Chapter 8. Hormones and Sex
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By Virginia Morell A fungal disease that has killed amphibians worldwide may be spreading by making the mating calls of infected males more attractive to females. The finding—one of the first—to show that the pathogen can alter a species’s reproductive behavior could explain why frogs and related animals continue to disappear across the globe. “If true—that the fungus is manipulating individuals’ behaviors to facilitate its spread—then this is extraordinary,” says Michael Ryan, a herpetologist at the University of Texas, Austin, who was not involved in the study. The pathogenic fungus, Batrachochytrium dendrobatidis (Bd), causes chytridiomycosis (also known as chytrid fungus disease, which kills amphibians by destroying their skin, disrupting their immune systems, and causing heart failure). Scientists first recognized its lethal effects in the 1990s when numerous species of frogs in Australia and Central and South America experienced massive die-offs; a related fungus attacks salamanders. Bd has been blamed for the extinction of hundreds of amphibian species, and poses a threat to up to one-third of the world’s frogs, salamanders, and other amphibians. There is no cure, but some frog species infected with the fungus are able to survive for years, indicating that they’ve adapted to the disease. Indeed, a recent study showed that Bd has been evolving with amphibians for some 40,000 years, although some species have only recently encountered it. But even amphibian populations adapted to Bd continue to suffer and decline from its effects, says Bruce Waldman, a behavioral ecologist at Seoul National University and one of the authors of the new paper. © 2016 American Association for the Advancement of Science
By SABRINA TAVERNISE WASHINGTON — Half of one satisfying sexual encounter a month. That is the average benefit a woman gets when she takes the new female libido drug, sometimes called the “female Viagra,” researchers reported Monday. Last year the Food and Drug Administration approved the drug, flibanserin, making it the first drug available to treat low sexual desire in women. It was promoted by a group of women’s rights activists who argued it was unfair that men had numerous drugs to boost sexual function while women had nothing. But public health groups and some other women’s groups contended that the science did not justify its approval. The drug’s effects were modest, they said, and not worth side effects such as sleepiness, dizziness, fatigue and nausea. And the risk of some side effects increased with alcohol consumption. In the new study, published in JAMA Internal Medicine, researchers found benefits that were slightly more modest than those submitted to the F.D.A. during the approval process. The researchers analyzed eight studies of about 5,900 women, using a method that involved pooling the data. They concluded that treatment with flibanserin, now marketed as Addyi, resulted in “one-half of an additional sexually satisfying encounter per month.” (The study did not define what “one-half” of a sexually satisfying encounter was.) That result was not very different from original findings of three clinical trials submitted to the F.D.A. as support for the drug’s approval. Those trials found that once women started taking the drug, they had an average of about one additional satisfying sexual encounter a month, on top of the two to three they were having already. That result lifted the benefits above the bar of being scientifically meaningful, but barely. Still, it was enough for the agency’s approval. © 2016 The New York Times Company
Keyword: Sexual Behavior
Link ID: 21938 - Posted: 03.01.2016
by Giuseppe Gangarossa When we think about sex hormones, notably estrogens and androgens, we usually associate them with sex, gender and body development. Like all hormones, they are chemical messengers, substances produced in one part of the body that go on to tell other parts what to do. However, we often have the tendency to forget the enormous impact that these steroid hormones have on brain functions. From animal studies, it has become clear that during early development, exposure of the brain to testosterone and estradiol, hormones present in both males and females, leads to irreversible changes in the nervous system (McCarthy et al., 2012). A growing and very appealing body of science suggests that sex hormones play a neuromodulatory role in cognitive brain function (Janowsky, 2006). Moreover, testosterone dysfunctions (hypogonadism, chemical castration, etc.) have shown to be associated with memory defects. However, in spite of these advances, it still remains an enigma how sex hormones affect the brain. In an interesting paper published in PLOS ONE, Picot and colleagues tried to fill in one piece of the puzzle. They investigated the neurobiological effects of cerebral androgen receptor (AR) ablation on hippocampal plasticity and cognitive performance in male rodents (Picot et al., 2016). Although several reports have already highlighted a link between sex hormones and cognitive function (Galea et al., 2008; Janowsky, 2006), much more needs to be done to fully elucidate the “non-sexual” functions of androgens.
