Понеделник, 27 Май 2013 12:20

The monkey that became a midwife

Giving birth can be a wonderful, literally life-affirming event. But one extraordinary monkey has taken it to a new level; by acting as a midwife to another monkey in the act of having a baby. The incident is so rare it has never been recorded before in detail, or filmed or photographed.

Публикувана в Планета
Вторник, 21 Май 2013 17:43

Did dinosaurs exist as dwarfs?

Bizarre diminutive dinosaurs might help explain why no large dinosaurs survive today. Imagine a dinosaur; a sauropod such as a Brachiosaurus, or Diplodocus, one of the largest animals ever to roam the land. A plant-gobbling true giant of a beast, with a graceful long neck and tail. Now imagine that same dinosaur shrunk down to the size of a cow.

Публикувана в Планета
Вторник, 21 Май 2013 17:20

The secret life of T. rex

It pierced and gripped the flesh of its prey with long, dagger-like teeth, could rip through 230kg (500lbs) of meat in one bite, and, despite its enormous size, is thought to have been not much slower than 100m world recorder holder Usain Bolt over the same distance. In short, it was pretty much the most effective killing machine ever to have stomped the Earth.

It’s an image that may now need a tweak, if the conclusions of a new study are to be believed.

Bruce Rothschild, a palaeopathologist at the University of Kansas, US, who examined tooth marks made by T. rex on the bones from its prey, believes the species sometimes took time out from bloodthirsty chasing, shredding, crunching and swallowing to engage a playful side.

His analysis suggests T. rex and possibly other dinosaurs played – or engaged in behaviours for no obvious purpose other than recreation - in the same way that some modern reptiles and birds do.

Rothschild began by noting differences in previous reports of tooth-marked dinosaur bones found at feeding sites and those found on their own.

At feeding sites they were more likely to be from body parts with high meat or bone marrow content. They also exhibited similarities to the remains left by contemporary predators when eating, including skeleton dismemberment, splintered bones, spiral fractures and deep tooth marks.

In contrast tooth-marked bones found in isolation were more likely to be from body parts of little nutritional value, and the markings did not correspond to those associated with feeding.

Rothschild was especially interested in markings on ball-shaped bones called occipital condyles, which are situated at the back of the lower skull and have no marrow content.

He re-analysed a previous study of markings on eight of these from Ceratopsids, a family of dinosaurs with facial horns and neck frills including the Triceratops, and examined three others from the collections of the Royal Tyrrell Museum, in Alberta, Canada, and of the University of Kansas.

T. rex, which became extinct around 65 million years ago, is believed to be responsible for the teeth marks on these bones because there is no fossil evidence of any other predatory species that were large enough, living at the right time, and in the places the bones were found.

Rothschild said differences in the types of bones and the marks on them provided important clues to the behaviours of the dinosaurs that made them.

“If I’m eating a piece of chicken, I avoid the cartilage at the end of a bone because it’s not very tasty, and if you look at the bones found at feeding sites you see the same thing,” he said.

“But if you look at isolated bones, especially these condyles, the patterns and characteristics are completely different, and the bones are not broken up, meaning we’re looking at different behaviours.”

Rothschild then adopted the deductive reasoning approach favoured by the fictional detective Sherlock Holmes, who famously said: “When you have eliminated all which is impossible, then whatever remains, no matter how improbable, must be the truth.”

With decay and weathering already having been ruled out as the cause of the markings by previous studies, Rothschild concluded, in a paper published in the journal Ethnology, Ecology and Evolution, that: “Deductive reasoning leaves a single conclusion: the activity resulting in the tooth marks on the bones discussed herein fulfils the definition of play.”

It is believed to be the first time a researcher has proposed the idea that dinosaurs liked to play.

Such behaviour has been identified in modern reptiles including the Orinoco crocodile, several species of monitor lizards and Komodo dragons, as well as in some birds, especially birds of prey.

“I think this extends the spectrum of behaviours we can attribute to T. rex and possibly other dinosaurs,” said Rothschild. “We see playful behaviours in many animals including our pets, so it’s certainly possible.”

However Steve Brusatte, a palaeontologist at the University of Edinburgh, UK, said the study did not provide enough evidence to back up the claim.

Публикувана в Планета
Вторник, 21 Май 2013 17:08

Are dolphins cleverer than dogs?

For decades now, dolphins and dogs have vied for the title of most intelligent animal. But which is actually cleverer, and can the two even be compared?

A lone bottlenose dolphin swam into the harbour at Tory Island off the north coast of Ireland in April 2006. Her playfulness quickly earned her an appreciative following among the locals who nicknamed her Duggie. Her biggest fan was a Labrador retriever named Ben, who began swimming out to meet her on a daily basis.

During a typical encounter, Ben would paddle frantically with his tail wagging happily above the waves while Duggie blew giant bubble clouds around his canine companion. Ask most people which of the two species in this touching tale is the most intelligent and there is unlikely to be much of a contest. Dolphins - with their sociability, communication skills, playfulness and ability to understand the complex commands of trainers – are widely considered to be the second most intelligent of all animals after humans.

