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Bats, with their superb ability to echolocate, are inspiring advanced technologies — from better Navy sonar to gadgets that might deliver packages or help farmers manage crops. And engineers aren’t waiting for neuroscientists to work out every detail of how the bats’ brains manage the task.

“We think we have enough information to be useful to us, to develop a bio-inspired sensor,” says research engineer Jason Gaudette of the Naval Undersea Warfare Center Newport Division in Rhode Island. Like bats, the Navy uses sonar to find and visualize objects in the deep. But current versions are far less elegant than the flying mammals’ system.
The Navy’s sonar arrays can be huge, encompassing hundreds of “ears” that listen for sonar pings from atop a submarine’s dome or trailing behind it in a long tail. Bats, Gaudette notes, dodge obstacles and find mosquito-sized meals with just two ears. He and colleagues have developed a bat-inspired prototype device that they hope can perform more like bats do. Mounted on the nose of a half-meter-long, torpedo-shaped autonomous undersea robot, the sonar system has one sound transmitter and three receivers (Gaudette hopes to eventually get that number down to two or even one).
The system uses algorithms inspired by research in bats to interpret returning sonar echoes for navigation. If it works, the system could help the Navy perform sonar imaging using less space and less money while offering sharper images, Gaudette says.

Researchers in Israel are hoping to help farmers with a bat-inspired kind of sonar. Neuroecologist Yossi Yovel of Tel Aviv University is creating computer algorithms describing how bats might interpret returning echoes to distinguish different plants.
Yovel collaborates with Avital Bechar, a researcher at the Institute of Agricultural Engineering near Rishon LeZion, Israel, who wants to help farmers predict their crops’ yield, which can vary widely from year to year. The same acre of tomato plants, for example, could yield 30 or 120 tons of fruit, Bechar estimates. Such a wide range puts farmers at a disadvantage in negotiating a price for crops and forces the farmers to guess how much equipment and how many pickers they’ll need at harvest time.

Bechar’s sonar system, which emits batlike sounds and records via microphones that mimic bat ears, can penetrate three rows of plants deep — farther than cameras could. Then it calculates the number of leaves and pounds of fruit per plant, based on Yovel’s algorithms. Bechar has mounted the scanner on a prototype robot and plans to affix it to a drone to count fruit in 15-meter-high date palms. The researchers also hope to add weed-detection capability. Bechar expects it to be “a game changer in agriculture, because it will reduce the unknowns.”
At Virginia Tech in Blacksburg, engineer Rolf Mueller is learning tricks from the physical structures of bats’ noses and ears. Certain bat groups, such as horseshoe bats (one species Mueller works with is Rhinolophus ferrumequinum), send out their echolocation calls through their noses, like a snort. Complex, fleshy formations called nose-leaves change the outgoing sound as it comes out of the nose. And the bats’ ears have more than 20 muscles, which rapidly change shape as the bat listens for echoes, Mueller says. That flexibility gives the animals more information, he suspects: “It’s like seeing the world with a different perspective, at the same time, [from] one echo.”

His group developed a prototype robot with mechanical “nose-leaves” and shape-shifting “ears,” and sent it zooming through forested areas on a zip line to record how the bot perceives trees and branches. Eventually, Mueller envisions an autonomous underwater bot or an airborne drone with a similar sonar setup. The drone could be useful for delivering packages in forested or otherwise complicated areas without crashing.

For an animal already amazing enough to walk on water, what could growing feather fans on its legs possibly add?

These fans have preoccupied Abderrahman Khila of the University of Lyon in France, who keeps some 30 species of bugs called water striders walking the tanks in his lab without getting their long, elegant legs wet.

“Walk” may be too humdrum a word. The 2,200 or so known species of water striders worldwide can zip, skim, skate and streak. Among such damp-defying acrobats, however, only the Rhagovelia genus grows a fan of delicate feathers on the middle pair of its six legs. Even little hatchlings head-banging their way out of underwater eggs have a pair of feathery microfluffs for their perilous swim up to cruise the water’s surface.
A first guess at a function — maybe plumes help support bigger adults — would be wrong, Khila says. The Rhagovelia are not giants among water striders. In a jar of alcohol in his lab, he treasures a specimen of a much bigger species, with a body about the size of a peanut and a leg span that can straddle a CD. Yet this King Kong among striders, found in Vietnam and China, slides over the water as other species do, cushioned by air trapped in dense hydrophobic leg bristles. No froufrou feathers needed.
Fans aren’t required either for water striders’ action-packed, often violent lives. “In the lab, they eat each other all the time,” Khila says. A newly molted strider, still soft and weak after 10 minutes of wriggling out of its old external skeleton, can get mobbed by cannibals. Any other insect, such as a mosquito, that lands on the water surface also triggers a frenzy. Small striders “start to attack the legs of the mosquito,” he says, “and seconds later there are 50 water striders gathered around.” With their tubelike mouthparts, the striders stab holes in the victim and inject enzymes to liquefy flesh into a meat shake to suck out.

For these Rhagovelia, Khila sees the fans as “one of those examples of ‘key evolutionary innovations,’” traits that just “pop up” in evolutionary history with no clear line of precursors or partial forms, he says. Now he and his colleagues have identified a fan benefit. When they removed plumes from the bugs or suppressed genes for fan formation, the mutant striders couldn’t turn as deftly or run upstream against the current as fully fanned Rhagovelia can, the researchers report in the Oct. 20 Science. Striders in a closely related but fanless genus were likewise hampered. The innovative fan opened up new territory, helping the insects navigate flowing water, the researchers conclude.

Fan-maker genes were intriguing in another way. Evolutionary biologists have long debated whether such evolutionary innovations just repurpose and recombine old developmental genes or actually rely on new ones. In the case of the fans, two genes, which the researchers named geisha and mother-of-geisha after geisha fans, are unique to this genus, but three other genes are repurposed. So in a twist on an old debate, Khila says, “neither hypothesis is wrong.”

It is “extremely likely” that humans are driving warming on Earth since the 1950s. That statement — which indicates a 95 to 100 percent confidence in the finding — came in a report released November 3 by the U.S. Global Change Research Program. This interagency effort was established in 1989 by presidential initiative to help inform national science policy.

The 2017 Climate Science Special Report, which lays out the current state of scientific knowledge on climate change, will be rolled into the fourth National Climate Assessment, set to be released in late 2018.
The last national climate assessment, released in 2014, also concluded that recent warming was mostly due to humans, but didn’t give a confidence level (SN Online: 5/6/14). Things haven’t gotten better. Ice sheet melting has accelerated, the 2017 report finds. As a result, projections of possible average global sea level rise by 2100 under a high greenhouse gas emissions scenario (in which emissions rise unabated throughout the 21st century) have increased from 2 meters to as much as 2.6 meters.

In addition, the report notes that three of the warmest years on record — 2014, 2015 and 2016 — occurred since the last report was released; those years also had record-low sea ice extent in the Arctic Ocean in the summer.

The report also notes some still-unresolved questions that have become increasingly active areas of research. One big one: How will climate change alter atmospheric circulation in the mid-latitude areas? Scientists are wrangling with whether and how these changes will affect storm patterns and contribute to extreme weather events, including blizzards and drought.