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The other Dodo: Extinct bird that used its wings as clubs

In the middle of the 18th Century, a large flightless bird became extinct on an Indian Ocean island.

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The extinct Dodo had a little-known relative on another island. This fascinating bird ultimately suffered the same fate as its iconic cousin, but we can reconstruct some of its biology thanks to the writings of a French explorer who studied it during his travels of the Indian Ocean.

In the middle of the 18th Century, at around the time the US was signing the declaration of independence, a large flightless bird quietly became extinct on an island in the Indian Ocean.

Today this bird is all but forgotten.

Early explorers to Rodrigues described a “Dodo” living on the tiny forested island. Males were grey-brown, and females sandy, both having strong legs and long, proud necks. But despite outward similarities to the iconic Mauritian bird, this wasn’t in fact a Dodo, but the Rodrigues solitaire.

If you look up Rodrigues in satellite images, you can see a huge ring of submerged land around the central island, over 50% of the original dry land is thought to have been lost under the waves due to sea-level rise and the island subsiding into the bedrock.

That was the stage for the evolution of the huge bird, over millions of years.

Image copyright Google Image caption The small island of Rodrigues is part of Mauritius in the Indian Ocean

It’s likely this shrinking habitat caused an increase in competition for food and territory between individuals of the species, and perhaps as a result of this, the solitaire evolved a club-like bone growth on the end of each wing.

It used this against other solitaires in territorial boxing matches. These would have been quite a sight, as the males stood almost a metre tall and weighed nearly 30kg, while the females were sandy-coloured and were half that size.

Considering its obscurity today, we have amazingly detailed descriptions of the solitaire’s behaviour.

This is because of the diary of a man named François Leguat.

He was part of a group of seven Huguenot men, who had set out from France to establish a colony of French protestant refugees on the island of Reunion.

Instead, they were marooned for two years on the island of Rodrigues from 1691 to 1693. In that time, they made the first attempts at establishing a settlement on the island.

Leguat encountered the solitaire in this time and wrote about it in his diary:

“Of all the birds in the island the most remarkable is that which goes by the name of the solitary, because it is very seldom seen in company, tho’ there are abundance of them… Its eye is black and lively, and its head without comb or cop. They never fly, their wings are too little to support the weight of their bodies; they serve only to beat themselves, and flutter when they call one another.”

Image copyright Alamy Image caption Francois Leguat was marooned on the island of Rodrigues in 1601 where he encountered, described and drew the forgotten Rodrigues solitaire

Leguat described how the birds used their short wings to make a loud rattling sound that could be heard “two hundred paces off”.

He also described the bone on their wing which grew larger at the end, forming a mass under the feathers “as big as a musket ball”.

This was used as a club-like weapon, and along with their beak, was “the chief defence of this bird”.

These are tantalising clues showing us what the species was like in life, and are some of the first detailed behavioural descriptions of any bird. It’s likely that the rattling sounds were used both to attract the attention of a mate and as a warning to same-sex rivals, but it’s highly unusual for birds to use their wings to make sounds for long-distance communication, making even more acute the loss of such a unique animal.

The solitaire would have been quite striking in life, and in his writings it is clear Leguat had some affection for them: “No one feather is straggling from the other all over their bodies, they being very careful to adjust themselves, and make them all even with their beaks. “

Today, we have numerous bone remains of the species, and these come from caves and deposits across the island.

They can be found reconstructed in museums on the island and elsewhere, but there are no records of a live specimen leaving the island, and there are no preserved skins of the animal left.

Studying these bones, scientists, including extinct bird expert Dr Julian Hume, have noticed an abundance of healed bone fractures on the sternum and wings.

Comparing these with Leguat’s descriptions, he theorises that the birds would frequently hit each other so hard with their wing-clubs that they were breaking the bones of their rivals.

So these descriptions from the marooned Huguenot are incredibly valuable, allowing us to interpret the specimens we have left.

They even show the breeding behaviour of the bird, which was likely monogamous:

“They never lay but one egg, which is much bigger than that of a goose. The male and female both cover it in their turns, and the young is not hatch’d till at seven weeks’ end: All the while they are sitting upon it, or are bringing up their young one, which is not able to provide itself in several months.”

Image copyright Getty Images Image caption The Victoria crowned pigeon is the biggest living pigeon species, closely related to the solitaire, it has a growth on the wing-wrist that it uses for defence

Monogamy and shared parental care are common in other pigeons we see today, including close living relatives of the solitaire: the nicobar pigeon and crowned pigeons.

Like these pigeons, the solitaires likely fed their chicks “pigeon milk”, a nutrient rich soup produced in the walls of the throat pouch of the parent birds.

Two parents are able to produce more food, and so a larger chick, increasing their competitive advantage against other birds in the fight for territory.

