Chinese pond turtles sunning themselves to regulate their body temperatures. Photo by Flickr user Peter

Visit a sunny pond in a meadow, park or zoo and you’ll likely see turtles basking on logs and small lizards hanging out on warm rocks. If you’re in the south, you may even spot an alligator lazing on a bright patch of shore.

Ectotherms (better known as cold-blooded animals) such as these reptiles have to shuttle back and forth between shade and sun in order to manually regulate their body temperature. Insects, fish, amphibians and reptiles all do it. Now, new research suggests that these animals begin their temperature-regulating tasks much earlier than previously thought–while they are embryos encased in their eggs.

Previously, researchers thought of developing embryos as cut off from the outside world. But back in 2011, researchers found that Chinese soft-shelled turtle embryos could move between warmer or cooler patches in their eggs, though they lacked any feet at such an early stage of development. Some of the same Chinese and Australian researchers who published that original finding decided to investigate further to see just how deliberate these movements are.

“Do reptile embryos move away from dangerously high temperatures as well as towards warm temperatures?” the team, writing in the journal Biology Letters, wondered. “And is such embryonic movement due to active thermoregulation, or (more simply) to passive embryonic repositioning caused by local heat-induced changes in viscosity of fluids within the egg?”

In other words, are unborn reptiles purposefully moving from one spot to another within their eggs, much like an adult animal does? The team decided to investigate these questions by experimenting on turtle embryos. They incubated 125 eggs from Chinese three-keeled pond turtles. They randomly assigned each of the eggs to one of five temperature groups: constant temperature, hot on top/cool on the bottom, or at a range of heats directed towards one end of the egg.

An embryo positioned in the center of one of the researchers’ eggs. Photo by Zhao et al, Biology Letters

When they began the experiment, most embryos sat in the middle of their eggs. A week after exposing them to the different temperature groups, the team again measured the baby turtles’ positioning within the eggs. At the 10-day mark, the researchers again measured the turtles’ positions, and then injected half of the eggs with a poison that euthanized those developing embryos. Finally, after another week, they took one last measurement of the developing turtles and euthanized turtles.

The turtles within the eggs held at constant temperature or those that were in the “warm on the top/cool on the bottom” group tended not to shift around in their eggs, the researchers found. Those belonging to the groups that experienced warm temperatures only on one end of their egg, however, did move around. They gravitated towards warm conditions (84-86°F), but if things heated up too extremely (91°F), they edged towards the cooler side of their egg. Crucially, the embryos that the researchers euthanized stopped moving after receiving the dose of poison. This shows that the embryos themselves, not some passive physical process, are doing the shifting. 

The turtle embryos, the researchers note, behave much like adult reptiles do when thermoregulating their bodies. They warm up and cool down by moving toward or away from heat sources. For species like turtles, temperature during development plays an important part of determining the embryo’s sex. Turtle nests, which are buried in the sand, often experience a range of different temperatures, so embryos could be playing a role in determining their own gender, edging towards the cooler side of the egg if they feel like becoming a male, or the warmer side if they’re more female-inclined, the authors write. 

Could this gator’s teeth hold clues for regenerating humans’ pearly whites? Photo by Flickr user montuschi

Humans drew the short end of the toothbrush when it comes to our pearly whites’ longevity. Other animals such as reptiles and fish frequently lose and replace their teeth by growing new ones, but people are stuck with the same set of mature adult teeth their entire lives. If they lose a tooth–or all 32–dentures are usually the only option.

Oddly enough, alligators’ deadly chomps may hold a clue for how scientists could coax humans into regrowing teeth. These reptiles belong to the order Crocodilia, who, with their famous cheerful grins, caused songwriters to warn that you should never smile at a crocodile. To the bane of Captain Hook and other victims of gator and croc attacks, the large reptiles often regrow their razor teeth multiple times. Researchers think that, given time, technology may advance so that we can borrow these reptilian smiles. But first, scientists need to understand just how these animals keep their smiles toothy.

In a paper published this week in the Proceedings of the National Academy of Sciences, an international team of researchers attempted to get at the mechanisms behind the superior tooth regenerating abilities of one species of Crocodilia–the American alligator–in the hopes of applying the results to humans.

In humans, organs such as hair, scales, nails and teeth “are at the interface between an organism and its external environment and therefore, face constant wear and tear,” the researchers write. But alligators have evolved ways to deal with these challenges. The carnivores can replace any of their 80 teeth up to 50 times throughout their 35 to 75-year lives. Small replacement teeth grow under each mature alligator tooth, ready to spring into action the moment a gator loses a tooth.

To figure out the molecules and cells responsible for replacement, the researchers used X-rays and small tissue samples from alligator embryos, hatchlings and 3-year old juveniles’ developing teeth. They also grew tooth cells in the laboratory and created computer models of the process. Alligator teeth appear to cycle continuously, they write, but in fact the animals’ teeth seem to go through three distinct phases: pre-initiation, initiation and growth.

Once an alligator loses a tooth, these three phases kick off. The dental lamina, or a band of tissue associated with the initial stages of tooth formation in many animals, begins to bulge. This triggers stem cells and an array of signaling molecules that direct the process of forming a new tooth.

These results may be applicable to humans’ pearly whites. Alligators’ flesh-chomping incisors are surprisingly similar to well-organized, complex vertebrate teeth such as ours. In humans, a remnant of the dental lamina–the structure crucial to tooth formation–still exists and sometimes wrongly activates and begins forming toothy tumors. If the researchers could better tease out the molecular signaling pathways behind alligator tooth replacement, they reason, they they may be able to induce those same chemical instructions in humans to coax the body into forming a new tooth after one gets kicked out in a soccer game or has to be removed after becoming infected.

Alternatively, doctors may be able to shut off the molecules responsible for conditions that cause uncontrolled tooth formation. Individuals suffering from cleidocranial dysplasia syndrome grow many unusually shaped, peg-like teeth, for example, and people with Gardner syndrome also grow supernumerary, or extra, teeth.

While the researchers still need to clarify more molecular details behind alligator tooth growth, this initial study does hint that doctors and dentists may someday be able to selectively bestow patients with the reptiles’ tooth-regenerating abilities.

