Links for Keyword: Sexual Behavior

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By Camilla Turner It is one of life’s most enduring mysteries. A question that music, poetry, myth and legend has, for thousands of years, tried but failed to answer. However, we may now be a step closer to discovering what love is, thanks to a scientific study that has obtained the first empirical evidence of love-related alterations in the brain. A team of researchers from universities in China and New York used MRI scans to track the physical effects of love on the brain and has pieced together a “love map” of the human mind. The study found that several areas of the brain showed increased activity in those who were in love, including in the parts of the brain linked to reward and motivation. The researchers said their results shed light on the “underlying mechanisms of romantic love” and would pave the way for a brain scan that could act as a “love test”. Scientists recruited 100 students from Southwest University in Chongqing, China, who were divided into three groups according to their relationship status: an “in-love” group, comprised of those who were in love at the time; an “ended-love” group, who had recently ended loving relationships; and a “single” group, who had never been in love. Participants were told not to think of anything while their brains were scanned, so that researchers could monitor the differences between the brains of students in all three groups. © Copyright of Telegraph Media Group Limited 2015

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Link ID: 20692 - Posted: 03.17.2015

by Penny Sarchet For some of us, it might have been behind the bikeshed. Not so the African cotton leafworm moth (Spodoptera littoralis), which can choose any one of a vast number of plant species to mate on. But these moths remember their first time, returning to the same species in search of other mates. In the wild, this moth feeds and mates on species from as many as 40 different plant families. That much choice means there's usually something available to eat, but selecting and remembering the best plants is tricky. So, recalling what you ate as a larva, or where you first copulated, may help narrow down which plants provide better quality food or are more likely to attract other potential mates. Magali Proffit and David Carrasco of the Swedish University of Agricultural Sciences in Alnarp and their colleagues have discovered that this moth's first mating experience shapes its future preferences. These moths have an innate preference for cotton plants over cabbage. But when the researchers made them mate for the first time on cabbage, the moths later showed an increased preference for mating or laying eggs on this plant. Further experiments revealed that moths didn't just favour plants they were familiar with, even in combination with a sex pheromone – mating had to be involved. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 13: Memory, Learning, and Development
Link ID: 20665 - Posted: 03.09.2015

By David Masci Potential Republican presidential candidate Dr. Ben Carson made news earlier this week when he said that being gay is a “choice,” but when it comes to public opinion, polls show that Americans remain divided over whether “nature” or “nurture” is ultimately responsible for sexual orientation. Four-in-ten Americans (42%) said that being gay or lesbian is “just the way some choose to live,” while a similar share (41%) said that “people are born gay or lesbian,” according to the most recent Pew Research Center poll on the issue, conducted in 2013. Fewer U.S. adults (8%) said that people are gay or lesbian due to their upbringing, while another one-in-ten (9%) said they didn’t know or declined to give a response. People with the most education are the most likely to say that gays and lesbians were born that way. Indeed, 58% of Americans with a postgraduate degree say that people are born gay or lesbian, compared with just 35% of those with a high school diploma or less. The percentage of all Americans who believe that people are born gay or lesbian has roughly doubled (from 20% to 41%) since 1985, when the question was asked in a Los Angeles Times survey. More than three decades of Gallup polls also show a considerable rise in the view that being gay or lesbian is a product of “nature” rather than “nurture.” But the most recent survey, in 2014, still finds that the nation remains split in its feelings on the origins of sexual orientation. Copyright 2015 Pew Research Center

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 20658 - Posted: 03.07.2015

By Nicholas Weiler The grizzled wolf stalks from her rival’s den, her mouth caked with blood of the pups she has just killed. It’s a brutal form of birth control, but only the pack leader is allowed to keep her young. For her, this is a selfish strategy—only her pups will carry on the future of the pack. But it may also help the group keep its own numbers in check and avoid outstripping its resources. A new survey of mammalian carnivores worldwide proposes that many large predators have the ability to limit their own numbers. The results, though preliminary, could help explain how top predators keep the food chains beneath them in balance. Researchers often assume that predator numbers grow and shrink based on their food supply, says evolutionary biologist Blaire Van Valkenburgh of the University of California, Los Angeles, who was not involved in the new study. But several recent examples, including an analysis of the resurgent wolves of Yellowstone National Park, revealed that some large predators keep their own numbers in check. The new paper is the first to bring all the evidence together, Van Valkenburgh says, and presents a “convincing correlation.” Hunting and habitat loss are killing off big carnivores around the world, just as ecologists are discovering how important they are for keeping ecosystems in balance. Mountain lions sustain woodlands by hunting deer that would otherwise graze the landscape bare. Coyotes protect scrub-dwelling birds by keeping raccoons and foxes in line. Where top carnivores disappear, these smaller predators often explode in numbers, with potentially disastrous consequences for small birds and mammals. © 2015 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 20629 - Posted: 02.28.2015

