Silicone liquid crystal stiffens with repeated compression

Public release date: 29-Apr-2013
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Contact: Mike Williams
mikewilliams@rice.edu
713-348-6728
Rice University

Rice University researchers say discovery may point toward self-healing materials

HOUSTON (April 29, 2013) Squeeze a piece of silicone and it quickly returns to its original shape, as squishy as ever. But scientists at Rice University have discovered that the liquid crystal phase of silicone becomes 90 percent stiffer when silicone is gently and repeatedly compressed. Their research could lead to new strategies for self-healing materials or biocompatible materials that mimic human tissues.

A paper on the research appeared this month in Nature's online journal Nature Communications.

Silicone in its liquid crystal phase is somewhere between a solid and liquid state, which makes it very handy for many things. So Rice polymer scientist Rafael Verduzco was intrigued to see a material he thought he knew well perform in a way he didn't expect. "I was really surprised to find out, when my student did these measurements, that it became stiffer," he said. "In fact, I didn't believe him at first."

The researchers had intended to quantify results seen a few years ago by former Rice graduate student Brent Carey, who subjected a nanotube-infused polymer to a process called repetitive dynamic compression. An astounding 3.5 million compressions (five per second) over a week toughened the material, just like muscles after a workout, by 12 percent. What Verduzco and lead author/Rice graduate student Aditya Agrawal came across was a material that shows an even stronger effect. They had originally planned to study liquid crystal silicone/nanotube composites similar to what Carey tested, but decided to look at liquid crystal silicones without the nanotubes first. "It's always better to start simple," Verduzco said.

Silicones are made of long, flexible chains that are entangled and knotted together like a bowl of spaghetti. In conventional silicones the chains are randomly oriented, but the group studied a special type of silicone known as a liquid crystal elastomer. In these materials, the chains organize themselves into rod-shaped coils. When the material was compressed statically, like squeezing a piece of Jell-O or stretching a rubber band, it snapped right back into its original shape. The entanglements and knots between chains prevent it from changing shape. But when dynamically compressed for 16 hours, the silicone held its new shape for weeks and, surprisingly, was much stiffer than the original material.

"The molecules in a liquid crystal elastomer are like rods that want to point in a particular direction," Verduzco said. "In the starting sample, the rods are randomly oriented, but when the material is deformed, they rotate and eventually end up pointing in the same direction. This is what gives rise to the stiffening. It's surprising that by a relatively gentle but repetitive compression, you can work out all the entanglements and knots to end up with a sample where all the polymer rods are aligned."

Before testing, the researchers chemically attached liquid crystal molecules similar to those used in LCD displays -- to the silicones. While they couldn't see the rods, X-ray diffraction images showed that the side groups and thus the rods had aligned under compression. "They're always coupled. If the side group orients in one direction, the polymer chain wants to follow it. Or vice versa," Verduzco said.

The X-rays also showed that samples heated to 70 degrees Celsius slipped out of the liquid crystal phase and did not stiffen, Verduzco said. The stiffening effect is reversible, he said, as heating and cooling a stiffened sample will allow it to relax back into its original state within hours.

Verduzco plans to compress silicones in another phase, called smectic, in which the polymer rods align in layers. "People have been wanting to use these in displays, but they're very hard to align. A repetitive compression may be a simple way to get around this challenge," he said.

Since silicones are biocompatible, they can also be used for tissue engineering. Soft tissues in the body like cartilage need to maintain strength under repeated compression and deformation, and liquid crystal elastomers exhibit similar durability, he said.

###

The paper's co-authors include Carey, a Rice alumnus and now a scientist at Owens Corning; graduate student Alin Chipara; Yousif Shamoo, a professor of biochemistry and cell biology; Pulickel Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of mechanical engineering and materials science, chemistry and chemical and biomolecular engineering; and Walter Chapman, the William W. Akers Professor of Chemical and Biomolecular Engineering, all of Rice; and Prabir Patra, an assistant professor of mechanical engineering at the University of Bridgeport with a research appointment at Rice. Verduzco is an assistant professor of chemical and biomolecular engineering.

The research was supported by an IBB Hamill Innovations Grant, the Robert A. Welch Foundation, the National Science Foundation and the National Institutes of Health, through the National Institute of Allergy and Infectious Diseases.

Read the abstract at http://www.nature.com/ncomms/journal/v4/n4/full/ncomms2772.html.

This news release can be found online at http://news.rice.edu/2013/04/29/silicone-liquid-crystal-stiffens-with-repeated-compression-2/

Follow Rice News and Media Relations via Twitter @RiceUNews.

