Category: Press releases

For leaders, looking intelligent is less important than looking healthy

Selected coverage: Washington Post, Harvard Business Review, TIME, Die Stern, The Times, Voice of America, Entrepreneur, Business Insider

People look for candidates with a healthy complexion when choosing a leader, but don’t favor the most intelligent-looking candidates except for positions that require negotiation between groups or exploration of new markets. These results are published in the open-access journal Frontiers in Human Neuroscience.

Brian Spisak from the VU University Amsterdam and colleagues studied people’s implicit preferences for traits of leaders, such as health, intelligence, and attractiveness, and how they look for information about these qualities in the physical appearance of others.

The researchers focused on facial traits because these provide a wealth of information about individuals. For example, in women as well as men, caring and cooperative personalities are statistically more likely to have a more “feminine” face, due to higher estrogen levels, while aggressive risk-takers tend to have higher testosterone levels and a more “masculine” face.

They asked 148 women and men to imagine that they were selecting a new CEO for a company and to repeatedly pick between two photos of male faces. For each choice, the participants were given a job description that specified the CEO’s main challenge. This was either to drive aggressive competition, renegotiate a key partnership with another company, lead the company’s shift into a new market, or oversee the stable, sustained exploitation of non-renewable energy.

In each choice, both photos were of the same man, whose face had been digitally transformed. His face had been made to look more or less intelligent while his complexion was changed to look more or less healthy.

A stronger general preference for health than intelligence was found. The participants chose more healthy-looking faces over less healthy-looking faces in 69% of trials, and this preference was equally strong irrespective of the future CEO’s main challenge. More intelligent-looking faces were only preferred over less intelligent-looking faces for the two challenges that would require the most diplomacy and inventiveness: renegotiating the partnership and exploring the new market.

“Here we show that it always pays for aspiring leaders to look healthy, which explains why politicians and executives often put great effort, time, and money in their appearance. If you want to be chosen for a leadership position, looking intelligent is an optional extra under context-specific situations whereas the appearance of health appears to be important in a more context-general way across a variety of situations,” says Spisak, lead author of the paper and Assistant Professor at the Department of Management and Organization of VU University Amsterdam.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2014-11/f-fll103114.php

Study: http://journal.frontiersin.org/article/10.3389/fnhum.2014.00792/full

Energy drinks may pose danger to public health

Selected coverage: The Guardian, TIME, BMJ, The Times, Yahoo!, Reuters, NHS Choices, Daily Telegraph

The heavy consumption of energy drinks risks becoming a significant public health problem, especially among young people, warns a team of researchers from the World Health Organization.

Increased consumption of energy drinks may pose danger to public health, especially among young people, warns a team of researchers from the World Health Organization Regional Office for Europe in the open-access journal Frontiers in Public Health.

Energy drinks are non-alcoholic beverages that contain caffeine, vitamins, and other ingredients for example, taurine, ginseng, and guarana. They are typically marketed as boosting energy and increasing physical and mental performance.

João Breda, from the WHO Regional Office for Europe, and colleagues reviewed the literature on the health risks, consequences and policies related to energy drink consumption.

“From a review of the literature, it would appear that concerns in the scientific community and among the public regarding the potential adverse health effects of the increased consumption of energy drinks are broadly valid,” write the authors.

Energy drinks first hit European markets in 1987 and the industry has since boomed worldwide. In the US, sales increased by around 10% per year between 2008 and 2012, and almost 500 new brands hit the market in 2006. The European Food Safety Authority estimates that 30% of adults, 68% of adolescents, and 18% of children below 10 years consume energy drinks.

High Caffeine in Energy Drinks

Part of the risks of energy drinks are due to their high levels of caffeine. Energy drinks can be drunk quickly, unlike hot coffee, and as a result they are more likely to cause caffeine intoxication. In Europe, a European Food Safety Authority (EFSA) study found that the estimated contribution of energy drinks to total caffeine exposure was 43% in children, 13% in teenagers and 8% in adults.

