, finding a way for them to plot their own course a bit more would save time and energy. Fortunately, experiments with distant pulsars have been suggesting that they can be used as reliable sign-posts as we push further and further into space.

A pulsar is a special type of neutron star. They’re incredibly dense collections of debris made of the remnants of an exploded star with the added twist of also being highly magnetized. This magnetic polarization means that a pulsar emits x-ray energy from its north or south pole, rather than in all directions at once. Since the closest pulsar is around 280 light years away, we only see the emitted energy from a pulsar when it’s pointed in our direction, which happens on a regular schedule thanks to the pulsar’s rotation. In some cases those rotations are so fast that we get what appears to be a pulse of energy on a millisecond timescale, turning the pulsar into a handy blinking landmark that our spacecraft can use as a relatively stable reference point.

Piloting by pulsar

Right now, no probe is navigating by pulsar, but several instruments have been collecting data on them. The United States Navy has concluded a test with a satellite navigating by pulsar, and instruments on the International Space Station like the Neutron Star Interior Composition Explorer (NICER) have been collecting data both on the size of pulsars and how quickly they appear to “blink” from the perspective of our solar system. With these data, researches have come up with formulas that allow for a location in space to be identified within three miles.

As we refine our pulsar tracking abilities, researchers hope to reduce that margin of error to a half-mile. Once we can reliably triangulate an object’s location in relation to the energy from distant pulsars, spacecraft should be able to handle more navigation commands without calling back to Earth for updates. Pulsar-based navigation could also be used as a secondary navigation system for more sensitive missions, such as when humans attempt our first trip to Mars. The fact that tracking pulsars only requires a modestly-sized sensor makes this method of navigation quite practical, even if it requires enormous amounts of energy being blasted from from collapsed stars light years away to work.

Source: NASA test proves pulsars can function as a celestial GPS by Alexandra Witze, Nature

On January 15th, 2018 we learned about

The surprisingly specialized movements that let snakes scoot in a straight line

At long last, one snakes’ defining abilities has been explained. While not quite as flashy as venomous fangs or heat-detecting sensory organs, a snake’s ability to crawl forward in a straight line without bending its body is a trait that was probably instrumental in their evolution, as it enabled them to invade the burrows of their prey more easily. As it turns out, scooting along without scrunching up isn’t such a straightforward process.

To measure exactly how a snake engages in “rectilinear locomotion,” or crawls in a straight line, researchers needed to measure their movements both inside and out. Boa constrictors were outfitted with electrodes for an electromyogram (EMG), which could keep track of the electrical impulses sent to different muscle groups in the crawling snake. While those readings kept track of the exact sequence of muscular activities inside the snake, it was also filmed while wearing reference markers on its skin, similar to motion-capture suits used in special effects. The combined data let researchers piece together exactly how the boa would manage its movement as it moves through the jungle.

Most of the propulsion is thanks to the snake’s abs. The skin along the stomach was seen to stretch forward in sections, followed by the muscles along the ribs and spine. Sections of the snake’s belly would “reach” forward at a time, almost like a pulse of movement that would start at the head then continue down towards the tail. Even though each muscle group would be making discrete cycles of movement, this activity was so coordinated that the backbones actually end up moving at a constant speed.

Sliding and sticking with scales

Previous studies have found that belly-flexing is likely aided by a snake’s scales. By dragging snakes across different surfaces, researchers found that the stomach scales reduce friction when moving forward, but resist sliding backwards. While a treaded stomach would greatly complement the belly-flexing motions measured with the boa constrictor above, it’s still only part of how a snake can maneuver. They were also found to employ “dynamic weight distribution,” wherein they can control which part of their body is pressing against the ground the most, further gaining traction while reducing friction at the same time. That movement may play a role in rectilinear locomotion, but it likely plays a bigger part in snakes’ other forms of slithering, like sidewinding and serpentine motions.

A boost to biomimicry

This understanding of snake movement is good news for robotisists. A snake’s ability to move through narrow spaces to catch prey makes them a great model for robots that need to investigate pipelines or look through rubble to find disaster victims. Those robots probably don’t need to worry about imitating a boa’s constricting motions, but being able to reliably crawl forward in a space just wider than their mechanical bodies would be of great use to engineers.