Claire Ainsworth As a clinical geneticist, Paul James is accustomed to discussing some of the most delicate issues with his patients. But in early 2010, he found himself having a particularly awkward conversation about sex. A 46-year-old pregnant woman had visited his clinic at the Royal Melbourne Hospital in Australia to hear the results of an amniocentesis test to screen her baby's chromosomes for abnormalities. The baby was fine — but follow-up tests had revealed something astonishing about the mother. Her body was built of cells from two individuals, probably from twin embryos that had merged in her own mother's womb. And there was more. One set of cells carried two X chromosomes, the complement that typically makes a person female; the other had an X and a Y. Halfway through her fifth decade and pregnant with her third child, the woman learned for the first time that a large part of her body was chromosomally male1. “That's kind of science-fiction material for someone who just came in for an amniocentesis,” says James. Sex can be much more complicated than it at first seems. According to the simple scenario, the presence or absence of a Y chromosome is what counts: with it, you are male, and without it, you are female. But doctors have long known that some people straddle the boundary — their sex chromosomes say one thing, but their gonads (ovaries or testes) or sexual anatomy say another. Parents of children with these kinds of conditions — known as intersex conditions, or differences or disorders of sex development (DSDs) — often face difficult decisions about whether to bring up their child as a boy or a girl. Some researchers now say that as many as 1 person in 100 has some form of DSD2. © 2015 Nature Publishing Group

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 20589 - Posted: 02.18.2015

By Anne Harding NEW YORK (Reuters Health) - Reduced sexual activity could cause a dip in testosterone levels in older men, new findings suggest. Among men 70 and older, those who reported a decline in sexual activity and desire over a two-year period also showed small declines in serum testosterone, Dr. David Handelsman of the ANZAC Research Institute at the University of Sydney and Concord Hospital in New South Wales, Australia, and colleagues found. They report their findings in the Journal of Clinical Endocrinology and Metabolism, online January 28. "Decline in serum testosterone is more likely to be the result rather than the cause of sexual dysfunction among older men who don't have reproductive disorders," Dr. Handelsman told Reuters Health by email. "The widely prevalent misinterpretation of this (as if the mild lowering of serum testosterone needs or might benefit from testosterone treatment) is one of the main drivers of the massive over-use of testosterone prescriptions in North America over the last decade." While declines in androgens and sexual function are both thought to be aging-related, Dr. Handelsman and his colleagues note in their report, the relationship between androgen levels and sexual function is not clear. To better understand the temporal and predictive relationship between androgen levels and sexual function, the researchers looked at 1,226 men participating in the Concord Health and Ageing in Men Project (CHAMP), measuring their levels of testosterone, dihydrotestosterone, estradiol, and estrone with liquid chromatography-tandem mass spectrometry. Men also reported on their sexual function using standardized questions, at baseline and two years later. © 2015 Scientific American

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 8: Hormones and Sex
Link ID: 20559 - Posted: 02.07.2015

By Nicholas Weiler When you spend your days battling giant squid, it’s good to have friends you can rely on. New research from the Caribbean suggests that female sperm whales (Physeter macrocephalus, pictured) swim with favored companions and form long-term family allegiances. Sperm whales raise their young in communal family groups of about a dozen related females, but mapping out the giant animals' social lives in much detail has been a challenge for scientists. The whales spend 60% of their lives hunting squid hundreds of meters below the waves, and researchers can watch them interact for only a few minutes at a time when they surface to breathe. But a new multiyear study has created the most detailed map yet of sperm whales’ social networks. Between 2005 and 2010, scientists followed nine whale families along the west coast of the Caribbean island of Dominica and mapped their social relationships by counting which females spent the most time together at the surface between dives. As expected, whales mostly preferred to relax with family members, but within families they played favorites, frequently swimming with the same sister, auntie, or aged granny, the researchers report online this week in Animal Behaviour. The network diagram also revealed three pairs of families that mingled frequently over the years to socialize and share babysitting duty. One of these pairs has been fraternizing since 1995, according to data from other researchers, suggesting that such allegiances can last more than a decade. These observations suggest sperm whale families may be similar to the matriarchal clans of elephants, which also form long-lasting family bonds, the researchers say. Further research may determine whether allied families are actually distant cousins and investigate whether whales use signature songs to find their best friends. © 2015 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 11: Emotions, Aggression, and Stress
Link ID: 20557 - Posted: 02.07.2015