Yet recent years have seen a growing interest in canine cognition. Researchers at institutes such as the Duke Canine Cognition Center, North Carolina, US, and the Dog Cognition Centre at the University of Portsmouth, UK, are concluding there is far more going on in the minds of dogs than we previously thought. In fact in some cognitive tests they outwit both great apes and dolphins. So what does the latest science say? Could dogs really be the intellectual rivals of dolphins?

“There's lots of evidence that dogs are more skilled than primates at thinking about a person's communicative intentions,” says Laurie R. Santos, a psychologist at Yale University in New Haven, Connecticut, US, who studies primates and canines to shed light on the human mind. “They understand that people are trying to communicate information and use such communicative signals way better than primates do.”

Understanding us

Dogs’ abilities to comprehend human communicative signals make them one of the only animals to understand what people mean when they point at something. Even our cognitive cousins the chimpanzees don’t look past the tip of an outstretched finger when a human points them in the direction of food. A dog can use pointing as well as eye-direction cues to locate objects in the distance. These abilities are rare in the animal kingdom, although dolphins have them too, so on this test alone dogs don’t best them in a contest of wits.

There is however one cognitive feat at which dogs, somewhat unexpectedly, outshine almost every other non-human animal. Chaser, a Border Collie trained by US psychologists, is reported to be able to understand over 1,000 words used by her trainers to label her toys. When asked to fetch Bamboozle, a stuffed orange horse, she is easily able to pick it out of a lineup of other toys. She is even able to understand simple sentences consisting of a preposition, two nouns, and a verb, like “to Frisbee take ball” (take the ball to the Frisbee). With research showing the famous language-trained apes like Kanzi the Bonobo top out at vocabularies of less than half those of Chaser, and the dolphin language prodigies from the Kewalo Basin Marine Mammal Laboratory only managing about 40 words, dogs come out top when it comes to learning the meaning of individual symbols.

More than words

But there’s more to language comprehension than just vocab. Although Chaser was able to understand some basic syntax-like structure, scientists working with dolphins have succeeded in combining up to five words in one sentence containing complex concepts like “through” or “imitate.” This allows dolphins to comprehend thousands of different sentences that involve much more complex behaviour than simply “fetching.”

In one experiment, dolphins were tasked with retrieving a series of weights scattered around their pool which they had to place on top of a box in order to release a food reward. Almost immediately they hit upon the idea of collecting all of the weights at the same time instead of placing them on the box one at a time. This apparent flash of insight suggests the dolphins were planning their behaviour and turning over possible solutions in their mind’s eye; a hallmark of complex thinking.

On top of this, dolphins are among the handful of animals that understand they are looking at themselves when put in front of a mirror (others include chimpanzees, elephants, and magpies). Researchers have used the mirror self-recognition test to determine whether animals understand that they exist as separate entities in the world, with their own thoughts and minds. This level of self-awareness opens the door to greater flexibility in the face of new problems, or when trying to figure out what’s going on inside the minds of other animals. In this particular test of intelligence, dogs don’t make the grade.

At first glance then, perhaps dolphins’ superior word-crunching skills, problem solving, and self-awareness mean the gut instincts of those who assume they outsmart dogs are supported by the evidence. But relying on our gut to evaluate intelligence is problematic.

For one thing, the concept of human intelligence itself is an ill-defined amalgamation of various different cognitive skills, and efforts to evaluate it such as IQ tests are plagued by cultural bias. Is someone who is good at solving algebraic equations more intelligent than someone who can quickly determine the motivations of others? Is being able to remember facts a mark of cleverness, and is it more or less important than logical reasoning?

The difficulties such questions pose help explain why many scientists object to subjective notions of human intelligence being applied to non-human animals. Furthermore, even if it were possible to agree on a constant and universally-accepted definition of human intelligence, why should this apply to non-human animals?

Dogs have been bred to thrive in a human-generated environment; they’re particularly adept at reading human social cues, and tugging on human heart strings. When we look into their eyes and see a glimmer of intelligence, we see a reflection of our own minds. The skills at which they excel – understanding pointing or object labels – are predominately a result of humans having spent thousands of years breeding them to understand concepts that are important to us. We are the architects of their minds in many ways, and we’ve shaped them to conform to our definitions of intelligence.

Dolphins, on the other hand, have evolved their cognitive skillset in a world untouched by humans. Yet they seem intelligent to us because their complex social behaviour reminds us of ourselves. We see reflections of humanity in their playful demeanour and intricate societies. And when scientists began digging into dolphin minds, they found abilities that closely resembled that of our fellow great apes, such as mirror self-recognition – an unexpected finding for an animal that looks more like a tuna than a chimpanzee. Dolphins are perhaps the most human-like of all non-primates, which is precisely why we consider them to be intelligent.

A question of intelligence

“We know animals are shaped for certain specific kinds of cognitive abilities by biology and evolution, so sometimes it just doesn't make sense to make comparisons,” says Santos.

A dolphin’s mind evolved to produce behaviour that helps a dolphin cope with dolphin problems, including finding fish buried in the sand with echolocation, or only sleeping one half of their brain at a time so they’re able to surface for a breath. The way a dolphin thinks is a direct result of their physical, social, and ecological needs. The same is true of dogs. And since each species has its own set of needs, each species has its own unique way of thinking.