By Michael Balter About 90% of bird species live in monogamous pairs, but that doesn’t mean they don’t fool around on the side. The females of most monogamous species breed with outside males at least occasionally. Male birds have evolved two main ways to combat such cuckoldry: They either aggressively drive away rival males, or they cement the pair bond by singing lovely duets with their partners. Which works better, making love or making war? Researchers working with the red-backed fairywren (Malurus melanocephalus), native to Australia, put the question to the test by conducting the experiment in the video above. The team mounted a taxidermically stuffed male fairywren on a branch (upper left) in a male-female pair’s territory and then observed what happened. In this case, the live male attacks its artificial rival once, but then spends most of the next minute duetting with its female partner (who is light gray and white). The researchers analyzed data from various trials involving up to 51 males, using parameters such as how long they delayed before attacking the artificial mount, how long before beginning a duet, and how many duets they sang with the females. These data were then correlated with genetic paternity tests of 186 offspring in the nests of the supposedly monogamous birds. Although the percentage of cuckoldry was high—47% of the offspring had been fathered by outside males—those males that quickly responded to the threat of a rival by repeatedly duetting with their partners were much more likely to be the fathers of the offspring in their nests, the team reports online today in Biology Letters. On the other hand, there was no correlation between how aggressive the males were to the artificial rival and the paternity rate, the researchers found. © 2016 American Association for the Advancement of Science
By Susana Martinez-Conde, Stephen L. Macknik In the forests of Australia and New Guinea lives a pigeon-sized creature that is not only a master builder but a clever illusionist, too. The great bowerbird (Chlamydera nuchalis)—a cousin of crows and jays—has an elaborate mating ritual that relies on the male's ability to conjure forced perspective. Throughout the year he painstakingly builds and maintains his bower: a 60-centimeter-long corridor made of twigs, leading to a courtyard decorated with gray and white pebbles, shells and bones. Some species also add flowers, fruits, feathers, bottle caps, acorns, abandoned toys—whatever colorful knickknacks they can find. The male takes great care to arrange the objects according to size so that the smallest pieces are closest to the bower's entrance and the largest items are farthest away. The elaborate structure is not a nest. Its sole purpose is to attract a female for mating. Once construction is complete, the male performs in the courtyard for a visiting female, who—poised like a critical American Idol judge—evaluates the routine from the middle of the corridor. He sings, dances and prances, tossing around a few select trinkets to impress his potential mate. Her viewpoint is very narrow, and so she perceives objects paving the courtyard as being uniform in size. This forced perspective makes the choice offerings appear grander and therefore all the more enticing. The offerings, and the male himself, appear larger than life because of an effect that visual scientists call the Ebbinghaus illusion, which causes an object to look bigger if it is surrounded by smaller objects. © 2016 Scientific American
By GINA KOLATA More than a million men have smeared testosterone gels on their bodies in recent years, hoping it would rejuvenate them, energize them, and increase their libido. But until now, there has never been a rigorous study asking if there were any real benefits to testosterone therapy for healthy men with so-called low T. The first results of such research were published Wednesday in The New England Journal of Medicine. Although it found at best modest benefits, mostly in sexual functioning, it is a landmark study, said Dr. Eric S. Orwoll, a professor of medicine at Oregon Health and Science University, because it provides the first credible data on testosterone’s effects on some of the problems it is thought to resolve. Some doctors said they hoped the modest results might bring some sanity to the testosterone frenzy of recent years. “Frankly,” said Dr. Sundeep Khosla, a dean at the Mayo Clinic College of Medicine, “there is a lot of abuse.” Men lured by advertisements seek the drug, and Dr. Khosla said he had heard of doctors who prescribed it without first measuring the man’s testosterone levels to see if they were low. “What I hope is that this will bring a more conservative approach,” Dr. Orwoll said. “There is a lot of prescribing out there, and it doesn’t look like, for the average man, it will have a big effect.” The study, led by the Perelman School of Medicine at the University of Pennsylvania and funded by the National Institutes of Health and AbbVie, the maker of the testosterone gel AndroGel, involved 790 men 65 and older with low testosterone levels for their age. Testosterone levels normally fall as men age, but these men had levels on the low end — below 275 nanograms per deciliter of blood. Some of the men said they had lost their sexual drive, others said they were walking much slower than they used to, and others said they just felt blah, as if they had lost their zest for life. The men were randomly assigned to use AndroGel or a placebo for a year. © 2016 The New York Times Company
