Links for Keyword: Aggression

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By Susan Milius OTTAWA — Larval fruit flies, supposedly relentless devourers of rotting fruit, at times leave their regular laboratory food to stalk, kill and group-cannibalize some of their older, fatter fellows, scientists report. This predatory cannibalism shows up in Drosophila melanogaster, the fly species that generations of biologists have grown in untold numbers, Roshan Vijendravarma of the University of Lausanne in Switzerland reported July 6 at the Evolution Ottawa scientific congress. He and Lausanne colleagues documented the behavior in both Canton S fruit flies, a strain raised in labs for more than six decades, and the Valais strain, brought into culture only in the last two years. Because fruit fly genetics is known in such detail, Vijendravarma said his discovery may allow researchers to study the evolution of predatory cannibalism at the DNA level. The closest reports Vijendravarma has found to what he’s witnessed describe larva of a different fruit fly, Drosophila hydei, dining on an already dead youngster of its own kind. What Vijendravarma reported is not just feeding on a happenstance free lunch, but hunting as well. He showed close-up videos of the dark, pronged mouthparts of a smaller larva scraping again and again against the wide, cream-colored body of a larger one. Finally the big larva’s body rips open, exposing softer flesh. Vijendravarma also showed photographs of clusters of small larvae side-by-side with their mouths against the flesh of a much larger one. © Society for Science & the Public 2000 - 2012

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress
Link ID: 17025 - Posted: 07.11.2012

by Michael Marshall Fancy getting into a fight? Here's a tip: don't. Even if you win you'll probably get hurt, and that will mean you have to spend weeks recovering when you could be doing something worthwhile, like curing cancer or having sex. Most animals know this instinctively and are reluctant to get into all-out fights. In particular, animals don't fight with members of other species. There's just no point: they aren't sexual rivals, and they have a different diet so they're not likely to steal food either. With some exceptions, including predator-prey struggles, animals only fight their direct competitors: members of their own species. Someone needs to tell the Dalmatian wall lizard about this unwritten rule – preferably through a megaphone from a safe distance. In field tests it picks fights with a neighbouring lizard species that poses no threat to it at all. Is it just a thug, or is there a good reason for its aggressive behaviour? Dalmatian wall lizards are named after the Dalmatia region of southern Croatia – as is the notoriously fecund breed of dog. As lizards go they look quite ordinary, measuring about 6 centimetres long, not counting their tails. They spend most of their time on the ground under vegetation or on low rocks. That keeps them separate from the neighbouring sharp-snouted rock lizards (Dalmatolacerta oxycephala), which tend to hang out on higher rocks where it's cooler. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress
Link ID: 16923 - Posted: 06.16.2012

By Bruce Bower PORTLAND, Ore. — In a cooperative venture aimed at understanding the most uncooperative of acts, researchers studying different African communities of wild chimpanzees have pooled their data and found that the apes sometimes kill each other nearly everywhere they’ve been studied. Chimp homicides occurred most frequently in groups with the most adult males, anthropologist Michael Wilson of the University of Minnesota in Minneapolis reported April 12 at the American Association of Physical Anthropologists’ annual meeting. Wilson persuaded researchers at 10 wild chimp sites, containing a total of 17 communities, to contribute their findings on lethal attacks collected over the past several decades. Chimps spend most of their time in peaceful pursuits, such as playing, foraging and grooming each other. Yet researchers, beginning with Jane Goodall more than 40 years ago, have described occasional chimp homicides. Some investigators have speculated that these animals get lethally riled up by human intrusions, such as deforestation, hunting and feeding of chimps by eco-tourists. But the new study found that chimp communities with the most documented killings had no or only rare encounters with humans. Groups of males carried out most killings, and most victims were male adults and infants in neighboring communities. “The new findings suggest that killing is an evolved strategy, mainly for adult males to eliminate rivals and competitors for mates,” Wilson said. © Society for Science & the Public 2000 - 2012

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress
Link ID: 16646 - Posted: 04.14.2012

