Study finds why bats crash into buildings
News and notes about science
Bat echolocation is a finely tuned sense. By emitting high-frequency calls and listening for returning echoes, bats can deftly navigate complex surroundings and precisely target moving prey in the dark. But this extraordinary capability is not foolproof. A study published Thursday in Science reveals a weak spot in bat echolocation: smooth, vertical surfaces such as the metal or glass plates on buildings can trick a bat into thinking it is flying in open air.
The findings may help explain why the creatures are often found dead or injured near buildings and other smooth structures, said Stefan Greif, an author of the study and a postdoctoral researcher affiliated with the Max Planck Institute for Ornithology in Germany and Tel Aviv University in Israel.
When a bat approaches a smooth, vertical surface from an angle — as it would when turning a corner in a rectangular tunnel — its echolocating calls mostly reflect away from it. It’s not until a bat gets very close to a flat, vertical surface that some of its calls end up hitting the plate at a 90-degree angle and bouncing right back. At this point, Greif and his collaborators noted, bats tended to change their echolocation patterns, shortening the time between calls, to collect more information. But it was often too late — out of 78 instances they observed of bats coming close to a vertical plate, 25 resulted in near misses while 53 resulted in crashes.
— Steph Yin
Starting fires to unearth how Neanderthals made glue
Neanderthals seem stuck with unflattering reputations. The entire species of early human ancestors has long been reduced to a pejorative for describing someone who isn’t very bright, despite growing evidence of the sophistication of Homo neanderthalensis. And recent research suggests another overlooked mark of their ingenuity: They made the first glues in the form of tar.
The tar was distilled from the bark of birch trees some 200,000 years ago, and seemed to have been used for hafting, or attaching handles to stone tools and weapons. But scientists did not know how Neanderthals produced the dark, sticky substance.
Now, in a study published last Thursday in the journal Scientific Reports, a team of archaeologists has used materials available during prehistoric times to demonstrate three possible ways Neanderthals could have deliberately made tar. While the study does not prove that Neanderthals used any of these methods, it aims to demonstrate that they had access to the ingredients and means to produce tar.
“There’s this popular perspective of Neanderthals as being these simple cave men and slowtype brutes,” said Paul Kozowyk, a graduate student at Leiden University in the Netherlands and lead author of the study. “This tar production, and its use for hafting, is evidence that this isn’t really true.”
— Nicholas St. Fleur
Overtreatment is common, doctors say
Most U.S. physicians believe that overtreatment is harmful, wasteful and common.
Researchers surveyed 2,106 physicians in various specialties regarding their beliefs about unnecessary medical care. On average, they believed that 20.6 percent of all medical care was unnecessary, including 22 percent of prescriptions, 24.9 percent of tests and 11.1 percent of procedures. The study is in PLOS One.
Nearly 85 percent said the reason for overtreatment was fear of malpractice suits, but that fear is probably exaggerated, the authors say. Only 2 to 3 percent of patients pursue litigation, and paid claims have declined sharply in recent decades.
Nearly 60 percent of doctors said patients demand unnecessary treatment. A smaller number said that limited access to medical records led to the problem.
More than 70 percent of doctors conceded that physicians are more likely to perform unnecessary procedures when they profit from them, while only 9.2 percent said that their own financial security was a factor.
“This study is essentially the voice of physicians about the problem,” said the senior author, Dr. Martin A. Makary, a professor of surgery at Johns Hopkins. “We’re told that there are too many operations done for narrowed blood vessels in the legs. Spine surgeons say that a quarter of all spine surgery may not be necessary. Half of stents placed may be unnecessary. These are significant opportunities to improve quality and lower costs.”
— Nicholas Bakalar
Wild dogs sneeze when they are ready to hunt
When they want to move as a group, meerkats call to each other. Capuchin monkeys trill. Gorillas grunt. Honeybees make what is called a piping sound.
African wild dogs sneeze. And that’s a first.
For one thing it seems to indicate a positive reaction to a proposal before a group of dogs. When a pack of these dogs is getting ready to hunt, scientists reported Tuesday, the more sneezes, the more likely they are to actually get moving.
