If geochronology is “the science of determining the ages of earth materials” (according to the center’s website), then Renne must know his gnat’s eyebrow. For those of us lay-folk, it’s about 5,000 years.

Renne and his colleagues have a new paper in Science pinpointing the dates of both the impact and the dinosaur extinction, placing them within the same time of each other—providing evidence, once again, for an asteroid or comet impact being the cause of extinction.

The 110 mile-wide Chicxulub (cheek’-she-loob) crater, off the Yucatan coast of Mexico, is likely the result of a six-mile in diameter asteroid or comet. Using and refining a technique called argon-argon dating, the scientists determined that the impact occurred 66,038,000 years ago, plus or minus 11,000 years.

The same argon-argon dating put the dinosaur extinction at 66,043,000 years ago, with the same margin of error.

The first link between the impact event and dinosaur extinction was published in 1980 by UC Berkeley’s Luis and Walter Alvarez. Since then, many other scientists have supported or refuted the theory, sometimes putting the extinction several hundred thousand years before the impact.

“When I got started in the field, the error bars on these events were plus or minus a million years,” says UC Berkeley paleontologist William Clemens. “It’s an exciting time right now, a lot of which we can attribute to the work that Paul and his colleagues are doing in refining the precision of the time scale with which we work.”

Despite the synchronous impact and extinction, Renne cautions that the impact was not the sole cause of extinction. Dramatic climate variation over the previous million years, including long cold snaps amidst a general Cretaceous hothouse environment, probably brought many creatures to the brink of extinction, and the impact kicked them over the edge.

“These precursory phenomena made the global ecosystem much more sensitive to even relatively small triggers, so that what otherwise might have been a fairly minor effect shifted the ecosystem into a new state,” Renne says. “The impact was the coup de grace.”

Most of the 800-plus species of hermit crabs live in the ocean and reside in easily-found discarded snail shells. But the dozen or so species of land-based hermit crabs—like the ones you may have kept as a pet as a kid—have a tougher time finding a home.

Empty shells are common in the ocean because of the prevalence of predators like shell-crushing crabs with wrench-like pincers, snail-eating puffer fish, and stomatopods, which have the fastest and most destructive punch of any predator.

On land, however, the only shells available come from marine snails tossed ashore by waves. With limited availability, land-based hermit crabs, unlike their under-the-sea brethren, hollow out and remodel their shells, sometimes doubling the internal volume. This provides more room to grow, more room for eggs—sometimes a thousand more eggs—and a lighter home to lug around as they forage.

But that can involve a lot of work. So when the hermit crabs need even bigger shells, they socialize, according to Mark Laidre, a UC Berkeley postdoc who reports this unusual behavior in the current issue of Current Biology.

Laidre watched the hermit crab species Coenobita compressu on the Pacific shore of Costa Rica, where the crabs are found by the millions along tropical beaches. He tethered individual crabs, the largest about three inches long, to a post and monitored the free-for-all that typically appeared within 10-15 minutes.

He discovered that when three or more terrestrial hermit crabs congregate, they quickly attract dozens of others eager to trade up. They typically form a conga line, smallest to largest, each holding onto the crab in front of it, and, once a hapless crab is wrenched from its shell, simultaneously move into larger shells.

It’s almost certain death for the crab who loses this musical shells game. “The one that gets yanked out of its shell is often left with the smallest shell, which it can’t really protect itself with,” says Laidre. “Then it’s liable to be eaten by anything. For hermit crabs, it’s really their sociality that drives predation.”

Laidre says the crabs’ unusual behavior is a rare example of how evolving to take advantage of a specialized niche—in this case, land versus ocean—led to an unexpected byproduct: socialization in a typically solitary animal. But socialization with potentially dangerous consequences…

So when does a children’s game turn lethal? When it’s played by Coenobita compressu.

Image: Mark Laidre, UC Berkeley

UC Berkeley’s Roland Burgmann is describing two large earthquakes that occurred in April of this year, in the Indian Ocean, off the coast of Sumatra. While the two ‘quakes caused little damage, the first, measuring magnitude 8.7, was the largest strike-slip temblor ever recorded, and the events seem to be triggering much more than shaking.

Three papers this week in Nature analyze the before, during, and after of the two earthquakes, and all three seem to arrive at the same conclusion: the Indo-Australian tectonic plate is breaking into two separate plates.

If you’ve visited the Academy’s Earthquake exhibit and planetarium show (and you can now do so virtually, through an iTunes course), you know that earthquakes result when continents break apart and plates grind against each other. Scientists say that’s exactly what is happening in this Indo-Australian region right now. Not surprisingly, very slowly.

Thorne Lay, of UC Santa Cruz and co-author on one of the Nature papers, says that the process of forming a new plate boundary will take millions of years and is likely to require hundreds if not thousands of earthquakes like the larger one in April. “This was a huge earthquake, but it’s going to happen again and again to make a through-going fracture that separates the plates.”

