'Supersized' monarch butterflies evolved to fly far

Monarch butterflies that migrate vast distances have grown larger bodies and wings, researchers have discovered.

These "super sized" butterflies have evolved to cope with the demands of long-distance flight.

In contrast, monarchs that live in one place all year have wings that are up to 20% smaller, report scientists in the journal Evolution.

Monarch butterflies undergo the longest recorded two-way migration of any insect.

Up to four generations of monarch butterfly complete a round trip of up to 8,000km, flying between northern US and Canada and Mexico in search of warmer temperatures.

Numerous studies have shown that species that migrate tend to evolve longer wings than those that do not.

But the new study is one of the first to show that populations within the same species can also evolve differently-shaped wings depending on their lifestyle.

"We were surprised that average wing size differences between migratory and non-migratory monarchs were so striking and consistent," says Professor Sonia Altizer of the University of Georgia, in Athens, US.

"Our findings indicate that large, elongated wings are better for monarchs that undertake long distance flights."

Despite being famous for flying such long distances, many monarch butterflies do not migrate at all.

FLIGHT OF THE MONARCHS: FIND OUT MORE Monarch butterflies navigate according to the position of the Sun, adjusting their calculations as it appears to move across the sky. This compass is located in their antennae, not their brain Of the insects, only some dragonflies may migrate further, though their exact journey has not been recorded

"When most people think about monarchs, they associate them with this incredible migration in North America, but a lot of people don't realise that monarchs also inhabit tropical locations such as Central America, the Caribbean islands, and Pacific islands, where they can breed year-round," explains Professor Altizer.

She and her colleague and husband Mr Andrew Davis, a PhD student at the University of Georgia, used digital imaging techniques to photograph and analyse the size of monarch butterflies from either wild migratory or non-migratory populations.

As well as width, the photographic technique allowed the researchers to precisely measure the surface area of each wing.

"Comparing the largest to the smallest population, wings of monarchs from eastern North America are 20% larger than those from Puerto Rico. Averaging across all populations, migratory monarchs have wings that are 14% larger than non-migratory monarchs," says Professor Altizer.

The researchers also reared monarch butterflies in the lab from different populations, to show that large wings were inherited, having a genetic basis, rather than being produced by butterflies in response to environmental factors such as warmer temperatures.

Taking flight from a wintering colony in Mexico

"That further supports the idea that differences between wild monarch populations are caused by evolution," says Professor Altizer.

"What we don't know is [exactly how much] this improves the flight performance of migratory monarchs; that would be an important next step."

Another surprise is that, although migratory monarchs from both the east and west coasts have large wings, the bodies of western monarchs are around 8% smaller than eastern monarchs.

This indicates that they might be better adapted to soaring or gliding flight as opposed to powered flight and speed, says Professor Altizer.

"A final surprise was that monarchs from Hawaii were small, but had the most angular wings," she adds.

"It would be interesting to know why that is. For example, do some monarchs in Hawaii cross the ocean to move around between islands?"

Professor Altizer and Mr Davis hope to measure differences in flight performance between individual monarchs with different wing traits, testing their speed and endurance.

Monkeys keep chatter 'short and sweet'

Monkeys avoid long-winded chatter, preferring to keep it brief, a new study suggests.

Scientists found that macaques use short calls far more often than lengthier vocalisations.

Humans also do this: the words that we use most often, such as "a", "of" and "the", do not take long to say.

The fact that we both share this vocal trait could shed more light on the origin of human language, the team writes in the journal Biology Letters.

The relationship between the length of a word and how often it is used is described by the "law of brevity".

Dr Stuart Semple, an author of the paper from Roehampton University, UK, said: "The law of brevity states that the words we use very often are very short and the words we use very rarely are long.

"If the words we used most frequently were very long, our conversations would go on forever, because you use them hundreds of times each day.

"This makes communication more efficient and this seems to hold across all languages," he added.

To find out if the urge to "keep it brief" occurred elsewhere in the animal kingdom, the researchers looked at Formosan macaque monkeys (Macaca cyclopsis) living on Mount Longevity, Taiwan.

Dr Semple said: "We know these macaques rely a great deal on vocal communication, but nobody had looked to answer this particular question."

Screams and whines

These primates have a repertoire of 35 different calls - although their precise meanings are yet to be determined - and the researchers studied the relationship between the call duration and the rate of its utterance.