By Julia Shaw The approach to Valentine's Day is a reminder that we humans are so intrigued by the idea of love that we have made it into something to celebrate in it’s own right. Love is something amazing. Love is something special. But what are the implications of love for our memories? Remember those “your brain on drugs” awareness posters? You can essentially substitute “love” for “drugs” and the same warnings apply. Scientists have found that being in love actually makes you activate some of the same brain regions as when you take addictive drugs, like ecstasy or cocaine. Neuroscientist Kayo Takahashi and his team have described passionate love as an “all-encompassing experience” which has “disorienting effects” and is generally considered “highly pleasurable”. While you probably don’t need a bunch of scientists to tell you that, you probably do need them to explain what that actually means in the brain. In 2015 Kayo and his team were keen on exploring the role of one particular culprit of the feel-good effects of love, the neurotransmitter dopamine. Among many other effects, dopamine generally makes us feel pleasure. Kayo and his team looked into the brains of people who were in the early stages of romantic relationships, and they found that when shown pictures of their romantic partners, participants experienced a flood of dopamine to parts of their brains. As it turns out, brains need to release dopamine in order to store long-term memories. © 2016 Scientific American
Rae Ellen Bichell There's been a male tilt to biomedical research for a long time. The National Institutes of Health is trying to change that and is looking to bring gender balance all the way down to the earliest stages of research. As a condition of NIH funding, researchers will now have to include female and male animals in their biomedical studies. As late as the 1990s, researchers worried that testing drugs in women who could be pregnant or become pregnant might lead to birth defects, so experimental drugs were mainly tested in men. Research in animals followed the same pattern. "There was not the understanding that it really isn't scientifically appropriate to study men and apply your findings to women. We just didn't know that back then," says Dr. Janine Clayton, director of the Office of Research on Women's Health at the NIH. When the drugs this way finally went to market and women took them, sometimes things went wrong. To try to fix the problem, the NIH and Congress required that women and men be included in research involving human subjects. Now, there are more women than men participating in clinical trials, at least in studies funded by the NIH. But there's still a mystery: Why do women still report many more bad reactions to medications than men do? "Men and women respond to medications differently. In fact, one study looked at the drugs that have been taken off the market and 8 of the 10 drugs taken off the market in that particular time period had more severe effects in women," says Clayton. © 2016 npr
Keyword: Sexual Behavior
Link ID: 21885 - Posted: 02.11.2016
By Jesse Singal On paper, Dr. Kenneth Zucker isn’t the sort of person who gets suddenly and unceremoniously fired. For decades, the 65-year-old psychologist had led the Child Youth and Family Gender Identity Clinic (GIC), in Toronto, one of the most well-known clinics in the world for children and adolescents with gender dysphoria — that is, the feeling that the body they were born with doesn’t fit their true gender identity. Zucker had built up quite a CV during his time leading the clinic: In addition to being one of the most frequently cited names in the research literature on gender dysphoria and gender-identity development, and the editor of the prestigious journal Archives of Sexual Behavior, he took a leading role helping devise diagnostic and treatment guidelines for gender dysphoric and transgender individuals. He headed the group which developed the DSM-5’s criteria for its “gender dysphoria” entry, for example, and also helped write the most recent “standards of care” guidelines for the World Professional Association for Transgender Health — one of the bibles for clinicians who treat transgender and gender-dysphoric patients. An impressive career, yes, but it’s doubtful any of this gave him much comfort on December 15. That was when he was called in from vacation for an 8:30 a.m. meeting with his employer, the Centre for Addiction and Mental Health (CAMH), one of the largest mental health and addiction research hospitals in Canada. Given the long-brewing investigation of his clinic by the hospital, it’s unlikely Zucker was feeling optimistic about what awaited him in downtown Toronto. The GIC, which operates out of CAMH, pronounced “Cam-H,” had been standing firm against a changing tide in the world of psychological treatment for children with gender dysphoria. The “gender-affirmative” approach, which focuses on identifying young transgender children and helping them socially transition — that is, express their gender to others through their everyday clothes, name changes, or other means — has been on the rise in recent years, and has become the favored protocol of many activists and clinicians. GIC clinicians, who saw clients between ages 3 and 18, had a much more cautious stance on social transitioning for their younger clients — they believed that in many cases, it was preferable to first “help children feel comfortable in their own bodies,” as they often put it, since in the GIC’s view gender is quite malleable at a young age and gender dysphoria will likely resolve itself with time. © 2016, New York Media LLC
By Sarah Knapton, Science Editor For women, shedding the pounds can feel like a unending struggle of dieting and exercise with little results. But a new study suggests that there could be a reason why females find it more difficult to lose weight than men. Researchers say hormones responsible for regulating appetite, physical activity and energy expenditure work differently in the sexes. "This could have broad implications for medications used to combat obesity, which at present largely ignore the sex of the individual." Professor Lora Heisler, University of Aberdeen The discovery could change the way obesity is tackled through targeted medication, experts at the University of Aberdeen believe. Working with teams from the University of Cambridge and the University of Michigan, they used a mouse model to study how weight gain differs in each sex depending on physical activity and energy expenditure. During the study, researchers were able to transform obese male into lean, healthy mice, but the same transformation did not occur in the female mice. Current obesity medications stimulate the production of POMC peptides in the brain which regulate appetite, increase energy expenditure through heat and encourage movement. But researchers found in female mice the hormones only regulated appetite - they did not have the extra benefits. © Copyright of Telegraph Media Group Limited 2016
