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Tuesday, February 3, 2015

Urban rabbits downsize to smaller, 'studio' warrens

European rabbits are in decline in rural areas, yet holding strong in cities. But urban living also comes with a changed lifestyle: instead of being packed into complex burrows, city rabbits seem to live a more solitary life in smaller burrows.

Madlen Ziege from the University of Frankfurt, Germany, and her colleagues studied the burrow structures of several populations of European rabbits from urban, suburban and rural sites in and around Frankfurt.

They found that the closer to the city the burrows were, the smaller, simpler and less populated they became. "I did not expect to find such a clear correlation," says Ziege.

So why are urban rabbits downsizing? For one thing, rabbits usually form larger groups when food and burrowing sites are in short supply. Surprisingly, this is not the case in cities, where rabbits may colonise parks, for example.

"Cities are providing a constant and high food supply through human waste and deliberate feeding, as well as access to vegetation cover, such as shrubs," says Ziege. "Many areas in modern cities are often structurally highly diverse and the urban rabbit population could be benefiting from this."

In contrast, she says, rural areas in Germany are now typically characterised by open landscapes with scarce vegetation cover.

Predator pressure

Living in large groups also helps rabbits conserve heat in winter, but there is less need to do that in cities where the microclimate tends to be warmer. Then there is the threat from predators.

"In rural areas, rabbits might be exposed to higher predator pressures and are therefore forced to live in large burrows," says Néstor Fernández of the Doñana Biological Station in Seville, Spain. Complex burrows with many exits help rabbits survive attack, but are clearly a major undertaking. "Building burrows requires investing a lot of energy, and individual rabbits can increase their fitness living and contributing to expand existing burrows, particularly under high predator pressure."

It's unclear whether similar patterns in burrow types will be found across Europe, but Ziege says more research could give us key insights into successfully managing rabbit populations and avoiding damage they may cause to vegetation and even buildings.

European rabbits are listed as near threatened by the IUCN, with populations in decline especially in Spain and Portugal, which they are native to.

Cities have the potential to serve as new habitats for wildlife and in the case of Germany they might even play an important role by acting as a "source" from which rabbits can recolonise rural areas, Ziege says.

Journal reference: Journal of Zoology, DOI: 10.1111/jzo.12207

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Cancer-warped skeletons imagined for building design

(Image: A project by Irene Cheng in collaboration with Dr Issam Hussain and Dr Francesco Proto)

This is what bone cancer looks like as it takes over the body – as interpreted by the artistic eye of Irene Cheng, who studies architecture at the University of Lincoln, UK.

Cheng used current knowledge about how the cancer mutates bone structure over time, acquired in a collaboration with Issam Hussain of the university's school of life sciences, to portray its extreme effects, as shown below in historical photos.

Cheng's project explores how the human body's adaptations to deformations could influence architecture. "It's not about trying to say that cancer is a good thing," she says. Rather, it's about learning from how the structure of the human body can accommodate such fast-growing, extensive changes – and what that could mean for buildings inspired by imperfection, adds Francesco Proto, who is supervising the project.

The project will culminate in April 2015 with a design for a building.

Proto, Cheng and colleagues previously won an honorary mention for their design for a new natural science museum in Berlin, Germany. That building was inspired by another extreme example of biological development: a butterfly's growth inside its cocoon.

Correction, 2 February 2015: The type of data underlying the illustration has been clarified since this article was first published.

Monday, February 2, 2015

Massive 'ocean' discovered towards Earth's core

A reservoir of water three times the volume of all the oceans has been discovered deep beneath the Earth's surface. The finding could help explain where Earth's seas came from.

The water is hidden inside a blue rock called ringwoodite that lies 700 kilometres underground in the mantle, the layer of hot rock between Earth's surface and its core.

The huge size of the reservoir throws new light on the origin of Earth's water. Some geologists think water arrived in comets as they struck the planet, but the new discovery supports an alternative idea that the oceans gradually oozed out of the interior of the early Earth.

"It's good evidence the Earth's water came from within," says Steven Jacobsen of Northwestern University in Evanston, Illinois. The hidden water could also act as a buffer for the oceans on the surface, explaining why they have stayed the same size for millions of years.

Pinging the planet

Jacobsen's team used 2000 seismometers to study the seismic waves generated by more than 500 earthquakes. These waves move throughout Earth's interior, including the core, and can be detected at the surface. "They make the Earth ring like a bell for days afterwards," says Jacobsen.

By measuring the speed of the waves at different depths, the team could figure out which types of rocks the waves were passing through. The water layer revealed itself because the waves slowed down, as it takes them longer to get through soggy rock than dry rock.

Jacobsen worked out in advance what would happen to the waves if water-containing ringwoodite was present. He grew ringwoodite in his lab, and exposed samples of it to massive pressures and temperatures matching those at 700 kilometres down.