Related Materials:

Verduzco Laboratory: http://verduzcolab.blogs.rice.edu

Images for download:

http://news.rice.edu/wp-content/uploads/2013/04/0429_VERDUZCO-1-web.jpg

A liquid crystal sample like this one, seen under a microscope, gets tougher when repeatedly compressed, according to research at Rice University. (Credit: Verduzco Laboratory/Rice University)

http://news.rice.edu/wp-content/uploads/2013/04/0429_VERDUZCO-2-web.jpg

Rice University researchers show a small sample of liquid crystal silicone that has been drastically toughened through repeated compression. From left: Walter Chapman, Aditya Agrawal, Pulickel Ajayan and Rafael Verduzco. (Credit: Jeff Fitlow/Rice University)

---

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AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.

Public release date: 29-Apr-2013
[ | E-mail | Share ]

Contact: Mike Williams
mikewilliams@rice.edu
713-348-6728
Rice University

Rice University researchers say discovery may point toward self-healing materials

HOUSTON (April 29, 2013) Squeeze a piece of silicone and it quickly returns to its original shape, as squishy as ever. But scientists at Rice University have discovered that the liquid crystal phase of silicone becomes 90 percent stiffer when silicone is gently and repeatedly compressed. Their research could lead to new strategies for self-healing materials or biocompatible materials that mimic human tissues.

A paper on the research appeared this month in Nature's online journal Nature Communications.

Silicone in its liquid crystal phase is somewhere between a solid and liquid state, which makes it very handy for many things. So Rice polymer scientist Rafael Verduzco was intrigued to see a material he thought he knew well perform in a way he didn't expect. "I was really surprised to find out, when my student did these measurements, that it became stiffer," he said. "In fact, I didn't believe him at first."

The researchers had intended to quantify results seen a few years ago by former Rice graduate student Brent Carey, who subjected a nanotube-infused polymer to a process called repetitive dynamic compression. An astounding 3.5 million compressions (five per second) over a week toughened the material, just like muscles after a workout, by 12 percent. What Verduzco and lead author/Rice graduate student Aditya Agrawal came across was a material that shows an even stronger effect. They had originally planned to study liquid crystal silicone/nanotube composites similar to what Carey tested, but decided to look at liquid crystal silicones without the nanotubes first. "It's always better to start simple," Verduzco said.

Silicones are made of long, flexible chains that are entangled and knotted together like a bowl of spaghetti. In conventional silicones the chains are randomly oriented, but the group studied a special type of silicone known as a liquid crystal elastomer. In these materials, the chains organize themselves into rod-shaped coils. When the material was compressed statically, like squeezing a piece of Jell-O or stretching a rubber band, it snapped right back into its original shape. The entanglements and knots between chains prevent it from changing shape. But when dynamically compressed for 16 hours, the silicone held its new shape for weeks and, surprisingly, was much stiffer than the original material.

"The molecules in a liquid crystal elastomer are like rods that want to point in a particular direction," Verduzco said. "In the starting sample, the rods are randomly oriented, but when the material is deformed, they rotate and eventually end up pointing in the same direction. This is what gives rise to the stiffening. It's surprising that by a relatively gentle but repetitive compression, you can work out all the entanglements and knots to end up with a sample where all the polymer rods are aligned."

Before testing, the researchers chemically attached liquid crystal molecules similar to those used in LCD displays -- to the silicones. While they couldn't see the rods, X-ray diffraction images showed that the side groups and thus the rods had aligned under compression. "They're always coupled. If the side group orients in one direction, the polymer chain wants to follow it. Or vice versa," Verduzco said.

The X-rays also showed that samples heated to 70 degrees Celsius slipped out of the liquid crystal phase and did not stiffen, Verduzco said. The stiffening effect is reversible, he said, as heating and cooling a stiffened sample will allow it to relax back into its original state within hours.

Verduzco plans to compress silicones in another phase, called smectic, in which the polymer rods align in layers. "People have been wanting to use these in displays, but they're very hard to align. A repetitive compression may be a simple way to get around this challenge," he said.

Since silicones are biocompatible, they can also be used for tissue engineering. Soft tissues in the body like cartilage need to maintain strength under repeated compression and deformation, and liquid crystal elastomers exhibit similar durability, he said.