Humans have been shaped by the need to navigate complex social situations and pass along learned information to our peers. This has resulted in the evolution of language and culture, which coincided with the rise of the kind of complex critical thinking that resulted in things such as agriculture, technology and science, and ultimately space exploration and nuclear fission. Granted, these things are extraordinary by-products of the way we are able to think about information. But that doesn’t make exchanging learned information the best or most intelligent way of thinking.

A good example of why intelligence is such a problematic term in this context is to consider how different species perform in tests of object permanence. This is the ability to understand that objects continue to exist even when out of view. In the most complex version of the test, an animal is shown an object such as a ball, which is then placed inside a container and covered with a sheet. The ball is then removed from the container while it is out of view, and the now empty container is pulled from behind the sheet. If the animal has a full understanding of object permanence, it should be able to work out what happened to the ball while it was out of view, and realise that it must now be behind the sheet.

Thinking differently

Human children work this out by the age of two, and other great apes have no trouble figuring this out. Dogs and dolphins however just don’t get it. So does this mean dolphins and dogs are not intelligent enough to have a full understanding of object permanence?

It could instead be a sign that dolphins and dogs think differently rather than less intelligently about the problem. Primates are a visual species, so our ability to visually track objects is how we relate to the presence or non-presence of things around us. But dogs live in a world of smells. Their understanding of objects in the world partly involves chemical trails that linger for hours or days. Perhaps dogs fail object permanence tests because objects that are no longer visually there might have a continued chemical presence, which makes it difficult for dogs to figure out what the researchers are asking of them.

Dolphins have visual systems that are similar to primates in many ways, but they also have an extra sense that renders object permanence a potentially troublesome concept. They are able to see through some materials by penetrating them with sound waves. So a fish hiding in the sand might be invisible to the naked eye, but be detectable to an echolocating dolphin. Perhaps objects rarely – if ever – simply disappear for dolphins.

It might then be that a dolphin’s brain cannot easily comprehend the idea of an object not being either visually or echoically accessible. Or maybe they have a totally different understanding of how objects move because they live in water where gravity sometimes plays second fiddle to buoyancy. A recent study found that dolphins can indeed pass the invisible displacement test using 2D objects projected on a screen. Scientists now think that dolphins were flummoxed in earlier studies by the idea of an object disappearing into a container – a scenario that almost never occurs in the wild. They seem to cope better with objects that pass behind – as opposed to into – a visual barrier.

It’s interesting to ask why dogs and dolphins have a hard time with object permanence, just as it’s interesting to wonder what Duggie and Ben’s friendship might tell us about the way dolphins and dogs think about the world. But ultimately, once subjective, human-centric value judgments are stripped out of the concept of intelligence, it makes about as much sense to ask which animal is cleverer as it does to ask whether a hammer or a screwdriver is the better tool. The answer is it depends on the task at hand.

Dr Justin Gregg is a research associate at the Dolphin Communication Project, and co-editor at the academic journal Aquatic Mammals.

Публикувана в Планета
Вторник, 21 Май 2013 16:59

Can frogs return from the dead?

For me, it all started with a small black harlequin frog, a creature no bigger than my thumb. Named after the local word for sadness, the frog was special, because it appeared to no longer exist.

It was an emblem of all the frogs that had disappeared from bubbling streams and cool forests of South America and beyond, as hundreds of species of amphibian succumbed the world over to a fungus responsible for the greatest disease-caused loss of biodiversity in human history.

I’d set off to scour a high mountain pass in southern Ecuador, seeking signs of the frog’s survival. I never did find it. The following year a team of local scientists returned to resume the search, and they made an astonishing rediscovery – of the black harlequin, clinging to life. But I had taken my first step of what would become a global quest for answers.

The black harlequin frog was not the only species to make a comeback - in Costa Rica and Australia frogs were also reappearing years, sometimes decades after they were thought to have vanished. What were these survivors among the carnage telling us? What clues did they hold that could help us stem the hemorrhaging of life from our planet?

In 2010 I decided to try to find out. As Director of the amphibian programme at Conservation International I was uniquely positioned to spearhead the largest coordinated global search for species lost to science. Over several months more than 120 scientists were deployed in 21 countries in search of frogs and salamanders that had not been seen for at least 15 years. Some had not been sighted for 160 years. The stories, discoveries and rediscoveries that they brought home captivated a global audience and shed new light on the biggest loss of biodiversity in 65 million years.

But first let’s address the question on so many lips: so what if frogs are disappearing?

Amazing creatures

To convey just why I care, let me travel back 30 years. As a young boy growing up in Scotland, long before I knew that amphibians were in trouble, frogs and newts granted me an entry point to nature – an invitation to study and understand my own little corner of a vast world. They opened my mind to scientific inquiry and inspired curiosity.

Every spring I would arrive at our neighbourhood pond to collect spawn and transfer several black pearls encased in jelly to a tank in my bedroom, where I would nurture rounded tadpoles as they floated belly up, smiling at me as they devoured fish flakes hovering like sheets of ice on the water’s surface. As they sprouted legs, hind ones first, and their tails began to shrink like a melting ice lolly, I would release the froglets into the tangle of grass next to the pond to embark on their life on land, and each and every time I would wonder: how do they do that?