Studies included in the review suggest that caffeine intoxication can lead to heart palpitations, hypertension, nausea and vomiting, convulsions, psychosis, and in rare cases, death. In the USA, Sweden, and Australia, several cases have been reported where people have died of heart failure or were hospitalized with seizures, from excess consumption of energy drinks.

Research has shown that adolescents who often take energy drinks are also more likely to engage in risky behaviours such as sensation seeking, substance abuse, and binge drinking.

Mixing Energy Drinks and Alcohol

Over 70% of young adults (aged 18 to 29 years) who drink energy drinks mix them with alcohol, according to an EFSA study. Numerous studies have shown that this practice is more risky than drinking alcohol only, possibly because these drinks make it harder for people to notice when they are getting drunk.

According to the National Poison Data System in the United States, between 2010 and 2011, 4854 calls to poison information centers were made about energy drinks. Almost 40% involved alcohol mixed with energy drinks. A similar study in Australia demonstrated a growth in the number of calls about energy drinks. Breda and colleagues say a similar investigation would be useful in Europe.

Energy drinks can be sold in all EU countries, but some countries have introduced regulations, including setting rules for sales to children. Hungary introduced a public health tax that includes energy drinks in 2012. In Sweden, sales of some types of energy drinks are restricted to pharmacies and sales to children are banned.

Way Forward

“As energy drink sales are rarely regulated by age, unlike alcohol and tobacco, and there is a proven potential negative effect on children, there is the potential for a significant public health problem in the future,” the authors conclude.

They make the following suggestions to minimize the potential for harm from energy drinks:

  • Establishing an upper limit for the amount of caffeine allowed in a single serving of any drink in line with available scientific evidence;
  • Regulations to enforce restriction of labelling and sales of energy drinks to children and adolescents;
  • Enforcing standards for responsible marketing to young people by the energy drink industry;
  • Training health care practitioners to be aware of the risks and symptoms of energy drinks consumption;
  • Patients with a history of diet problems and substance abuse, both alone and combined with alcohol, should be screened for the heavy consumption of energy drinks;
  • Educating the public about the risks of mixing alcohol with energy drinks consumption;
  • Further research on the potential adverse effects of energy drinks, particularly on young people.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2014-10/f-edm100914.php

Study: http://journal.frontiersin.org/article/10.3389/fpubh.2014.00134/full

Biodiversity in the Mediterranean is threatened by alien species

Millions of tourists visit the Mediterranean each year, but its deep-blue waters host the largest invasion currently underway on Earth. Almost 1,000 alien species, including fish, crustaceans, and algae are now established from other seas through human activities. In the open-access journal Frontiers in Marine Science, a multinational team of researchers analyzed data from a new information system developed by the European Commission to show how the introduction of alien species has changed the native biodiversity within the Mediterranean.

A hotspot for marine biodiversity, the Mediterranean includes 17,000 described species, of which around 20% occur nowhere else. But invasive species can disrupt this delicate balance. For example, Siganus luridus and S. rivulatus fish from the Indian Ocean have invaded the eastern Mediterranean, where they overgraze on forests of brown algae in the shallows, stripping them bare to the rocks, with devastating effects on the animal species within this ecosystem. Elsewhere, communities of native algae, corals, and invertebrates die because they are starved of oxygen, light, and food beneath the fast-growing invasive alga Caulerpa cylindracea, which forms mats of up to 15 cm thick.

Stelios Katsanevakis, a researcher at the European Commission’s in-house science service, the Joint Research Centre (JRC), and colleagues looked at data on 986 alien species and tracked their spread. They used the new online platform, called the European Alien Species Information Network (EASIN). Developed by the JRC, EASIN allows for European-wide assessments of the pathways of introduction, the spread, and the impacts of alien species. Analyzing this online resource, the researchers show severe consequences for food webs and ecosystem services as invasive species expand their range and native species are driven to local extinction.