###

The paper's co-authors include Carey, a Rice alumnus and now a scientist at Owens Corning; graduate student Alin Chipara; Yousif Shamoo, a professor of biochemistry and cell biology; Pulickel Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of mechanical engineering and materials science, chemistry and chemical and biomolecular engineering; and Walter Chapman, the William W. Akers Professor of Chemical and Biomolecular Engineering, all of Rice; and Prabir Patra, an assistant professor of mechanical engineering at the University of Bridgeport with a research appointment at Rice. Verduzco is an assistant professor of chemical and biomolecular engineering.

The research was supported by an IBB Hamill Innovations Grant, the Robert A. Welch Foundation, the National Science Foundation and the National Institutes of Health, through the National Institute of Allergy and Infectious Diseases.

Read the abstract at http://www.nature.com/ncomms/journal/v4/n4/full/ncomms2772.html.

This news release can be found online at http://news.rice.edu/2013/04/29/silicone-liquid-crystal-stiffens-with-repeated-compression-2/

Follow Rice News and Media Relations via Twitter @RiceUNews.

Related Materials:

Verduzco Laboratory: http://verduzcolab.blogs.rice.edu

Images for download:

http://news.rice.edu/wp-content/uploads/2013/04/0429_VERDUZCO-1-web.jpg

A liquid crystal sample like this one, seen under a microscope, gets tougher when repeatedly compressed, according to research at Rice University. (Credit: Verduzco Laboratory/Rice University)

http://news.rice.edu/wp-content/uploads/2013/04/0429_VERDUZCO-2-web.jpg

Rice University researchers show a small sample of liquid crystal silicone that has been drastically toughened through repeated compression. From left: Walter Chapman, Aditya Agrawal, Pulickel Ajayan and Rafael Verduzco. (Credit: Jeff Fitlow/Rice University)

---

[ | E-mail | Share ]

?

AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.

Source: http://www.eurekalert.org/pub_releases/2013-04/ru-slc042913.php

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Italy's new economy minister aims to cut taxes and spending

ROME (Reuters) - Italy's new economy minister Fabrizio Saccomanni plans to cut taxes and public spending and lower borrowing costs, according to an interview published on Sunday in daily la Repubblica.

Saccomanni, formerly deputy governor of Italy's central bank, was sworn in as minister on Sunday as part of Prime Minister Enrico Letta's new coalition cabinet, a mix of center-right and center-left politicians and technocrats like Saccomanni.

Saccomanni told Repubblica he wanted to "restructure the state budget" to support companies and low-earners, while cutting some unproductive public spending to create resources needed to reduce taxes.

The confidence generated by these measures could allow Italy's borrowing costs to fall sharply, he said.

The interest rate differential between Italian benchmark bonds and their safer German equivalent benchmark bonds, often seen as the main indicator of investor confidence could fall to 1 percentage point or less from the current level of almost 3 points, he said.

In an interview with few direct quotes, Saccomanni said it was vital to remove political uncertainty and instill confidence to kick-start Italy's recession-bound economy.

To do this, he said he would propose a "pact" between banks, firms and consumers to boost lending, investments and consumption. He did not elaborate on what this pact could entail.

Saccomanni faces a tough task to revive the economy without allowing public finances to go off the rails and the political risks were spelled out on Sunday by a close ally of center-right leader Silvio Berlusconi whose support Letta depends on.

HOUSING TAX

Renato Brunetta, lower house leader of Berlusconi's People of Freedom party (PDL) said the government would fall unless Letta promises in his maiden speech to urgently abolish an unpopular housing tax and repay the 2012 levy to taxpayers.

"If the prime minister doesn't make this precise commitment we will not give him our support in the vote of confidence," Brunetta told daily Il Messaggero.

Brunetta, who was himself a candidate for the post of economy minister said that during negotiations for the formation of the government Letta had "given his word" on the abolition and repayment of the tax, which would leave an 8 billion euros hole in public accounts.

Moody's analyst Dietmar Hornung said Italy's fiscal "maneuver space" was quite limited after its debt-to-GDP ratio had further increased from levels that were already high.

In an interview with Il Sole 24 Ore on Sunday, Hornung, who oversees Italy, said Rome needed to boost its competitiveness by reforming its labor market, although he said prospects of a progression in economic reforms were "quite weak".

On Friday, Moody's kept Italy's sovereign debt rating at Baa2 thanks to the country's reasonably low current cost of funding and its primary surplus but kept its negative outlook.

(Writing by Gavin Jones, additional reporting by Danilo Masoni; Editing by Elaine Hardcastle)

Source: http://news.yahoo.com/italys-economy-minister-aims-cut-taxes-spending-102649094.html

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Will Virgin Galactic's SpaceShipTwo Take 1st Rocket-Powered Flight Monday?