By Laurel Hamers As one person at the dinner table leans back, stretches, and opens their mouth in a gaping yawn, others will soon follow suit. Catching a yawn is more likely to occur between relatives than strangers, and scientists believe it’s sign of empathy. Plus, other social primates like chimps and bonobos do it, too. A new study suggests that women (traditionally branded the more empathetic sex) might be more susceptible to copycat yawning than men. Researchers surreptitiously analyzed more than 4000 real-world yawns on planes and trains, in restaurants, and in offices. They noted when someone yawned, and then whether a nearby acquaintance or friend did the same within a 3-minute period. Men and women spontaneously yawned with about the same frequency. But when someone else yawned first, women were more likely than men to follow suit. Women picked up yawns about 55% of the time, whereas men only did so 40% of the time. Women tend to score higher than men on tests of empathy, and traditional female social roles (like child-rearing) place a higher emphasis on those traits. That might make women more attuned to others’ yawns, the researchers suggest. Gender roles aren’t as rigid in our modern society—but the yawning gap appears to linger. © 2016 American Association for the Advancement of Science
By SINDYA N. BHANOO Several studies suggest that men find women more attractive when they are in the ovulatory phase of their menstrual cycle. The thesis takes a strange turn in a new study in which women were questioned: Each subject was asked whether a woman in an image was likely to entice a man that she was dating. Although women do not find images of ovulatory women particularly attractive, scientists found, women with higher estrogen levels did perceive such images to be more threatening. Women with high estrogen, the researchers noted, have a high potential for fertility. “We’re still trying to pinpoint exactly what all is involved in this,” said Janek S. Lobmaier, a psychologist at the University of Bern. © 2016 The New York Times Company
By PAM BELLUCK Women should be screened for depression during pregnancy and after giving birth, an influential government-appointed health panel said Tuesday, the first time it has recommended screening for maternal mental illness. The recommendation, expected to galvanize many more health providers to provide screening, comes in the wake of new evidence that maternal mental illness is more common than previously thought; that many cases of what has been called postpartum depression actually start during pregnancy; and that left untreated, these mood disorders can be detrimental to the well-being of children. It also follows growing efforts by states, medical organizations and health advocates to help women having these symptoms — an estimated one in seven postpartum mothers, some experts say. “There’s better evidence for identifying and treating women with depression” during and after pregnancy, said Dr. Michael Pignone, a professor of medicine at the University of North Carolina at Chapel Hill and an author of the recommendation, which was issued by the United States Preventive Services Task Force. As a result, he said, “we specifically called out the need for screening during this period.” Answers to questions about depression screening and maternal mental illness, following new recommendations saying that women should be screened for depression during pregnancy and after childbirth. The recommendation was part of updated depression screening guidelines issued by the panel, an independent group of experts appointed by the Department of Health and Human Services. In 2009, the group said adults should be screened if clinicians had the staff to provide support and treatment; the new guidelines recommend adult screening even without such staff members, saying mental health support is now more widely available. The 2009 guidelines did not mention depression during or after pregnancy. © 2016 The New York Times Company
Jim Pfaus Self-labeled sex addicts often speak about their identities very clinically, as if they’re paralyzed by a scientific condition that functions the same way as drug and alcohol addiction. But sex and porn “addiction” are NOT the same as alcoholism or a cocaine habit. In fact, hypersexuality and porn obsessions are not addictions at all. They’re not included in the Diagnostic and Statistical Manual of Mental Disorders (DSM), and by definition, they don’t constitute what most researchers understand to be addiction. Here’s why: addicts withdraw. When you lock a dope fiend in a room without any dope, the lack of drugs will cause an immediate physiological response — some of which is visible, some of which we can only track from within the body. During withdrawal, the brains of addicts create junctions between nerve cells containing the neurotransmitter GABA. This process more or less inhibits the brain systems usually excited by drug-related cues — something we never see in the brains of so-called sex and porn addicts. A sex addict without sex is much more like a teenager without their smartphone. Imagine a kid playing Angry Birds. He seems obsessed, but once the game is off and it’s time for dinner, he unplugs. He might wish he was still playing, but he doesn’t get the shakes at the dinner table. There’s nothing going on in his brain that creates an uncontrollable imbalance.
