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Spider's amorous song lures mates
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D. Harley
HOW do you locate small, shy and speedy possums that hang out at the top of the tallest trees? You talk to them, of course. Leadbeater’s or fairy possums (Gymnobelideus leadbeateri) are critically endangered and only a few thousand remain, in a small stretch of swampy forest north-east of Melbourne, Australia. Their population at one site, the Yellingbo Nature Conservation Reserve, has declined by more than 60 per cent over the past decade and now numbers just 40 individuals, says Dan Harley at Zoos Victoria in Melbourne. “Severe deterioration in habitat conditions has driven the decline.” Knowing how many possums are left is crucial to determining if conservation measures are working, he says. Checking the nest boxes supplied for the possums to live in isn’t enough. If they’re not in, it is hard to know if the family has moved to a new nest, left the area – or worse. So, Harley tried using the possum’s own chattering call. He found they often approach and replied to his efforts (Australian Mammalogy, doi.org/4rx). The technique isn’t perfect, says Harley, but it could complement other counting methods. There are false negatives: 31 per cent of his calls didn’t elicit responses, despite him seeing a possum nearby.
Vesta has no moons – is it unlucky or did it eat them? THE biggest asteroids are loners. A decades-long search for moons orbiting Vesta, the secondheaviest object in the asteroid belt, has come up fruitless, raising questions about how such massive rocks remain alone. Nearly 100 main-belt asteroids have satellites, most of which were found without a dedicated search. But although we have looked for moons around Vesta since 1987, none has turned up. Finding and studying one could give insight into Vesta’s orbital stability and the evolution of the
solar system, because any moon would be a physical record of its past. So when NASA’s Dawn spacecraft approached Vesta in 2011, “we couldn’t pass the opportunity to look one more time”, says Lucy McFadden of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. McFadden and her colleagues analysed close-up images of Vesta’s environment collected over three months in 2011 and 2012, finding no trace of any companion object larger than 6 metres wide
(Icarus, doi.org/4r6). The lack of moons is puzzling, especially given Vesta’s two huge impact craters, which are the source of a family of asteroids. “Those impacts should have produced a lot of debris that should have been very good at forming satellites,” says William Bottke of the Southwest Research Institute in Boulder, Colorado. Nick Gorkavyi at NASA Goddard has another idea: moons existed, but crashed into Vesta long ago, digging huge canyons such as the enigmatic Divalia Fossa. JOHN BURCHAM/National Geographic Creative
Chat to possums to save them
Spider’s amorous song lures mates THEY don’t have ears but they still sing. For the first time, a spider has been recorded making what appears to be an audible courtship signal – a sort of a soft purr. “It’s very quiet, but it’s what you would hear if you were in the room with a courting spider,” says George Uetz of the University of Cincinnati in Ohio, who described the work last week at a meeting of the Acoustical Society of America in Pittsburgh, Pennsylvania. Many spider species shake leaves or strands of their webs, creating vibrations that nearby spiders feel directly. But Uetz and his colleague Alexander Sweger showed that male purring wolf spiders (Gladicosa gulosa) vibrate dead leaves to create an audible thrumming sound. Only females respond to a recording of it, suggesting it is used in courtship. Uetz and Sweger think that females pick up on the sound indirectly, when it causes the leaves they are standing on to vibrate. “We think that’s how she ‘hears’ the sound,” says Sweger. He says the findings suggest that animals could have used vibrations as a stepping stone in evolving the ability to communicate acoustically.
Awesome views make you... awesome SELF-help gurus extol the benefits of “awakening the giant within” – but don’t dismiss the benefits of feeling small. A diminished sense of self-importance caused by feeling awe can make people more considerate and generous. Paul Piff of the University of California, Irvine, and his colleagues instilled a sense of awe in a group of volunteers by asking them to spend 60 seconds staring up at a grove of 60-metre-tall Tasmanian eucalyptus trees. A control group stared up at a less awe-inspiring building. The researchers then staged an accident,
dropping a box of pens. The group that had gazed at the trees were more helpful and picked up more pens. Further studies involving the tree-gazing exercise showed that awe also encourages people to endorse more ethical decisions and lower their sense of entitlement (Journal of Personality and Social Psychology, doi.org/4r5). “No matter who you are, awe has that effect,” says Piff – but many of us are unaware of the fact. “We’re in the midst of an awe deficit. People are prioritising other things.”