Helen Fisher, a biological anthropologist at Rutgers University responds: Several years ago I embarked on a project to see if the seven-year itch really exists. I began by studying worldwide data on marriage and divorce and noticed that although the median duration of marriage was seven years, of the couples who divorced, most did so around their fourth year together (the “mode”). I also found that divorce occurred most frequently among couples at the height of their reproductive and parenting years—for men, ages 25 to 29, and for women, ages 20 to 24 and 25 to 29—and among those with one dependent child. To try to explain these findings, I began looking at patterns of pair bonding in birds and mammals. Although only about 3 percent of mammals form a monogamous bond to rear their young, about 90 percent of avian species team up. The reason: the individual that sits on the eggs until they hatch will starve unless fed by a mate. A few mammals are in the same predicament. Take the female fox: the vixen produces very thin milk and must feed her young almost constantly, so she relies on her partner to bring her food while she stays in the den to nurse. But here's the key: although some species of birds and mammals bond for life, more often they stay together only long enough to rear their young through infancy and early toddlerhood. When juvenile robins fly away from the nest or maturing foxes leave the den for the last time, their parents part ways as well. Humans retain traces of this natural reproductive pattern. In more contemporary hunter-gatherer societies, women tend to bear their children about four years apart. Moreover, in these societies after a child is weaned at around age four, the child often joins a playgroup and is cared for by older siblings and relatives. This care structure allows unhappy couples to break up and find a more suitable partner with whom to have more young. © 2015 Scientific American

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 20496 - Posted: 01.20.2015

ByDavid Malakoff This bird might look like a holiday ornament, but it is actually a rare half-female, half-male northern cardinal (Cardinalis cardinalis, pictured with female plumage on the left and male plumage on the right) spotted a few years ago in Rock Island, Illinois. Researchers have long known such split-sex “gynandromorphs” exist in insects, crustaceans, and birds. But scientists rarely get to extensively study a gynandromorph in the wild; most published observations cover just a day or so. Observers got to follow this bird, however, for more than 40 days between December 2008 and March 2010. They documented how it interacted with other birds and even how it responded to recorded calls. The results suggest being half-and-half carries consequences: The cardinal didn’t appear to have a mate, and observers never heard it sing, the researchers report this month in The Wilson Journal of Ornithology. On the other hand, it wasn’t “subjected to any unusual agonistic behaviors from other cardinals,” according to the paper. Intriguingly, another gynandromorph cardinal sighted briefly in 1969 had the opposite plumage, they note: the male’s bright red plumes on the right, the drabber female feathers on the left. © 2014 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 20442 - Posted: 12.27.2014

Katie Langin In the first couple of years after birth, sea lion sons seem to be more reliant on their mothers—consuming more milk and sticking closer to home—than sea lion daughters are, according to a study on Galápagos sea lions published in the December issue of the journal Animal Behaviour. The young males venture out to sea on occasion, but their female counterparts dive for their own food much more often. The curious thing is, it's not like the young males aren't capable of diving. As one-year-olds, males can dive to the same depth as females (33 feet, or 10 meters, on a typical dive). It's also not like their mother's milk is always on hand. Sea lion moms frequently leave their growing offspring for days at a time to find food at sea. (Watch a video of a Galápagos sea lion giving birth.) And yet, despite all this, for some reason sons are far less likely than daughters to take to the sea and seek out their own food. "We always saw the [young] males around the colony surfing in tide pools, pulling the tails of marine iguanas, resting, sleeping," said Paolo Piedrahita, a Ph.D. student at Bielefeld University in Germany and the lead author of the study. "It's amazing. You can see an animal—40 kilograms [88 pounds]—just resting, waiting for mom." © 1996-2014 National Geographic Society.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 20384 - Posted: 12.03.2014