Sure enough, they found signs of wet ringwoodite in the transition zone 700 kilometres down, which divides the upper and lower regions of the mantle. At that depth, the pressures and temperatures are just right to squeeze the water out of the ringwoodite. "It's rock with water along the boundaries between the grains, almost as if they're sweating," says Jacobsen.

Damp down there

Jacobsen's finding supports a recent study by Graham Pearson of the University of Alberta in Edmonton, Canada. Pearson studied a diamond from the transition zone that had been carried to the surface in a volcano, and found that it contained water-bearing ringwoodite, the first strong evidence that there was lots of water in the transition zone (Nature, doi.org/s6h).

"Since our initial report of hydrous ringwoodite, we've found another ringwoodite crystal, also containing water, so the evidence is now very strong," says Pearson.

So far, Jacobsen only has evidence that the watery rock sits beneath the US. He now wants to find out if it wraps around the entire planet.

"We should be grateful for this deep reservoir," says Jacobsen. "If it wasn't there, it would be on the surface of the Earth, and mountain tops would be the only land poking out."

Journal reference: Science, DOI: 10.1126/science.1253358

Cancer-warped skeletons imagined for building design

(Image: A project by Irene Cheng in collaboration with Dr Issam Hussain and Dr Francesco Proto)

This is what bone cancer looks like as it takes over the body – as interpreted by the artistic eye of Irene Cheng, who studies architecture at the University of Lincoln, UK.

Cheng analysed data from patients, acquired in a collaboration with Issam Hussain of the university's School of Life Sciences, showing how the cancer mutates bone structure over time – with extreme effects, as shown below in historical photos.

The project will culminate in April 2015 with a design for a building.

Sunday, February 1, 2015

Möbius strips of light made for the first time

Twist a two-dimensional strip of paper then tape its ends together and it transforms into a one-sided loop. It's not magic; it's a Möbius strip. These mathematical structures show up everywhere from M.C. Escher drawings to electrical circuits, but almost never in nature. Now, a team of physicists have shown for the first time that light can be coaxed into a Möbius shape.

"Light can kind of turn one-sided and single-edged under certain conditions," says Peter Banzer of the Max Planck Institute for the Science of Light in Erlangen, Germany.

Banzer and his colleagues were following up on predictions made by Isaac Freund at Bar-Ilan University in Israel, who first suggested in 2005 that light's polarisation, a property that describes how its electric field moves, could become twisted. If proved experimentally, the phenomenon could pave the way for fundamental studies of how light and matter interact, such as using light to trap tiny particles Movie Camera for biomedical purposes.

Let's twist again

In 2010, Freund proposed a way to test this: prepare two polarised beams of light and allow them to interfere with each other in a particular way. The interference will cause the polarisation to twist, forming a Möbius strip.

Banzer's team scattered two polarised green laser beams off a gold bead that was smaller than the wavelength of the light. The resulting inference introduced a polarisation pattern with either three or five twists, giving it a Möbius-like structure.

"These results are the first (experimental) proof that polarisation Möbius strips really exist, which has been a decade-long question in the community," Banzer says. "These findings emphasise the richness of light and its properties."

"The study is a brilliant tour de force at the cutting edge of optical technology," says Freund. "The real significance of this study goes far beyond verifying a particular prediction, because it demonstrates that it is possible to measure the full three-dimensional polarisation structure of light."

Journal reference: Science, DOI: 10.1126/science.1260635

Correction, 29 January 2015: When this article was first published, it said Möbius strips are one-dimensional. They have one side, but dimensions of length and width.

The world's wellness obsession has gone too far

Being urged to optimise every aspect of our lives to improve well-being is sometimes counterproductive, say two organisation researchers

Fitter, happier, more productive. If you need a wry slogan for the growing pursuit of wellness or well-being at every turn then Radiohead's lyric seems a good fit. And if there is a natural home for talking up wellness, then medicine may be it. American surgeon and writer Atul Gawande recently argued medics should not just ensure the health and survival of patients, they should also seek to enhance well-being. For Gawande, that means nothing less than "sustaining the reasons one wishes to be alive".

But medicine is far from the only walk of life to embrace this idea. It has crept into much of society. The UK's Office of National Statistics now measures national well-being to gauge policy impact. Museums justify their existence on the basis of their contribution to well-being. Each year, thousands of university students in the US sign voluntary "wellness contracts", pledging to abstain from anything vaguely unhealthy. You can even find such initiatives in prisons.

Perhaps most pervasive though are the growing number of companies, in the US and UK, that offer corporate well-being or workplace wellness programmes. In the US, around half of all employers with 50 or more staff offer such schemes.

It sounds like a good idea. But, given the enthusiasm with which they are promoted, are wellness programmes always wonderful? A body of research points to unexpected side effects and impacts that don't always match expectations.