Just about all social organisms make group decisions that require reaching a consensus. Bacteria use chemical signals but larger animals often use sounds as a way of saying, I’m in. However, among grunts, huffs, piping signals and others, the sneeze had not been reported as one of those signals until a group of American, British and Australian researchers published their observations of African dogs in the Proceedings of the Royal Society B.
Unlike the one-person, onevote rules of human elections, members of the group were not limited to one sneeze. And if a dominant pack member started a rally, fewer sneezes were needed from the other dogs to get the hunt off the ground, one researcher said.
— James Gorman
New study favors fat over carbs
High carbohydrate intake is associated with a higher risk of mortality, and high fat intake with a lower risk, researchers report.
An international team of scientists studied diet and mortality in 135,335 people between 35 and 70 years old in 18 countries, following them for an average of more than seven years. Diet information depended on self-reports, and the scientists controlled for factors including age, sex, smoking, physical activity and body mass index. The study is in The Lancet.
Compared with people who ate the lowest 20 percent of carbohydrates, those who ate the highest 20 percent had a 28 percent increased risk of dying earlier. But high carbohydrate intake was not associated with cardiovascular death.
People with the highest 20 percent in total fat intake — an average of 35.3 percent of calories from fat — had about a 23 percent reduced risk of death compared with the lowest 20 percent (an average of 10.6 percent of calories from fat). Consuming higher saturated fat, polyunsaturated fat and monounsaturated fat were all associated with lower mortality. Higher fat diets were also associated with a lower risk of stroke.
“Guidelines recommend low saturated fat, and some recommend really low amounts,” said a co-author, Andrew Mente, an epidemiologist at Mcmaster University in Ontario. “Our study, which captures intake at the lowest levels, shows that this may be harmful.”
Current federal guidelines recommend a diet that provides no more than 35 percent of calories from fat.
— Nicholas Bakalar
Satellite images of North Korea show landslides at nuclear test site
Analysts peering at satellite images of North Korea after the latest nuclear test reported that they had spotted many landslides and wide disturbances at the country’s test site, in the North’s mountainous wilds. Tunnels for the nuclear blasts are deep inside Mount Mantap, a mile-high peak.
“These disturbances are more numerous and widespread than what we have seen from any of the five tests North Korea previously conducted,” three experts wrote in an analysis for 38 North, a website run by the U.s.-korea Institute of the Johns Hopkins University School of Advanced International Studies.
The new satellite images of the Punggye-ri nuclear test site were taken Monday, the day after the nuclear detonation. Planet, a company in San Francisco that owns swarms of tiny satellites, reconnoitered the secretive nuclear test site.
The three analysts — Frank V. Pabian, Joseph S. Bermudez Jr., and Jack Liu — said the wide disturbances appeared to include numerous landslides throughout the rugged site “and beyond.”
They added that they could find no evidence of a surface crater that would have formed if the cavern carved out within the mountain by the blast’s violence and high temperatures had suddenly collapsed.
— William J. Broad
Treating reflux with diet
A small study has found that a plant-based diet is just as effective as proton pump inhibitors in treating laryngopharyngeal reflux, or LPR.
LPR is a disease in which stomach acid comes up into the throat to the level of the laryngopharynx. It is not the same as gastro-esophageal reflux, or GERD, which involves a backflow of stomach acid into the lower esophagus.
The retrospective study, in JAMA Otolaryngology — Head and Neck Surgery, included 85 patients with an average age of 60 treated with the PPIS Nexium and Dexilant, and 99 treated with alkaline water and the Mediterranean diet, a regimen low in meat and dairy, and rich in olive oil, fish, beans, fruits and vegetables.
The scientists used an index that measures severity of symptoms — excess throat mucus, heartburn and others — on a 0 to 45-point scale.
In the PPI group, 54 percent achieved a clinically significant 6-point reduction on the index, compared with 63 percent for the diet cohort.
“If you think you have LPR, you should do a diet-based approach, instead of initiating these drugs that have potential side effects,” said the lead author, Dr. Craig H. Zalvan, chief of otolaryngology at Phelps Hospital in Sleepy Hollow, N.Y.
— Nicholas Bakalar