Traffic Jams Lend Insight Into Emperor Penguin Huddle

Emperor penguins maintain the tight huddle that protects them from the harsh conditions of an Antarctic winter with stop-and-go movements like cars in a traffic jam, a new study has shown. (Credit: Daniel Zitterbart)

 

Dec. 16, 2013 — Emperor penguins maintain the tight huddle that protects them from the harsh conditions of an Antarctic winter with stop-and-go movements like cars in a traffic jam, a new study has shown.

 

By using a mathematical model that recreated the positions, movements and interactions of individual penguins in a huddle, researchers have revealed that an individual penguin only needs to move 2 cm in any direction for its neighbour to react and also perform a step to stay close to it. 

 

These movements then flow through the entire huddle like a travelling wave and play a vital role in keeping the huddle as dense as possible to protect the penguins from the cold; the wave also helps smaller huddles merge into larger ones.

The results have been published today, 17 December, in the Institute of Physics and German Physical Society's New Journal of Physics and are accompanied by a video abstract. An advanced set of videos can be viewed here -- http://www.youtube.com/playlist?list=PLx-sGUtkV82eZJHWNyJ4uxPCBtb1GlWgw
In a previous study, the same group of researchers studied time-lapse videos and showed that instead of remaining static, penguins in a huddle actually move every 30-60 seconds, causing surrounding penguins to move with them.

Co-author of the study Daniel Zitterbart, from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), said: "Our previous study showed how penguins use travelling waves to allow movement in a densely packed huddle, but we had no explanation as to how these waves propagate and how they are triggered."

To investigate this, the researchers used a mathematical model, which has previously been used to study traffic jams, and compared the results with an analysis of video recordings of a real-life penguin huddle.
Unlike a traffic jam, the researchers found that the waves of movements in a penguin huddle can originate from any single penguin and can propagate in any direction as soon as a sufficient gap, known as a "threshold distance," develops between two penguins.

This threshold distance was estimated to be around 2 cm, which is twice the thickness of a penguin's compressive feather layer, suggesting the penguins touch each other only slightly when standing in a huddle without compressing the feather layer so as to maximize huddle density without compromising their own insulation.

"We were really surprised that a travelling wave can be triggered by any penguin in a huddle, rather than penguins on the outside trying to push in," continued Zitterbart. "We also found it amazing how two waves, if triggered shortly after each other, merged instead of passing one another, making sure the huddle remains compact."

The emperor penguin is the only vertebrate species that breeds during the severe conditions of the Antarctic winter. At this time of year temperatures can get as low as -50°C and winds can reach speeds of up to 200 km/h.

To cope with the harsh conditions, the male penguins form dense huddles, often consisting of thousands of individuals, to maintain their body temperatures. Unlike other species of penguin, the male emperors are solely responsible for incubating their single egg during the winter, covering it in an abdominal pouch above their feet while the female returns to sea to feed.

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Story Source:

The above story is based on materials provided by Institute of Physics, via EurekAlert!, a service of AAAS.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

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Journal Reference:

1. R C Gerum, B Fabry, C Metzner, M Beaulieu, A Ancel, D P Zitterbart. The origin of traveling waves in an emperor penguin huddle. New Journal of Physics, 2013; 15 (12): 125022 DOI: 10.1088/1367-2630/15/12/125022

Institute of Physics (2013, December 16). Traffic jams lend insight into emperor penguin huddle. ScienceDaily. Retrieved December 17, 2013, from http://www.sciencedaily.com­ /releases/2013/12/131216204020.htm

2 Profs Head to Antarctica for Penguin Studies

Penguin study

Posted: Dec 12, 2013
  San Diego, California News Station - KFMB Channel 8 - cbs8.com

By Natasha Stenbock, Weather

SAN DIEGO (CBS 8) - Funding is a dilemma researchers always face. Luckily for one local scientist, private funding paved the way from San Diego to the South Pole, with the benefit of using new technology that's cutting down on time in the field with better accuracy. In this week's earth 8 we bring you part 2 of the science behind this penguin study.
Senior research scientist Dr. Brent Stewart hopes to answer many important questions about several penguin species living on the South Pole.