Watching black eggs transform into tadpoles and then froglets was like bearing witness to evolution – the great exodus of life from water to land - in miniature. Frogs are the largest animals to undergo such a dramatic metamorphosis.

Just when I think I am getting a handle on the diversity of colours, shapes, sizes and behaviours, another frog, salamander or caecilian (a kind of long, worm-like amphibian that lives underground) comes along that blows my mind.

I remember vividly the first time I learned about the axolotl – the Peter Pan of the animal world – a salamander that spends its entire life (and even breeds) in the larval form, with feathery gills billowing from either side of its head. From browns to whites and pinks, their ability to exist in such an eclectic array of colour forms is a subject of research, as is their remarkable ability to regenerate limbs.

While many more of us are drawn to the furry and the feathered than the scaly and moist, frogs and salamanders have always resonated with me because they extended an invitation to develop a personal relationship with them from an early age.

Had I raised a panda cub in my wardrobe my life may have played out differently. But amphibians were simply more tightly woven into my life, as they are into the lives of many people around the world. To some they are consumers of crop pests or of mosquitoes, to others they are a source of medicinal compounds. But to many they represent a source of wonder – and thankfully, I am not alone.

The late Wangari Maathai, a Kenyan social and environmental activist who was awarded the Nobel Peace Prize of 2004, made a special place for frogs in her acceptance speech when she spoke of growing up in rural Kenya; “I saw thousands of tadpoles: black, energetic and wriggling through the clear water against the background of the brown earth. This is the world I inherited from my parents.” Protecting frogs is an investment in the future of our children and children’s children.

Back from the dead

As a child I never imagined that frogs would, or could, suddenly disappear. It was a couple of decades later when I really became aware that frogs and salamanders were in trouble, and that understanding deeply saddened me.

After gaining a PhD (studying frogs, of course), I joined Conservation International in the hope that I could play my part in protecting these underappreciated creatures. Amid stories of loss, I found myself increasingly interested in an emerging phenomenon that provided a glimmer of hope: the reappearance of frogs that had been given up as extinct.

The first Lazarus frog that captured my imagination was the Variable Harlequin Frog of Costa Rica – a beautiful animal with lemon yellow to flame-red against mottled black (their name came from the variability in their colouration), that disappeared suddenly and rapidly throughout Costa Rica and Panama in the 1990s. After years without trace the species was considered to be extinct.

But then, in 2003, a young herpetologist by the name of Justin Yeager was doing a study abroad program on poison dart frogs in Costa Rica, when his guide started to talk to him about a yellow and black frog living in the rainforest. You must be mistaken, Yeager had told the guide, who was clearly describing the Variable Harlequin Frog. Two days later, the guide appeared holding a pair of the very frogs that were believed extinct.

Further surprise reappearances over the following years, including the black harlequin frog in Ecuador, a couple of species from Costa Rica and a couple of species in Australia, suggesting that the Variable Harlequin Frog was not a unique case. And so the question started to grow in my mind: how many frogs were out there, waiting to be rediscovered?

The quest begins

Early in 2010, the seed was planted for a global hunt for lost species. First, I solicited the help of experts around the world to compile a list of frogs, salamanders and caecilians that had not been seen in at least a decade and were feared extinct. As the list grew to 100, I produced a top ten “Most Wanted” poster of the most iconic species. We rallied some funding and within a few months more than 120 researchers in 21 countries were on a quest to find some of the most elusive creatures on earth.

Following the launch of the campaign, my own journey in search of lost species took me first to the steamy jungles of Colombia – preserved by years of armed conflict – to search for the Mesopotamia Beaked Toad, one of our top ten Most Wanted and last seen in 1914.

In my new book, In Search of Lost Frogs, I describe how the hunt proved to be both tragic and joyous.

For three days we searched, without success. To increase our chances of discovering the toad, we then pushed further into uncharted forest, plunging into the steamy depths of the Chocó, one of the wettest places on earth, where steam rises from thick jungle undulating as far as the eye can see. The rugged terrain and 16 to 18 metres of rainfall a year prevented even the conquistadores from settling here.

As night fell, we were greeted by a chorus of frogs, a soundscape of chirps and wheeps. We homed in on the calls of glass frogs with translucent bellies, finding many of them up the first river - a good sign that the forests are healthy, for these amphibians are among the most sensitive to change.

The following day and night became a blur of frogs of all shapes and sizes. Large tree frogs clasped thick stems with toes separated by a shock of red webbing, and small rocket frogs with red thighs skipped through the shallows. Masked treefrogs peered from behind elephant ear leaves, and splendid poison dart frogs with yellow splashed on black induced “oohs” and “aahs” from the team. A more colourful assortment of frogs would be hard to imagine.

We never did find the Mesopotamia Beaked Toad, however. The last embers of hope died with the final day of the search, as the light was sucked from the forest, the last leaf had been turned and the mud had been kicked off the boots. The realisation that you are not going to find a lost species seeps in imperceptibly, like cold into tired muscles.

