How do you count endangered species? Look to the stars
News and notes about science
The conversation started over a fence dividing two backyards. On one side, an ecologist remarked that surveying animals is a pain. His neighbor, an astronomer, said he could see objects in space billions of light years away.
And so began an unusual partnership to adapt tools originally developed to detect stars in the sky to monitor animals on the ground.
The neighbors, Steven Longmore, the astronomer, and Serge Wich, the ecologist, both of Liverpool John Moores University in England, made their backyard banter a reality that may contribute to conservation and the fight against poaching.
The scientists developed a system of drones and special cameras that can record rare and endangered species on the ground, day or night. Computer-vision and machine-learning techniques that help researchers study the universe’s oldest and most distant galaxies can now be used to find animals in video footage.
Claire Burke, an astrophysicist at the university now leading the project, presented the team’s latest findings at the European Week of Astronomy and Space Science last week.
Cameras made for daylight can miss animals or poachers moving through vegetation, and the devices do not work at night. Infrared cameras can help.
These cameras yield large amounts of footage that cannot be analyzed fast enough. So what do animals and stars have in common? They both emit heat. And much like stars, every species has a recognizable thermal footprint.
“They look like really bright, shining objects in the infrared footage,” Burke said.
To build up a reference library of different animals in various environments, the team is working with a safari park and zoo to film and photograph animals. With these thermal images — they will need thousands — they will be able to better calibrate algorithms to identify target species in ecosystems around the world.
Last September, the scientists honed their tools in the first field test in South Africa. There, they found five Riverine rabbits in a relatively small area. These shy rodents are among the world’s most endangered mammals.
The tests helped the scientists calculate an optimal height to fly the drones. The team also learned that animals change shape in real time (rocks don’t) as drones fly over.
— Joanna Klein
In footprints on Scotland’s Isle of Skye, signs of a dinosaur playground
Gigantic dinosaurs frolicked and splashed some 170 million years ago in the lagoons of what is now Scotland. That’s what a team of paleontologists has determined after discovering dozens of jumbo-sized footprints belonging to longnecked sauropods on the Isle of Skye. Mixed with the herbivores’ tracks were a few clawed impressions left behind by two-legged meat-eaters known as theropods.
The footprints present a snapshot of life during an important period in dinosaur history that has yielded relatively few fossil remains. In the mid-jurassic, sauropods necks grew longer and the first birds were figuring out flight.
Identifying two types of footprints in the same place also challenges the idea that long-necked dinosaurs waded into shallow, muddy waters to escape predators, said Stephen Brusatte, a paleontologist at the University of Edinburgh in Scotland and an author of the new study.
“We’re actually seeing these dinosaurs interacting with each other and interacting with their environment,” he said.
The team reported their findings recently in the Scottish Journal of Geology.one of Brusatte’s graduate students, Davide Foffa, stumbled upon the first tracks in 2016 while the team explored the coasts for bones and teeth. Amid the tidal pools, he found a large impression that had been colored pinkish-purple by algae. Upon closer inspection, he discovered the outlines of toes and a fleshy heel pad — a sauropod footprint.
That print became known as “the money track.”
“Once I saw that track, it was like I put on a different kind of glasses or something,” said Paige depolo, who was then a master’s student working under Brusatte and is lead author of the new paper. “It helped me to see these other less distinct tracks.”
Her team helped identify about 50 footprints, including a few with heels and claws belonging to theropods that were early relatives of Tyrannosaurus rex.
The long-necked dinosaur footprints were each about the size of a trash can lid, depolo said, with the largest being more than 2 feet in diameter. She and her colleagues estimated that the sauropods who left the tracks were about 6 feet tall at the hips, much smaller than the titanosaurs that would later roam the Earth.
— Nicholas St. Fleur
Why do cracking knuckles make that sound? You might need a calculator
You might be surprised to learn that where exactly the sound of cracking knuckles is coming from — what precisely in the knuckle produces it — is still a subject of scientific research.
For more than 50 years people have been publishing scholarly papers about what is going on in your finger as you pull it. Lately an older theory, that the sound arises from the popping of a bubble in the joint, has been challenged by one that holds that the formation of the bubble itself is responsible. Recently in the journal Scientific Reports, the saga continued: A pair of researchers at the Ecole Polytechnique in France reveal a mathematical model of a cracking knuckle and suggest that the old theory could accurately explain the sound.
Where the two bones of the finger meet, a little lake of synovial fluid keeps them from grinding on each other. There is gas dissolved in the synovial fluid, mostly carbon dioxide, and it usually stays there. However, when the bones are pulled away from each other, there’s a sudden drop in pressure in the middle of the joint. Lower pressure allows the gases to come together, forming bubbles. Earlier work had suggested the collapse of such structures was behind the noise.
In 2015, however, Greg Kawchuk of University of Alberta and collaborators used an MRI scanner to record what was happening in the finger of a volunteer who was a frequent knuckle-cracker. In the images, you can see the sudden appearance of a bulge in the knuckle as it is cracked.
This is the result, Kawchuk and colleagues wrote, of the formation a bubble, which persisted for some time afterward, and whose creation might be responsible for the cracking noise.
Abdul Barakat, a professor of biomechanics at the Ecole Polytechnique in France, and Vineeth Suja, then a master’s student, came across the 2015 paper. To see whether even the old theory could produce a sound of that magnitude, they created a simplified mathematical model of a joint with a bubble in it and ran simulations, comparing the theoretical sounds of the bubble collapsing in the model with recordings of Suja and others cracking their knuckles.
They found that the sounds predicted by the model would have the volume and frequency to match the recordings fairly well — even if the bubble only shrank suddenly, rather than disappearing.
— Veronique Greenwood
The crystals that may have helped Vikings navigate northern seas
When the Vikings left the familiar fjords of Norway for icy, uncharted territories, they were at the mercy of weather. They had no magnetic compasses, and no way to ward off stretches of heavy clouds or fog that made it difficult to navigate by sun. How the explorers traversed open ocean during these times is a mystery that has long captivated scholars.
Norse sagas refer to a sólarstein or “sunstone” that had special properties when held to the sky. In 1967, a Danish archaeologist named Thorkild Ramskou suggested these were crystals that revealed distinct patterns of light in the sky, caused by polarization, which exist even in overcast weather or when the sun dips below the horizon.
Multiple translucent crystals fit the bill, namely calcite, cordierite and tourmaline. None have ever been found at Viking archaeological sites, but a calcite crystal was discovered in the wreck of a British warship from the 1500s, indicating it might have been a tool known to advanced ocean navigators.
A study published recently in Royal Society Open Science advances this idea, suggesting the Vikings had a high chance of reaching a destination like Greenland in cloudy or foggy weather if they used sunstones and checked them at least every three hours.
“This study is an important step forward because it addresses the issue of cloudy conditions in a systematic way,” said Stephen Harding, author of the book “Science and the Vikings” and a biochemistry professor at the University of Nottingham who was not involved in the study.
If the Vikings oriented their ship with calcite, cordierite or tourmaline at least every three hours, the model showed, they had a 92 to 100 percent chance of getting within sight of Greenland. These are “surprisingly large success rates” for navigating in overcast conditions, the authors noted.
When polarized light passes through calcite, it splits into two beams. By rotating a calcite crystal against the sky and noting changes in brightness between these beams, one can find the atmosphere’s polarization rings and figure out where the sun is.
— Steph Yin