Parts of the behaviour of the solitaire described by Leguat, including the aggression, can be seen in the crowned pigeons, which will hit anything that approaches them on the nest with small bone spurs on their wing-wrists.

But in the solitaire, with its evolutionary cauldron of the shrinking island of Rodrigues, these adaptations were pushed to an extreme.

The story of the solitaire may sound like deja vu. When Leguat and his fellow castaways eventually escaped Rodrigues on a cobbled together raft, they drifted 200 miles to Mauritius, the island home of the Dodo.

This was strangely coincidental because 1693 was the very year that the Dodo is thought to have gone extinct.

Sadly, it meant that he couldn’t put his descriptive writing to work on the solitaire’s better known relative. Yet despite this, today the comically described Dodo is far better known than its elegant relative.

That’s likely because it was initially thought the solitaire was a Dodo living on Rodrigues.

Early observers on Rodrigues called the solitaire the “Rodrigues Dodo”. But the two birds were really subtly different evolutionary outcomes to similar selective pressures and, as such, represent an incredible experiment in evolution.

The two birds were, however, close cousins.

Image copyright olivierdesigns Image caption Paradise island: Rodrigues today

Both birds descended from a small species of pigeon that likely flew to the islands about 10 million years ago.

On arrival, they found an abundance of food and an absence of predators on both islands.

This was a fruit-eating pigeon’s paradise, so flying became unnecessary, and they lost the ability in favour of larger size. This is where the biology of the bird challenges some recent scientific dating of the rocks of the island.

Genetic evidence suggests a gap of around 12 million years between the last gene exchange between the Dodo and the solitaire, while some rocks dated on Rodrigues suggest the island is 1.5 million years old.

Dr Julian Hume suggests it is likely the species island-hopped down to the Mascarene islands before becoming genetically isolated due to the loss of flight on the islands some 12 million years ago, showing how the age of the island is in dispute.

Despite arising in very similar environments, the two birds evolved different adaptations for the same problems.

The Dodo, on the larger island of Mauritius, had a much larger beak with a hooked tip. Dr Hume believes that they probably used that bill to hit each other in territorial disputes.

So it’s quite possible that the Dodo was similar to the solitaire in being highly aggressive and territorial, yet lacking the specific adaptation of the rattling clubbed-wings for defence.

In fact, the Dodo’s wings were tiny and it’s thought they were used just for balance.

We have no descriptions from life of how the Dodo reproduced, but Leguat wrote that the solitaire laid a single egg on a nest raised off the ground on pine leaves.

It’s likely the Dodo behaved in a very similar way, and bird palaeontologists now think this was the Achilles heel of both species.

Mauritius had been settled by the early Portuguese and then Dutch mariners as a stop-off on their trading journeys. These groups brought rats, cats and domestic pigs with them to the island, and these were left to run feral.

Unfortunately, the large single egg of the Dodo was a perfect feast for the invading mammals, and despite their formidable ability to fight each other for territory, they had lost any instinct to protect their egg against these invaders.

Likewise the solitaire. It was protected for a hundred years by the isolation of its remote and tiny island, but, ultimately, a combination of development, rats, and cats sent the other Dodo to the same fate.

This article was inspired by research for the radio documentary ‘Can we revive extinct species like the Dodo?‘ CrowdScience was on the BBC World Service at 20.35 on Friday 1 December, or afterwards you can download the CrowdScience Podcast to listen on demand.

Science & Environment

RemoveDebris: Space junk mission prepares for launch

A spacecraft that will test the best methods to clean up space debris is nearing completion.

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A mission that will test different methods to clean up space junk is getting ready for launch.

The RemoveDebris spacecraft will attempt to snare a small satellite with a net and test whether a harpoon is an effective garbage grabber.

The probe has been assembled in Surrey and will soon be packed up ready for blast off early next year.

Scientists warn that the growing problem of space debris is putting spacecraft and astronauts at risk.

It is estimated that there are about half a million pieces of man-made rubbish orbiting the Earth, ranging from huge defunct satellites, to spent rocket boosters and nuts and bolts.

Any collisions can cause a great deal of damage, and generate even more pieces of debris.

The RemoveDebris mission is led by the Surrey Space Centre at the University of Surrey.

The assembly of the spacecraft, which is about the size of a washing machine, has taken place at Surrey Satellite Technology Ltd (SSTL) and is almost complete.

Dr Jason Forshaw, project manager on the RemoveDebris team, said: “RemoveDebris will be one of the world’s first missions in this area…. We have technologies on here that have never been demonstrated in space before.”

Image copyright Max Alexander Image caption The spacecraft has been assembled in the UK and will soon be packed up for launch

The spacecraft will first head for the International Space Station on a resupply rocket.

It will then be unpacked by astronauts before being launched from the orbiter to begin its experiments.

