Bats and dolphins are two of the most celebrated users of echolocation, employing high-frequency sounds to locate prey, find their way, or to communicate. Now a new set of findings in Current Biology show that not only do the two different kinds of mammals use the same method, they also evolved nearly the exact same molecular means for hearing at high frequencies.
That second part was a surprise, study author Stephen Rossiter says: “It’s common on a morphological scale but it’s assumed not to occur at a DNA level because there are so many different ways to arrive at the same solution” [BBC News]. That is, while it’s quite common for different species to separately evolve similar features—like the tusks of elephants and walruses—it’s quite unlikely that natural selection working in separate species would settle an essentially identical gene and protein for growing tusks, hearing high-frequency sounds, or anything else. Or so the thinking went.
Besides the challenges of integrating variable wind power into an electrical grid built with fossil fuel plants in mind, wind farms also must clear the hurdle of showing that their turbines don’t pose a danger to wildlife. The latter issue has now thrown a wrench into the construction of a $300 million West Virginia wind farm, after a judge ruled it would threaten endangered bats.
U.S. District Judge Roger W. Titus ruled that Chicago-based Invenergy can complete 40 windmills it has begun to install on an Appalachian ridge in Greenbrier County. But he said the company cannot move forward on the $300 million project — slated to have 122 turbines along a 23-mile stretch — without a special permit from the U.S. Fish and Wildlife Service [Washington Post].
Male Brazilian free-tailed bats sing intricate songs to attract females and deter other males using a set syllabic order and syntax, according to a study published in the journal PLoS One. The bats can even add their own creative touches to the croonings.
By examining 400 songs produced by 33 free-tailed bats, researchers found that all the bats produce songs with a common hierarchical structure. “All are constructed from the same four types of syllables and all syllables are combined in the same way to form three types of phrases,” says [lead author Kirsten] Bohn. These phrases can be either chirps, trills or buzzes [BBC News], and the complexity of the songs rival those only of birds and whales, leaving those produced by mice in the dust. The bats may vary their songs to appeal more to females or to convey different sentiments. “Within the broad rules, the bats are quite versatile” [BBC News], Bohn says.
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Video: Kirsten Bohn, et al. The slowed-down video shows a male bat singing while performing a wing-flapping display for roosting females.
Wind power may prove to be a promising source of clean energy, but it can also be deadly to bats. Not only can the animals be sliced by the blades of wind turbines, but the sudden drop in air pressure around the turbines can also cause bats’ lungs to explode. An electromagnetic field emitted near the turbines, however, may help bats steer clear of them, according to a new study published in the Public Library of Science One.
Bat casualties near wind turbines have proven to be significant: In 2004, over the course of six weeks, roughly 1,764 and 2,900 bats were killed at two wind farms in Pennsylvania and West Virginia, respectively [LiveScience]. If wind power continues to become increasingly prevalent, so too might the turbines become a growing threat to bat populations. “Given the growing number of wind turbines worldwide, this is going to be an increasing problem, no question about that,” said [co-author] Paul Racey [LiveScience].
Scientists have long been impressed with bats’ echolocation calls, the brief bursts of sound that bounce off surrounding objects and allow the bats to navigate in the dark. But now researchers have found a new level of sophistication in those cries. A new study of greater mouse-eared bats proves that bats can distinguish between the calls of different individual bats. Researchers say this could explain how they remain in a group when flying at high speeds in darkness, and how they avoid interference with one another’s echo-location calls [The Guardian].
In the study, published in the journal PLoS Computational Biology, lead researcher Yossi Yovel played the recordings of bat cries back to his test subjects. “Each bat was assigned two others it had to distinguish between,” Dr Yovel explained. “So we trained bat A on a platform, playing a sound from bat B on one side and from bat C on the other. He had crawl to where the ‘correct’ sound was coming from” [BBC News]. For a correct answer, the bat was rewarded with a mealworm.
Researchers have learned the universal secret behind the graceful, aerial turns executed by everything from insects to cockatoos. And it’s a surprisingly simple process: To turn left, all a bird has to do is flap its right wing a little bit harder than the left wing. To end the turn, the bird simply returns to flapping its wings in unison [Discovery News]. Researchers hope to duplicate the simple set of motions to create more nimble and acrobatic flying robots.
Though the dynamics probably can’t work at large scales — building-sized robotic birds won’t ever be as agile as a swallow — they could be harnessed in small drones used by explorers or the military. Compared to the average hummingbird or fruit fly, such craft are now clumsy and unstable. “The results will inform all future research into maneuvering flight in animals and biomimetic flying robots” [Wired], wrote biomechanicist Bret Tobalske in a commentary.
With the cause of a rampantly deadly bat illness still unknown, biologists have no solution to the problem but have proposed at least a quick fix that may be able to slow it down. At least half a million bats throughout the northeast United States have died from white-nose syndrome (WNS), a fungal infection that was first observed only two years ago. The fungus is thought to grow on bats’ facial skin and flight membranes, possibly causing them to starve. No one knows where the fungus came from, or if it is what is directly killing the bats. But in caves where it has been observed, bats have suffered morality rates ranging from 75 to 100 percent [Scientific American]. With the cause of the fungus not yet determined, researchers worry about the fate of bats, which play an important role in controlling the populations of insects that can damage wheat, apples and dozens of other crops [AP].
While it won’t solve the problem, a temporary stop-gap is now being considered that would place battery-operated heated boxes inside bats’ hibernation caves, and may give the animals the energy they need to fight off, or at least survive, the fungal infections [Scientific American]. The idea is based on the fact that the bats with WNS appear emaciated, as if they’ve starved to death during their winter hibernation; researchers theorize that afflicted bats rouse from hibernation more often than normal bats and thus burn more fat to stay warm [AP]. When they temporarily stir, the bats’ body temperature and metabolism spike.
Researchers have gathered some clues to solve the mystery of what’s killing off hibernating bats throughout New England, but say they’re still far from knowing how to halt the strange die-off. In a new study, researchers identified the characteristic white fungus that has been found on the noses of dead and dying bats, and say it’s a new species of mold that thrives at low temperatures like those found in caves in the winter. But debate still continues over whether the fungus is the cause of death, or simply a secondary infection that takes advantage of bats with already weakened immune systems.
Bats covered with the fungus, a sickness now called white-nose syndrome, were first spotted in Howes Cave near Albany, N.Y., during the winter of 2006. At that time, field biologists reported caves that were typically covered with hibernating bats had loads of vacancies…. In one case, a cave floor was littered with dead bats [LiveScience]. Since then, the epidemic has spread throughout Connecticut, Massachusetts, Maine, and Vermont, with 80 to 100 percent of bats dying in some caves.
Wind turbines may be killing bats without touching them: A new study suggests that the localized drop in air pressure caused by the whirling blades is causing the delicate lungs of bats to burst. While environmentalists previously worried about birds getting slashed by the turbines’ blades, researchers realized a year ago that bats are more at risk from the the turbines. In May 2007, the US National Research Council published the results of a survey of US wind farms showing that two bat species accounted for 60% of winged animals killed [New Scientist]. But until now, the bats’ mode of death was unknown.
Because bats navigate using a sophisticated echolocation system, researchers thought it was unlikely that the bats were getting caught in the turbines. Says lead researcher Erin Baerwald: “When people were first starting to talk about the issue, it was ‘bats running into the turbine blades.’ We always said, ‘No, bats don’t run into things.’ Bat’s can detect and avoid all kinds of structures.” In fact, they are even better at detecting moving objects, Baerwald said. “This kind of answers that mystery,” she added. “It was something nobody could have predicted” [Discovery News].