Dr Semple said: "The calls they used most often - greetings, grunts and coos - are really short. This is their everyday chatter, if you like. They keep it short and sweet.

"The ones that you hear very rarely - the screams and whines - are very long.

"This is the first time we have seen this in a non-human vocal communication."

The researchers say that doing this not only saves time and energy for the macaques, but it also helps to avoid drawing too much unwanted attention from potential predators.

The similarity between humans and macaques suggested that our common ancestor could also have employed this "law of brevity", helping to reveal more about why we communicate as we do.

The next stage for the researchers is to see if any other species, including non-primates, also make these vocal short-cuts.

Charting unknown Himalayan waters

In the wake of a recent controversy over the retreat of Himalayan glaciers in which the UN's climate science body admitted that it was an error to assert that they would disappear by 2035, water availability has emerged as a key issue with even more uncertainty.

Receding Himalayan glaciers grabbed headlines because they feed major rivers in South Asia and some parts of Southeast Asia, which is home to a sizeable proportion of the planet's population.

If the glaciers significantly retreated or even disappeared, it would be an issue of life and death for many millions of people who depend on these rivers.

But now that the Intergovernmental Panel on Climate Change (IPCC) has said that it was a mistake to say the glaciers will be gone in a matter of decades, does that mean water is not a worrying issue any more?

Many scientists believe it is - even more so more given the uncertainty surrounding the future impacts of climate change in a region of not only high population, but one of high population growth.

The broad consensus is glaciers themselves are indeed retreating, although the rate of the recession may be debatable.

However, there are other climate-influenced factors that affect river flows, such as changes in precipitation, snowfall and regional temperature.

Uncertain times

"There has been too much focus on glaciers whereas there are other factors like precipitation and snowfall that affects the levels of waters in rivers downstream the eastern Himalayas," says Mats Eriksson, a senior hydrologist with Nepal-based International Centre for Integrated Mountain Development (ICIMOD), which has carried out several studies on the glaciers in the Hindu Kush Himalayas.

Without monsoon rains, young crops soon perish and die

Below the eastern part of the Himalayas are major rivers like the Ganges and the Bramhaputra, as well as their tributaries.

These are vital lifelines for millions of people in India, Bangladesh, Nepal, Bhutan and Tibet.

A recent study for the World Bank has shown that the volume of water resulting from glacial melt in Nepal makes up less than 5% of the flows of rivers leaving the country and contributing to the Ganges downstream.

"That is, about 95% or more of the river flow is the result of rain and melting seasonal snow," said report co-author Richard Armstrong, a glaciologist from the University of Colorado at Boulder in the US.

If that is true, rivers downstream of the eastern Himalayas will hardly be affected, even if the glaciers recede or disappear.

However, would the other contributing factors to the rivers' flow, such as precipitation and snowfall, remain the same in the changing climate?

No, say scientists, but whether that will lead to rise or fall of rivers' levels - and by how much and when - are the questions still waiting to be answered.

"We are seeing some changes in the monsoon," Dr Eriksson said of the seasonal precipitation system that shapes the climate in this part of the region.

"Last year, for example, the monsoon arrived one month late in Nepal and then some places saw 80mm of water in a day during the delayed rainy season.

"But there has been no consistent measurement of precipitation and temperature and there is a lack of proper studies."

'Heat trapping aerosols'

Some scientists believe absorption of solar radiation by aerosols (dust particles and carbon soots) can heat the atmosphere and accelerate regional impacts of global warming, which in turn affect water resources.

The monsoon plays a vital role in South Asian economies

William Lau, who heads the atmospheric sciences branch at Nasa's Goddard Flight Center, carried out a study in India last year and found that, as a result of aerosols, regional temperature was rising much faster than expected.

And that, he said, could influence the monsoon systems, resulting in less water availability in the region.

But Dr Armstrong said a warming climate could also mean a stronger monsoon bringing more precipitation that could increase stream flows.

"Having said that, it should be noted that future precipitation patterns predicted by climate models are highly variable and there is a very little regional agreement among the models," he said.

High variability is also an issue with the flow of rivers in the western Himalayas that do not fall within the monsoon regime.

"There is no clear-cut signal as there is a large variation between average annual flows," said Arshad Muhammad Khan, a physicist who heads the Global Change Impact Studies Centre in Pakistan.

"For example, in the Indus River, the maximum flow is twice of that of the minimum."