RemoveDebris has its own space junk on board – small satellites. It will release one of these into space and then will use a net to recapture it.

It will also fire a small harpoon at a target plate to see if the technology can accurately work in the weightless environment.

It will finally test future de-orbiting technology. As the orbiter descends to Earth it will deploy a 10sq m sail, which will change the spacecraft’s speed and ensure it burns up as it enters the atmosphere.

“It will prevent the spacecraft from becoming space junk itself,” explained Dr Forshaw.

The hope is that the technology-testing mission, which has cost £15m, will lead to larger clean-up efforts.

“People are starting to realise the significance of space junk and the problem it presents,” Dr Forshaw said.

Image copyright RemoveDebris Mission Image caption The spacecraft will establish whether a net could ensnare a small satellite

Scientists estimate that there are about 7,500 tonnes of rubbish in space and we are reaching a critical point. .

Dr Hugh Lewis, senior lecturer in aerospace engineering at the University of Southampton, said: “For some people, space debris is one of these things that is out of sight, out of mind.

“But from my perspective it is one of the worst environmental catastrophes that we have encountered.”

Even very small pieces of junk can do a great deal of damage.

Last year a loose fleck of paint is thought to have caused a crack in a window on the International Space Station.

Image copyright ESA Image caption Last year a small piece of debris chipped a window on the International Space Station

The largest pieces, though, present a pressing problem.

In 2012, a European satellite called Envisat, the size of a double decker bus, suddenly stopped working.

Since then it’s been circling the Earth, threatening other key satellites in its path.

Dr Lewis explained: “The biggest pieces of space debris have huge amounts of mass in them. If they were to be hit by something, they would release all that mass in the form of thousands and thousands of more fragments.”

More debris, could lead to more collisions – a cascade effect known as the Kessler syndrome. The fear is that space could eventually become inoperable.

“The environment provides us with really important services – like navigation, timing, communications, weather forecasting and so on,” Dr Lewis added.

“The worst case scenario is probably the loss of some vital satellites… it would mean stepping back probably decades in terms of our technology we take for granted on Earth.”

Image copyright Hugh Lewis Image caption It is estimated that there are about half a million pieces of space junk the size of a marble or larger

The European Space Agency is now looking at how larger satellites like Envisat can be destroyed – but cleaning up space piece by piece will be difficult and extremely expensive.

International space guidelines suggest that satellites should de-orbit themselves after 25 years – but it is difficult to ensure everyone plays by the rules.

Some experts are also concerned that the new push to launch small satellites (known as cubesats) in increasingly large numbers could add to the problem.

Martin Pointer from SSTL said: ” Space junk is definitely a concern for us. As more and more satellites are put up – especially some of the constellations of small satellites – the likelihood of collisions is much greater.

“I think it’s our responsibility to ensure we don’t cause more junk in space and find ways of either removing those at the end of life or for mitigating against problems.”

Follow Rebecca on Twitter.

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River departed ‘before Indus civilisation emergence’

One of the world’s earliest urban civilisations thrived in the absence of a big Himalayan river, a new study finds.

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Further light has been shed on the emergence and demise of one of the earliest urban civilisations.

The Indus society came to prominence in what is now northwest India and Pakistan some 5,300 years ago thanks in large part to the sustenance of a long-lost Himalayan river.

Or so it was thought.

New evidence now indicates this great water course had actually changed its path and disappeared before the Indus people had even settled in the region.

That they lacked the resource offered by a big, actively flowing river will come as a surprise to many; the other early urban societies of the time, in Egypt and Mesopotamia, certainly benefitted in this way.

The new research was led from the Indian Institute of Technology Kanpur and from Imperial College London.

Image copyright NASA/USGS Image caption Infrared satellite imagery picks out the distinctive sediments of the ancient channel Image copyright S.Gupta Image caption Remnant of a street in the urban centre of Kalibangan

The group’s scientists do not disagree that the Bronze Age settlements would have needed a good water supply, but argue that this requirement could have been met instead by seasonal monsoon rains that still collected and ran through the valley abandoned by the old river.

“Our paper clearly demolishes the age-old river-culture hypothesis that assumed that the disappearance of the river triggered the demise of the Harappan civilisation,” said IITK’s Prof Rajiv Sinha.

“We have argued that while large rivers have important connections with ancient societies, it is their departure that controls their stabilisation rather than their arrival.

“This has clearly been demonstrated by the large difference in age data between the demise of the river (8,000-12,000 years ago) and the peak of mature civilisation (3,000-4,000 years ago),” he told BBC News.

Prof Sinha and colleagues report their findings in this week’s Nature Communications journal.

Image copyright A.Carter/Birkbeck, University of London Image caption A collection of mineral grains that helped trace the origin of the palaeo-river

They have examined afresh the course of what is referred to as the Ghaggar-Hakra palaeo-channel, from satellite data and from field investigations.