“Using the information in EASIN, we could map in unprecedented detail how far each alien species has already spread. We found that the composition of marine communities, which in the past was shaped solely by climate, the environment, and oceanographic barriers, now greatly depends on the human activities. In many areas, shipping, aquaculture, and the opening of navigational canals are now becoming the main drivers of species distribution. Proper management of the pathways of introduction of alien species is urgently needed, such as the entry into force of the Ballast Water Management Convention, to prevent new introductions”, says Dr Katsanevakis.

The researchers found that around 60 species, mainly algae, have been introduced accidentally through aquaculture, especially off the coast of Venice and southwestern France. More than 400 species of alien fish and invertebrates in the Mediterranean have come by way of the 145-year-old Suez Canal. The rate of their arrival is increasing: over 80% first arrived less than 50 years ago.

The researchers believe that “stowaway” species have profited from increasing shipping activities over this period, but the invasion has also been helped by global warming. Especially the waters between southern Turkey, Syria, Lebanon, Israel, Gaza, Cyprus, and Egypt have become markedly warmer over the past 20 years, well suited for species from the Red Sea, the Arabian Sea, and the Indian Ocean. In this region of the Mediterranean, conveniently located near the exit of the Suez Canal, up to 40% of the marine fauna is now of alien origin.

“These invasions will continue and will keep affecting biodiversity in the Mediterranean. Its future ecosystems will likely be very different to what they are now,” warns Dr Katsanevakis. “We need further research to better understand what effect these changes will have, including on the vital services that humans obtain from marine ecosystems, such as food provision, coastal protection, recreation and tourism.”

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2014-09/f-bit092614.php

Study: http://journal.frontiersin.org/article/10.3389/fmars.2014.00032/full

Junk food makes rats lose appetite for balanced diet

Coverage: Scientific American, TIME, CNN, Discovery News, IFLS, Newsweek, RedOrbit

A diet of junk food not only makes rats fat, but also reduces their appetite for novel foods, a preference that normally drives them to seek a balanced diet, reports a study published in the open-access journal Frontiers in Psychology.

The study helps to explain how excessive consumption of junk food can change behavior, weaken self-control and lead to overeating and obesity.
The team of researchers, led by Professor Margaret Morris, Head of Pharmacology from the School of Medical Sciences, UNSW Australia, taught young male rats to associate each of two different sound cues with a particular flavor of sugar water – cherry and grape.

Healthy rats, raised on a healthy diet, stopped responding to cues linked to a flavor in which they have recently overindulged. This inborn mechanism, widespread in animals, protects against overeating and promotes a healthy, balanced diet.

But after 2 weeks on a diet that included daily access to cafeteria foods, including pie, dumplings, cookies, and cake – with 150% more calories – the rats’ weight increased by 10% and their behavior changed dramatically. They became indifferent in their food choices and no longer avoided the sound advertising the overfamiliar taste. This indicated that they had lost their natural preference for novelty. The change even lasted for some time after the rats returned to a healthy diet.

The researchers think that a junk diet causes lasting changes in the reward circuit parts of the rats’ brain, for example, the orbitofrontal cortex, an area of the brain responsible for decision-making. They say these results may have implications for people’s ability to limit their intake of certain kinds of foods, because the brain’s reward circuitry is similar in all mammals.
“The interesting thing about this finding is that if the same thing happens in humans, eating junk food may change our responses to signals associated with food rewards,” says UNSW Professor Morris. “It’s like you’ve just had ice cream for lunch, yet you still go and eat more when you hear the ice cream van come by.”

The World Health Organization estimates that over 10% of the world’s adult population is obese and at least 2.8 million people die each year as a result of being overweight or obesity. Overweight and obesity are major risk factors for a number of chronic diseases, including diabetes, cardiovascular diseases and cancer.