The space tourism company Virgin Galactic appears to be go for its first rocket-powered test flight of SpaceShipTwo ? a commercial rocket ship for passenger space travel.

There is a palpable buzz of a possible test flight of SpaceShipTwo?on Monday (April 29) at the Mojave Air and Space Port in Mojave, Calif. The test is rumored to be a 20-second burn of SpaceShipTwo's novel hybrid rocket motor in flight.

SpaceShipTwo is designed to use the rocket motor to power private launches that will carry six passengers and two pilots to suborbital space and back. So the possible test flight would be a major milestone for the spacecraft and Virgin Galactic. [See amazing photos of SpaceShipTwo test flights]

Virgin Galactic's founder, the British billionaire Sir Richard Branson, hinted at a powered flight test on April 23 during an interview with the Las Vegas Sun newspaper at an event for his other company, Virgin Atlantic, which began Los Angeles to Las Vegas service last week.

"We're hoping to break the sound barrier. That's planned Monday," Branson told the Las Vegas Sun. "It will be a historic day."

Mum's the word, with fingers crossed

Despite Branson's tantalizing comments, Virgin Galactic and Mojave officials are tight-lipped on Monday's test, given the fact that technical or weather delays could affect their plans.

"Test flight schedules have to remain flexible to be responsive to weather and a host of other factors, so can't give you a specific date," said Virgin Galactic CEO and President George Whitesides. "But what is certain is that the team is getting close to first rocket-powered flight, which is an important milestone for the company and the program."

?Whitesides told SPACE.com that whenever the first flight occurs, the primary goal "is smooth and safe demonstration of the vehicle system in terms of rocket ignition, shut off, and aerodynamic controls."

Officials in Mojave were also short on details for any SpaceShipTwo tests on Monday.

"While we can't comment on tenant test plans, we always strive to accommodate our friends in the press," Stuart Witt, CEO and general manager of the Mojave Air and Space Port, told SPACE.com in response to a query.

"Flight Research Tests require three things: airspace allocation, vehicle in a ready state and acceptable weather," Witt said.

While a pilot hitting the start button on SpaceShipTwo's motor is not a hosted event for press and public, Witt added, "we try to accommodate the interest of the public. We never know times or dates ? it is the nature of flight test."

According to Mojave-based company Scaled Composites, which is building SpaceShipTwo and its WhiteKnightTwo carrier plane for Virgin Galactic, the piloted craft has undergone 25 glide flight tests since October 2010. The latest SpaceShipTwo drop test on April 12 was a nitrous vent test and was labeled as powered flight number 1 "mission rehearsal."

Hybrid rocket motor 101

According to Virgin Galactic's website, SpaceShipTwo's ?hybrid motor stands apart from all-liquid and all-solid rocket engines.

"Here the fuel is in solid form and the oxidizer is a liquid. The passage of the oxidizer over the fuel is controlled by a valve which allows the motor to be throttled or shut down as required," the website explains.

Hybrid motors offer both simplicity and safety, Virgin Galactic officials added. According to the company description: "This is the type of motor that SpaceShipTwo will employ and that was used by SpaceShipOne. It means that the pilots will be able to shut down the SpaceShipTwo rocket motor at any time during its operation and glide safely back to the runway. The oxidizer is Nitrous Oxide and the fuel a rubber compound; both benign, stable as well as containing none of the toxins found in solid rocket motors."

Looking good for flight

SpaceShipTwo's hybrid motor supplier, the commercial spaceflight company Sierra Nevada Corporation (SNC), has performed over 300 hybrid rocket test firings. The company also developed the rocket engine for the first private spacecraft to reach space, SpaceShipOne, which won the $10 million Ansari X Prize in 2004.

Furthermore, Sierra Nevada is developing a similar hybrid engine to power its reusable Dream Chaser space plane, a spacecraft that is vying to provide astronaut flights for NASA.

As for the prospects of an upcoming SpaceShipTwo hybrid motor flight, Mark Sirangelo Corporate Vice President, SNC?s Space Systems, told SPACE.com: "We are looking good for the flight. Motor passed all its multiple qualification burns and tests with no issue."

Leonard David has been reporting on the space industry for more than five decades. He is former director of research for the National Commission on Space and is co-author of Buzz Aldrin's new book "Mission to Mars ? My Vision for Space Exploration" out in May from National Geographic. Follow us on?Twitter,?Facebook?and?Google+. Original article on?SPACE.com.