But we did get a big, and extremely happier, surprise. During the search, one of the team found another species of beaked toad – one entirely new to science. In the search for one lost beaked toad we had found another, new one.

Musical frogs and tiny frogs

After Colombia I swapped lush jungle for the remote limestone peaks of southwest Haiti, whose cloud forests boast more than a dozen frogs found nowhere else in the world. Most of these had not been seen in close to two decades.

A week spent scouring the forests during hurricane season resulted in six rediscoveries, including Mozart’s Frog (named because an audiospectogram of its call resembled the musical notes of a Mozart symphony), the Ventriloqual Frog (named because – yup, it can throw its voice) and one of the smallest frogs in the world, the miniscule Macaya Breast-spot Frog. The frogs became beacons of hope for the preservation of the last remnants of cloud forest.

My journey in search of lost frogs then led me to India, where I rediscovered a small frog that had not been seen in 30 years inside a rubbish bin in a tiger reserve, Israel, to try to find the Hula Painted Frog which had reappeared after being missing for 55 years, and Costa Rica, on a quest to find and photograph the iconic Variable Harlequin Frog.

Overall, the Search for Lost Frogs produced over a dozen rediscoveries of species thought to be extinct.

These Lazarus frogs have provided an opportunity for scientists to investigate what sets them apart from all those that died around them, feeding into efforts to combat a fungal disease that has caused the biggest loss of biodiversity in human history.

Some frogs survived by raising their temperature to fight the fungus, others seemed to have moved to more conducive habitats. But most promising is the discovery on the skin of some survivors of beneficial bacteria capable of staving off infection. By augmenting the skin of other frogs with these bacteria – in the same way that we augment our stomach bacteria with probiotic yogurt – we may, so the thinking goes, be able to give Lazarus frogs a second chance.

Beyond the science, the Search for Lost Frogs achieved something that I had previously failed to do in my attempts to communicate the plight of amphibians – it captured the imagination of the global public.

The way in which it did so opened my eyes to the reality that the way in which we deliver information is as important as the information itself.

The Search for Lost Frogs drew people in through stories of discovery, disappointment, perseverance and ultimately of hope, delivered in a package decorated with striking photographs. It opened the eyes of battle-weary adults to the wonder and awe of the natural world, and reminded us that the world still holds secrets.

By speaking to hearts – and not just minds – around the world, the Search for Lost Frogs continues to grow our army of supporters and give many frogs a second chance.

Публикувана в Планета
Вторник, 21 Май 2013 16:48

How do you entertain a fish?

On a cloudy day a few years ago, Heikki Hirvonen sat on the banks of the River Varisjoki. As he watched its high, fast water sluicing through Finland’s remote northern spruce forest, his mind drifted back to the year before, when the river was almost dry. He thought of the juvenile salmon he’d then released into a nearby stream, hoping they would one day return from the ocean to spawn.

And then he did something remarkable. He stopped thinking like a human, and began to think like a fish.

By looking at the world around him as a fish might, Hirvonen, a behavioural ecologist at the University of Helsinki in Finland, had come to realise that the salmon he bred lived, until their release, pretty dull lives. Raised in barren tanks, they swam in water that flowed at a constant, sluggish rate. They ate the same food pellets, at the same time, each day.

Having so little to do, he pondered how woefully unprepared they must be for the wild future that awaited them; a world of turbulent, ever-changing rivers and oceans, where young fish must learn to eat and not be eaten, where they must learn the deadly art of survival.

Hirvonen, like other scientists, has come to question how fish are raised in hatcheries. Every year, all around the world, billions of these hatchery fish are released into the wild to bolster dwindling wild populations. Typically, less than seven of every 100 survive.

Could that be, some of these scientists are increasingly wondering, because these fish learn so little during their upbringing? Do young fish need to be motivated and intellectually stimulated?

In short, do they need to be entertained?

And could enriching their lives, and teaching them new skills, be key to the survivorship of countless individuals, and even the very future of a few endangered species?

Fish aren’t stupid

It is unsurprising that people forget to think as a fish.

Fish are hard to relate to, says Culum Brown, a childhood snorkeler who grew up to raise and study fish and their behaviour at his laboratory at Macquarie University in Sydney, Australia. They aren’t expressive, we hear little of the noise they make and can’t read their faces. Such prejudice has limited the amount of money spent on fish conservation, and led to a dearth of research into fish cognition, perhaps explaining why we tend to think of fish as stupid, citing anecdotal research that they have no more than a three-second memory.

“They’re a lot smarter than that,” says Victoria Braithwaite, a biologist at The Pennsylvania State University in University Park, Pennsylvania, US. Research is slowly revealing that fish can make friends and use them as allies when hunting, engage in tool use, a trait once attributed only to “higher” species such as humans and birds, and store information for several days or more. Fish from coral reefs and rocky shores that have to actively hunt for a living tend to be more intelligent than fish from duller environments, Brown adds.