“Based on our study, it may be possible to identify the regulatory network for tooth cycling,” the researchers conclude. “This knowledge will enable us to either arouse latent stem cells in the human dental lamina remnant to restart a normal renewal process in adults who have lost teeth or stop uncontrolled tooth generation in patients with supernumerary teeth.”

Either way, they note that “Nature is a rich resource from which to learn how to engineer stem cells for application to regenerative medicine.”

Scientists believe the absence of seed-dispersing birds is thinning the forests on the island of Guam. Photo by Isaac Chellman

Visitors to Guam’s forests find them quiet–eerily so: No chirping of birds can be heard overhead. But slithering in the shadows on the ground are snakes, each some six feet long. Brown tree snakes made their debut on Guam, the southernmost island in the Mariana Archipelago, when islanders were rebuilding after World War II. Most likely, they were stowaways in lumber shipments heading north through the Pacific Ocean from New Guinea. They quickly began feasting on the birds and small lizards they discovered in Guam’s dense forests, and–free to slither through the mountainous terrain without predators of their own–they completed an invasion of the island at a pace of one mile per year. By the late 1940s, the forests had largely fallen silent, and now, all of Guam’s native bird species are history.

Last fall, scientists from Rice University and the University of Guam published one of the first studies of the island’s extinct forest birds, which include species such as the Mariana fruit dove, Guam flycatcher and Rufous fantail. They focused on how the absence of birds has caused a spike in the spider population, which is 40 times greater on Guam than nearby islands.

Now, the researchers are turning their attention to the issue of Guam’s thinning forests—a consequence, they also believe, of the bird deficit. This summer they’ll launch a four-year study of 16 tree species, looking at how the loss of birds, which scatter seeds, is affecting tree distribution.

The brown tree snake has obliterated nearly all of Guam’s bird species since it was introduced during World War II. Photo by Isaac Chellman

The study has its roots in an a-ha moment that lead scientist Haldre Rogers recently had while conducting another seed-dispersal study in Guam’s forests. “I noticed that there seemed to be a lot of gaps [in the trees] and that the pioneer tree species–such as papaya and sumak–were difficult to find on Guam, compared to nearby islands,” she explained to Surprising Science. She discovered that there were in fact twice as many such gaps on Guam per unit area of forest. 

Pioneer trees, which are the first to appear after a disruption to the ecosystem and thrive in the full sunlight of open spaces in the forest, have small seeds that are consumed by small birds. “Without birds to move their seeds to these sunny spots in the forest, these quick-growing trees may be less likely to germinate or grow to their full size,” Rogers hypothesized.

The problem with such thinning is that it could change the structure of Guam’s forests. “There’s a concern that [they] may become filled with open areas and start to look more like Swiss cheese than a closed canopy forest,” Rogers said. In other words, what were once cool, dark forests could transform into hot, open sunny ones.

There are other possible explanations for the tree-thinning: An undiscovered forest disease could be targeting pioneer species, or mammals like pigs and deer might have a strong taste for the trees. But according to Rogers, there isn’t strong evidence to support either of these scenarios. The upcoming study will attempt to determine the cause definitively.

The Mariana fruit dove was driven to extinction by the brown tree snake on Guam and is highly endangered on other islands in the Mariana Archipelago. Photo by Isaac Chellman

To that end, the researchers will cut down individual trees in various spots within Guam’s forests, creating new gaps in the forest. They’ll also remove trees from locations on two nearby islands that are still brimming with birds. Then they’ll monitor how long it takes the spaces to fill in and take note of which seedlings thrive on Guam versus on the other islands. It may seem that to get their results they’re destroying what they’re trying to study, but in actuality they’re taking down a tiny percentage of the island’s trees–20 total.

Guam’s situation is similar to that of tropical regions worldwide. “Animals involved in seed-dispersal are in decline in a lot of tropical forests around the world right now,” the co-principal investigator of the study, Amy Dunham, said in a statement. “It’s very important to understand the implications of those declines.” So far scientists have looked into the role of endangered mammals like lemurs, giant tortoises (PDF) and African forest elephants (PDF) in seed dispersal, but the upcoming study will be one of the first to focus on endangered birds.

It’s also the rare study to examine what happens when seed dispersal completely ceases–Guam being the only place in the world to experience whole-island forest bird loss in modern times. “The situation on Guam–which is tragic–provides us with a unique opportunity to see what happens when all seed-dispersal services provided by animals are lost from an entire ecosystem,” Dunham said. 

The snakes, meanwhile, continue to dominate the island of Guam. The U.S. Department of Agriculture traps approximately 6,000 brown tree snakes each year, and yet there are still nearly two million slithering around the island. The snakiest patches contain 14,000 of the reptiles per square mile–one of the highest snake concentrations in the world.

In February, the Department of Agriculture embarked on a new tactic for tackling the snake problem: dropping dead mice laced with acetaminophen, which is fatal to them, into the jungle. ”We are taking this to a new phase,” Daniel Vice of the Department of Agriculture’s branch that focuses on wildlife services in Hawaii, Guam and other U.S. held Pacific Islands, said in a recent interview. “There really is no other place in the world with a snake problem like Guam.”

A handsome tokay gecko. Photo: Ethan Knapp and Alyssa Stark

Anyone who lives in or has visited a tropical country is likely familiar with the chipper chirping of the gecko. These friendly little lizards inhabit homes and jungles stretching from Indonesia to Tanzania to the Dominican Republic. They emerge after sunset, taking advantage of their night vision eyesight—which is 350 times more powerful than a human’s—and are welcome guests in homes and hotels since they gobble up mosquitoes and other insect pests.

In addition to the locals, scientists also love these colorful lizards. Geckos possess the unique ability among lizards to run up flat walls and scamper across ceilings, even if the surface is very smooth. Researchers have been puzzling over this ability for years, and dozens of labs have tested gecko adhesion in the hopes of harnessing this superpower for potential use in everything from robotics to space technology to medicine to “gecko tape.”

Gecko toes, it turns out, contain hair-like structures that form a multicontact interface, meaning geckos grip with thousands of tiny adhesive structures rather than what appears to be a single uniform foot.

Gaps remain, however, in researchers’ understanding of how gecko feet interact with surfaces in their natural environment, especially in dry versus wet conditions. Scientists know that gecko toe pads are superhydrophobic, or water repelling, yet geckos lose their ability to cling to glass when it becomes wet. Why don’t they just repel the water and cling to the glass surface below? Similarly, scientists wonder how geckos deal with wet leaves in the forest during rain storms.