Copyright 2013 SPACE.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Source: http://news.yahoo.com/virgin-galactics-spaceshiptwo-1st-rocket-powered-flight-monday-153906529.html

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J. Cole's Born Sinner Tosses Old Basketball Theme Out Of Bounds

That metaphor and that storyline has really ended, Cole tells MTV News of his mixtapes and Sideline Story album.
By Nadeska Alexis

J. Cole
Photo: MTV News

Source: http://www.mtv.com/news/articles/1705462/j-cole-born-sinner-basketball-themes-over.jhtml

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92% No

All Critics (92) | Top Critics (30) | Fresh (85) | Rotten (7)

"No" is a picture that perches precariously on the cusp of a paradox.

A cunning and richly enjoyable combination of high-stakes drama and media satire from Chilean director Pablo Larrain.

A mesmerizing, realistic and often hilarious look at the politics of power and the power of ideas ...

A political drama, a personal drama, a sharp-eyed study of how the media manipulate us from all sides, No reels and ricochets with emotional force.

It's a funny look at the way the media warp public opinion, and a curiously hopeful one.

On every level, "No" leaves one with bittersweet feelings about democracy, love and the cost of compromise.

...a bitter and knowing meditation on media manipulation and political subversion.

Larrain deftly mixes social satire and historical drama.

All historical and little drama.

Larrain does a fine job of making No look and sound authentic to its time period, although the VHS-quality photography, all washed-out with colors bleeding together as camcorders did in the '80s, is an occasional irritant.

Silliness is on the side of the angels in a brilliant and highly entertaining film that's part political thriller, part media satire.

It's clear that the language of advertising has become universal, and that political commodities can be sold like soap. But toppling a dictatorship? Now there's a story.

A reflection of a moment in time, made in the image of that moment.

Bernal deftly explores the layers of the character's complexity, including his political apathy.

"No" is filmmaking of the first order.

Old technology plus the packaging of a revolution add up to a Yes

Freshens up a decades-old story with vibrant humor and a good sense of storytelling.

No continually impresses for its slyness and savvy -- rarely has such an eyesore been so worth watching.

Larrain fashions an unlikely crowd-pleaser from a historical episode that has its share of tragedy as well as triumph.

Stirring as a celebration of voter empowerment, No may also inspire pangs of wistful nostalgia.

Fascinating work from director Pablo Larrain and screenwriter Pedro Peirano, who manage to slip into the skin of a beleaguered country and detail the urgency of a revolution, sold one jingle at a time.

Swims upstream against high-definition with a defiantly lo-fi approach that's also ingeniously evocative of the historical period.

No quotes approved yet for No. Logged in users can submit quotes.

Source: http://www.rottentomatoes.com/m/no_2012/

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Revealing the scientific secrets of why people can't stop after eating one potato chip

Apr. 11, 2013 ? The scientific secrets underpinning that awful reality about potato chips -- eat one and you're apt to scarf 'em all down -- began coming out of the bag today in research presented at the 245th National Meeting & Exposition of the American Chemical Society.

Tobias Hoch, Ph.D., who conducted the study, said the results shed light on the causes of a condition called "hedonic hyperphagia" that plagues hundreds of millions of people around the world.

"That's the scientific term for 'eating to excess for pleasure, rather than hunger,'" Hoch said. "It's recreational over-eating that may occur in almost everyone at some time in life. And the chronic form is a key factor in the epidemic of overweight and obesity that here in the United States threatens health problems for two out of every three people."

The team at FAU Erlangen-Nuremberg, in Erlangen, Germany, probed the condition with an ingenious study in which scientists allowed one group of laboratory rats to feast on potato chips. Another group got bland old rat chow. Scientists then used high-tech magnetic resonance imaging (MRI) devices to peer into the rats' brains, seeking differences in activity between the rats-on-chips and the rats-on-chow.

With recent studies showing that two-thirds of Americans are obese or overweight, this kind of recreational over-eating continues to be a major problem, health care officials say.

Among the reasons why people are attracted to these foods, even on a full stomach, was suspected to be the high ratio of fats and carbohydrates, which send a pleasing message to the brain, according to the team. In the study, while rats also were fed the same mixture of fat and carbohydrates found in the chips, the animals' brains reacted much more positively to the chips.

"The effect of potato chips on brain activity, as well as feeding behavior, can only partially be explained by its fat and carbohydrate content," explained Tobias Hoch, Ph.D. "There must be something else in the chips that make them so desirable," he said.