Yet despite mounting evidence that captive fish are capable of learning basic life skills before entering the wild, hatcheries across the globe continue to measure success in the number of fish released. “Every year in Australia, the fisheries minister gets up and says something like, ‘This year, we released 15 million fish from hatcheries,’” Brown says. “Everyone thinks, ‘Wow’.” But it’s the number that survive that counts. And that’s where learning how to entertain fish comes into its own.

A tale of two fish

Anne Gro Vea Salvanes, a behavioural ecologist at the University of Bergen in Norway, tells a tale of two fish she has studied.

One juvenile salmon navigates a maze with four cup-shaped exits on one side. Three exits lead to a dead end. The little fish swims into one cup, hits a dead end, and tries another cup before successfully escaping (see video. Credit: Anne Gro Vea Salvanes et al). A second juvenile fish swims into the same dead end repeatedly, never to escape (see second video. Credit: Anne Gro Vea Salvanes et al). The clever fish, Salvanes says, was raised in a hatchery with rocks, pebbles, and plastic plants, adornments that provide mental stimulation. The dumb fish was raised in a bare tank, the usual environment for billions of hatchery fish.

When Salvanes and her colleagues examined the fishes’ brains, they found that the fish raised with adornments had increased brain activity in a region linked to spatial learning.

It would seem simple then, to embellish fish tanks the world over. But adding rocks and plants has a drawback - they get covered in food pellets and fish excrement, making tanks difficult to clean and encouraging bacteria to grow. That raises the costs of rearing fish, damaging the profits of commercial hatcheries.

Some researchers have started experimenting with items that can be easily removed and cleaned or discarded.

Joacim Näslund, a graduate student at the University of Gothenberg in Sweden, adorned tanks at a hatchery in Norway with plastic pipes and shredded plastic bags.

Публикувана в Планета
Понеделник, 20 Май 2013 13:04

Corals come back from the dead

Last year, marine biologist Peter Mumby took a dive into the Rangiroa lagoon, in French Polynesia. What he saw shocked him so much he thought he might be lost.

He’d expected to be surrounded by death, by a reef of dying coral whose skeletons were slowly crumbling into the sea. Instead, majestic, olive-green Porites corals, the size of large hippos, carpeted the sea floor, providing a playground for parrotfishes and the occasional shark that weaved between the cauliflower-shaped giants.

“I was absolutely astonished and delighted,” says Mumby, a professor at the Marine Spatial Ecology Lab of the University of Queensland, Australia.

He had good reason to be. In 1998, a heatwave, which raised ocean temperatures, had caused corals worldwide to go a deathly white - a process called bleaching - and die.

When Mumby had visited Tivaru on the Rangiroa lagoon six months later, he’d found a vast majority of the region’s prolific Porites coral, normally the hardiest of coral species, had followed suit. Based on the known growing rates for the species, Mumby predicted it would take the Porites nearly 100 years to recover, not 15.

“Our projections were completely wrong,” he says. “Sometimes it is really nice to be proven wrong as a scientist, and this was a perfect example of that.”

Mumby’s discovery marks a high point spot in the scientific community’s research into, and gloomy prognosis for, coral reefs around the world. The single bleaching event of 1998 killed nearly 16% of the world’s corals.

The damage is caused when the heat forces the corals to expel symbiotic algae living in their tissues, turning the corals white. Corals usually rely on the algae to convert sunlight to energy.

With ocean temperatures expected to increase an additional 1 to 2 degrees Celsius over the next century, scientists estimate such disasters to become more frequent. Eventually, they predict the majority of the world’s corals will bleach and die.

But some corals aren’t complying with their death sentence.

The 1998 heatwave also bleached and killed corals on the outer exposed reefs of Palau in the western Pacific Ocean. But by 2005 they’d made a full recovery.

James Gilmour, a coral ecologist at the Australian Institute of Marine Science, in Crawley, Western Australia, also watched his research site, Scott Reef, in the Kimberly region of northwestern Australia, make a robust recovery from the 1998 heatwave. The site has since survived a category-five cyclone and further bleaching events in 2010 and 2011 (see video below of a bleached Scott Reef credit: J. Gilmour).

“We are learning rapidly about coral reefs that there is a lot that we didn't know,” Gilmour says.

Mumby concurs. “It makes us realise that some corals have a number of strategies to cope with stress that we don't understand very well,” he says. “That is good news and we now need to understand exactly how they do it.”

Rising from the ashes

“The Phoenix Effect” is a term coined in 1992 by David Krupp, a coral researcher based in Hawaii. He used it to describe how some corals can spring back to life from an almost imperceptible fragment of themselves.

When Mumby first surveyed the corals in the Rangiroa lagoon he noted something unusual. Some Porites corals, while appearing dead, had a few small slivers of live tissue on them “about the width of a finger and maybe as long as a finger.”

These surviving strips of coral lay deep in shadowy recesses, so they suffered less from the combined effects of heat and sunlight. It could be that these tiny shards of life were able to regrow and rebuild the immense Porites once conditions became more normal, Mumby says.

But so fast?

Starting from scratch a Porites coral starts off the size of a marble and grows like an onion, depositing a mere centimetre or so of new skeleton each year on its surface. That means it usually takes nearly 600 years to reach a height of five metres and a width of seven metres.