A new paper published in Proceedings of the National Academy of Sciences investigates these mysteries. The authors decided to test gecko grip on a range of wet and dry materials that both attract and repel water. To perform their experiments, they outfitted six tokay geckos with gecko-sized harnesses. They placed the geckos onto four different types of materials, such as glass, plastic and a substance designed to mimic waxy tropical leaves. After giving the lizards some time to adjust to their new surroundings, the researchers applied a uniform tugging pressure onto the geckos’ harnesses, pulling in the opposite direction of where the animals were walking. Eventually, the geckos could cling no longer and lost their grip. This allowed the team to measure the adhesive force required to displace the animals. They repeated the same experiments under very wet conditions, too.

The authors found that materials that are more “wettable”—an indication of the degree to which a surface attracts water molecules—the less force it took to disrupt the clinging geckos’ grips. Glass had the highest wettability of the surfaces the researchers tested, and geckos easily slipped from wet glass compared to dry glass. When that material gets wet, water forms a thin, attractive film that prevents the gecko’s tiny toe hairs from coming into contact with the surface.

The low wettability properties of waxy leaves, on the other hand, allow geckos to establish a sturdy grip, even in rain storms, because leaves actively repel water. Geckos performed equally well in wet and dry conditions on the leaf-mimicking surface, the researchers found. 

How the geckos interact with surfaces depends upon a thermodynamic theory of adhesion, the authors conclude. These features are dictated by Van der Waals force, or the sum of attractive and repulsive interactions between gecko toes and the characteristics of the surfaces they come into contact with. So long as those attractive forces jibe, geckos are in luck for getting a grip on whatever surface they come into contact with, regardless of whether it’s wet or dry.

Using our whole-animal adhesion results, we found that wet surfaces that are even weakly [water repulsive] allow the gecko adhesive system to remain functional for clinging and likely locomotion as well.

Our findings suggest a level of versatility in the gecko adhesive system that previously was not accounted for and calls into question interesting evolutionary, ecological, and behavioral predictions.

In addition to shedding light on how gecko adaptations help the lizards cope with their natural environment, the authors think their findings may contribute to designing new synthetic gecko robots that may overcome real-life geckos’ wet glass Achilles’ heel, useful perhaps for cleaning skyscraper windows, spying on suspected terrorists, or simply changing a hard-to-reach light bulb.

The new robot runs across an uneven surface in a way modeled off a zebra-tailed lizard. Image courtesy of Chen Li, Tingnan Zhang, Daniel Goldman

Designing a robot that can easily move across loose terrain—say, a rover meant to traverse the surface of Mars—poses a unique engineering challenge: Wheels commonly sink into what engineers call “flowable ground” (mixtures of sand, soil, mud and grass).

Given the many biologically-inspired innovations in robotics, a team of researchers from Georgia Tech had an idea—to base a design on desert creatures such as zebra-tailed lizards that are able to scramble across a loose, sandy surface without slowing down. Their efforts allowed them to create this small six-legged device, presented in an article published today in Science, which can run across a granular surface in a way uncannily reminiscent of a reptile.

The research team, led by Chen Li, designed the device after studying the locomotion of various creatures and mathematically simulating the performance of different types of legs (varying in number, shape and length) in several distinct environments. They hope their research will spur the development of a field they’ve termed “terradynamics”—just as aerodynamics is concerned with the performance of winged vehicles in air, their field will study the motion of legged vehicles on granular surfaces.

To design their robot, they used these simulations to determine the exact leg lengths, movement speeds and levels of force that would propel devices across a loose surface without causing them to sink in too deeply. They then printed a variety of leg types with a 3D printer, and built robots to test them in the lab.

One of their most interesting findings is that the same types of design principles apply for locomotion on a variety of granular surfaces, including poppy seeds, glass beads and natural sand. Their simulations and real-world experiments revealed that C-shaped legs generally worked best, but that any type of bow-shaped limbs worked relatively well because they spread out the weight of the device over long (albeit narrow) leg surfaces as the legs come into contact with the ground over the course of a stride.

The researchers found that C-shaped limbs work best for moving quickly over granular surfaces, both in lizards and robots. Dashed, solid, and dotted depictions in C and D are early, middle, and late leg positions during a stride. Arrows indicate directions of motion for specific leg regions. Image via Science/Li et. al.

The applications of this kind research are broad: This particular robot, the researchers say, could be developed into a useful search-and-rescue or scouting device, while the principles derived from the field of terradynamics could be useful in designing probes to explore other planets in the future. They could also help biologists to better understand the how life forms here on earth have evolved to move across our planet’s surface.

A Komodo dragon lounges near the Komodo National Park welcome center on Rinca Island. Photo: Rachel Nuwer

Mr. Safina, a local guide working at Komodo National Park, took a particular relish in describing the way a Komodo dragon’s strong jaws can snap a man’s leg in two. He’d lived on Rinca – a speck of land off Indonesia’s Flores Island, and one of the five places Komodo dragons reside – his whole life, and he was used to the various horror stories that surfaced every now and then after a tourist wandered off the trail or a kid got ambushed while playing in the bush. Standing in front of an assembly line of water buffalo, deer and wild horse skulls – dragon chow – Mr. Safina laughed while gesturing to a row of little wooden crosses stuck in the nearby mud. On each stick, a date and a foreigner’s name was scrawled in white paint. “Those are tourist graves!” Mr. Safina joked. “No really, they’re actually just baby mangrove markers that tourists bought to restore the forest. Now, are you ready to go see the dragons?” 

Like so many other tourists, for me, a trip to Indonesia was not complete without a detour to see the world’s largest lizard in its natural habitat. (Read Brendan Borell’s dispatch from his trip to Komodo Island, as featured in our special “Evotourism” issue of Smithsonian magazine.) In recent years, visitors have increasingly flooded this corner of Indonesia, drawn in by the thrill of brushing close to something wild and dangerous. Dragons are not to be taken lightly: male lizards can grow up to 10 feet long, weigh 150 pounds and eat up to 80 percent of their own body weight in one sitting. Though attacks are exceptionally rare, they do occasionally occur, mostly when a park guard lets his focus slip for a moment, or a villager has a particularly unlucky day.