When you're surrounded by hundreds of thousand of birds, the only way to get a better count is to fly high above them. As we showed you in part one of this series, a drone-like aircraft was used to collect more precise scientific data.
"What I really like about it is it can be a stable platform rather than flying over very quickly, we can hover. We can quickly move it in one direction, spin it around to get different perspectives," Stewart said. "But it's going to take another month, two months to count each bird at the two colonies. The big ones, the king penguins St. Andrews Bay, Salsbury Plains, they're probably 200,000 to 300,000 birds at each one of those colonies."

Although it looks crowded, Stewart says some colonies are not doing as well as others.
"Adelie penguins on the peninsula, we know that their populations are changing very rapidly as the climate there changes very rapidly. But other species are coming in and doing very well, so there are local colonies which are sustaining and are vital and other colonies are declining," he said.

Aside from a variable climate, penguins will always have natural predators.
"For Antarctic penguins, leopard seals are predators, they eat them. Particularly in the peninsula, killer whales, I think the ultimate predators are parasites which they're always dealing with. Infectious disease is a key issue in their population, biology. But it's really leopard seals and killer whales are their primary predators other than humans used to be.

"We're starting to plan for the next season next year for the Antarctic trip. Locally it's elephant seal season that's coming up in December, so I spend a lot of time out in San Nicholas & San Miguel Islands to study populations there, and we're trying to use the same kind of tools to help us with that," Stewart said.

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Citadal professor headed to Antarctica to study penguins

• Diane Knich
• Posted: Thursday, December 12, 2013

 

 

ProvidedA rockhopper penguin warms its young chick and guards against predators during Citadel professor Paul Nolan's 2006 research trip to the Falkland Islands.

Penguins are the proverbial canary in a coal mine when it comes to gauging climate change, says Citadel biology professor Paul Nolan.

So he packed his freezing-weather gear and is headed to Antarctica Friday to study them.

• Citadel biology professor Paul Nolan packs cold-weather gear for a research trip to Antarctica to study penguins.

Nolan, who studies animal behavior focusing mostly on birds, said he's been studying penguins for more than a decade, including taking several trips south of the equator to observe the waddling black and white creatures in their natural habitats.

He'll be working on the penguin study with Oxford University professor Tom Hart. People can learn more about the work, at PenguinLifelines.org.

Nolan, who also runs the nonprofit group CharlestonAudubon.org,said The Citadel Foundation gave him a $3,000 grant to help him with his research. He expects to share much of what he experiences with his students in future classes.

Jay Dowd, the foundation's chief executive officer, said Nolan's research is one of many ground-breaking projects conducted on campus by faculty, graduate students, and cadets to which the foundation contributes.

Nolan said it's important to go to Antarctica because "ongoing climate change is most pronounced at the poles." In Antarctica, there's been a 5- to 6-degree temperature increase in the past 100 years," he said.

The researchers plan to study the birds in two major ways. They will collect and analyze feathers that drop from the birds, he said, because feathers contain stress hormones, an indicator of environmental change.

They also will place cameras in penguin colonies that snap pictures every hour. The cameras will remain in place for about a year, he said, then researchers will go back and collect the cards from the cameras and study the photos. "The big idea behind this is that we want to monitor the behavior without bothering the birds."

A huge number of photographs will be collected, Nolan said, and members of the public can volunteer to help annotate them. The photographs will be available on April 25, which is International Penguin Day, he said.

Nolan said his unique role in the project is to study the color and color changes of the birds, especially in their beaks and feet. Color can reveal a great deal about an animal's health, he said.

Temperatures in Antarctica this time of year range from 0 to 20 degrees, he said, but he's ready for the cold.

The research team will travel on a cruise ship, and take Zodiac boats to various penguin colonies each day, he said. It's very difficult to find a way to travel in that part of the world, he said, but cruise ships work well. The researchers will make some presentations on penguins to other travelers, he said.

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A Penguin's Tale: Diet Linked to Breeding Failure

 

The Little Penguin 

 

Dec. 12, 2013 — A study on a Victorian penguin colony has revealed new insight into the link between seabird diet and breeding success.