By Kerry Klein With their suction cup mouths filled with concentric circles of pointy teeth that suck the body fluid of unsuspecting victims, lampreys may seem like the stuff of horror movies. And indeed the 50-centimeter-long, eellike creatures can wreak havoc on freshwater communities when they invade from the sea, with a single sea lamprey able to kill 18 kilograms of fish in its lifetime. Now, the U.S. government has approved of a new way to combat these fearsome fish by using their own sense of smell against them. Sea lampreys are a particular problem in the Great Lakes regions of the United States and Canada. They hitchhiked into the region more than a century ago, likely attaching themselves to ships or fish that traveled along shipping channels from the Atlantic Ocean. Although most lampreys are mere parasites in their native habitats, those in the Great Lakes are far worse, says Nicholas Johnson, a research ecologist at the U.S. Geological Survey’s Hammond Bay Biological Station on Lake Huron in Millersburg, Michigan. “They kill their host, they get too big, they eat too much,” he says. “They’re really more of a predator.” After the toothy invaders proliferated in the mid-20th century, ecosystems all but collapsed, taking prosperous fishing and tourism industries with them. “It’s fair to say that lamprey[s] changed the way of life in the region,” says Marc Gaden of the Great Lakes Fishery Commission, a joint U.S. and Canadian organization based in Ann Arbor, Michigan, that’s tasked with managing the rebounding ecosystems. “Just about every fishery management decision that we make to this day has to take lamprey into consideration.” © 2016 American Association for the Advancement of Science
By SINDYA N. BHANOO Male zebra finches learn their courtship songs from their fathers. Now, a new study details the precise changes in brain circuitry that occur during that process. As a young male listens to his father’s song, networks of brain cells are activated that the younger bird will use later to sing the song himself, researchers have found. As the learning process occurs, inhibitory cells suppress further activity in the area and help sculpt the song into a permanent memory. “These inhibitory cells are really smart — once you’ve gotten a part of the song down, the area gets locked,” said Michael Long, a neuroscientist at NYU Langone Medical Center and an author of the new study, which appears in the journal Science. Zebra finches learn their courtship song from their fathers and reach sexual maturity in about 100 days. At this point, they ignore their fathers’ tutoring altogether, Dr. Long said. In their study, he and his colleagues played recorded courtship songs to young and old birds and monitored neural activity in their brains. In sexually mature birds, the courtship song did not elicit any neural response. Understanding the role of the inhibitory cells in the brain could help researchers develop ways to manipulate this network, Dr. Long said. “Maybe we could teach old birds new tricks,” he said. “And extrapolating widely, maybe we could even do this in mammals, maybe even humans, and enrich learning.” © 2016 The New York Times Company
By Emily Underwood The boisterous songs a male zebra finch sings to his mate might not sound all that melodious to humans—some have compared them to squeaky dog toys—but the courtship tunes are stunningly complex, with thousands of variations. Now, a new study helps explain how the birds master such an impressive repertoire. As they learn from a tutor, usually their father, their brains tune out phrases they’ve already studied, allowing them to focus on unfamiliar sections bit by bit. The mechanism could help explain how other animals, including humans, learn complex skills, scientists say. The study is a “technical tour de force,” and “an important advance in our understanding of mechanisms of vocal learning and of motor learning generally,” says Erich Jarvis, a neuroscientist at Duke University in Durham, North Carolina. Many species—including humans, chimpanzees, crows, dolphins, and even octopuses—learn complex behaviors by imitating their peers and parents, but little is known about how that process works on a neuronal level. In the case of zebra finches, young males spend the whole of their teenage lives trying to copy their fathers, says Michael Long, a neuroscientist at New York University in New York City. It comes out “all wrong” at first, but after practicing hundreds of times, the birds “sound a lot like dad.” In the new study, Long’s graduate student Daniela Vallentin used a tiny electrode implant to record the activity of neurons in a region of the finch brain called the HVC, which is essential for birdsong learning and production. Weighing less than a penny, the implant can be affixed to a bird’s head and record activity in the brains of freely moving and singing birds, Long says. The researchers also used a powerful light microscope to visualize the activity of individual neurons as the birds listened to a fake “tutor” bird that taught young finches only one “syllable” of a song at a time. © 2016 American Association for the Advancement of Science.