By Ferris Jabr Rhesus macaques, which are some of the best studied of all monkeys, establish hierarchies in their social groups. Whenever two macaques tussle over a piece of food, say, or the right to mate, the monkey with the higher rank usually wins. Primatologists have established that monkeys of a lower social status are generally more stressed out than their dominant peers—low-ranking monkeys have higher levels of stress hormones, for instance. But what about differences in gene activity? Does one’s social stature change how one’s genes are expressed. Yes, concludes a new study that used differences in gene expression to identify a monkey’s social status with around 80 percent accuracy. Jenny Tung of Duke University and her colleagues—including several collaborators at the Yerkes National Primate Research Center—studied 10 groups of adult female rhesus macaques made up of five females each. Researchers formed the groups one female at a time, which allowed them to carefully construct the social hierarchy: females introduced earlier generally assumed a higher rank. In this way, the scientists knew exactly which monkey held rank 1, 2, 3, 4 and 5 in each group. Tung and her colleagues collected blood samples from the rhesus macaques, isolated the white blood cells and analyzed the DNA in those cells. They found 987 genes whose activity depended on social rank: 535 genes that were more highly expressed in high-ranking individuals and 452 genes with higher activity in low-ranking individuals. Many of these genes were involved with the immune system; in particular, genes involved in inflammation were more active in low-ranking individuals. Further testing revealed that low-ranking monkeys also had fewer cytotoxic T-cells, a kind of white blood cell that attacks infected and cancerous cells. Earlier research suggests that the stress of a low social rank compromises the immune system—which fits with the finding about T-cells—but may also trigger the immune system to respond when it does not need to, which fits with the finding about inflammation. Findings about the relationship between stress, social status and the immune system are not clear cut, however; for example, some studies have found that having a higher rank is more stressful than having a lower rank. © 2012 Scientific American

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress; Chapter 13: Memory, Learning, and Development
Link ID: 16632 - Posted: 04.10.2012

by Sarah C. P. Williams Ten minutes after they play in a competitive soccer match with an audience of friends and family cheering them on, men from the Tsimane people in lowland Bolivia have testosterone levels 30% higher than they were before the game. If the players were athletes in the United States, this number wouldn't be surprising. But Tsimane men have much lower levels of testosterone throughout their lives than do men in developed countries. The findings may provide clues to how the body regulates short-term versus long-term increases in the hormone. The Tsimane, a population of 15,000 spread among small villages in the Amazon, rely on farming, hunting, and gathering to survive. With only recent exposure to immunizations and modern sanitation methods, the people are plagued by infections, pathogens, respiratory illnesses, and gastrointestinal diseases. This disease burden suggested to anthropologist Benjamin Trumble of the University of Washington, Seattle, that the men would likely have low testosterone levels. "Testosterone is quite energetically expensive and is also thought to interfere with immune functioning," he notes. "So if you're part of a population that faces lots of parasites and pathogens, generally you've adapted to have less testosterone." To confirm his hypothesis, Trumble and colleagues recruited 88 Tsimane men who were playing in a competitive inter-village soccer tournament. Despite their hunter-gatherer lifestyle, the Tsimane have had increasing contact with other populations over the past few decades and have become avid fans of soccer. Men who were participating in the tournament play, on average, three times a week. © 2010 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress; Chapter 8: Hormones and Sex
Link ID: 16585 - Posted: 03.29.2012

By Victoria Gill Science reporter, BBC Nature Japanese honeybees' response to a hive-invading giant hornet is efficient and dramatic; they form a "bee ball" around it, serving to cook and asphyxiate it. Now, researchers in Japan have measured the brain activity of honeybees when they form this killer ball. One highly active area of the bees' brains, they believe, allows them to generate the constant heat which is deadly for the hornet. The team published their findings in the open-access journal, PLoS One. Prof Takeo Kubo from the University of Tokyo explained that "higher centres" of the bee's brain, known as the mushroom bodies, were more active in the brains of Japanese honeybees when they were a part of the "hot defensive bee ball". To find this out, the team lured the bees to form their ball by attaching a hornet to the end of a wire and inserting the predator into the hive. This simulated invasion caused the bees to swarm around the hornet. The researchers then plucked a few of the bees from the ball and measured, throughout each of their tiny brains, the relative amount of a chemical that is known to be a "marker" of brain activity. "We found that similar [brain] activity is evoked when the Japanese honeybees are simply exposed to high temperature (46C) in the laboratory," the researcher told BBC Nature. BBC © 2012

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress; Chapter 13: Homeostasis: Active Regulation of the Internal Environment
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress; Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 16526 - Posted: 03.17.2012