In a study published in Functional Ecology, Nicole Kowalczyk and Associate Professor Richard Reina of Monash University's School of Biological Sciences, in collaboration with Andre Chradia from Phillip Island Nature Parks, studied Melbourne's St Kilda little penguin colony over two years.

They detailed how changes to prey abundance or food sources influenced reproductive success, tracking the penguins' nesting and feeding behaviour during the 2010 and 2011 breeding season.

Given previous data had shown that the colony fed mainly on anchovy which accounted for up to 78 per cent of their diet between years 2004 and 2008, the researchers predicted that changes in abundance would impact on the reproductive success of the colony -- but they were surprised to find the little penguins were resilient to changing conditions only if alternative prey such as sardines could be found.

Ms Kowalczyk said breeding failure in seabirds has been associated with declines in prey abundance, and the quality and diversity of prey -- but identifying which aspect of diet was responsible was challenging.
"The St Kilda little penguin colony has a short foraging range and displays narrow dietary diversity so this gave us the unique ability to identify how changes in food supply influence their reproduction," Ms Kowalczyk said.

"We found that a sharp decline of anchovy in 2010 had a negative impact on little penguin reproduction. However, in 2011, despite the relatively low anchovy abundance, their breeding success was extremely high.
"We believe the decrease of anchovy itself was not the only cause for low breeding success in 2010 but in combination with the scarcity of alternative prey. Our results show that little penguins are resilient to changes in their preferred prey but their ability to adapt to these changes is limited by the availability of alternative prey species."

Ms Kowalczyk said understanding seabird diet was integral to their conservation and management.
"Our results highlight that resource abundance and the availability of a variety of prey are critical factors in enabling this inshore seabird to adjust to changes in environmental conditions and fluctuations in their primary source of prey," Ms Kowalczyk said.

"Dietary changes have been linked to population declines and provide information about foraging conditions, particular prey species and foraging locations that require protection."

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Story Source:

The above story is based on materials provided by Monash University.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

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Journal Reference:

1. Nicole D. Kowalczyk, Andre Chiaradia, Tiana J. Preston, Richard D. Reina. Linking dietary shifts and reproductive failure in seabirds: a stable isotope approach. Functional Ecology, 2013; DOI: 10.1111/1365-2435.12216

Monash University (2013, December 12). A penguin's tale: Diet linked to breeding failure. ScienceDaily. Retrieved December 13, 2013, from http://www.sciencedaily.com­ /releases/2013/12/131212103351.htm

The mystery of Captain Scott's penguin eggs

Posted by GrrlScientist, Thursday 21 November 

 

Specimens for scientific study can be extremely difficult to collect, as Captain Robert Falcon Scott learned on his last expedition to Antarctica.

During the past few days, I've been sorting and organising the photographs from my recent trip to London, and shared the above image on twitter. In this photograph, you see a rather large eggshell with a more-or-less rectangular window cut into the shell. According to the museum label that accompanies this specimen, this is one of three emperor penguin eggs that had been collected -- fresh -- by Captain Scott on his last expedition to Antarctica.

But because I had copied the tweet to the Natural History Museum, and because a knowledgeable person was monitoring their twitter feed, I soon learned that the museum tag accompanying this egg shell was not-quite-correct: in fact, Bill Wilson, Apsley Cherry-Garrard and Henry "Birdie" Bowers actually collected this egg in 1911. These three men were part of Captain Scott's last Antarctic expedition.

But that is only a small part of the story. Since emperor penguins breed in the middle of the Antarctic winter, this meant the explorers had to hike 70 miles from Scott's base camp on Ross Island to the penguin breeding colony on Cape Crozier, locate and collect these eggs during the worst possible time: not only was it perpetually dark, but they faced extreme cold, powerful winds and intense blizzards. Why would three well-educated humans knowingly subject themselves to the worst weather imaginable on Earth to collect five fresh penguin eggs -- two of which they accidentally broke during their return journey? Were these guys mad?