But the regrowing corals have a head start, provided by the skeleton left behind by the corals that have died. “The actual body of the coral, which is a soft gelatinous bit of stuff, a bit like a sea anemone, doesn't have to build any skeleton,” Mumby says. “It just has to shoot across the existing skeleton.”

He also has another theory to explain the Porites corals’ stunning recovery; they may not have been as dead as first thought.

These species have a thick body that extends more than a centimetre into the skeleton. “It is not impossible that deeper into that skeleton there is still living coral even though it wasn't extending back up to the surface.” This “inner coral” may have taken more than a year to recover. But once it did, it could quickly grow back to the surface and across the skeleton.

Millions of tiny survivors

At Palau in the western Pacific, a survey completed just three years after the 1998 bleaching event showed more coral had recovered on reefs within protected bays and on deep slopes.

Scientists suggest this is because heat and light serve as a double-whammy to coral health and corals that hang out in shady zones will escape the scorching combination, upping the chances that remnants will survive.

Seven years after the bleaching event, some reefs had regained nearly 40 per cent of their corals, with two species of plate-like acroporid coral, A. digitifera and A. hyacinthus, particularly prevalent. “We sampled plating coral colonies there a few years ago and found them to be pool-table size,” says Stephen Palumbi, Director of Stanford University's Hopkins Marine Station, in Pacific Grove, California, US.

On Scott Reef, the speed and extent of the recovery were influenced by environmental factors such as water quality and the number of herbivores present, according to James Gilmour’s research.

Polluted water and high nutrients encourage harmful algae, while herbivores, such as urchins or fish, keep such algae in check. When corals’ surfaces are clear from algal growth, new baby corals can then settle on them and grow. “So you see quite high survival and quite high growth under natural conditions,” Gilmour says.

Early research on coral degradation in the Caribbean, where herbivore numbers have fallen, determined that new coral roots had very low survival rates. “They struggled to settle and they got outcompeted by the algae,” Gilmour says, “and consequently there was this belief that the tiniest corals had very low survival rates.”

But Gilmour’s findings contradicted this assumption. Because the local conditions at Scott Reef were so good, the algae didn’t edge out the tiny corals and they survived as well as the adults. Corals produce millions of eggs but typically very few make it to adulthood.

“But the real surprise was after the bleaching we’d find millions and millions of surviving little corals,” Gilmour says, “and then they reproduced and then the recovery happened quite quickly.”

Better understanding the lifecycles of corals might provide insights into the resilience of coral reefs. “What you see on the reef is a consequence of how many new corals were born, how they competed, how they survived,” he says. The same could be said of a reef that bounces back.

“What we didn't know is that there are these tiny, tiny bits of tissue remaining and that tissue can grow quite quickly,” Gilmour says. “All of a sudden, you might see coral following a disturbance, when you thought it was 100 per cent dead.”

Environmental conditions influence whether a bleached or damaged reef will survive or crumble. But “if conditions are good after, then these little remaining bits can really recover quite quickly,” Gilmour says.

Quest to save the corals

The rebirth of the Porites corals in French Polynesia had shocked Peter Mumby. But the extent of their death in 1998 surprised him too. These hardy corals typically prove resistant to heat stress: when a bleaching event hits Porites, they may go white but then they’ll typically return to normal within a few weeks. The 1998 heatwave served such a bitter blow, however, that even Porites corals suffered.

“When we found that a quarter of the [Porites] corals had died entirely, we concluded that this was the most severe impact on these corals that anyone had ever observed,” Mumby says.

So in a quest to save coral species around the world, scientists are not just looking at how corals recover, but what makes some of them able to withstand high ocean temperatures to begin with.

Using Ofu Island in American Samoa as his laboratory, Palumbi is investigating which populations within a species, even which individual corals within a population, are heat resistant, and why.

“If corals can adapt their own physiology to adjust to heat, does that mean they have a little way of responding individually to gradually increasing ocean temperatures?” Palumbi says. “And if they do, then that changes how we look at the future. Maybe that gives them a bit of extra time before things get dramatically awful.”

Scientists might exploit this and protect specific regions of reefs that are home to the most heat resistant corals, similar to the corals on Ofu Island. They can also try to limit the impacts of pollution and overfishing, in a bid to create healthy protected reefs that will survive 50 years hence.

They could even transplant heat-resistant corals to other reefs. Palumbi is trying this experiment, testing to see if corals retain their resistance when moved. Early results suggest that about half do.

“Part of our job as conservation biologists is to take a triage approach, letting us buy some time to save as much as possible now,” Palumbi says. “So when we come to grips with climate change, which we will have to do, then there is something to grow reefs back from.”

Although ambitious bioengineers may one day find ways of propagating corals that could resist bleaching altogether, Palumbi isn’t taking that approach. “We prefer to let the corals do the seeding themselves because they have a quarter of a billion years doing that and they are good at it,” he says.

Over that very long time, corals have evolved, partially dying off and rising again like a phoenix, producing a group of organisms that seem able to cling to life in ways that science still does not understand. And comprehending why corals bounce back, or resist bleaching in the first place, could help preserve whole corals species and create a legacy for the future.

