Science  11 Mar 2011:
Vol. 331, Issue 6022, pp. 1248

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  1. Elephants Can Lend a Helping Trunk

    We humans readily understand when we need another person's help to solve a problem. That kind of cooperative skill is an indication of our higher social cognition, psychologists say, and it's rarely found in other species. But a new study, published online in the Proceedings of the National Academy of Sciences, shows that elephants, too, can easily see when a goal is only attainable with another elephant—and his or her trunk.

    Elephants cooperate to move a sliding table.


    To test elephants' cooperative skills, Joshua Plotnik, then a psychology graduate student at Emory University in Atlanta and now at the University of Cambridge in the United Kingdom, used a sliding table bearing treats that could be moved only if two elephants pulled simultaneously on the ends of a single rope threaded through the table; otherwise, the rope would just come out. Twelve Asian elephants (Elephas maximus) were grouped in pairs and taught the pulling task. In a test of whether they understood that they needed help, the animals waited for their partners, sometimes for as long as 45 seconds, before pulling their end of the rope. “People might not be surprised that chimpanzees can solve this task,” says Satoshi Hirata, a primatologist at the Great Ape Research Institute in Okayama, Japan, who invented this dual rope-pulling exam. “But it is more surprising, even for researchers, that elephants can do it, too. It shows that they are highly socially intelligent.”

  2. Bad for the Bone

    Last November, failure-weary HIV prevention researchers were energized by news that taking anti-HIV drugs could thwart transmission of the virus in transgender women and men who have sex with men. That success now comes with a new caveat. Two groups reported last week in Boston at the Conference on Retroviruses and Opportunistic Infections that the two drugs used together for what is known as Pre-Exposure Prophylaxis (PrEP) reduced bone density in trial participants. Researchers have long known that one of the drugs, tenofovir, causes 2% to 4% bone density loss in HIV-infected people who use the compound as part of their treatment regimen. The PrEP data suggest the loss is only 1%, and no one has suffered bone fractures as a result. Still, concerns about side effects from PrEP run especially high because the anti-HIV drugs are being given to otherwise healthy people.

  3. Battle-Scarred Mars


    High-resolution images released last week by the European Space Agency reveal new details about an unusually elongated crater on Mars that may have been blasted by several objects striking the planet's surface at a shallow angle. The unnamed crater, located in a heavily blemished portion of the Red Planet's southern hemisphere, is about 78 kilometers long, approximately 25 kilometers across at its widest point, and about 2 kilometers deep. Two distinct blankets of material blasted from the impact zone suggest that at least two projectiles, possibly fragments of a once-intact body, gouged the crater. Three particularly deep spots in the crater (depicted in blue, inset) bolster the notion of multiple impactors, as does the presence of another elongated crater nearby that has a similar alignment.

  4. More Evidence That Chimps Die From AIDS

    Researchers at this year's Conference on Retroviruses and Opportunistic Infections, held in Boston last week, have found iron-clad evidence of AIDS in a wild chimp.

    At the 2009 conference, researchers who studied fecal samples from chimpanzees at Gombe Stream National Park in Tanzania—communities that have been followed since Jane Goodall started working there in 1960—showed that individuals infected with SIVcpz, a cousin of HIV, had shorter life spans. Necropsies of dead chimps revealed immune destruction, but for ethical reasons, the researchers could not prove their case by sampling chimp blood over time to track the decline of CD4 white blood cells, the virus's main target.

    Now Lucie Etienne, who works with Martine Peeters at the Institute of Research for Development in Montpellier, France, has solid evidence from a wild-born male chimpanzee that tested positive for SIVcpz when he arrived at a chimpanzee sanctuary in Cameroon in November 2003. A test a few months later showed that he had 700 CD4 cells per microliter of blood. By August 2009, the count had dropped to 287; the average CD4 count of a healthy, age-matched chimpanzee tested at the sanctuary was 1256. The SIVcpz-infected chimp has had many infections and lost 21% of his weight between August 2009 and January 2010, Etienne and her colleagues reported online 13 January in Retrovirology. Etienne says they may treat the chimpanzee with anti-HIV drugs.

  5. Shedding Light on Anxiety

    Tucked deep inside the brain, the amygdala is the seat of fear and anxiety. Now researchers have used newly developed “optogenetic” methods to indentify a subset of the amygdala's neurons that seems to regulate anxiety levels.


    Mice are naturally anxious, says Karl Deisseroth, a neuroscientist at Stanford University and the senior author of the paper, which appears in Nature this week. In the lab, for example, mice hug the walls when placed in a big, open enclosure. To address these nervous tendencies, Deisseroth and colleagues focused on a specific group of neurons that originate in one part of the amygdala and terminate in another. After inserting a gene that made the neurons sensitive to light, they stimulated the neurons' terminals via laser light pulsed through an optical fiber. Mice given this treatment were less afraid of open spaces.

    By clarifying the neural circuits affected by anxiety disorders, such studies could eventually lead to more targeted treatments, says neuroscientist Stephen Maren of the University of Michigan, Ann Arbor.