These three men might have been mad, but the reason for their five-week-long expedition was not. Penguin eggs were important at that time because they were thought to be integral to confirming a scientific hypothesis popularised by Ernst Haeckel. This hypothesis, famously known as "ontogeny recapitulates phylogeny", proposed that development from a fertilised egg through adulthood re-enacts evolution via stages that resemble the ancient ancestors that gave rise to that particular species:

 

"Ontogeny recapitulates phylogeny." George Romanes' 1892 copy of Ernst Haeckel's controversial -- allegedly fraudulent -- embryo drawings. Romanes' version is often attributed incorrectly to Haeckel. [Romanes, G. J. (1892). Darwin and After Darwin. Open Court, Chicago.] This image is in the public domain due to its age.

This was a controversial hypothesis, but at least some scientists of that time thought they could watch the evolution of bird feathers from reptilian scales by documenting various stages of embryonic development of a primitive bird. At the time, penguins were thought to be the most primitive of birds (actually, this is not true) so this was the rationale for collecting penguin eggs for study instead of, say, chicken eggs.

Eventually, these eggs were added to the collection at the Natural History Museum. Twenty-three years after they had been collected -- after the "ontogeny recapitulates phylogeny" hypothesis had been discredited -- a study was published by zoologist CW Parsons, who concluded that "they did not greatly add to our understanding of penguin embryology."

Although Wilson, Cherry-Garrard and Bowers miraculously managed to return to Scott's base camp with three of the five eggs intact, perhaps most remarkable aspect of this adventure was the mystery that the intrepid explorers had missed: they never noticed that each bird's single precious egg, which was balanced on the parent's feet, was actually being incubated by the father.
Here's a video of Douglas Russell, curator of eggs at the Natural History Museum, telling us a little more of the story about this particular egg:


The pencil drawing of the penguin embryo (above right) is by Dorothy Thursby-Pelham.

NOTE [23 November 2013, Saturday, 0830]: this piece incorrectly stated that the NHM tag on this egg was incorrect. In fact, although captain Scott did not personally collect the penguin eggs, he did make it possible for this to happen by providing access to Antarctica and some information to Wilson, Cherry-Garrard and Bowers about the colony's location. This piece has been amended to correct that inaccuracy.

GrrlScientist can also be found here: Maniraptora. She's very active on twitter @GrrlScientist and sometimes lurks on social media: facebook, G+, LinkedIn, and Pinterest.

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A Heat Map Of Penguins Explains How They Stay Warm

Mac Irvine, Popular Science
Nov. 23, 2013,

courtesy Université de Strasbourg and Centre National de la Recherche Scientifique (CNRS), Strasbourg, France

As if their home in Antarctica weren’t cold enough, emperor penguins allow their exteriors to drop at least 7°F below their surroundings. The change helps the penguins stay warm, a recent paper showed. When the outer layer of feathers radiates heat to the sky, it becomes colder than its immediate environment, so heat flows back in. The cycle keeps the temperature underneath the plumage constant—and the penguin alive.

This article originally appeared in the December 2013 issue of Popular Science.
This article originally appeared on Popular Science

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Did Ancient Climate Change Spur Penguin Evolution?

A new study on the last common ancestor of today's penguins.

A cooling spell in Antarctica may have helped penguins diversify into the numerous species alive today, such as this Gentoo penguin. Photograph by Paul Souders, Corbis

Ker Than

for National Geographic

Published November 12, 2013

When did the earliest common ancestor of the penguins we know today first waddle the Earth, and why?

The question is surprisingly controversial, and may become more so with a new study suggesting a climate-change connection.

Possible dates for the last common ancestor of living penguins have differed by tens of millions of years. According to DNA evidence, the early ancestor lived some 40 million years ago, while fossil evidence puts the date closer to 10 million years ago.

Now a new genetic study, detailed in this week's issue of the journal Biology Letters, suggests that today's major penguin lineages began diverging from one another about 11 to 16 million years ago, and that their common ancestor first appeared 20 million years ago.

The study also suggests that a prolonged cooling spell in Antarctica may have helped spur penguins to diversify into the 18 species living today.

Reconciling Evidence

The new finding, based on more DNA points than past studies, helps reconcile the genetic and fossil evidence, explained study leader Sankar Subramanian, a postdoctoral student at Griffith University in Australia.

"For the first time we showed a more recent time of origin of penguins, which was in agreement with that based on morphological data," he said.