If a similar bleaching event were to happen now in Tivaru, Mumby says he’d immediately visit where Porites bleached and core out sections of the coral to see if any living tissue still exists inside. “This is one of the great things about ecosystems - they have a natural ability to surprise us.”

Mumby has no illusions that corals face anything but a challenging future. Although the Porites at Tivaru look to have recovered, telltale signs of stress remain on the reef, he says.

But when he investigated the site last year, the underwater scene ignited a slim spark of hope. “It just made me feel that maybe, just maybe, it is not going to be as bad as we think,” Mumby says.

Публикувана в Планета
Понеделник, 20 Май 2013 12:07

Octopus that strangled its lover

Octopuses make for unusual lovers. To mate successfully, a male octopus must approach a female, and gently probe her with a single arm. He may grab her, but carefully, before inserting his arm up into her body, injecting packets of sperm. After sex, a male octopus is probably not expecting to be probed by a female. He is not expecting to feel the brush of her arm, as it maliciously coils around his body. He is not expecting her to squeeze, cutting off the supply of water to his gills. He is not expecting to be held in a deadly, suffocating embrace. Yet that exact fate befell one male common reef octopus swimming in the seas of Fiabacet Island, Indonesia. In an extraordinary act, witnessed by scientists, the male octopus was strangled to death by his female lover, just moments after having mated with her. The behaviour is so rarely seen that the incident, and a couple of others like it, may change our understanding of octopus behaviour.

Octopuses have long been considered relatively gentle creatures. Though they use their eight arms to catch prey, which is devoured using a large, sharp beak in their mouths, they tend to avoid aggression. Octopuses are more likely to retreat from a threat, such as a predator, than to fight, and they tend to shy away from most confrontations with other animals, says Christine Huffard, a marine biologist at the Monterey Bay Aquarium Research Institute, at, Moss Landing, California, US. In fact, octopuses spend most of their time, and use a variety of strategies, trying not to be seen. “Being overly aggressive to other animals on the sea floor would defy that strategy by attracting attention,” she says.

They can become aggressive with each other, particularly when fighting over food, dens, and mates. But they tend to grapple, pushing at each other, and pulling at their respective arms. They weren’t thought to be constrictors, strangling each other as a snake might suffocate its prey. However, Christine Huffard and colleagues have witnessed two separate incidents of octopuses doing just that in the wild. The first occurred during a dive within 10 metres of water off Fiabacet Island, when the researchers came upon a female common reef octopus sitting exposed on a coral reef outside her den. Nearby, sat a slightly smaller male. For 15 minutes the two animals mated. Then the female unexpectedly lunged forward, and with two arms, grabbed the male around his mantle, a structure octopuses use as a respiratory chamber to pass water through a funnel and across their gills. She dragged the male towards her. After two minutes, she then wrapped an arm around the opening to the mantle, and squeezed tight. After another two minutes, the male stopped moving. The female then enveloped the male’s body with her own and dragged him into her den, where the scientists presume she ate him.

Then, divers observed a wonderpus octopus repeatedly approach and chase a mimic octopus foraging for food. The encounter seemed to end peacefully, but when reviewing images taken of the event, the scientists realised that the wonderpus octopus had actually wrapped an arm around the mantle of its rival, trying to strangle it. Both incidents are reminiscent of another witnessed in 2007, when scientists observed one merciless female spend two days cannibalising a small male, having previously attacked and suffocated him after having mated with him 13 times. For now, scientists do not know how common constricting might be in these or other octopuses in the wild. But such deadly struggles do appear to make octopuses unique; as the first invertebrates known to aggressively grasp and kill another animal using constricting. Constricting might also prevent the subordinate octopus repelling the attack by expelling ink, which is also released through the funnel in the mantle. Expelling ink is a defensive tactic usually used to repel predators, as it clouds the water, and potentially contains irritating chemicals. For zoologist Mark Elgar of the University of Melbourne, Australia, an expert on invertebrate mating behaviour, the actions of the female octopuses make sense, given their eight-pronged anatomy. “The specific method by which the female octopus captures and kills her mate – constricting him with her many legs – is novel, but only because this can be done only by an octopus,” says Elgar. Huffard agrees. Octopuses are a type of mollusc known as a cephalopod, a group that also includes squid. “This unique anatomy opens doors to many behaviours that are unavailable to other molluscs, constricting being just one of them.” Other invertebrates, such as insects and nudibranchs, are known to engage in sexual cannibalism. Female black widows and praying mantis are notorious for killing and eating males before, during or after sex. And similarly gruesome attacks have been observed in chironomid flies. A female chironomid uses her mouthparts to pierce the head of her male mate and, after extracting his body fluids as he transfers sperm to her, carries his desiccated carcass against her body for days. Males are thought to be eaten as, once they have mated, they can be a valuable source of food. Male Argiope spiders, for example, tend to be consumed by the female after their second insemination. For Huffard, this is a subject ripe for research: “People have studied that topic extensively in arthropods, especially arachnids, but not in rigorous studies using cephalopods.” “The more we get into the water and watch animals quietly from a distance, the more likely we might be to understand one day why female cephalopods might kill their mate,” she says.

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