“As the global obesity epidemic intensifies, advertisements may have a greater effect on people who are overweight and make snacks like chocolate bars harder to resist,” adds Dr Amy Reichelt, lead author of the paper and UNSW postdoctoral associate.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2014-08/f-jfm082514.php

Study: http://journal.frontiersin.org/article/10.3389/fpsyg.2014.00852/full

Job insecurity in academia harms the mental wellbeing of non-tenure track faculty

Non-tenure-track academics experience stress, anxiety, and depression due to their insecure job situation, according to the first survey of its kind published in the open-access journal Frontiers in Psychology.

There were 1.4 to 1.5 million contingent faculty workers in the USA, according to a report by the American Association of University Professors. These faculty members, such as research adjunct faculty, lecturers and instructors, are off the so-called “tenure track”. They work under short-term contracts with limited health and retirement benefits, often part-time and at different institutes simultaneously. Among them, women, African Americans, Hispanics, and Native Americans are overrepresented.

Gretchen Reevy from California State University and Grace Deason from the University of Wisconsin-La Crosse, USA, used extensive self-report questionnaires to survey almost 200 non-tenure-track academics – mainly from medium-sized universities in the USA, and of whom around two-thirds were women. Questions focused on work-related sources of stress, mental wellbeing, and coping mechanisms, as well as about their background, family situation, and income.

Almost one-third of the participants (31%) replied that the lack of job security was among the most stressful aspects of their work. Other frequently named sources of stress were a high workload; lack of support and recognition; low and unequal pay; and feeling excluded from the infrastructure and governance at their institute.

Non-tenure track faculty who wished for a permanent position, or whose family income was low, were more prone to depression, anxiety, and stress. They were also more likely to suffer from these if they felt personally committed to the institution where they worked. On average, women reported encountering more sources of stress at work than men.

The authors call on universities to attend more to the specific needs of their non-tenure-track faculty to avoid negative outcomes for institutions, students, and faculty. Suggestions include alleviating the sources of stress listed above and considering increasing the rate of hiring into more secure, tenure-track positions.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2014-08/f-jii080614.php

Study: http://journal.frontiersin.org/article/10.3389/fpsyg.2014.00701/full

Smells like deceit: Record number of species use the same odor to exploit each other

The open-access journal Frontiers in Ecology and Evolution reports the first known case where four species, all at different levels in the food chain, use a single odor to communicate with and ruthlessly exploit each other.

Plant-feeding insects are often attracted to odors that are released by damaged plant tissue because these plants are already under attack and so a good place to look for food, sexual partners, and egg-laying sites. The jumping plant louse Diaphorina citri hones in on the odor methyl salicylate that is released by damaged young leaves of citrus trees, whose sap is the only food of the young lice. But other species have evolved the capacity to take advantage of its attraction to methyl salicylate.

One of these is the bacterium Canditatus Liberibacter asiaticus, which infects citrus trees, hijacks its odor production, and forces it to release methyl salicylate to mimic an attack by plant lice. Jumping plant lice that fly towards the source of the odor are duped: they will not find enough food there, as the bacterium has drastically lowered the nutritional quality of infected leaves. This is a trick that forces the lice to quickly seek out another tree again, this time with the bacterium hitching a ride on their body. In this way, the bacterium can infect new citrus trees, where it causes the incurable and deadly disease huánglóngbìng.

Enter the wasp Tamarixia radiata, which lays its eggs on young jumping plant lice, so that the wasp larvae can feed on them. Lukasz Stelinski and colleagues from the University of Florida asked whether the wasp is likewise attracted to the odor of methyl salicylate while hunting for plant lice. They placed female wasps in an olfactometer, a Y-shaped device that delivers two opposing air flows, each carrying a different odor. The wasps had the choice of flying towards methyl salicylate or to a control odor such as limonene, another compound produced by citrus trees.