Intriguingly, the date that Subramanian's team estimates for the diversification of modern penguins coincides with a time 10 to 15 million years ago when scientists think Antarctica underwent a period of rapid cooling that covered the continent in ice.

"So we connected these two dots and speculated [about] a possible relationship," Subramanian said in an email. He cautioned, however, that he and his colleagues "don't have any proof for this connection, which is indeed hard to obtain."

A Mysterious Gap

Paleontologists have found penguin-like fossils dating as far back as 62 million years, tens of millions of years before the first ancestor of today's penguins emerged on the scene.

"The big gap between these two times raises questions like: What happened to the older lineages of penguins? What caused the extinction of all other older lineages? Could that be due to any change in Antarctic or global climate?" Subramanian said.

Subramanian said his team is planning to look next at the molecular signatures of penguins living in very different environments, from the tropical Galápagos Islands to the frozen Antarctic.

"This might reveal valuable information, such as how they could adapt to live in these diverse climates," he said.

story source 

Download paper in PDF form here 

Australian climate change researchers look to penguin poo

Climate change -- October 15, 2013

By: News Desk

If you're going to study the effects of climate change on a food chain, you have to look at how that food, ahem, ends up. Researchers from the Australian government's Antarctic Division will study the Antarctic food chain, specifically, the historical feeding habits of Adelie penguins and impacts of ocean acidification on phytoplankton and bacteria, the smallest building blocks of the southern continent's ecosystem, according to a report from AFP.

Seabird expert Barbara Wienecke will lead the survey as the team excavates ancient droppings to dertermine changes in the penguins' diets over time.

She explained the research to AFP:

"We will be digging down into the old soils formed from bird waste and looking for the remains of prey, such as fish ear-bones and squid beaks," said Wienecke.
"It is the first time this type of work has been done in the Davis region and we are hopeful of finding out whether Adelie diets changed in the past, for example, from krill to fish-based diets," she added.
"Gaining this knowledge can help manage Southern Ocean fisheries to avoid disrupting the Antarctic food chain."

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Longer Life for Humans Linked to Further Loss of Endangered Species

Endangered yellow eyed penguin. New Zealand has a high percentage of endangered birds. (Credit: © paradoxdes / Fotolia)

 

Oct. 9, 2013 — As human life expectancy increases, so does the percentage of invasive and endangered birds and mammals, according to a new study by the University of California, Davis.

The study, published in the September issue of Ecology and Society, examined a combination of 15 social and ecological variables -- from tourism and per capita gross domestic product to water stress and political stability. Then researchers analyzed their correlations with invasive and endangered birds and mammals, which are two indicators of what conservationist Aldo Leopold termed "land sickness," the study said.

Human life expectancy, which is rarely included among indexes that examine human impacts on the environment, surfaced as the key predictor of global invasions and extinctions.

"It's not a random pattern," said lead author Aaron Lotz, a postdoctoral scholar in the Department of Wildlife, Fish and Conservation Biology when the study was conducted. "Out of all this data, that one factor -- human life expectancy -- was the determining factor for endangered and invasive birds and mammals."

The study analyzed data from 100 countries, which included roughly 87 percent of the world's population, 43 percent of global GDP per capita, and covered 74 percent of Earth's total land area.

Additional factors considered were agricultural intensity, rainfall, pesticide regulation, energy efficiency, wilderness protection, latitude, export-import ratio, undernourishment, adult literacy, female participation in government, and total population.
The findings include:

• New Zealand, the United States and the Philippines had among the highest percentages of endangered and invasive birds.
• New Zealand had the highest percentage of all endangered and invasive species combined, largely due to its lack of native terrestrial mammals. The study said that in the past 700 to 800 years since the country was colonized, it has experienced massive invasion by nonindigenous species, resulting in catastrophic biodiversity loss.
• African countries had the lowest percentage of invasive and endangered birds and mammals. These countries have had very little international trade, which limits opportunities for biological invasion.
• As GDP per capita -- a standard measure of affluence -- increased in a country, so did the percentage of invasive birds and mammals.
• As total biodiversity and total land area increased in a country, so did the percentage of endangered birds. (Biodiversity in this context is not a measure of health but refers to the number of species in an area.)