30 May 2015 | NewScientist | 19
D. Harley
HOW do you locate small, shy and speedy possums that hang out at the top of the tallest trees? You talk to them, of course. Leadbeater’s or fairy possums (Gymnobelideus leadbeateri) are critically endangered and only a few thousand remain, in a small stretch of swampy forest north-east of Melbourne, Australia. Their population at one site, the Yellingbo Nature Conservation Reserve, has declined by more than 60 per cent over the past decade and now numbers just 40 individuals, says Dan Harley at Zoos Victoria in Melbourne. “Severe deterioration in habitat conditions has driven the decline.” Knowing how many possums are left is crucial to determining if conservation measures are working, he says. Checking the nest boxes supplied for the possums to live in isn’t enough. If they’re not in, it is hard to know if the family has moved to a new nest, left the area – or worse. So, Harley tried using the possum’s own chattering call. He found they often approach and replied to his efforts (Australian Mammalogy, doi.org/4rx). The technique isn’t perfect, says Harley, but it could complement other counting methods. There are false negatives: 31 per cent of his calls didn’t elicit responses, despite him seeing a possum nearby.
Vesta has no moons – is it unlucky or did it eat them? THE biggest asteroids are loners. A decades-long search for moons orbiting Vesta, the secondheaviest object in the asteroid belt, has come up fruitless, raising questions about how such massive rocks remain alone. Nearly 100 main-belt asteroids have satellites, most of which were found without a dedicated search. But although we have looked for moons around Vesta since 1987, none has turned up. Finding and studying one could give insight into Vesta’s orbital stability and the evolution of the
solar system, because any moon would be a physical record of its past. So when NASA’s Dawn spacecraft approached Vesta in 2011, “we couldn’t pass the opportunity to look one more time”, says Lucy McFadden of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. McFadden and her colleagues analysed close-up images of Vesta’s environment collected over three months in 2011 and 2012, finding no trace of any companion object larger than 6 metres wide
(Icarus, doi.org/4r6). The lack of moons is puzzling, especially given Vesta’s two huge impact craters, which are the source of a family of asteroids. “Those impacts should have produced a lot of debris that should have been very good at forming satellites,” says William Bottke of the Southwest Research Institute in Boulder, Colorado. Nick Gorkavyi at NASA Goddard has another idea: moons existed, but crashed into Vesta long ago, digging huge canyons such as the enigmatic Divalia Fossa. JOHN BURCHAM/National Geographic Creative
Chat to possums to save them
Spider’s amorous song lures mates THEY don’t have ears but they still sing. For the first time, a spider has been recorded making what appears to be an audible courtship signal – a sort of a soft purr. “It’s very quiet, but it’s what you would hear if you were in the room with a courting spider,” says George Uetz of the University of Cincinnati in Ohio, who described the work last week at a meeting of the Acoustical Society of America in Pittsburgh, Pennsylvania. Many spider species shake leaves or strands of their webs, creating vibrations that nearby spiders feel directly. But Uetz and his colleague Alexander Sweger showed that male purring wolf spiders (Gladicosa gulosa) vibrate dead leaves to create an audible thrumming sound. Only females respond to a recording of it, suggesting it is used in courtship. Uetz and Sweger think that females pick up on the sound indirectly, when it causes the leaves they are standing on to vibrate. “We think that’s how she ‘hears’ the sound,” says Sweger. He says the findings suggest that animals could have used vibrations as a stepping stone in evolving the ability to communicate acoustically.
Awesome views make you... awesome SELF-help gurus extol the benefits of “awakening the giant within” – but don’t dismiss the benefits of feeling small. A diminished sense of self-importance caused by feeling awe can make people more considerate and generous. Paul Piff of the University of California, Irvine, and his colleagues instilled a sense of awe in a group of volunteers by asking them to spend 60 seconds staring up at a grove of 60-metre-tall Tasmanian eucalyptus trees. A control group stared up at a less awe-inspiring building. The researchers then staged an accident,
dropping a box of pens. The group that had gazed at the trees were more helpful and picked up more pens. Further studies involving the tree-gazing exercise showed that awe also encourages people to endorse more ethical decisions and lower their sense of entitlement (Journal of Personality and Social Psychology, doi.org/4r5). “No matter who you are, awe has that effect,” says Piff – but many of us are unaware of the fact. “We’re in the midst of an awe deficit. People are prioritising other things.”
30 May 2015 | NewScientist | 19