Lay and his colleagues’ paper analyzes what happened during the 8.7 quake. It appears that it ruptured over a complex network of at least four faults lying at right angles to one another. According to Lay, the energy released on each fault individually was about magnitude 8, adding up to a total event magnitude of 8.7 (a revised estimate higher than the 8.6 value initially reported). The initial shock was followed two hours later by a magnitude 8.2 aftershock on yet another fault to the south.

The paper by Burgmann and his colleagues from the USGS in Menlo Park, takes it from there. The study shows that these two quakes triggered other, distant earthquakes hours and days later. In fact, the seismologists’ analysis found five times the expected number of quakes during the six days following the April 11 quake and aftershock!

“We found a lot of big events around the world, including a 7.0 quake in Baja California and quakes in Indonesia and Japan, that created significant local shaking,” Burgmann says. “If those quakes had been in an urban area, it could potentially have been disastrous.

“Until now, we seismologists have always said, ‘Don’t worry about distant earthquakes triggering local quakes.’ This study now says that, while it is very rare—it may only happen every few decades—it is a real possibility if the right kind of earthquake happens.”

Image: Thorne Lay/UCSC

This week, UC Berkeley announced the amazing growth of its project, AmphibiaWeb, an online catalogue of the world’s amphibians created to encourage more field monitoring and lab studies of the threatened animals.

David Wake, an Academy fellow from UC Berkeley, started the project in 2000 because amphibians were declining at a terrifying rate and he was concerned we’d lose species we didn’t even know existed. “In 1985, there were a handful of amphibian biologists in the whole world,” he says. “Now, the numbers [of scientists] have increased dramatically, and we are getting to the ends of the earth.”

The Academy’s amphibian biologist Dave Blackburn has contributed to AmphibiaWeb for about ten years and recently became more involved in expanding the project. “I joined the steering committee nearly three years ago. I actively work as part of a team on issues related to the systematics displayed on AmphibiaWeb, but, perhaps more importantly, am actively invested in ways of improving our services, such as an iPhone app (available for download now, but major improvement coming soon!), summary diagrams of evolutionary relationships among amphibian groups, and general ideas for improving the content for diverse viewers.”

The more viewers the better. Earlier this summer, the International Union for the Conservation of Nature and Natural Resources (IUCN) assessed that about 41 percent of amphibian species are at risk of extinction, and some are already extinct. These charismatic creatures are disappearing for many reasons—a warming Earth, increasing population, widespread use of pesticides and a deadly fungus.

But AmphibiaWeb is succeeding! With only about 4000 species known in 1985, AmphibiaWeb now boasts 7,000 species! Woo-hoo! (Fist-pump or –bump!)

Now that’s something to sing about! “An undergraduate researcher assisting with AmphibiaWeb suggested the idea of a song when it came to celebrating the scientific description of the 7,000th amphibian,” Dave explains. “We’ve known since early this year that we’d probably hit number 7,000 some time in the summer based on the rate of descriptions of new species over the past few years. I happen to have a good friend (Conor Loughridge, performing as The Wiggly Tendrils) from college that writes songs for a living. We asked if he would be willing to help us out, and when he said yes, Conor and I worked together on content for the song (though the rest was left up to him to make it catchy and fun!).

“The general idea is to simply catch attention,” Dave adds. “The idea is to highlight the excellent work done by amphibian biologists around the world and the fact that we are still in a crisis. We are losing many populations and species of amphibians around the world due to climate change, habitat degradation and destruction, disease and pollution. In some cases, we’ve lost them before we even knew they existed.”

What a great way to spread the news! Is the tune stuck in your head yet? Pass it along!

Image: Alessandro Catenazzi

Oops!

Last winter we attended the AAAS Meeting in Vancouver, BC and listened to the University of Texas’ Charles Groat downplay the effects of fracking. We posted a bit of that news in an article about increased fracking regulations in April.

This week, Science Insider reports that Groat neglected to mention that he serves on the board of (and receives quite a bit of funding from) an oil and gas company that conducts fracking. Sounds like a bit of a conflict of interest, doesn’t it?

Really Old Polar Bears

In April we also ran a story about polar bear evolution. Researchers, studying nuclear DNA, put polar bears’ origin to 600,000 years ago.

But a new study, published earlier this week in the Proceedings of the National Academy of Sciences, suggests that polar bears evolved into a distinct species as many as 4-5 million years ago and did not recently descend from brown bears, despite shared genetic material.

The authors conclude that brown bears and polar bears interbred intermittently over the years. The New York Times compares this to humans in a funny, relatable way:

The progress of species formation, at least in this case, is a bit like a long, ambivalent divorce in which the two parties separate but occasionally fall back into bed even after the official decree.

Drought

Last week, we wrote about the devastating drought engulfing our country. This week Brandon Keim, writing in Wired, describes how this tragedy could reach beyond our borders and create global unrest.