The wasps were strongly attracted to the smell of both bacteria-infected and louse-infested citrus plants, and also to pure methyl salicylate. A further experiment revealed that the wasps were more likely to find and attack young plant lice on plants infected with the bacterium, or on plants that had been treated with methyl salicylate. This proves that the wasp finds its prey by eavesdropping on the odor signal exchanged between bacteria, citrus trees, and plant lice.

“Communication between species is widespread in nature, but almost always involves only two or three species. Here, we show for the first time that the same signal connects four different species, each at a different level in the food chain. Through their separate evolutionary histories, they independently hit on the use of methyl salicylate as a way to take advantage of their prey,” says Stelinski.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2014-05/f-sld052314.php

Study: http://journal.frontiersin.org/article/10.3389/fevo.2014.00008/full

The brain’s reaction to male odor shifts at puberty in children with gender dysphoria

The brains of children with gender dysphoria react to androstadienone, a musky-smelling steroid produced by men, in a way typical of their biological sex, but after puberty according to their experienced gender, finds a study for the first time in the open-access journal Frontiers in Endocrinology.

Around puberty, the testes of men start to produce androstadienone, a breakdown product of testosterone. Men release it in their sweat, especially from the armpits. Its only known function is to work like a pheromone: when women smell androstadienone, their mood tends to improve, their blood pressure, heart rate, and breathing go up, and they may become aroused.

Previous studies have shown that, in heterosexual women, the brain region that responds most to androstadienone is the hypothalamus, which lies just above the brainstem and links the nervous system to the hormonal system. In men with gender dysphoria (formerly called gender identity disorder) – who are born as males, but behave as and identify with women, and want to change sex – the hypothalamus also reacts strongly to its odor. In contrast, the hypothalamus of heterosexual men hardly responds to it.

Girls without gender dysphoria before puberty already show a stronger reaction in the hypothalamus to androstadienone than boys, finds a new study by Sarah Burke and colleagues from the VU University Medical Center of Amsterdam, the Netherlands, and the University of Liège, Belgium.

The researchers used neuroimaging to also show for the first time that in prepubescent children with gender dysphoria, the hypothalamus reacts to the smell of androstadienone in a way typical of their biological sex. Around puberty, its response shifts, and becomes typical of their experienced gender.

The reaction to the smell of androstadienone in the hypothalamus of 154 children and adolescents, including girls and boys, both before (7 to 11-year-old) and after puberty (15 to 16-year-old), of whom 74 had been diagnosed with gender dysphoria.
Results showed that the hypothalamus was more responsive to androstadienone in 7 to 11-year-old girls than in boys, both without gender dysphoria, although not yet as much as in adolescent girls. This means that the greater receptiveness of women to its odor already exists before puberty, either as an inborn difference or one that arises during early childhood.
Before puberty, the hypothalamus of boys with gender dysphoria hardly reacted to the odor, just as in other boys. But this changed in the 15 to 16-year-olds: the hypothalamus of adolescent boys with gender dysphoria now lit up as much as in heterosexual women, while the other adolescent boys still did not show any reaction. Adolescent girls with gender dysphoria showed the same reaction to androstadienone in their hypothalamus as is typical for heterosexual men.

These results suggest that as children with gender dysphoria grow up, their brain naturally undergoes a partial rewiring, to become more similar to the brain of the opposite sex – so corresponding to their experienced gender.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2014-05/f-tbr052714.php

Study: http://journal.frontiersin.org/article/10.3389/fendo.2014.00060/full

Citizens help researchers to challenge scientific theory

Selected coverage: The Independent, Daily Mail

Science crowdsourcing was used to disprove a widely held theory that “supertasters” owe their special sensitivity to bitter tastes to an usually high density of taste buds on their tongue, according to a study published in the open-access journal Frontiers in Integrative Neuroscience.