Source: Researchers explain how snakes can crawl in a straight line by Michael Miller, Phys.org

On January 15th, 2018 we learned about

Sifting through the causes, concepts and misconceptions of quicksand

Despite growing up in tame suburban landscape of sidewalks and lawns, my kids are very concerned about how to deal with quicksand. I can only assume that repeated viewings of Wreck It Ralph and The Force Awakens (no Princess Bride yet) have helped build up the mystery of watery sand, particularly since fiction usually portrays it as something perilous that can capture a hero without warning. Of course, having seen DuckTales and G.I. Joe, I know that my kids’ concerns are unfounded, and that we’ll never run into quicksand near our home. Or so I thought.

Sources of soupy sand

Well, I was right about the general composition of quicksand. It’s any loose, grainy soil with a large concentration of water in it to turn it into a fluid. One of the most common places to run into quicksand is at the beach when water rushes into loose sand. Sand that’s only moist is likely to clump together, but with enough water flowing through the sand, each grain will separate and basically roll around independently of each other. The resulting soup can then look like solid ground from above, but has a consistency just a bit thicker than water when you step into it. While quicksand in nature is going to involve water, Mark Rober has a great demonstration of how sand can behave like a fluid using air as well.

Now, not every puddle turns into quicksand, obviously, mainly because the water needs to flow in a way that helps separate the grains of sand or soil. A great way to break up clumped soil turns out to be vibrations from earthquakes, and tremblors are a major cause of quicksand in all kinds of environments. Quake-produced quicksand is actually a significant safety hazard, not so much for people suddenly in need of conveniently placed vines, but for buildings that partially sink into the ground, stressing or warping their structural integrity. As such, researching the exact combinations of vibrations, soil composition and water flow has been the subject of research looking to predict which locations are most likely to suddenly turn to soup when the ground shakes.

Saving yourself from sinking

Aside from our next trip to the beach, the intersection of quakes and quicksand adds sudden legitimacy to my kids’ concerns about sinking into the soil. We don’t live especially close to a marsh or lake, but earthquakes aren’t uncommon in the Bay Area. Unless a water pipe bursts at just the right spot, it still seems unlikely that we’ll run into quicksand nearby, but there aren’t many conveniently placed vines to grab hold of if we did. Despite what cartoons and movies have taught us, that’s probably ok, since most quicksand isn’t likely to swallow you up in the first place.

While drowning in fluidized soil can happen, most instances of quicksand in nature aren’t that deep, so you aren’t likely to be fully submerged in order to drown. You might get stuck though, and trying to lift your legs straight up to take a step would be very difficult. Your best option is to try to lean back and spread your arms, letting buoyancy help lift you up. Small movements of your legs will help loosen them, but sharp vertical yanks aren’t going to be practical. This isn’t to say that people don’t die after getting stuck in quicksand, but some of those cases are due to other factors, like rising water levels, than the quicksand on its own.

Source: How Quicksand Works by Kevin Bonsor, How Stuff Works

On January 14th, 2018 we learned about

Differing degrees of intervention needed to protect endangered birds’ nests

One of the jobs of many bird nests is to keep the eggs, and later chicks, safe from harm. Different species have come up with a huge range of nest designs, although none are so perfect that they couldn’t use a helping hand in certain situations. In some cases, help means keeping people away from nests, while in others it means adding light sensors and mechanization to deal with threats that birds just haven’t had time to adapt to. Granted, those threats can often be traced back to human activity, but that shouldn’t preclude people from doing what we can to help keep these endangered birds as safe as possible.

Avoiding the eagles

Bald eagle (Haliaeetus leucocephalus) populations in the United States have been slowly recovering since the pesticide DDT was banned in 1970, but they’re certainly not in the clear yet. Researchers have been keeping a close eye on breeding pairs, but not in a way that would be obtrusive to the birds themselves. In Minnesota national parks, this respect for the birds’ sanctity also led to the sequestering of around nine eagle nests each year. The goal was to keep people away from any nests that might be home to eggs or eaglets, under the assumption that human interference would reduce the reproductive success of the nesting birds.

The effort to keep humans away from nesting eagles seemed to be moderately successful at first. When the nests were first protected in 1991, nests, eggs and offspring were counted from aerial surveys, and found that protected nests where eight percent more likely to have at least one offspring, and 13 percent more likely to have more offspring than an unprotected nest. These counts were later realized to overlook some variables, like the frequency of egg predation in unprotected nests. Fortunately, a more thorough analysis yielded good news— protected nests were more successful, and were credited with boosting the number of breeding pairs by 37 percent.