By Rebecca Cheung When it comes to male crayfish, not all claws are created equal. In these crustaceans, the left and right claws might be very different sizes — and the larger one isn’t necessarily stronger, researchers report online March 14 in Biology Letters. This deceptiveness could help crayfish bluff or trick an opponent during a fight, says study coauthor Robbie Wilson, a biologist at the University of Queensland in Brisbane, Australia. What’s more, the findings suggest that within a species, “dishonesty occurs in nature more commonly than we expect,” Wilson says. During a clash, a male crayfish sizes up his opponent when deciding whether to fight or flee. Previously, scientists found that stronger, smaller-clawed crayfish would back down from weaker, larger-clawed opponents. So, it was clear that some bluffing occurred between these crustaceans. In this new work, Wilson and his colleague Michael Angilletta Jr., of Arizona State University in Tempe, compared claw size and strength in the slender male crayfish, Cherax dispar, a species native to Queensland. By having crayfish squeeze down on instruments that resembled tweezers, researchers could measure the force exerted by individual claws. © Society for Science & the Public 2000 - 2012

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress; Chapter 14: Attention and Consciousness
Link ID: 16517 - Posted: 03.15.2012

Europe's top human rights watchdog, the Council of Europe, has urged Germany to end the practice of surgically castrating sex offenders. The council's anti-torture committee said such voluntary treatment, albeit rare in Germany, was "degrading". In Germany no more than five sex offenders a year have been opting for castration, hoping it will lower their sex drives and reduce their jail term. The committee's recommendations are not binding but have great influence. The committee's official title is the European Committee for the Prevention of Torture and Inhuman or Degrading Treatment or Punishment (CPT). "Surgical castration is a mutilating, irreversible intervention and cannot be considered as a medical necessity in the context of the treatment of sexual offenders", the CPT report said. It was based on an investigation in Germany carried out in November-December 2010. The BBC's Stephen Evans in Berlin says the German authorities argue that castration is not a punishment but a treatment which enables, as a government statement put it, "suffering tied to an abnormal sex drive… to be cured, or at least alleviated". Research for the report revealed that of the 104 people operated on between 1970 and 1980, only 3% reoffended, compared with nearly half of those who refused castration or were denied it by the authorities. BBC © 2012

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: 16425 - Posted: 02.25.2012

By DOUGLAS QUENQUA Tropical fish hobbyists will tell you their tanks are a source of relaxation, but recent research suggests the fish might disagree. Nearly 13 million American households contain a fish tank, and the average tank size is less than 10 gallons. Yet a study comparing the behavior of common freshwater fish in a variety of habitats found that those kept in such small tanks were considerably more aggressive than those in larger ones — more likely to fight, flare their gills and guard whatever tiny alcoves they could find. “In larger tanks, the fish were not in continuous eyesight of each other, and were swimming around checking everything out rather than beating the heck out of each other,” said the study’s author, Ronald G. Oldfield, a professor of biology at Case Western Reserve University. The fish in question were Midas, or “red devil” cichlids, a species popular among hobbyists for their brilliant colors and active swimming habits. Dr. Oldfield used only very young fish to eliminate aggressive behaviors associated with mating. Dr. Oldfield concedes that the emotional well-being of fish may not tug many heartstrings. “It’s probably not the end of the world,” he said in a telephone interview. Even the Humane Society, which routinely has commercials featuring slow-motion video of abused pets, does not offer guidelines for the treatment of pet fish. © 2011 The New York Times Company

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress
Link ID: 16192 - Posted: 12.27.2011

By Gary Stix What was up with a world leader who thought he could control the weather while engaging in his passion for Elizabeth Taylor movies? No one knows for sure, but a few years ago, two psychologists took a crack at a long-distance analysis. In the September 2009 edition of Behavioral Sciences of Terrorism and Political Aggression (Editor’s note: nice journal name), Frederick L. Coolidge and Daniel L. Segal tried to develop a psychological profile of the “Dear Leader” (in 1992 changed to “Dear Father”). Coolidge had developed a means of psychological evaluation using “informants,” people who knew or had historical or other expertise about a person. This test had been used previously to assess Hitler and Saddam Hussein and had been found to have a high-level of statistical reliability. The two psychologists used the test with a South Korean psychiatrist who was an expert on Kim Jong-il. The results showed that Kim Jong-il had an identical overall statistical measure with Hitler and Saddam on 14 personality disorders (r=7.6). (The top six of the 14 are: sadistic, paranoid, antisocial, narcissistic, schizoid and schizotypal.). Additional analysis showed that Dear Father was more like Saddam than Der Fuhrer. All three also showed evidence of psychotic thinking. Coolidge and Segal make recommendations about how to engage in diplomatic talks with someone with this type of personality. “In negotiations with Kim Jong-il over nuclear weapons, he might trust higher-level government officials more than lower ones,” they write. “Perhaps, more reflective of Kim Jong-il’s narcissistic traits, he initially balked over six-country negotiations, demanding to meet with the United States only. It would be predicted that secondary or lower level emissaries might have immediately been at a disadvantage.” © 2011 Scientific American