In the study, rats were offered one out of three test foods in addition to their standard chow pellets: powdered standard animal chow, a mixture of fat and carbs, or potato chips. They ate similar amounts of the chow as well as the chips and the mixture, but the rats more actively pursued the potato chips, which can be explained only partly by the high energy content of this snack, he said. And, in fact, they were most active in general after eating the snack food.

Although carbohydrates and fats also were a source of high energy, the rats pursued the chips most actively and the standard chow least actively. This was further evidence that some ingredient in the chips was sparking more interest in the rats than the carbs and fats mixture, Hoch said.

Hoch explained that the team mapped the rats' brains using Manganese-Enhanced Magnetic Resonance Imaging (MEMRI) to monitor brain activity. They found that the reward and addiction centers in the brain recorded the most activity. But the food intake, sleep, activity and motion areas also were stimulated significantly differently by eating the potato chips.

"By contrast, significant differences in the brain activity comparing the standard chow and the fat carbohydrate group only appeared to a minor degree and matched only partly with the significant differences in the brain activities of the standard chow and potato chips group," he added.

Since chips and other foods affect the reward center in the brain, an explanation of why some people do not like snacks is that "possibly, the extent to which the brain reward system is activated in different individuals can vary depending on individual taste preferences," according to Hoch. "In some cases maybe the reward signal from the food is not strong enough to overrule the individual taste." And some people may simply have more willpower than others in choosing not to eat large quantities of snacks, he suggested.

If scientists can pinpoint the molecular triggers in snacks that stimulate the reward center in the brain, it may be possible to develop drugs or nutrients to add to foods that will help block this attraction to snacks and sweets, he said. The next project for the team, he added, is to identify these triggers. He added that MRI studies with humans are on the research agenda for the group.

On the other hand, Hoch said there is no evidence at this time that there might be a way to add ingredients to healthful, albeit rather unpopular, foods like Brussels sprouts to affect the rewards center in the brain positively.

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Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

Source: http://feeds.sciencedaily.com/~r/sciencedaily/~3/qDgUX6F_P9M/130411194252.htm

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Beavers use their noses to assess their foes

Wednesday, April 10, 2013

For territorial animals, such as beavers, "owning" a territory ensures access to food, mates and nest sites. Defending that territory can involve fights which cause injury or death. How does an animal decide whether to take on an opponent or not? A new study by Helga Tinnesand and her colleagues from the Telemark University College in Norway has found that the anal gland secretions of beavers contain information about age and social status which helps other beavers gauge their level of response to the perceived threat. The study is published online today in Springer's journal Behavioral Ecology and Sociobiology.

Beavers are monogamous, highly territorial rodents with a territory usually consisting of a dominant pair in a long-term relationship and their offspring. Offspring usually leave to find their own mates and territories at the age of two and aggressive encounters are common at this time. Beavers use anal gland secretions to mark their territories and this has been found to contain a variety of information such as animal species, subspecies, gender, individuality and kinship.

The researchers hypothesized that information about social status and age or body size may also be contained in the anal gland secretions of male beavers. This would enable established territory owners to accurately assess the level of threat posed by an intruder.

To find out whether this might be the case, anal gland secretions samples were taken from a territory owner and one of his sons, with the son being either aged 2-7 or a yearling. The researchers placed the samples in other beavers' territories within sniffing distance of each other so the beaver could detect them both at a similar time. This allowed an accurate assessment of which anal gland secretions sample the resident beavers showed the most interest in.

Tinnesand and her colleagues found that resident beavers spent more time sniffing anal gland secretions from older sons and yearlings than their fathers. They also showed a stronger physical response towards scent from older sons. The authors contend that this is because the older sons, who are sexually mature, would be more likely to get involved in a physical confrontation to obtain a territory. Yearlings are sexually immature, are usually still living in their family unit and would also be too small to constitute a real threat. Other territory owners are not seen as potential opponents, as they are already well established in their own dwellings.

The authors conclude that "resident territorial beavers showed the strongest territorial response towards older subordinate sons, suggesting that they are considered a bigger territorial threat. These results indicate that territory owners can be identified by scent."

###

Tinnesand, H.V. et al. (2013) The smell of desperadoes? Beavers distinguish between dominant and subordinate intruders. Behavioral Ecology and Sociobiology. DOI 10.1007/s00265-013-1512-y

Springer: http://www.springer.com

Thanks to Springer for this article.

This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.

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Source: http://www.labspaces.net/127674/Beavers_use_their_noses_to_assess_their_foes

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