Lotz said the study's results indicate the need for a better scientific understanding of the complex interactions among humans and their environment.

"Some studies have this view that there's wildlife and then there's us," said Lotz. "But we're part of the ecosystem. We need to start relating humans to the environment in our research and not leave them out of the equation. We need to realize we have a direct link to nature."

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Story Source:

The above story is based on materials provided by University of California - Davis.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

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Journal Reference:

1. Aaron Lotz, Craig R. Allen. Social-Ecological Predictors of Global Invasions and Extinctions. Ecology and Society, 2013; 18 (3) DOI: 10.5751/ES-05550-180315

 

University of California - Davis (2013, October 9). Longer life for humans linked to further loss of endangered species. ScienceDaily. Retrieved October 10, 2013, from http://www.sciencedaily.com­ /releases/2013/10/131009130122.htm

An ancient dinosaur-era bird turns out to have two tails

Two-Tailed Ancient Bird Uncovered

... one perhaps for flying and the other for showing off.

A reconstruction of a two-tailed 120-million-year-old Jeholornis.

Illustration courtesy Aijuan Shi

Dan Vergano

National Geographic

Published October 7, 2013

The early bird gets two tails? A 120-million-year-old bird sported a long tail and a second, unexpected tail frond, paleontologists suggest. The discovery points to a complicated evolutionary path for the tails we see in birds today.

One of the oldest known birds, Jeholornis, lived in what is today China, along with a trove of other feathered dinosaurs discovered in the region over the last decade. It was also thought to sport only a long fan-feathered tail at its back end. Now, however, paleontologists are claiming discovery of a second tail frond adorning the bird.

"The 'two-tail' plumage of Jeholornis is unique," according to the study, which was led by Jingmai O’Connor of the Chinese Academy of Sciences in Beijing. The report of the discovery of the tail frond was published in the Proceedings of the National Academy of Sciences.

Of 11 Jeholornis fossils that retain evidence of ancient plumage, 6 have signs of this frond of 11 feathers, which would have jutted above the bird's back at a jaunty, upright angle in a "visually striking" manner, according to the study.

Two-Tailed Display

"Clearly the display aspect of the frond would have been undeniable," says paleontologist Mark Norell, of the American Museum of Natural History in New York, who was not part of the study. "It calls to mind living birds, even peacocks, which display broad plumes of feathers."

In peacocks and other birds, such feathery features are more for attracting the attention of potential mates than for any functional purpose.

Since male birds today are the ones with the striking plumage, the authors suggest that perhaps only one sex of Jeholornis sported the eye-catching tail fronds.

Early Aviation Advantage?

Jeholornis is not thought to be directly related to modern birds, which seem to have evolved from a different line of early avians. The study authors suggest that the tail frond may have played a stabilizing role in the flight of these early birds and that if the arrangement of feathers had proven advantageous enough, modern birds might have evolved to sport such two-tailed features. They see the fronds as flattening to offer a streamlined appearance when the bird was in flight.

Other researchers aren't convinced the newly discovered tail frond played much of a role in aviation, however. "Feathering in the new specimens is quite interesting, but we have to remember it is a feature so far only known in one species," says University of Texas paleontologist Julia Clarke, who adds the frond wasn't seen in all the fossils.

"Thus, its implications for the origin of flight are unclear," she says. "It could have been a peculiarity of the one species, as the authors note." Perhaps more likely, she suggests the frond simply evolved as an easy-to-notice "sexual display" flaunted by these early birds.

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The Victory Squawk of the Little Blue Penguin

Apr. 03, 2012

by Kara Rogers

Little Penguin (Eudyptula minor) family exiting burrow, Bruny Island, Tasmania, Australia. Photo by Noodle snacks.

Victory is sweet, so much so that we often feel compelled to rejoice with a cry of triumph. For some animals, that cry not only announces a win to all those within earshot but also serves surprisingly complex social functions. Take, for instance, the call of the victorious little blue penguin (Eudyptula minor), which a recent study in the journal Animal Behavior revealed has a direct effect on the behavior of “social eavesdroppers” -- penguins who, from the safety of their burrows, assess the quality of fighting individuals based solely on their vocalizations.