Unlike the Ganges, rivers like the Indus in the western part of the Himalayas are heavily dependent on glaciers, as this region does not get monsoon rains.

But even here, glacial status is not reported to be uniform.

Rising or falling flows?

Some scientists say increasing temperature has meant that glaciers don't get enough snowfall during winter and therefore river flow during summer is dwindling.

"We have seen the decline in the flow of the Indus, Chenab and Jhelum rivers," says Professor Mohammad Sultan Bhat of Kashmir University, who has conducted field studies with India's flood and irrigation department.

"We have recorded a decrease of 40% in the flow of Jhelum's tributary river… that is fed by the receding Kolahi glacier."

But, Kenneth Hewitt, a glaciologist from Canada who has been doing field studies in Pakistan's Karakoram mountains, told BBC News last October that he had seen at least half a dozen glaciers there advancing since he saw them five years ago.

With glaciers offering such complex pictures, combined with precipitation and temperature patterns becoming increasingly complicated, the region's river systems that depend on all these factors cannot be simpler.

Politics and geography, experts say, have made understanding the situation even more difficult.

"Some countries in the region are not willing to share water-related data because they regard it as confidential," said Dr Eriksson of ICIMOD.

"Since it is difficult to access them, proper studies on water availability remain a major challenge."

Nasa accepts Spirit Mars rover 'stuck for good'

The US space agency (Nasa) has admitted defeat in its battle to free the Spirit rover from its Martian sand trap.

The vehicle became stuck in soft soil back in May last year and all the efforts to extricate it have failed.

Nasa says Spirit, which landed on the Red Planet just over six years ago, will now live out its remaining days as a static science station.

The robot geologist has taken thousands of images and found evidence in Mars' rocks of a wetter, warmer past.

"Spirit has encountered a golfer's worst nightmare - the sand trap that no matter how many strokes you take, you can't get out of it," said Doug McCuistion, director of the Mars exploration programme at Nasa headquarters in Washington DC.

"But this is not a day to mourn Spirit; this is not a day of loss at this point. Spirit will continue to make contributions to science."

Like a 'polar bear'

The robot's predicament has been exacerbated by the failure of two of its six wheels. Without the additional traction, the agency now accepts that further efforts to try to escape the soft soil will be fruitless.

Instead, the mission team is concentrating on trying to get the rover tilted in a manner that will maximise the amount of sunlight falling on its solar panels during the approaching winter months. Engineers have a plan to rock the vehicle back and forth to acquire a more favourable posture.

Even so, it is likely Spirit will maintain so little energy in its batteries that it will go into hibernation, perhaps as soon as April. It will not emerge from that state until August or September, when the Sun gets high enough in the Martian sky to power up the rover's systems.

"The rover will be like a polar bear, hibernating; and it could be for many months - of the order of six months," explained John Callas, Spirit's project manager at Nasa's Jet Propulsion Laboratory.

"We have to be prepared to go through a period where we are not hearing from the rover for an extended length of time."

Far from being downbeat, Professor Steve Squyres, the rover's principal investigator, expressed some excitement at the scientific possibilities of a static vehicle.

He said the signal from a stationary Spirit could be tracked very accurately, to measure how much Mars wobbles on its axis. This could establish definitively whether the planet had a solid or a liquid core - information that scientists could use to better understand the planet's magnetic history.

This was, he said, "totally new science, never been done before - really fundamental stuff".

"This is something that I didn't really think very much about when we put a rover on the surface of Mars because we were thinking about the geology on the surface. But when you delve deeply into what this vehicle is capable of, you find new tricks; and it's something we're really excited about."

Watery past

Spirit was one of two rovers that Nasa landed on the planet in the January of 2004. The second vehicle, Opportunity, continues to roll freely on the surface.

Spirit was targeted at the 170km-wide Gusev Crater, a near-equatorial location in the southern hemisphere that orbital images had suggested might once have held a giant lake.

The investigation of this watery history got off to a slow start. Spirit initially found rocks that had undergone very limited alteration by exposure to moisture.

It was only after a 2.5km drive to nearby hills that the instrumented robot discovered rocks and soils that had experienced extensive exposure to water.

Nasa has spent more than $900m (£560m) on its Mars Exploration Rover programme, from design through to current operations. At the moment, the agency is spending about $20m a year.

The data acquired by the vehicles has generated about 100 scholarly papers, including special editions of the leading international journals Science and Nature.

Spirit became embedded in the area the mission team calls "Troy"