Supertasters are people who can detect and are extremely sensitive to phenylthiocarbamide and propylthiouracil, two compounds related to the bitter molecules in certain foods such as broccoli and kale. Supertasting has been used to explain why some people don’t like spicy foods or “hoppy” beers, or why some kids are picky eaters.

The sensitivity to these bitter tastants is partly due to a variation in the taste receptor gene TAS2R38. But some scientists believe that the ability to supertaste is also boosted by a greater-than-average number of “papillae”, bumps on the tongue that contain taste buds. Nicole Garneau, Curator and Chair of the Department of Health Sciences, Denver Museum of Nature & Science, and colleagues tested if this is true.

“There is a long-held belief that if you stick out your tongue and look at the bumps on it, then you can predict how sensitive you are to strong tastes like bitterness in vegetables and strong sensations like spiciness,” says Garneau. “The commonly accepted theory has been that the more bumps you have, the more taste buds you have and therefore the more sensitive you are.”

Over 3000 visitors to the museum’s Genetics of Taste Lab volunteered to stick their tongue out so that their papillae could be counted and their sensitivity to phenylthiocarbamide and propylthiouracil measured. In total, 394 study subjects were included in the analysis. Cell swabs from volunteers were taken to determine their DNA sequence at TAS2R38. Results confirmed that certain variations in TAS2R38 make it more likely that somebody is sensitive to bitter, but also proved that the number of papillae on the tongue does not affect increased taste sensitivity.

“No matter how we looked at the data, we couldn’t replicate this long held assumption that a high number of papillae equals supertasting,” says Garneau.

The authors argue against the continued misuse of the term supertaster, and for the use of the more objective term hypergeusia – abnormally sensitized taste – to describe people who are sensitive to all tastes and sensations from food.
“What we know and understand about how our bodies work improves greatly when we challenge central dogmas of our knowledge. This is the nature of science itself,” adds Garneau. “As techniques improve, so too does our ability to do science, and we find that what we accepted as truth 20, 30, or 100 years ago gets replaced with better theories as we gather new data, which advances science. In this case, we’ve proven that with the ‘Denver Papillae Protocol’, our new method for objective analysis for papillae density, we were unable to replicate well-known studies about supertasting.”

What make this study unique is that most of the results were collected by citizen scientists including over 130 volunteers who had been specially trained by Garneau and her colleagues. The Genetics of Taste Lab is located in the heart of the museum, uniquely situated to attract volunteers and dedicated citizen scientists who conduct population-based research about human genetics, taste, and health.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2014-05/f-chr052314.php

Study: http://journal.frontiersin.org/article/10.3389/fnint.2014.00033/full

Smart drugs pose special risks to the developing brain of young people

Selected coverage: TIME

Over a million American students misuse prescription drugs or take illegal stimulants to increase their attention span, memory, and capacity to stay awake. Such “smart drugs” become more and more popular due to peer pressure, stricter academic requirements, and the tight job market. But young people who misuse them risk long-term impairments to brain function, warn Kimberly Urban at the University of Delaware and Wen-Jun Gao at Drexel University College of Medicine, USA, in a NIH-funded review published in the open-access journal Frontiers in Systems Neuroscience.

The latest research on the potential lasting side-effects of the most important smart drugs on the uniquely delicate, developing brain of young people was reviewed. It was found that any short-term boost in mental performance due to smart drugs may come at a heavy cost: a long-term decrease in brain plasticity, necessary for task switching, planning ahead, and adaptive flexibility in behavior.

Special risks for young brains

Methylphenidate is the most popular smart drug among kids today and often sold on the black market. It was originally developed as a prescription-only drug (sold as Ritalin and Concerta) to treat ADHD, and works by increasing the level of neurotransmitter in the nervous system. Around 1.3 million American teenagers misused or abused methylphenidate without prescription in the previous month, according to The Partnership at Drugfree.org and the MetLife Foundation.
Trials on rats have shown that young, developing brains are particularly sensitive to methylphenidate: even low dosages early in life can reduce nerve activity, working memory, and the ability to quickly switch between tasks and behaviors. Such mental flexibility is important for complex motoric learning, interpersonal skills, and work performance.
Another popular smart drug is modafinil, sold under the name Proviigil against narcolepsy and other sleep disorders. Believed to work by raising the levels of dopamine in between synapses of brain nerve cells, it can boost memory as well as the ability to work with numbers and do other mental tasks. But research indicates that modafinil could have similar long-term undesired effects as methylphenidate on the developing brain.