Reporting on a recent study by the New England Complex Systems Institute, Keim says that commodity speculation (that food prices will rise due to the drought) may drive conflict in developing countries. The study reports that recent history demonstrates this trend:

During the last six years, high and fluctuating food prices have lead to widespread hunger and social unrest.

An article in Nature also explores this global impact.

Rain, rain…

Finally, earlier this summer, before drought was a harsh reality, we described mosquitoes amazing ability to fly through the rain. Now, a new study in Proceedings of the Royal Society B, demonstrates that hummingbirds are equally as adept in heavy downpours.

According to the abstract, UC Berkeley’s Victor Manuel Ortega-Jimenez and Robert Dudley found that:

…birds hovering in heavy rain adopted more horizontal body and tail positions, and also increased wingbeat frequency substantially, while reducing stroke amplitude when compared with control conditions.

These dynamics can be applied to robots, say the authors. No surprise, given both scientists are part of Berkeley’s Integrative Biology department—where many bio-inspired robotic ideas come from.

Image: User:Mdf/Wikipedia

Among their subjects are geckos and cockroaches. “Cockroaches continue to surprise us,” says Full, a professor of integrative biology who 15 years ago discovered that when cockroaches run rapidly, they rear up on their two hind legs like bipedal humans. “They have fast relay systems that allow them to dart away quickly in response to light or motion at speeds up to 50 body lengths per second, which is equivalent to a couple hundred miles per hour, if you scale up to the size of humans. This makes them incredibly good at escaping predators.”

Besides their speed to evade predators, cockroaches are also able to flip under ledges and disappear in the blink of an eye, the UC Berkeley researchers report recently in PLoS ONE. The cockroach does this by grabbing the edge with grappling hook-like claws on its back legs and swinging like a pendulum 180 degrees to land firmly underneath, upside down.

This pendulum swing subjects the animal to 3-5 times the force of gravity (3-5 gs), similar to what humans feel at the bottom of a bungee jump, lead author Jean-Michel Mongeau says.

(Video of the feat is available here.)

Surprisingly, the researchers observed geckos using this same escape technique both in the lab and in the rain forest at the Wildlife Reserves near Singapore.

“This behavior is probably pretty widespread, because it is an effective way to quickly move out of sight for small animals,” Full says.

Full and his colleagues make good with these obsessions with animal movements. They use the mechanics found in nature for robotics. Nature has had millions of years to develop the engineering, so why not borrow it?

“This work is a great example of the amazing maneuverability of animals, and how understanding the physical principles used by nature can inspire design of agile robots,” UC Berkeley engineering professor Ron Fearing says.

With the help of Poly-PEDAL Lab’s observations, Fearing’s team created a robot that can turn onto ledges like the roaches and geckos.

This new robot could help in dangerous search and rescue missions, according to Full. “That’s really the challenge now in robotics: to produce robots that can transition on complex surfaces and get into dangerous areas that first responders can’t get into.”

Photo by Jean-Michel Mongeau and Pauline Jennings, courtesy of PolyPEDAL Lab, UC Berkeley

ScienceNOW reports that:

Tails are often an enigma; many creatures have them, but scientists know little about their function, particularly for extinct species. Dinosaur tails are no exception. Researchers have speculated that some species’ tails were used in fighting, whereas others for stability.

Our friend Robert Full and his colleagues at UC Berkeley found how when leaping, red-headed African Agama lizards swing their tails upward to prevent them from pitching head-over-heels into a rock. You can see a video of this feat here.

“We showed for the first time that lizards swing their tail up or down to counteract the rotation of their body, keeping them stable,” says Full. “Inspiration from lizard tails will likely lead to far more agile search-and-rescue robots, as well as ones having greater capability to more rapidly detect chemical, biological or nuclear hazards.”

While Full is a biology professor, he is no stranger to robots, Scientific American reports.

These are just the latest developments in Full’s full-on flirtations with robots. He has worked with engineers since the mid-1990s when he helped to develop the crab-inspired Ariel, a minesweeping robot… that can look for buried explosives in surf zones. In 2008 Full co-founded the Center for Integrative Biomechanics in Education & Research (CiBER) at University of California, Berkeley, to further integrate the work of biologists and engineers when designing technology.

“Engineers quickly understood the value of a tail,” UC Berkeley engineering graduate student Thomas Libby explains. “Robots are not nearly as agile as animals, so anything that can make a robot more stable is an advancement, which is why this work is so exciting.”

Full and his team received a surprise benefit from the lizard tail research: understanding how dinosaur tails function.  The new research tested a 40-year-old hypothesis that the two-legged theropod dinosaurs—the ancestors of birds—used their tails as stabilizers while running or dodging obstacles or predators.

Indeed, just like the velociraptor depicted in the movie Jurassic Park, these agile dinosaurs may also have used their tails as stabilizers to prevent forward pitch, Full says. “Muscles willing, the dinosaur could be even more effective with a swing of its tail in controlling body attitude than the lizards.”

The research is published in the recent edition of Nature.

Image: Robert Full lab, UC Berkeley