Building parrot-protecting boxes

While signs may successfully keep humans from bothering a nest, they’re not as effective at deterring egg-gobbling sugar gliders. Sugar gliders (Petaurus breviceps) are a species of possum that can glide through trees like a flying squirrel, and they have been a growing problem for endangered swift parrots (Lathamus discolor) since they were imported to Tasmania in the mid-19th century. As the parrot population plummets thanks to habitat loss, the nocturnal sugar gliders are making things worse by raiding the remaining 2,000 birds’ nests for food.

Ending deforestation or removing the invasive sugar gliders currently seems like an overwhelming task, but conservationists have made some progress at protecting the swift parrots’ eggs. The Difficult Bird Research Group has designed special nesting boxes for the endangered parrots that take advantage of the birds’ and possums’ different schedules. A light sensor built into the box closes the door at night when it gets dark, keeping the sugar gliders out, then opens the door in the morning when the parrots are ready to start their day.

The so-called “possum keeper-outers” have been working so far, although they can’t save the swift parrots on their own. To really stabilize the species, the logging and agriculture interests need to drastically change course, and stop cutting down the critical habitats the swift parrots normally nest in.

Source: Scouting the eagles: Evidence that protecting nests aids reproduction by David Tenenbaum, University of Wisconsin-Madison News

On January 14th, 2018 we learned about

Stands of trees can function as shields against some seismic vibrations

A well-placed tree can do wonders for your home. It can provide shade that lowers your cooling bill, increase property values, and lower stress levels, absorb carbon dioxide, prevent erosion, etc. Researchers are now realizing that a properly-arranged group of trees may even be able to help your home survive an earthquake, based on the same principles that are being used to develop invisibility cloaks.

Rerouting seismic waves

That may sound like some sort of science fiction word salad, but the ideas behind it have been tested in controlled conditions. Lots of work is being done with metamaterials, which can control how light, as electromagnetic energy, interacts with their surface. Instead of reflecting off an object, light can be bent and routed around an object, like water flowing around a rock in a stream. This allows an object to effectively become invisible, as a viewer ends up seeing whatever is behind the cloaked object as if it weren’t there.

When it comes to trees and earthquakes, the trees act like a metamaterial, and the vibrations in the ground act like light, moving around a space without hitting it directly. Researchers first tested this idea by making a grid of posts in the ground, then pumping sound waves through the ground, since an actual earthquake isn’t terribly practical to plan around. As the vibrations moved through the dirt, they would interact with the posts in one of two ways: Smaller posts would shake in response to the incoming wave, dissipating much of its energy straight down. Large posts could vibrate in a way that actually reflected the wave back in the opposite direction. The combination of different sizes of posts, or better yet, trees, could then stop a seismic vibration from reaching a nearby structure at full strength.

Practical earthquake protection?

So how practical is “arboreal shielding” at this point? No tests have been conducted with actual trees and buildings yet, mainly because of the logistics involved. More simulations are being done to better understand optimal spacing and sizing for the trees involved, as the heights of the trees is an important factor in just how well they’ll reroute incoming seismic vibrations. Early simulations have used trees arranged in a grid, but ideally models will be developed that can account for more naturalistic distribution of tree growth, in case this concept is beneficial for more than the most carefully controlled green spaces. Additionally, researchers are finding that it’s easier to block horizontal pulses of energy, such as those found in Love waves, than tremors that also move vertically, as in Rayleigh waves.

Nonetheless, the potential benefits would be very significant. For a 10-story building, a 30- to 50-foot tree could make a huge difference. These trees could be planted around buildings that can’t use traditional seismic reinforcements, such as historical structures and monuments. Even if the trees couldn’t completely protect a structure, they could reduce the amount of protection that would be needed in the building itself, potentially cutting engineering costs, and adding all that shade, erosion control, green space, etc.


My third-grader asked: Wouldn’t wooden buildings work just as well?

Aside from the structural limitations wood creates when compared to concrete and steel, the wood itself isn’t the key ingredient in this seismic shielding. An early test actually replaced the trees or posts with holes in the ground, as the key was their size and placement in the ground. As long as those were properly calibrated to divert vibrations that might match the resonant frequency of the building, no lumber was necessary.

Source: How forests could limit earthquake damage to buildings by Edwin Cartlidge, Physics World