Here are some of the most infamous attacks, as described by Mr. Safina and corroborated by media reports: 

A Tragic Playdate

In 2007, a dragon killed an 8-year-old boy on Komodo Island, marking the first fatal attack on a human in 33 years, the Guardian reported. The attack took place in March’s dry season, so rangers speculate that the murderous lizard may have been particularly hungry given that the watering holes – and the prey that gather there – had dried up. The dragon lunged when the boy went behind a bush to use the bathroom, MSNBC writes.

Mr. Safina recalls the boy’s friends – who had been playing together in the scrubland near their village – rushing to get help from their parents. According to the Guardian, the boy’s uncle came running and threw rocks at the lizard until it released his nephew. While the Guardian writes that the boy died from massive bleeding from his torso, Mr. Safina recalls the boy being bitten in half.

In light of the tragedy, park wardens launched an island-wide hunt for the man-eating lizard, though whether or not these efforts produced results remains unclear.

Shipwrecked with Dragons 

In 2008, a group of SCUBA divers found themselves swept from waters near their boat by the Flores region’s infamously strong current. After spending 10 hours spinning in the tide, around midnight the group washed up on the beach of what seemed like a deserted island, approximately 25 miles from where their ordeal had begun. Their troubles, however, were far from over. They had found their way to Rinca Island, where an estimate 1,300 dragons live.

The attacks began almost immediately, the Telegraph reports. A relentless lizard repeatedly came at a Swedish woman, who smacked it with her diving weight belt. It chewed at the lead belt while other divers threw rocks at its head, she said, all the while eyeing her bare feet.

For two days and two nights, the traumatized divers contended with dragons and the tropical heat, surviving off of shellfish they scraped from rocks and ate raw. Finally, an Indonesian rescue crew spotted the diver’s orange emergency floats spread out on the rocks. Though in shock, the group rehydrated at the local hospital on Flores Island and celebrated their survival at the town’s Paradise Bar.

Death in the Garden 

In 2009, 31-year-old Muhamad Anwar set out to gather sugar apples from an orchard on Komodo Island. A misstep that sent him falling from the tree proved to be his undoing. Two Komodo dragons were waiting below, and sprang on Anwar. His neighbors heard the commotion, and ran to his rescue minutes later. By the time they arrived, however, Anwar had already suffered fatal injuries, and was bleeding from bites to his hands, body, legs and neck, the Guardian reports.  Anwar died shortly after the attack, in a clinic on Flores Island.

Other accounts, however, contest some of these details. CNN writes that Anwar – a fisherman – was actually trespassing on the island, and was in an area forbidden for people to enter. This account also reports that Anwar bled to death on the way to the hospital, and was declared dead upon arrival. Even if CNN got this right and Anwar was guilty, however, death by dragon seems an overly steep punishment for eating a bit of forbidden fruit from the garden of Komodo.

Dragon Under the Desk  

In 2009, Maen, a fellow guide like Mr. Safina, headed to the staff office as he would any other morning. Like all the other buildings on Rinca Island, Maen’s unit sat on stilts, and hungry dragons would often gather below to wait for the occasional food scrap. On this morning, however, Maen sensed that he was not alone. Just settling in at his desk, he looked down. At his sandled feet lay a dragon, peering back up at him.

As it turned out, one of the cleaning crew had left the office door open the night before and the hungry predator had crept in, likely in search of food. Heart pounding, Maen attempted to slowly withdraw his leg from the dragon’s vicinity. But he moved too quickly, cueing the motion-sensitive carnivore to lunge. The dragon chomped down on Maen’s leg, clenching its jaw shut. Maen kicked at the dragon’s neck, then grabbed its jaws with his hands and wrenched its mouth open, slicing open his arm in the process.

Although Maen shouted for help, most of the rangers were in the cafeteria and could not hear his screams. Only one picked up on the noise, and came to investigate.

“I shouted and he came to help me but he didn’t like to come up because the dragon was still moving around,” Maen explained to travel writer Michael Turtle, of Time Travel Turtle. “Then he saw the blood on the floor and he got everyone from the kitchen. All the people come running here, but other dragons follow along as well.”

The dragons – which can smell blood and the scent of death from nearly 6 miles away – followed the crowd. Some rangers fended off the would-be feeding frenzy, while a couple others darted into Maen’s office to help their colleague fight free from his attacker. Maneuvering their injured friend through the pack of dragons waiting outside, they managed to carry him to the island’s dock, where he was rushed to Flores Island’s hospital. The injuries were too much for the small medical center to contend with, however, and Maen wound up being flown to Bali for six hours of emergency treatment and 55 stitches, MSNBC reports. All in all, it took him six months to recover from his brush with the dragon.

Despite the encounter, Maen went back to work, although he only stays indoors now so he does not have to deal directly with the animals. “The dragon, I can’t remember which one, he’s still alive,” he told Turtle. “But I think now he’ll be bigger. If he had a bigger neck then, I couldn’t have hold it open.”

Horror in Hollywood  

Dragon attacks can occur outside of Komodo National Park, too. More than 50 zoos around the world keep the animals as attractions. In 2001, Phil Bronstein, an investigative journalist formerly married to actress Sharon Stone, suffered an unfortunate encounter with a Komodo dragon at the Los Angeles Zoo. Stone had arranged a private visit to the zoo’s dragon pen as a present for her husband, who, according to a Time Magazine interview with Stone, had always wanted to see a Komodo dragon up close. Stone described the incident:

Phil didn’t know where we were going or why we were going there. It was a complete surprise. So we came around the corner and he was like, ‘Oh my god this is so fabulous, I’ve always wanted to see this.’ And the zookeeper said, ‘would you like to go in the cage? It’s very mild mannered. Everybody goes in there. Kids pet him. It’s fine.’

Bronstein accepted the invitation and went into the dragon’s cage with the zoo keeper. The lizard began licking at Bronstein’s white shoes, which the keeper thought must remind the animal of it’s white rat meals. Following the keeper’s advice, Bronstein removed his shoes and socks to avoid tempting the lizard. Then, as he moved into a better position to take a photo with the animal, it lunged.

So there was that hideous moment where the three of us… It’s such a break in reality, it’s so inconceivable that it’s happening, but there’s that moment of stillness where you just stare in disbelief. Then Phil screamed and we heard this crunching sound.