Much of the archaeology of Indus cities, such as Kalibangan and Banawali, is scattered along this old river course.

The team shows the relict valley to be the former trace of today’s big Sutlej River, which must have abruptly changed course – as many Himalayan rivers are prone to do.

“They tend to switch on 100-year timescales,” explained Prof Sanjeev Gupta from Imperial College.

“But because the Sutlej became incised in its new course, it never switched back and that left the paleo-channel protected. That allowed, I believe, the Indus communities to flourish because they were saved from devastating floods.

“Some of their sites were actually built in the palaeo-channel itself and that makes no sense if there was a big raging Himalayan river there at the time because these people would have been wiped out.”

Image copyright S.Gupta Image caption Broken pieces of Indus pottery exposed at the surface at Kalibangan

Dating of the sediments in the palaeo-channel was done using a technique known as optically stimulated luminescence.

It reveals that the initial abandonment of the valley by the Sutlej River commenced after about 15,000 years ago, with complete “avulsion” to its present course shortly after 8,000 years ago.

Prof Gupta said the Indus people were competent engineers and so would have been able to manage their water needs, potentially even accessing underground supplies. But precisely how they operated in these circumstances of reduced water possibilities was now really a question for the archaeologists to answer, he added.

“What is clear though is that this culture had a diverse landscape and they were able to adapt to it,” he told BBC News.

Prof Rita Wright is an anthropologist at New York University and unconnected to the new research.

She said it represented a “major building block” in our understanding but stressed also that it concerned just a part of the region occupied by Harappan society.

“It is focused primarily on a single area in northwest India, [but] enormously important.

“In contrast to the Indus Valley, it presents (and provides evidence for) a very different water ecology. No denying that water was one of the major resources in the Indus, so here we have evidence for significant differences between the Indus valley alluvial plain and the Ghaggar monsoon-driven water system.”

Image copyright NASA/USGS Image caption Indus civilisation urban settlements were spread across what is now NW India and Pakistan Image copyright Spl Image caption The Harappan site at Mohenjo-daro, Pakistan. It was built on the banks of the Indus River

Prof Gupta has written a longer account of the research which can be read here.

Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos

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Trophy hunting removes ‘good genes’ and raises extinction risk

Hunting animals with the biggest horns, tusks or manes could lead to extinction, according to a study.

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Hunting animals that stand out from the crowd because of their impressive horns or lustrous manes could lead to extinction, according to a study.

Research predicts that removing even 5% of high-quality males risks wiping out the entire population, for species under stress in a changing world.

Animals prized by trophy hunters for their horns, antlers or tusks usually have the best genes, say UK scientists.

Removing these could push a species over the edge, they warn.

There is intense global debate over trophy hunting. Some argue that it should be banned or restricted, while others say it can provide valuable revenue for conservation.

Dr Rob Knell of Queen Mary, University of London, who led the research, said the assumption that so-called selective harvesting is not especially threatening to a population of animals does not take into account recent work.

”Because these high-quality males with large secondary sexual traits tend to father a high proportion of the offspring, their ‘good genes’ can spread rapidly, so populations of strongly sexually selected animals can adapt quickly to new environments,” he said.

”Removing these males reverses this effect and could have serious and unintended consequences.”

Human hunting is different from natural predation in that big-game trophy hunters target large animals, usually males.

They may be awarded prizes for killing animals with exceptionally large antlers, horns or manes.

And illegal poaching of animals such as elephants for the ivory trade also targets animals with the biggest tusks.

Using a computer simulation model, the scientists were able to predict the impact of selectively targeting males on the basis of their secondary sexual traits.

”If the population is having to adapt to a new environment and you remove even a small proportion of these high quality males, you could drive it to extinction,” said Dr Knell.

”You’re removing the genes from the population that would otherwise allow the population to adapt.”

In the past, human hunting has led to the extinction of many animals, from the zebra-like Quagga, which was once common in Southern Africa, to the Tasmanian tiger of mainland Australia and Tasmania.

Hunting is still legal in many countries; trophy hunting takes place over a larger area in Sub-Saharan Africa than is conserved in national parks.

In the US and Canada, there is also a lucrative trophy hunting industry, for the likes of deer and big-horn sheep.

Some argue that revenue from trophy hunting can support conservation efforts and local livelihoods.

The scientists said age restrictions that allow males to breed before being removed could reduce the impact of trophy hunting.

This is already recommended with some species, such as lions.

“When properly regulated trophy hunting can be a powerful force for conservation which is why we’re suggesting a different management approach as opposed to calling for a ban,” said Dr Knell.

The study is published in Proceedings of the Royal Society B: Biological Sciences.

Follow Helen on Twitter.

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