Discussing disgust

For starters, there is evidence suggesting that paying attention to your happiness, a crucial part of well-being, can actually make you less happy. In one study, two groups watched a video that usually makes people happy – a figure skater winning a prize. Afterwards, participants filled in a questionnaire to assess happiness. The only difference was that before viewing the video, one group read a statement emphasising the importance of happiness and the other group did not. Those who did not read the statement were more happy after the video. Consciously focusing on our happiness can backfire.

An obsessive focus on wellness can also make us more judgmental, potentially worsening societal divisions. Those who highly value well-being tend to view those who don't come up to their high standards as "disgusting", even if the truth is they can't afford a personal yoga instructor or the latest lifelogging technology.

A fascinating stream of research in moral psychology has found that when feelings of disgust are triggered, we tend to rapidly make highly punitive moral judgements. For example, we are more likely to harshly judge people who "turn our stomach" and we ascribe morally unattractive traits to them, such as being lazy and untrustworthy.

While workplace programmes promise great things, they sometimes deliver disappointing results. For instance, some studies have found wellness initiatives only helped a small number of employees lose on average half a kilogram over a year. While any weight loss is not to be sniffed at, it is uncertain whether such modest results are worth the billions spent achieving them.

It is hard to argue against a healthy diet, regular exercise, not smoking and drinking in moderation. However, we say wellness can become a problem and deserves greater scrutiny when it is an unceasing command people feel they must live up to and it becomes a moral demand. When this happens, it can actually undermine the very thing it tries to promote.

Profile

André Spicer is a professor of organisational behaviour at Cass Business School, London, and Carl Cederström is associate professor in organisation theory at Stockholm University, Sweden. Their new book is The Wellness Syndrome (Polity)

Zoologger: Spider has sex, then chews off own genitals

Zoologger is our weekly column highlighting extraordinary animals – and occasionally other organisms – from around the world

Species: Herennia multipuncta (South-East Asian coin spider)
Habitat: Tree trunks and walls across tropical South-East Asia

Sex for the male coin spider resembles war more than love.

First it must mate successfully with a female four times its size that would prefer to eat it than have its babies. Then, the male must do everything possible to keep eager rivals away from the impregnated female. In the macabre world of spider sex, this means self-emasculation.

That's right: coin spiders voluntarily bite off their own genitals. This habit, practised by around 30 spider species, is not the most obvious way to improve sexual performance. But according to Matjaž Kuntner from the Slovenian Academy of Sciences and Arts, eunuchs have an advantage over their intact neighbours.

For one thing, coin spiders only produce enough sperm for a single sexual adventure in their lifetime. So getting rid of the extra baggage - the two sperm-transferring organs known as palps, which can make up around a tenth of their bodyweight – after one use makes them leaner, meaner and better suited to holding off the advances of competing males.

Keeping other males away after mating with a female is particularly important for spiders as several males can fertilise the same batch of eggs. Only by sticking like glue to its mate can a male guarantee that the next generation will carry its genes.

Extreme monogamy

"It is an extreme form of monogamy. Males put all their eggs in one basket and focus on a single female," Kuntner says.

That is what Kuntner suspected, at any rate. He has previously showed with his collaborators that another species of spider that breaks off its genitals during mating – rather than biting them off afterwards – does it to become a more effective bodyguard. So Kuntner and his team set out to discover if this even more destructive behaviour could have similar benefits.

Individual males were given seven days to mate with a female. The researchers then compared the behaviour of eunuchs with spiders that had never mated.

They found that spiders that were lacking one or both sperm organs after mating were far more feisty than the rival males. The loss of their genitals seemed to give them an extra boost – an arachnid double espresso, if you will.

The eunuchs remained around 50 per cent closer to females and attacked rivals much more aggressively than their virgin competitors. They also stayed active for around 40 per cent longer compared with non-maters when harassed by a researcher's paintbrush, presumably because they did not have large palps weighing them down. Self-emasculation, it would appear, produces better bodyguards.

Eunuch aggression

Kuntner could not discount the possibility that the act of copulation itself was responsible for giving the spiders a boost – virgin males have little reason to want to protect the female. But he thinks that self-emasculation almost certainly increases the spider's motivation and aggression. When they only have one chance, they will do whatever it takes to stay ahead.

For the female, this possessive behaviour is actually against her interests, as having multiple mates allows for more varied offspring – which in turn increases the chances of the female's genes being passed on down generations. But then, she does try to eat the male, so a lasting relationship is hardly the first thing on either spider's mind.

Kuntner thinks that this very real danger of becoming lunch rather than lover was directly responsible for the evolution of self-emasculation. Coin spiders are much better off minimising their sexual encounters with hungry females, and so a one-off mating strategy becomes the most successful option.

This adaptation in turn drove the limited sperm production and the self-emasculating behaviour – although which of these traits came first is a chicken-and-egg question.

Journal reference: Behavioral Ecology and Sociobiology, DOI: 10.1007/s00265-014-1824-6