Bronstein managed to pin the lizard’s head down with his other foot, but the animal began jerking back and forth in an attempt to maul and eat its prey. Children gathered around the cage’s glass wall, Stone recalled, taking in the spectacle.

Bronstein managed to wrench the dragon’s jaw’s open and throw it from his foot, then dragged himself out of the cage as the lizard came at him from behind. The top half of Bronstein’s foot was gone, Stone said, and he was covered in scratches from the animal’s lunges at his back. Bronstein survived the incident and did not press charges, though Stone complained that the zoo allegedly continued to allow close-up encounters with dangerous animals following the incident.

An Aguilla Bank skink, one of the 24 new species discovered. Photo by Karl Questel

We live in an age of alarming extinction, in which many species are lost in large part due to human activity. At the same time, the natural world is so complex that even after centuries of research, scientists are still rapidly discovering new species everywhere from mountain tops to rain forests to the ocean floor.

This paradox is aptly illustrated by an announcement made yesterday: 24 new species of lizards, known as skinks, have been discovered in the Caribbean islands. But half of them may be close to extinction, and some may already extinct in the wild.

The research was conducted by a team led by Blair Hedges, a biologist at Penn State University and one of the world’s foremost experts at identifying new forms of life. Previously, Hedges has been involved with the discovery of what were then the world’s smallest snake, lizard and frog. The two dozen species named in this paper, published in the journal Zootaxa, constitute one of the largest mass discoveries of lizards in centuries.

To identify the many species of skinks (formally, members of the family Scincidae), Hedges and his team examined specimens housed at zoos and conservation centers around the world. By comparing taxonomic features of the lizards (such as the shapes of scales) and using DNA analysis, they determined that there are a total of 39 distinct species of skinks that live in the Caribbean—6 species that were previously recognized, 9 that had been named long ago but had been considered invalid and the 24 entirely new ones.

A Caicos Islands skink. Photo by Joseph Burgess

“Now, one of the smallest groups of lizards in this region of the world has become one of the largest groups,” Hedges said in a press release. “We were completely surprised to find what amounts to a new fauna, with co-occurring species and different ecological types.” He has determined that the skinks came to the Americas roughly 18 million years ago, likely arriving from Africa on floating rafts of vegetation.

How did the skinks go unnoticed for so long? Hedges speculates that because large numbers of skinks had already disappeared by the start of the 20th century, scientists, tourists and local residents have been much less likely to encounter them in the years since. Additionally, many of the characteristics that distinguish the species from one another have been overlooked or weren’t detectable until now, especially those indicated by DNA analysis.

The researchers determined that the skinks have long been most threatened by an exotic intruder: the mongoose, introduced from India to Cuba in 1872 with the intention of reducing rat populations in sugarcane fields. Rat populations were partially controlled, but by 1900, nearly half of the islands to which the mongoose had spread were also without skinks, and the remaining lizards have dwindled in population ever since. Additionally, the researchers note, current human activities such as forest removal are likely contributing to the skinks’ endangered status. The research team hopes that their data will be used to plan future conservation efforts.

Theoretically, if you’re in the U.S. Virgin Islands, Trinidad and Tobago, or Martinique, you might try looking for a skink. But because each of the species is remarkably rare—with even the non-endangered ones qualifying as vulnerable—it’ll certainly be difficult. Above all, if you do want to find one, hurry up: there may not be much time left.

A cane toad is highly toxic and should not be eaten or even licked. Photo from Wikicommons.

American cane toads (Rhinella marina), native to Central and South America, are an invasive species in Australia. These toads contain a substance called “bufotoxin” that makes a lot of predators ill, sometimes fatally. (Warning: This is very poisonous stuff. Do not even lick a cane toad!)

Australian animals that eat this toad are typically poisoned by it, but one animal, the bluetongue skink (Tiliqua scincoides), appears to be able to eat the toad with few or no ill effects. Or, more exactly, some bluetongue skinks can eat the cane toads, depending on where they live.

Many animals and plants produce complex molecules (like bufotoxin) that have been shaped by natural selection to be toxic to predators. Some of our favorite spices, such as basil, chili peppers and other aromatic plants, owe their culinary properties to these molecular adaptations to herbivory. Only a few mammals produce molecular toxins, but many frogs and toads do.

The bluetongue skink. Note the blue tongue. Photo from Wikicommons.

If a weapon evolves in nature, there is a certain chance that a counter-weapon will also evolve. Many insects that feed on toxic plants have evolved the ability to sequester the poisonous molecules produced by those plants, rendering them harmless to the insect, and in some cases concentrating the undesirable substance in the insect’s own body to be used as a defense against insect-eating animals (usually other insects). Many mammals have enzymes in their digestive tract that detoxify plants that would otherwise be harmful. The evolution of toxicity and the evolution of anti-toxin strategies is considered an arms race between the eaten and the eaters.

So, it would be reasonable to suspect that the bluetongue skink has evolved a physiological mechanism to combat the bufotoxin produced by the cane toads. But it turns out that the explanation for the ability of some skinks to snack on the toxic toads is a little more complicated.

Another invasive species found in Ausralia is the ornamental “mother-of-millions” plant, a Bryophyllum from Madagascar. This plant produces a toxin that is chemically similar to bufotoxin. Why is it chemically similar to bufotoxin? This is probably a coincidence. If you have a large number of animals and plants producing toxins, sometimes there are going to be accidental similarities.

Mother-of-millions plant. Image from Wikicommons.

The mother-of-millions plant is invasive and found in the wild in certain areas of Australia, but it is not common everywhere. Bluetongue skinks that live where mother-of-millions is common appear to have adapted to eating them, and as such posses the ability to neutralize bufotoxin-like molecules. When these skinks encounter cane toads, they eat them without consequence. In fact, the skinks living in these area regularly eat both the mother-of-millions plants and the cane toads.

This research was was carried out by scientists at the Richard Shine Lab at the University of Sidney.

Price-Rees, Samantha J. Gregory P. Brown, Richard Shine, 2012. Interacting Impacts of Invasive Plants and Invasive Toads on Native Lizards. Natural History Editor: Craig W. Benkman. Published online Jan 25, 2012

How do boa constrictors know when to stop constricting? Image courtesy of Flickr user wwarby

Ed. note: We welcome back guest blogger Greg Laden for a two-week blogging tour on Surprising Science.