David Cox In the spring of 1930, Danish artist Einar Wegener arrived in Berlin for a consultation that he hoped would both save and change his life. Wegener had spent the previous twenty years dressing as a woman, Lili Elbe. In public, his wife, painter Gerda Gottlieb, introduced Elbe as Wegener’s sister . But by 1930 he could not bear his double life any longer. He resolved to commit suicide, even naming a date – May 1. Instead, Wegener made a different choice, electing to undergo a series of pioneering gender reassignment operations, transitioning into Lili Ilse Elvenes, better known as Lili Elbe. Elbe’s extraordinary story remains controversial; indeed, the film The Danish Girl, starring Eddie Redmayne and based on Elbe’s life was this week banned from Qatari cinemas after protests about its “depravity”. Elbe’s revolutionary transition would not have been possible without the contribution of the sexologist Magnus Hirschfeld, a man who had become both renowned and notorious across Europe for his groundbreaking research into human gender and sexuality. While Elbe’s posthumous 1933 biography, “Man into Woman: The First Sex Change”, made her story internationally famous, Hirschfeld is a less well-known figure today. As both a Jew and gay activist, much of his legacy was burnt to ashes when his Institute for Sexual Research was targeted by a Nazi attack in 1933. But through colleagues and pupils, his work has gone on to transform the way we view sexual minorities and has helped make gender reassignment surgery the widely accepted procedure it is today. © 2016 Guardian News and Media Limited o
Keyword: Sexual Behavior
Link ID: 21786 - Posted: 01.14.2016
Eva Emerson Chronic stress takes its toll on everyone. But it may hit women harder (or at least differently) than men, much research finds. New studies in rodents show that females remain sensitive to ongoing stress longer than males do, as Susan Gaidos reports. It remains to be seen whether such results can explain the differences in rates of depression and anxiety disorders in men and women. (Perhaps women are more likely to discuss their symptoms and be diagnosed. Men, on the other hand, are more likely to abuse drugs and alcohol, disorders which may also be related to stress.) Still, the new work offers an intriguing idea: If stress induces distinct biochemical signaling in men and women, perhaps therapies should also be tailored to each sex. Another fascinating line of research mentioned in Gaidos’ story involves altering female mice’s response to chronic stress (making it more like a male’s) by targeting DNA modifications known as epigenetic tags. Consisting of chemicals such as methyl groups, these tags are attached to DNA and influence gene activity. They seem like a perfect target for drugs. Epigenetic tags don’t change the underlying genes, just the instructions for turning those genes on or off, up or down. In the mice, scientists used enzymes to alter the chemical tags on genes involved in the response to chronic stress. It’s an exciting approach, one I’m sure many scientists will try in efforts to modulate the body’s response, not just to stress, but also to other threats to health. Maybe even to fat. A woman’s extra fat can trigger metabolic changes in a developing fetus, Laura Beil reports. Beil describes the latest research about the risks faced by children of obese moms or moms who have gained too much weight while pregnant. Neurological effects are the new twist, and a scary one, given the prevalence of obesity among women of childbearing age. © Society for Science & the Public 2000 - 2015
By Virginia Morell When you hear a bird warbling, you probably think the crooner is a male. And chances are if you’re in the Northern Hemisphere, you would be right. But females also evolved to sing, and many still do—although generally less than the males. One reason may be that it’s more dangerous for them to sing especially when nesting, scientists report today. At least, that’s the case for female fairywrens, the most vocal of which are the most likely to have their eggs and chicks eaten. The study “provides some of the first field evidence indicating why females of so many songbird species might have lost song,” says Karan Odom, a Ph.D. candidate at the University of Maryland, Baltimore, and the lead author of a 2014 study on the evolution of birdsong. Female superb fairywrens (Malarus cyaneus)—a small Australian species—aren’t the only female songbirds that sing. In fact, females sing in 71% of songbird species, often for territorial defense. In species like the superb fairywren, some females even sing when they’re on their nests, a place where, at least theoretically, they should pipe down so as not to attract predators. Rodents, birds, cats, and foxes have all been seen preying on the fairywrens’ nests. “People had observed [this singing in the nest behavior], but they hadn’t investigated it,” says Sonia Kleindorfer, a behavioral ecologist at Flinders University in Adelaide, Australia. “It struck me as odd, and very risky.” © 2016 American Association for the Advancement of Science