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress; Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress; Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders
Link ID: 16168 - Posted: 12.20.2011

By Laura Sanders Brain differences might help explain psychopaths’ cold, calculated and often antisocial behavior, and perhaps even point out better ways to treat or prevent the disorder, a study of Wisconsin prison inmates suggests. Compared with a group of 13 non-psychopathic criminals, a group of 14 psychopaths had weaker connections between an area near the front of the brain called the ventromedial prefrontal cortex, or vmPFC, and the amygdala, a pair of almond-shaped structures deep in the brain. Earlier studies have hinted that this particular link is important for emotional regulation and aggression. Neuroscientist Michael Koenigs of the University of Wisconsin–Madison and colleagues discovered the weaker connection by taking a mobile brain scanner to a medium-security prison. Psychopaths are overrepresented in prison populations thanks to their lack of empathy and tendency toward antisocial behavior. After interviewing inmates and scrutinizing their disciplinary records to determine whether they were psychopaths, the scientists conducted two kinds of brain scans. The first measured the strength of brain connections called white matter tracts, which are bundles of nerves that serve as information superhighways that shuttle information between different brain regions. It was those scans that revealed the weaker link between the vmPFC and the amygdala in psychopaths, the team reports November 30 in the Journal of Neuroscience. © Society for Science & the Public 2000 - 2011

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress
Link ID: 16096 - Posted: 12.01.2011

By CARL ZIMMER CAMBRIDGE, Mass. — Steven Pinker was a 15-year-old anarchist. He didn’t think people needed a police force to keep the peace. Governments caused the very problems they were supposed to solve. Besides, it was 1969, said Dr. Pinker, who is now a 57-year-old psychologist at Harvard. “If you weren’t an anarchist,” he said, “you couldn’t get a date.” At the dinner table, he argued with his parents about human nature. “They said, ‘What would happen if there were no police?’ ” he recalled. “I said: ‘What would we do? Would we rob banks? Of course not. Police make no difference.’ ” This was in Montreal, “a city that prided itself on civility and low rates of crime,” he said. Then, on Oct. 17, 1969, police officers and firefighters went on strike, and he had a chance to test his first hypothesis about human nature. “All hell broke loose,” Dr. Pinker recalled. “Within a few hours there was looting. There were riots. There was arson. There were two murders. And this was in the morning that they called the strike.” The ’60s changed the lives of many people and, in Dr. Pinker’s case, left him deeply curious about how humans work. That curiosity turned into a career as a leading expert on language, and then as a leading advocate of evolutionary psychology. In a series of best-selling books, he has argued that our mental faculties — from emotions to decision-making to visual cognition — were forged by natural selection. © 2011 The New York Times Company

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress
Link ID: 16087 - Posted: 11.29.2011

By Rick Nauert PhD Senior News Editor Researchers have learned that a psychopaths brain structure is significantly different from others. University of Wisconsin-Madison researchers discovered the variance studying images of prisoners’ brains. The results could help explain the callous and impulsive anti-social behavior exhibited by some psychopaths. The study showed that psychopaths have reduced connections between the ventromedial prefrontal cortex (vmPFC), the part of the brain responsible for sentiments such as empathy and guilt, and the amygdala, which reconciles fear and anxiety. Structural changes in the brain were confirmed using two different types of brain images. Diffusion tensor images (DTI) showed reduced structural integrity in the white matter fibers connecting the two areas, while a second type of image that maps brain activity, a functional magnetic resonance image (fMRI), showed less coordinated activity between the vmPFC and the amygdala. “This is the first study to show both structural and functional differences in the brains of people diagnosed with psychopathy,” says Michael Koenigs. “Those two structures in the brain, which are believed to regulate emotion and social behavior, seem to not be communicating as they should.” © 1992-2011 Psych Central

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress; Chapter 14: Attention and Consciousness
Link ID: 16073 - Posted: 11.26.2011