By Kelly Servick Dean Hamer finally feels vindicated. More than 20 years ago, in a study that triggered both scientific and cultural controversy, the molecular biologist offered the first direct evidence of a “gay gene,” by identifying a stretch on the X chromosome likely associated with homosexuality. But several subsequent studies called his finding into question. Now the largest independent replication effort so far, looking at 409 pairs of gay brothers, fingers the same region on the X. “When you first find something out of the entire genome, you’re always wondering if it was just by chance,” says Hamer, who asserts that new research “clarifies the matter absolutely.” But not everyone finds the results convincing. And the kind of DNA analysis used, known as a genetic linkage study, has largely been superseded by other techniques. Due to the limitations of this approach, the new work also fails to provide what behavioral geneticists really crave: specific genes that might underlie homosexuality. Few scientists have ventured into this line of research. When the genetics of being gay comes up at scientific meetings, “sometimes even behavioral geneticists kind of wrinkle up their noses,” says Kenneth Kendler, a psychiatric geneticist at Virginia Commonwealth University in Richmond. That’s partially because the science itself is so complex. Studies comparing identical and fraternal twins suggest there is some heritable component to homosexuality, but no one believes that a single gene or genes can make a person gay. Any genetic predispositions probably interact with environmental factors that influence development of a sexual orientation. © 2014 American Association for the Advancement of Science.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 13: Memory, Learning, and Development
Link ID: 20325 - Posted: 11.18.2014

Carl Zimmer In the early 1970s, Sarah Blaffer Hrdy, then a graduate student at Harvard, traveled to India to study Hanuman langurs, monkeys that live in troops, each made up of several females and a male. From time to time, Dr. Hrdy observed a male invade a troop, driving off the patriarch. And sometimes the new male performed a particularly disturbing act of violence. He attacked the troop’s infants. There had been earlier reports of infanticide by adult male mammals, but scientists mostly dismissed the behavior as an unimportant pathology. But in 1974, Dr. Hrdy made a provocative counter proposal: infanticide, she said, is the product of mammalian evolution. By killing off babies of other fathers, a male improves his chances of having more of his own offspring. Dr. Hrdy went on to become a professor at the University of California, Davis, and over the years she broadened her analysis, arguing that infanticide might well be a common feature of mammalian life. She spurred generations of scientists to document the behavior in hundreds of species. “She’s the goddess of all this stuff,” said Kit Opie, a primatologist at University College London. Forty years after Dr. Hrdy’s initial proposal, two evolutionary biologists at the University of Cambridge have surveyed the evolution of infanticide across all mammals. In a paper published Thursday in Science, the scientists concluded that only certain conditions favor the evolution of infanticide — the conditions that Dr. Hrdy had originally proposed. “My main comment is, ‘Well done,'” said Dr. Hrdy. She said the study was particularly noteworthy for its scope, ranging from opossum to lions. The authors of the new study, Dieter Lukas and Elise Huchard, started by plowing through the scientific literature, looking for evidence of infanticide in a variety of mammalian species. The researchers ended up with data on 260 species, and in 119 of them — over 45 percent — males had been observed killing unrelated young animals. © 2014 The New York Times Company

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 20312 - Posted: 11.15.2014

Carl Zimmer Milk is not just food. The more closely scientists examine it, the more complexity they find. Along with nutrients like protein and calcium, milk contains immune factors that protect infants from disease. It hosts a menagerie of microbes, too, some of which may colonize the guts of babies and help them digest food. Milk even contains a special sugar that can fertilize that microbial garden. Now, it turns out, milk also contains messages. A new study of monkeys, published in the journal Behavioral Ecology, demonstrates that a hormone present in milk, cortisol, can have profound effects on how babies develop. Infant monkeys rely on cortisol to detect the condition of their mothers, the authors suggest, then adjust their growth and even shift their temperaments. Jeffrey French, a neuroendocrinologist at the University of Nebraska at Omaha who was not involved in the study, praised its “remarkable sophistication” and said that it helped to change how we think about breast milk. “Milk serves almost like a pheromone, a chemical signal sent from one individual to another,” he said. Katie Hinde, a behavioral biologist at Harvard and lead author on the new study, and her colleagues studied 108 rhesus macaque mothers nursing infants at the California National Primate Research Center. The researchers collected samples of milk, measuring how much energy each provided and the cortisol it contained. Dr. Hinde and her colleagues also measured how much weight each nursing monkey gained and tracked its behavior. Cortisol serves many functions in mammals, but it is best known as a stress hormone. When cortisol courses through our bodies, it prepares us to handle alarming or fearful situations, increasing the brain’s consumption of glucose and suppressing the digestive system. © 2014 The New York Times Company