New smart drugs also pose risks

Not yet widely used are ampakines, an emerging class of drugs currently studied by the US military with the aim of increasing alertness in soldiers. Ampakines bind to so-called AMPA receptor molecules in the nervous system and boost the response of nerve cells and strengthen connections between them. Known to improve memory and cognition in rats and healthy humans volunteers, ampakines are often considered to be relatively safe potential smart drugs. But they are not without dangers for young people: uncontrolled use might over-excite the nervous system, damaging or killing nerve cells, caution the authors.

Many “known unknowns”

More research on the long-term effects of methylphenidate, modafinil, ampakines, and other smart drugs, especially in young people, is urgently needed, the authors caution.

“What’s safe for adults is not necessarily safe for kids,” warns Urban. “The human brain continues to develop until our late twenties or early thirties. Young people are especially prone to abuse smart drugs, but also more vulnerable to any side-effects. We simply don’t know enough about the long-term effects of these drugs on the developing brain to conclude they are safe.”

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2014-05/f-sdp050814.php

Study: http://journal.frontiersin.org/article/10.3389/fnsys.2014.00038/full

Color of passion: Orange underbellies of female lizards signal fertility

Selected coverage: NY Times

Australian lizards are attracted to females with the brightest orange patches – but preferably not too large – on their underbelly, according to research published in the open-access journal Frontiers in Ecology and Evolution.

Lake Eyre dragon lizards, Ctenophorus maculosus, are found exclusively in salt deserts in southern Australia, where they feed on dead insects blown onto the salt crust. When females become fertile they develop bright orange patches on their normally pale underbelly and change their behavior towards males: instead of “waving them away” with their forelegs or fleeing, they let the males court them with showy behavior like push-ups and head bobs.

Dr. Devi Stuart-Fox and Jennifer Goode, both of the Zoology Department at the University of Melbourne, Australia, attempted to determine what was more important in driving courtship: the female’s color or the behavior that accompanies different reproductive statuses.

Females at different reproductive stages – fertile, pregnant, or non-receptive – were decorated with paints closely matched to the natural colors of the female lizard. The paints were used to either cover up natural orange patches or apply fake ones. As natural lizard color reflects ultraviolet (UV) light, the researchers used specialized UV-reflecting paints to accurately mimic female coloration. The painted females were then allowed to interact with males and the behavior of both sexes was observed.

Males targeted the orange painted females more frequently than white ones, regardless of the females’ actual reproductive state. They were most attracted to females with small, bright orange patches and tended to avoid those with larger, paler ones. It is thought that bright color is attractive as it indicates peak female fertility. Pregnant females retain their coloration until laying and very large orange spots suggest the female is swollen with eggs and no longer interested in mating.

But male behavior was more strongly determined by the female’s reproductive status. Males also mated more frequently with fertile females than pregnant ones or those outside of the breeding cycle. This is consistent with female behavioral acceptance of courting and mating during this stage. Frustrated males often behaved aggressively – with chases and bites – towards pregnant females.

If males persist with sexually aggressive behavior, pregnant females have a final ace up their sleeves – they flip over onto their backs and display their orange patterning. This position prevents copulation and the bright orange color displayed is believed to have the added benefit of confusing and warding off predatory birds who might catch sight of the vulnerable female lizard.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2014-02/f-cop022414.php

Study: http://journal.frontiersin.org/article/10.3389/fevo.2014.00002/full