By ANDREW JACOBS BEIJING — Big Red Belly, his thick limbs nourished by a strict liver-tofu-ginger diet, should have been a contender. Instead, as his trainer watched in dismay, the young fighter nervously circled his more menacing adversary and then skittered to a corner of the ring, prompting jeers from a half-dozen spectators. “Worthless,” his patron, Chang Hongwei, a retired mechanical engineer, growled as he yanked Big Red Belly from the arena and unceremoniously ended his brief fighting career. “Next!” Countless members of the Gryllus bimaculatus clan, also known as field crickets, have faced off in the capital’s narrow alleys this fall in a uniquely Chinese blood sport whose provenance extends back more than 1,000 years. Nurtured by Tang Dynasty emperors and later popularized by commoners outside the palace gates, cricket fighting was banned as a bourgeois predilection during the decade-long Cultural Revolution, which ended in 1976. But like many once-suppressed traditions, among them Confucianism, mah-jongg and pigeon raising, cricket fighting is undergoing a revival here, spurred on by a younger generation — well, mostly young men — eager to embrace genuinely Chinese pastimes. Cricket-fighting associations have sprung up across the country, as have more than 20 Web sites devoted to the minutiae of raising critters whose daily needs can rival those of an Arabian steed. Last year, more than 400 million renminbi, or about $63 million, were spent on cricket sales and upkeep, according to the Ningyang Cricket Research Institute in Shandong Province. © 2011 The New York Times Company

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress
Link ID: 15996 - Posted: 11.08.2011

by Ferris Jabr What got you interested in the history of violence? I was struck by a graph I saw of homicide rates in British towns and cities going back to the 14th century. The rates had plummeted by between 30 and 100-fold. That stuck with me, because you tend to have an image of medieval times with happy peasants coexisting in close-knit communities, whereas we think of the present as filled with school shootings and mugging and terrorist attacks. Then in Lawrence Keeley's 1996 book War Before Civilization I read that modern states at their worst, such as Germany in the 20th century or France in the 19th century, had rates of death in warfare that were dwarfed by those of hunter-gatherer and hunter-horticultural societies. That too, is of profound significance in terms of our understanding of the costs and benefits of civilisation. Isn't this topic a departure for you? Your earlier books focus on how the mind and brain work... Two of my earlier books, How The Mind Works and The Blank Slate, were not about language or even cognition, narrowly, but about human nature. In them I talked about violence, for example, the abolition of barbaric customs such as torturing people to death for religious heresy, to reinforce the point that human nature comprises many components, some of which incline us toward violence, some of which pull us away from it. The fact that violence has declined and what this implied for human nature were spelled out in both books, but I decided that those paragraphs deserved to be expanded into a book of their own. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress
Link ID: 15931 - Posted: 10.22.2011

by Sara Reardon As the Thirty Years' War between Europe's ruling dynasties dragged on during the 17th century, soldiers suffered through the coldest few decades Europe had experienced for some time. Far to the east, armies from Manchuria (present day northern China) swept down from the snowy north and breeched the Great Wall of China. Not long after, a plague swept Europe. Why so much tumult? A controversial new study suggests that most of humankind's maladies—from wars to epidemics to economic downturns—can be traced to climate fluctuations. Advances in paleoclimatology have enabled researchers to look back further in time than they ever could before. One of these scientists, geographer David Zhang of the University of Hong Kong, was particularly interested in how hot and cold spells affect human civilization. He and colleagues loaded a powerful statistical analysis tool with socioeconomic, ecological, demographic, and other data. They collected data on 14 variables, such as human height, the price of gold, tree ring width, and temperature from preindustrial Europe between the years 1500 and 1800. The team then performed a statistical analysis called a Granger causality analysis to establish whether cause-effect relationships existed between any of them. This type of powerful analysis allows researchers to look at a time series of data and form relationships in which one type of event consistently leads to another. Finally, the researchers divided the time period into four smaller slices, ranging from 40 to 150 years each, to ascertain whether major events during these eras are actually caused by temperature differences within a given period, not just correlated with it. © 2010 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress
Link ID: 15870 - Posted: 10.04.2011