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 20291 - Posted: 11.08.2014

Joan Raymond TODAY contributor It’s well established that baby talk plays a huge role in helping the wee widdle babies learn to tawk. And — no surprise — moms talk more to babies than dads do. But it seems that the baby's sex plays a role, too: Moms may be talking more to their infant daughters than their sons during the early weeks and months of a child’s life. In a new study published Monday in the online edition of Pediatrics, researchers looked at the language interactions between 33 late preterm and term infants and their parents by capturing 3,000 hours of recordings. Somewhat surprisingly, the researchers found that moms interacted vocally more with infant daughters rather than sons both at birth and 44 weeks post-menstrual age (equivalent to 1 month old.) Male adults responded more frequently to infant boys than infant girls, but the difference did not reach statistical significance, say the researchers. “We wanted to look more at gender and factors that affect these essentially mini-conversations that parents have with infants,” says lead author and neonatologist Dr. Betty Vohr, director of the Neonatal Follow-Up Program at Women & Infants Hospital of Rhode Island. “Infants are primed to vocalize and have reciprocal interactions.”

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 13: Memory, Learning, and Development
Link ID: 20273 - Posted: 11.04.2014

by Bethany Brookshire In many scientific fields, the study of the body is the study of boys. In neuroscience, for example, studies in male rats, mice, monkeys and other mammals outnumber studies in females 5.5 to 1. When scientists are hunting for clues, treatments or cures for a human population that is around 50 percent female, this boys-only club may miss important questions about how the other half lives. So in an effort to reduce this sex bias in biomedical studies, National Institutes of Health director Francis Collins and Office of Research on Women’s Health director Janine Clayton announced in May a new policy that will roll out practices promoting sex parity in research, beginning with a requirement that scientists state whether males, females or both were used in experiments, and moving on to mandate that both males and females are included in all future funded research. The end goal will be to make sure that NIH-funded scientists “balance male and female cells and animals in preclinical studies in all future [grant] applications” to the NIH. In 1993, the NIH Revitalization Act mandated the inclusion of women and minorities in clinical trials. This latest move extends that inclusion to cells and animals in preclinical research. Because NIH funds the work of morethan 300,000 researchers in the United States and other countries, many of whom work on preclinical and basic biomedical science, the new policy has broad implications for the biomedical research community. And while some scientists are pleased with the effort, others are worried that the mandate is ill-conceived and underfunded. In the end, whether it succeeds or fails comes down to interpretation and future implementation. © Society for Science & the Public 2000 - 2014

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 5: The Sensorimotor System
Link ID: 20247 - Posted: 10.27.2014

Daniel Cressey The history of sex may have to be rewritten thanks to a group of unsightly, long-extinct fish called placoderms. A careful study1 of fossils of these armour-plated creatures, which gave rise to all current vertebrates with jaws, suggests that their descendants — our ancient ancestors — switched their sexual practices from internal to external fertilization, an event previously thought to be evolutionarily improbable. “This was totally unexpected,” says John Long, a palaeontologist at Flinders University in Adelaide, Australia, and lead author of the study, published in Nature1. “Biologists thought that there could not be a reversion back from internal fertilization to external fertilization, but we have shown it must have happened this way.” Go back far enough in your family tree — before placoderms — and your ancestors were rather ugly jawless fish who reproduced through external fertilization, in which sperm and eggs are expelled into the water to unite. Some of these distant relatives later gave rise to the jawless fish called lampreys that lurk in seas today and still use this method of reproduction. Bony organ Long's team studied placoderms, one of the earliest groups of jawed animals, and found structures in fossils that they interpret as bony ‘claspers’ — male organs that penetrate the female and deliver sperm. © 2014 Nature Publishing Group,

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 20220 - Posted: 10.20.2014

by Penny Sarchet He's sexy and he knows it. The little devil frog is noisy in pursuit of a partner, and doesn't care who hears him. The little devil frog's fearlessness in the face of hungry predators could be down to his toxicity. The little devil, Oophaga sylvatica, is a member of the dendrobatid group of poisonous frogs. His bright colours warn predators that he is unsafe to eat, which Juan Santos of the University of British Columbia in Vancouver, Canada, believes has allowed the evolution of more flamboyant mating calls. Santos and his colleagues examined the calls, colourings and toxicity of 170 species of frog, including the little devil. They found a strong relationship between the volume of a frog's call and its aposematism – markings that warn of its toxicity. In general, the more toxic a frog, the brighter and more noticeable it is – and the louder and more rapidly it sings (Proceedings of the Royal Society B ). Non-toxic frogs are camouflaged and call from less exposed perches, says Santos. "Females can have a significant effect on the selection of the most noisy males, given that predators will avoid these aposematic individuals," says Santos. The male's calls can travel over long distances, in an attempt to attract a mate. But it's not just about attracting a female frog's attention – it's about letting her know how desirable he is. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 20212 - Posted: 10.18.2014