This is a story of snakes, islands and students. Let’s start with the snakes.

Among the many different kinds of snakes are the constrictors: boas and pythons. They are close relatives that diverged millions of years ago. Pythons are found in the Old World (Africa and Asia) as well as Australia. Boas (family Boidae) are found in the New World (North, Central and South America including some Caribbean islands). All of them kill their prey by wrapping around it and squeezing it to death.

Among the boas there is an island-dwelling form in Belize that is the subject of interest to conservationists, ecologists and, lately, behavioral biologists. This is the miniature boa of Snake Cayes, a group of islands off the coast of southern Belize. When I say “miniature” I mean that they range in length from 30 cm to about 2 meters (1 to 6 feet). This is small compared to the mainland boas of the same species, which can reach 4 meters (13 feet) in length.

It is common for animal populations that live on islands to exhibit differences in size from those on the mainland. Medium and larger mammals like deer tend to be smaller on islands, small mammals like rodents tend to be larger. Something like this may happen with snakes as well.

Allison Hall (left) says “It’s a normal thing to be a little afraid of snakes, but you really get into the project and come to love the animals.” Amanda Hayes is on the right. Image provided by Dickinson News and Events.

Scott Boback is an expert on these animals, and from the time he was a graduate student at Auburn University, he’s been trying to answer the question “how and why are these snakes small?”

The most likely explanations for size differences would seem to be either diet or other features of the environment, or genetics. Perhaps there is a limited food supply on the islands, so snakes grow slowly, and thus there are few or no large ones. It would take them so long reach a large size that somewhere along the line they would have met their demise. Alternatively, it could be that snakes that grow slowly or nearly stop growing as they approach a certain size survive longer or reproduce more effectively (probably owing to food supply being limited). If so, the genes involved in growth would be shaped by natural selection and over time the island snakes would be small because they are genetically different. You can easily imagine how the two processes would work together, perhaps with environmental effects working initially but genetic changes accruing over time.

Boback did eventually come to a conclusion about the small size of the island boas. He recently told me, “we determined that there is some genetic component to dwarfism on islands. However, we believe that it is actually a combination of genetic and environmental effects that ultimately determine island boa size. That is, growth rates are different between island and mainland boas and this appears to be determined partly by genetics.” (See below for the reference to his paper on this research.)

More recently, Boback and his students at Dickinson College have been addressing a different question about boas: How do they know when to stop squeezing their prey? This is an interesting question because, as you might imagine, contracting the majority of muscles in one’s body for an extended period of time is energetically costly, but letting go of prey before it is fully dead may cause the loss of a meal. As an informal experiment, I asked five different people this question over the past two days, after reading of Boback’s research, and everyone gave approximately the same answer: The snakes let go when the prey is dead and stops struggling.

Well, it turns out that we do science to prove ourselves wrong, because that is not the answer. Suspecting a particular mechanism, Boback his students, who maintain a colony of these boas in their lab at Dickinson, devised a brilliant experiment. They took a number of dead rats that would normally be fed to the snakes, and installed robotic “hearts” in them. When the snakes constricted the rats, the hearts were allowed to beat for a while, then they were turned off. Soon after, the snakes loosened their grip, then let go.

It turns out that boas have the ability to detect a heartbeat in the prey, and they use this information to determine how much pressure to apply. Snakes that had never killed or eaten live prey acted the same as snakes with experience with live prey, suggesting that this behavior is innate and not learned.

“Many of us think of snakes as audacious killers, incapable of the complex functions we typically reserve for higher vertebrates,” says Boback. “We found otherwise and suggest that this remarkable sensitivity was a key advancement that forged the success of the entire snake group.”

One of the neat things about this project is that it involved the efforts of undergraduate researchers. The undergraduates not only participated in the research, but they helped produce the peer reviewed paper and are listed as authors. Katelyn McCann, who was a student on this project and now works as a clinical-research coordinator at Children’s Hospital in Boston, notes, “I got to experience the true collaborative nature of research as well as the hours of independent work that go into the final product. Now, working in research I feel like I truly understand the scientific method and what goes into any study.” Boback adds, “student-faculty research at Dickinson is an opportunity for students to experience science in action. It is the most fundamental level of learning in science as the student actively participates in the process of discovery.”

Source:
Boback, S., Hall, A., McCann, K., Hayes, A., Forrester, J., & Zwemer, C. (2012). Snake modulates constriction in response to prey’s heartbeat Biology Letters DOI: 10.1098/rsbl.2011.1105

Boback, S. M. and D. M. Carpenter. 2007. Body size and head shape in island boas (Boa constrictor) in Belize: Environmental versus genetic contributions. Pages 102-116 in R. W. Henderson and R. Powell, editors. Biology of the boas, pythons, and related taxa. Eagle Mountain Publishing, Eagle Mountain, UT.

Additional information for this story came from Dr. Scott Boback, and a press release from Dickinson College.

A dragon statue in Ljubljana, Slovenia. Photo courtesy Wikimedia Commons user Dani_7C3.

Around the world, people are celebrating the Chinese New Year and the start to the Year of the Dragon. This got us wondering: Where did the myth of the dragon come from in the first place? Scholars say that belief in dragons probably evolved independently in both Europe and China, and perhaps in the Americas and Australia as well. How could this happen? Many have speculated about which real-life animals inspired the first legends. Here’s our run-down of the likeliest suspects.

Dinosaurs. Ancient people may have discovered dinosaur fossils and understandably misinterpreted them as the remains of dragons. Chang Qu, a Chinese historian from the 4th century B.C., mislabeled such a fossil in what is now Sichuan Province. Take a look at a fossilized stegosaurus, for example, and you might see why: The giant beasts averaged 30 feet in length, were typically 14 feet tall and were covered in armored plates and spikes for defense.

The Nile Crocodile. Native to sub-Saharan Africa, Nile crocodiles may have had a more extensive range in ancient times, perhaps inspiring European dragon legends by swimming across the Mediterranean to Italy or Greece. They are among the largest of all crocodile species, with mature individuals reaching up to 18 feet in length—and unlike most others, they are capable of a movement called the “high walk,” in which the trunk is elevated off the ground. A giant, lumbering croc? Might be easy to mistake for a dragon.