By Ella Davies Reporter, BBC Nature The secret to social dominance for bank voles appears to be the size of their genitals, according to scientists. The link was made by researchers from Europe who were studying the small brown mammals' reproductive behaviour. The study, in Behavioural Ecology and Sociobiology, found dominant males had wider penis bones, also called baculum. Although not present in humans, these bones are found in many other species of mammal but their exact function has not been confirmed. A scan of the baculum bone (c) Jean-Francois Lemaitre The bank vole's penis bone is trident-shaped with a wide base The study was conducted by Dr Jean-Francois Lemaitre from the University of Liverpool with colleagues in France and Switzerland. Bank voles live for a maximum of 18 months and females give birth to four or five litters per year. "This species is particularly interesting for study... because females mate with several males during a single reproductive bout," explained Dr Lemaitre. Researchers suggest that this competition may have driven evolutionary adaptations in genital anatomy to improve males' chances of reproduction. To test their theory, the team collected wild bank voles in Cheshire and studied their lab-reared offspring to understand which were dominant and which were subordinate. BBC © 2011

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: 15869 - Posted: 10.04.2011

by Andy Coghlan Video: Meek mouse yields in dominance duel Dominant mice can be humbled and wimps made mighty by altering the strength of electrical connections in their brain. The crucial connections dictating a mouse's place in the social hierarchy appear to sit in the part of the brain called the medial prefrontal cortex (mPFC), responsible for emotion and decision-making. To investigate the impact of the mPFC on social ranking, Hailan Hu of the Chinese Institute of Neuroscience in Shanghai and her colleagues first worked out the social hierarchy of mice through challenges between pairs of the animals in transparent tubes. When the mice came face to face, the subordinate animal would retreat and back out of the tube. The team then injected a virus into some of the mice that inserts a gene called GluR4 into mPFC neurons. GluR4 amplifies transmission of electrical signals – a key step in strengthening connections. When the dominance tests were repeated, previously subordinate mice that had received the virus were propelled to the top of the social ladder. "These mice also tended to gain more food in competition with their cage-mates, mark more territories and sing more courtship songs than their subordinate counterparts," says Hu. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress; Chapter 8: Hormones and Sex
Link ID: 15864 - Posted: 10.01.2011

by Michael Marshall If there's one word that sums up a newborn human baby, it's "helpless". Newly hatched greater honeyguide chicks are far more capable: chillingly so. They emerge into pitch darkness, inside a tunnel dug by another bird where their mother has left them. They will soon be joined by the host bird's own chicks when they hatch. If this was a slasher movie, now would be the time to cover your eyes. The young honeyguide kills the other chicks within an hour. All this from a bird that as an adult helpfully guides humans to bees' nests, which the humans then raid for honey. Honeyguides lay their eggs in other birds' nests, just like cuckoos. Claire Spottiswoode of the University of Cambridge studies them in southern Zambia, where they tend to parasitise little bee-eaters. These birds dig tunnels in the sandy ground, often in the roofs of aardvark holes, where they lay their eggs. Spottiswoode was able to insert video cameras into these nests. Female honeyguides slip into the tunnels and lay their own eggs there. If there are any little bee-eater eggs in place, the honeyguide mother punctures them with her beak. That's not always enough, however, because eggs sometimes survive and the little bee-eater may lay more. Spottiswoode found that only 67 per cent of host eggs were punctured in parasitised nests. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress; Chapter 8: Hormones and Sex
Link ID: 15773 - Posted: 09.08.2011

Roger Highfield, editor, New Scientist magazine This hyperaggressive rat is a legacy of a remarkable experiment started in the former Soviet Union in 1972 by Dmitry Belyaev. Like Charles Darwin before him, he was interested in the process of domestication. But while Darwin thought the process must be "insensibly slow", Belyaev suspected otherwise. He caught wild rats around the Siberian city of Novosibirsk and selectively bred two colonies on a farm a few kilometres away, hoping to mimic the process by which Neolithic farmers first domesticated animals. One colony was selected for tameness, the other for aggression. Belyaev died in 1985, but the experiment was continued by his successor, Lyudmila Trut, at the city's Institute of Cytology and Genetics. In 2003, geneticist Svante Pääbo visited Novosibirsk and the experiment. He was stunned by the vast changes in the animals' behaviour and how quickly these had been induced. The rats bred for tameness were incredibly easy to handle, while the aggressive ones were so prone to scream and bite that Pääbo said: "I got the feeling that 10 or 20 of them would probably kill me if they got out of the cages." Since returning to the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, Pääbo and colleague Frank Albert have been researching which of the rats' genes were selected for by the domestication process. They have now found several key regions of the genome that have a strong effect on tameness and suspect at least half a dozen genes are involved. The next step is to locate individual genes that influence tameness and aggression. "We're currently pursuing several approaches to home in on the genes and all of them are in their early days," says Albert. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress
Link ID: 15685 - Posted: 08.16.2011