By Melissa Hogenboom Science reporter, BBC News A small group of neurons that respond to the hormone oxytocin are key to controlling sexual behaviour in mice, a team has discovered. The researchers switched off these cells which meant they were no longer receptive to oxytocin. This "love hormone" is already known to be important for many intimate social situations. Without it, female mice were no more attracted to a mate than to a block of Lego, the team report in journal Cell. These neurons are situated in the prefrontal cortex, an area of the brain important for personality, learning and social behaviour. Both when the hormone was withheld and when the cells were silenced, the females lost interest in mating during oestrous, which is when female mice are sexually active. At other times in their cycle they responded to the males with normal social behaviour. The results were "pretty fascinating because it was a small population of cells that had such a specific effect", said co-author of the work Nathaniel Heintz of the Rockefeller University in New York. "This internal hormone gets regulated in many different contexts; in this particular context, it works through the prefrontal cortex to help modulate social and sexual behaviour in female mice. "It doesn't mean it's uniquely responsible because the hormone acts in several important places in the brain but it does show that this particular cell type is required for this aspect of female social behaviour," Dr Heintz told BBC News. To silence the neurons, the team used toxins that block the ability of the cells to transmit signals to other neurons - technology that has recently revolutionised the ability to study small populations of neurons. BBC © 2014

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 8: Hormones and Sex
Link ID: 20195 - Posted: 10.11.2014

BY Sarah Zielinski Bird’s nests come in a wide variety of shapes and sizes, and they’re built out of all sorts of things. Hummingbirds, for instance, create tiny cups just a couple centimeters wide; sociable weavers in Africa, in contrast, work together to build huge nests more than two meters across that are so heavy they can collapse trees. There are nests built on rocky ledges, in mounds on the ground, high in trees and on the edges of buildings. Bowerbirds even construct their nests as tiny houses decorated with an artistic eye to attract the ladies. So perhaps it’s not all that surprising the no one had ever investigated whether birds camouflage their nests to protect their eggs against potential predators. It would make sense that they do, but if you were to test it, where would you start? For Ida Bailey of the University of St. Andrews in Fife, Scotland, and colleagues, the answer was zebra finches. Male finches usually build nests in dense shrubs and layer the outside of the nests with dry grass stems and fine twigs. Predators, usually birds, take a heavy toll on the zebra finches, though. Since birds tend to hunt based on sight rather than smell, camouflaging a nest might work to protect the eggs sequestered inside. And even better, because zebra finches have good color vision, building a camouflaged nest might be possible. So Bailey’s team gathered 21 pairs of zebra finches, some of which were already housed at the University of Glasgow in Scotland, while others were bought from a local pet store. The researchers set each pair up in its own cage. Two walls of the cage were lined with colored paper, and a nest cup was placed in that half of the cage. Then the birds were given two cups containing colored paper — one color that matched the walls and a second contrasting color. The results of the study appear October 1 in The Auk. © Society for Science & the Public 2000 - 2014.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 20184 - Posted: 10.09.2014

By Sarah C. P. Williams When a group of male katydids croon a tune in nearly perfect synchrony, it means the insects are after the ladies. But they’re not aligning their singing with each other to come across as larger or louder, a new study finds; each male is trying to beat out the others to be the first—by mere milliseconds—to hit a note. Katydids, also known as bush crickets (Mecopoda elongata), are among a handful of insects that make noise by rubbing a hind leg on one wing. Scientists knew that the sound attracted females, but they didn’t know why the males sang in synchrony. In the new study, researchers recorded and analyzed the choral performances of 18 different groups of four male katydids. Then, they let females choose between the males in each group. Females preferred males that were the first to broadcast each tone, even if it were only 70 milliseconds ahead of others in the group, the team reports online today in Royal Society Open Science. Moreover, the females preferred these lead singers to katydids that were singing alone—but the increased volume of the chorus didn’t seem to draw more females to the group as a whole. Singing in a group, the authors of the new study hypothesize, might help keep males on a steady rhythm—another trait that female katydids in the study preferred. But more work is needed to figure out why females chose the steadiest, leading singer, and whether the observation holds true in all species of katydids, like the round-headed katydid (pictured) that's more common in North America. © 2014 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 20177 - Posted: 10.08.2014