The Goanna. Australia is home to a number of species of monitor lizards, also referred to as Goannas. The large, predatory animals have razor-sharp teeth and claws, and they are important figures in traditional Aboriginal folklore. Recent studies even indicate that Goannas may produce venom that causes bite victims’ wounds to develop infections after an attack. At least in Australia, these creatures may be responsible for the dragon myth.

Whales. Others argue that the discovery of megafauna such as whales prompted stories of dragons. Ancient humans encountering whale bones would have no way of knowing that the animals were sea-based, and the idea of such gargantuan creatures might well have led people to assume that whales were predatory. Because live whales spend up to 90 percent of their time underwater, they were poorly understood for most of human history.

The Human Brain. The most fascinating explanation involves an unexpected animal: the human. In his book An Instinct for Dragons, anthropologist David E. Jones argues that belief in dragons is so widespread among ancient cultures because evolution embedded an innate fear of predators in the human mind. Just as monkeys have been shown to exhibit a fear of snakes and large cats, Jones hypothesizes that the trait of fearing large predators—such as pythons, birds of prey and elephants—has been selected for in hominids. In more recent times, he argues, these universal fears have been frequently combined in folklore and created the myth of the dragon.

A side-blotched lizard in Utah (courtesy of flickr user utahmatz)

You probably already know how to play rock-paper-scissors. Perhaps you’ve even participated in the world championships. But do you know about the lizards that live this game?

Side-blotched lizards (Uta stansburiana) are a small lizard species found in many states in the American West and Mexico. Males come in three varieties, each with a different throat color: orange, yellow or blue. Those throat colors announce to the lizard world what mating strategy a male will use. Orange-throated males are bigger and more aggressive, and they have large territories with several females. Blue-throated males have smaller territories with only one female, and they cooperate with other blues for defense. Yellow-throated males, whose markings and behaviors mimic those of females, are known as “sneakers”; they don’t keep a territory but instead cluster around and sneak into the territories of other males to mate with their females.

And like a big game of rock-paper-scissors, each variety has its pluses and minuses in the mating game. The result is that once every few years, the original study in Nature found, the dominant variety changes.

If we start with the orange males, they have the advantage over blues in terms of territory size and numbers of females they control. But with more territory controlled by orange males, the more opportunities for sneaky yellow males to mate, and then the yellow population begins to grow. But the yellows are vulnerable to the blues, who can easily defend their females because they cooperate with other blues, so then they take over. But then oranges mate with more females and grow in numbers again. Orange is most successful when blues are greater in number; yellows are most successful when oranges are greater in number; blues are most successful when yellows are greater in number. The result is a cycle that has persisted for millions of years.

But not everywhere. Further research into this species, published in PNAS, has found that there are many populations of this species that have lost one or two of the color varieties. The yellows were always the first to go; something (not yet known) had changed the game’s rules so that they no longer had any advantages over orange or blue. Some places had also lost their oranges and others had also lost their blues. And that loss of a color variety or two had further consequences: It was accompanied by rapid changes in traits like body size in the remaining lizard types, changes that could lead to the evolution of new species.

These lizards came up in a conversation among some of my friends earlier this year (a mathematician in the group told me about the lizards, which, along with the rock-paper-scissor game, have been studied in game theory). One of them was wearing a rock-paper-scissors-lizard-Spock T-shirt, illustrating that lesser-known variant of the game. I am disappointed to report, however, that I was unable to find any link between it and the discovery of the lizards’ mating strategy.

Several crocodile species are known to attack humans (photo courtesy of flickr user Fayes4Art)

We started out Predator Week on Monday with a study that looked at what happens when predators disappear from an ecosystem. But why do we get rid of predators in the first place? Some of them go after things we care about, like our livestock, but an even more understandable motivation for eliminating a species is that it attacks (and eats) us. Humans and our ancestors have been dealing with that problem for forever (check out the top 10 deadliest animals of our evolutionary past), and while many of us are able to live our lives without ever coming in contact with a deadly predator, there are still enough encounters to remind us that humans are not always the top of the food web. (That said, we’ve had enough reminders lately that these species are important to their ecosystems, important enough that we need to keep them around.) Here are the predators that humans had best avoid:

Cats: We’re not talking about your cute little housecat (though a nasty scratch or bite can be troublesome). Leopards, lions and tigers are the scary man-eaters of the cat world. Just this week a leopard in India was taken down after going on a rampage and mauling several people. And tiger attacks in India may be on the rise as their habitat shrinks. But when I think of man-eating cats, my mind goes to the lions of Africa, and stories like the movie The Ghost and the Darkness. If you want to avoid being eaten, a new study finds that lions take advantage of their better night vision and most often attack humans in the nights after the full moon, when the moon rises an hour or more after sunset.

Bears: Earlier this summer, a hiker was attacked and killed by a grizzly bear in Yellowstone National Park. It was the first fatal bear attack in Yellowstone since 1986. Your best option when traveling in bear country is to find out which species you may encounter, learn about them and prepare yourself with the proper knowledge and equipment so you can be ready in the case of an attack.

Sharks: What would summer be without stories of shark attacks? These attacks are real—there are several dozen each year worldwide and a few fatalities—though the hype some years is far greater than the danger. The Florida Museum of Natural History has a good list of advice for avoiding a shark encounter, much of it common sense (don’t go in the water if bleeding; don’t harass a shark). Sharks aren’t just terrifying nightmares, though; they’re smart—for fish—and many of their “attacks” may just be the shark investigating its environment.

Komodo dragons: The most famous victim of a komodo dragon attack has to be Phil Bronstein who, in 2001 when he was married to Sharon Stone, lost his big toe to one of these big lizards. These giant, carnivorous lizards, native to Indonesia, use sharp teeth, and possibly venom, to bring down large prey, such as pigs, deer and water buffalo. They’ll also attack humans and even dig up bodies from shallow graves.

Crocodiles and alligators: These are both big reptiles with pointy teeth that like to hang out in the water and wait for a meal. In the United States, we worry about the freshwater alligators (Florida’s Sun-Sentinel newspaper keeps an online database of attacks) while in Asia, Australia and Africa, the saltwater croc finds humans to be tasty meals. The easiest way to avoid them both is to stay away from waters where they may be found, and that includes the shores where the reptiles may be lying in wait for their prey.