Male little blue penguins are fierce defenders of their territories and frequently become engaged in flipper-slapping territorial disputes. At the conclusion of a scuffle, the winner celebrates with a so-called triumph display, in which he delivers a victory bray -- a distinctive squawk that according to the new study serves as a sort of warning signal to other males in the colony, potentially mitigating future confrontations for the winner and preventing embarrassing defeats for lesser male challengers.
Little blue penguins, which are the smallest penguins in the world, are social animals that use vocalization during activities such as courtship and foraging and as a way of announcing their arrival at their home burrows. However, while much is known about the various functions of many of the penguins' calls, the social significance of vocalization associated with victory calls had remained unclear.

To assess the impact of triumph brays on the behavior of eavesdropping penguins, the scientists played a recording of a vocal exchange and flipper-slapping fight between territorial males and then played recordings of both the victor's triumph call and the loser's call. They then measured the heart rates of eavesdroppers in response to the sounds using heart monitors hidden in artificial eggs that were placed in the penguins' nests. The team found that eavesdropping males' heart rates increased in response to the victor's call when compared with the loser's call. In addition, in simulated approach experiments in which the loser's or winner's call was played just outside the entrance of an eavesdropper's burrow, the scientists discovered that eavesdropping males challenged the loser's call with vocalizations of their own but fell silent when the triumph call was played.

Triumph displays and other forms of postconflict signaling have been documented in a variety of species, including birds such as the Canada goose (Branta canadensis), the greylag goose (Anser anser), and the bell shrike (Laniarius aethiopicus), as well as animals such as the green frog (Rana clamitans) and an insect known as the Wellington tree weta (Hemideina crassidens). Postconflict signaling in these species appears to function either as a form of advertising, in which the winner's display communicates his dominance to eavesdroppers, or as a form of intimidation, in which the winner's display serves to reduce the chance that the loser will initiate a future challenge. Thus, in many ways, by showing off a little after a victory, these animals are simply establishing their reputation as winners. In other words, they're behaving very much like humans.

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Ten-Year Project Redraws the Map of Bird Brains

 

A revised map of the bird brain shows cortical areas organized in columns, as in mammals and humans. (Credit: Image courtesy of Duke University)

Sep. 17, 2013 — Explorers need good maps, which they often end up drawing themselves.

Pursuing their interests in using the brains of birds as a model for the human brain, an international team of researchers led by Duke neuroscientist Erich Jarvis and his collaborators Chun-Chun Chen and Kazuhiro Wada have just completed a mapping of the bird brain based on a 10-year exploration of the tiny cerebrums of eight species of birds.

In a special issue appearing online in the Journal of Comparative Neurology, two papers from the Jarvis group propose a dramatic redrawing of some boundaries and functional areas based on a computational analysis of the activity of 52 genes across 23 areas of the bird brain.

Jarvis, who is a professor of neurobiology at Duke, member of the Duke Institute for Brain Sciences, and a Howard Hughes Medical Institute investigator, said the most important takeaway from the new map is that the brains of all vertebrates, a group that includes birds as well as humans, have some important similarities that can be useful to research.

Most significantly, the new map argues for and supports the existence of columnar organization in the bird brain. "Columnar organization is a rule, rather than an exception found only in mammals," Jarvis said. "One way I visualize this view is that the avian brain is one big, giant gyrus folding around a ventricle space, functioning like what you'd find in the mammalian brain," he said.

To create different patterns of gene expression for the analysis, the birds were exposed to various environmental factors such as darkness or light, silence or bird song, hopping on a treadmill, and in the case of migratory warblers, a magnetic field that stimulated their navigational circuits.

The new map follows up on a 2004 model, proposed by an Avian Brain Nomenclature Consortium, also lead by Jarvis and colleagues, which officially changed a century-old view on the prevailing model that the avian brain contained mostly primitive regions. They argued instead that the avian brain has a cortical-like area and other forebrain regions similar to mammals, but organized differently.

"The change in terminology is small this time, but the change in concept is big," Jarvis said. For this special issue, the of Journal of Comparative Neurology commissioned a commentary by Juan Montiel and Zoltan Molnar, experts in brain evolution, to summarize the large amount of data presented in the studies by the Jarvis group.