Wolves: People who live in wolf territory often fear that these dogs will attack them or their children. In North America, wolf attacks on humans are incredibly rare, fatal ones even more so; one report counts around 20 to 30 in the 20th century. Wolves are more bold (or more desperate) in some other parts of the world, however. In Uttar Pradesh in India, wolves killed or injured 74 people in 1996 and 1997.

Hippos: Hippos are mostly herbivorous animals, but that’s a bit misleading because they seem to have a great enough dislike for humans that they’ll attack people even when the humans think they’re safe in a boat. More people are supposedly killed by hippos than by any other animal in Africa. They weigh several tons and can run as fast as, or perhaps faster than, a human on land, so it’s best to stay in the safari vehicle when traveling through hippo country.

Snakes: While poisonous snakes can kill you, tales of man-eating snakes center on species like pythons that are big enough to swallow a human child whole. Confirmed stories of such deaths, however, are extremely rare.

A pig-nosed turtle at the Shedd Aquarium (courtesy of flickr user happy via)

The pig-nosed turtle–a freshwater species found in Papua New Guinea (PNG) and northern Australia–is a strangely cute little critter. It’s also evolutionarily important because not only is it the last member of its once widespread family (Carettochelyidae), but it also shares features with marine turtles and might represent a transition as turtles moved from freshwater to the oceans. In addition, the turtle is a key source of protein for people in PNG, particularly in areas where protein is scarce.

For years, researchers have suspected that the pig-nosed turtle has been declining in numbers, and the IUCN even listed the species as Vulnerable in 2000. But they had little more than anecdotes and suspicion until recently. A new study in Biological Conservation confirms their fears: the pig-nosed turtle in PNG is disappearing.

In Australia, the turtle suffers from habitat loss, but the problem in PNG is different—people eat the turtles and their eggs in large quantities. And so scientists not only surveyed adult turtles and their nests but also looked at turtle and egg sales in the local markets.

They found that female turtles had gotten smaller over the last 30 years; larger turtles were taken for food. In addition, local villagers intensively harvested turtle nests for eggs. And as eggs and turtles became rarer, prices increased in the markets.

“The level of harvest involved is unlikely to be sustainable,” the scientists write. And any management plan cannot be a simple one focused on eliminating hunting. The species will have to be managed more like a fishery. “We need to provide win win outcomes to both local and conservation communities,” the study’s lead author, Carla Eisemberg of the University of Canberra, told BBC News.

But there are several roadblocks to conservation: The local human population is growing. Tribal warfare has ended and people have now settled along the riverbanks, where they can more easily find turtles. And new technologies, such as modern fishing equipment, have also aided the turtle harvest. In addition, scientists are missing much of the information about the species’ life history that would let them design a conservation plan. And then it would take decades for the turtle to recover after such a plan was implemented.

Don’t expect the scientists to give up, however. The turtle is important both to them and to the local PNG people who depend on them for food. Surely the two groups can work together to let the pig-nosed turtle survive.

Scientists are still trying to figure out why primates have excellent vision. (langur monkey photo courtesy of flickr user Troup Dresser)

We humans aren’t alone in our aversion to snakes. Our primate cousins also fear serpents. And for good reason—snakes eat primates. Snakes have been preying on primates for millions of years, and some researchers think they might be the reason we—and our fellow primates—have such good eyesight.

Good vision is a hallmark of the primate order. Compared with many other mammals, primates have more closely spaced, forward-facing eyes that allow for a lot of overlap between each eye’s visual field, which in turn gives primates 3-D, or stereoscopic, vision and a good sense of depth perception.

In the early 20th century, scientists attributed primates’ keen sense of sight to their arboreal lifestyle. The ancestors of primates needed to accurately judge the distances between tree branches before taking a leap, so the theory went. But that hypothesis lost favor in the 1970s after biological anthropologist Matt Cartmill, now at Boston University, pointed out that many other acrobatic, tree-dwelling animals like squirrels get by without such an advanced visual system.

Cartmill offered his own explanation, called the “visual predation hypothesis”: early primates needed superb visual skills to hunt and grab insects. Another hypothesis is that primates needed to see well to pluck fruits from the ends of tree branches.

More recently, snakes came into the picture. In 2006, anthropologist Lynne Isbell of the University of California at Davis argued that early primates were stalked by constricting snakes, and it was highly beneficial to see these camouflaged predators before it was too late. Later, some monkeys and apes in Africa and Asia started to live alongside venomous snakes, which led to even more visual advancements.

But the idea may not hold up, according to the authors of a recent study in the Journal of Human Evolution. Led by behavioral ecologist Brandon Wheeler of the Cognitive Ethology Laboratory at the German Primate Center, the team tested the snake hypothesis by looking at variations in modern primates’ visual skills (in terms of stereoscopic vision, as measured by the closeness of the eyes) to see if the primates with the best eyesight had the longest evolutionary history of coexisting with snakes and the greatest likelihood of encountering and being attacked by them.

The team didn’t find any correlations between snake exposure and primate vision, concluding that snake attacks did not drive the evolution of better eyesight. Still, the researchers say, detecting snakes was definitely a beneficial side effect regardless of why better vision evolved.

A female striped plateau lizard shows off her mothering potential (credit: University of Puget Sound)

Good moms make sure their kids eat well. Lizard moms only get one chance to do that; in most species, their mothering ends when they lay their eggs. So their one and only chance to be a good mom is to create high-quality eggs, and particularly ones with higher levels of antioxidants. But lizard dating isn’t particularly drawn out and a female lizard needs a quick way to tell a potential mate she’d make a good mom. How does she do it?

Female striped plateau lizards (Sceloporus virgatus), which live on the rocky slopes of mountains in southeastern Arizona, do this with bright orange patches underneath the jaw. Scientists from the University of Puget Sound and elsewhere, reporting in the Journal of Animal Ecology, found that the size of those patches correlates with the concentration and amount of antioxidants in the yolk of her eggs, and the richness of color with antioxidant concentration.

“Thus, in female S. virgauts, female ornaments [the orange patches] may advertise egg quality. In addition these data suggest that more-ornamented females may produce higher-quality offspring, in part because their eggs contain more antioxidants,” said lead author Stacey Weiss, of the University of Puget Sound.

That advertising appears to work; previous research has shown that male striped plateau lizards prefer females with darker orange spots.