One of the major findings is that two populations of cells on either side of a void called the ventricle are actually the same cell types with similar patterns of gene expression. Earlier investigators had thought of the ventricle as a physical barrier separating cell types, but in development studies led by Jarvis' post doctoral fellow Chun-chun Chen, the Duke researchers showed how dividing cells spread in a sheet and flow around the ventricle as they multiply.

The new map simplifies the bird cortex, called pallium, from seven populations of cells down to four major populations. Humans have five populations of cells in six layers.

Part of this refinement is simply that the tools are getting better, says Harvey Karten, a professor of neurosciences at the University of California-San Diego who proposed a dramatic re-thinking of bird cortical organization in the late 1960s. The best tools in that era were microscopes, specific cell stains and electrophysiology. Karten and colleagues are authors of a fourth paper in the special issue which announces a database of gene expression profiles of the avian brain containing some of the data that the Jarvis group used.

Jarvis said having a more specific map is necessary for properly sampling cell populations for gene expression analysis to do even more functional analysis of how the brain operates. As a next step, his team is considering doing an even more detailed bird map with "several hundred" genes rather than the 52 used to make this map.

Jarvis and colleagues are working now on a similar mapping of the crocodile brain with the ultimate goal of being able to say something about how dinosaur brains were organized, since both birds and crocs are descended from them. At a Society for Neuroscience conference in November, they'll be presenting some early findings from that project.

Though the specifics of this newest map may only be of interest within the bird research community, Jarvis said, it builds the awareness that birds can be a useful model for many questions about the human brain.

"Where does the mammalian brain come from?" Karten asks. "And what's the origin of these structures at the cellular and molecular level?" Some neuroscientists have argued that the mammalian cortex -- the one we have -- is something apart from the brains of other vertebrates. Jarvis and Karten now think vertebrate brains have more commonalities than differences.

That awareness is making birds an ever more useful model for questions about the human brain. "There are very few animal models where you can learn -- at the molecular level -- what's going on in vocal learning," Karten said. Birds are also being used as models for research on Parkinson's, Huntington's, deafness and other degenerative conditions in humans.

The work was supported by grants from Human Frontiers in Science Program, The National Science Foundation, NIMH (R01-MH62803), NIDCD (R01-DC007218), NIH ARRA Supplement 3DP10D000448-04S1 and the Howard Hughes Medical Institute.

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Story Source:

The above story is based on materials provided by Duke University.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

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Journal References:

1. Erich D. Jarvis, Jing Yu, Miriam V. Rivas, Haruhito Horita, Gesa Feenders, Osceola Whitney, Syrus Jarvis, Electra R. Jarvis, Lubica Kubikova, Ana E. P. Puck, Connie Siang-Bakshi, Suzanne Martin, Michael McElroy, Erina Hara, Jason Howard, Henrik Mouritsen, Chun-Chun Chen, Kazuhiro Wada. A global view of the functional molecular organization of the avian cerebrum: Mirror images and functional columns. Journal of Comparative Neurology, 2013; DOI: 10.1002/cne.23404
2. Chun-Chun Chen, Candace M. Winkler, Andreas R. Pfenning, Erich D. Jarvis. Molecular profiling of the developing avian telencephalon: regional timing and brain subdivision continuities. Journal of Comparative Neurology, 2013; DOI: 10.1002/cne.23406

Duke University (2013, September 17). Ten-year project redraws the map of bird brains. ScienceDaily. Retrieved September 18, 2013, from http://www.sciencedaily.com­ /releases/2013/09/130917093924.htm

 

How Birds Got Their Wings: Fossil Data Show Scaling of Limbs Altered as Birds Originated from Dinosaurs

Archaeopteryx lithographica, specimen displayed at the Museum für Naturkunde in Berlin. Believed to be a transitional species between theropod dinosaurs and birds, Archaeopteryx had longer forelimbs and shorter hind limbs than its ancestors. (Credit: By H. Raab (User:Vesta) (Own work) [CC-BY-SA-3.0 or GFDL], via Wikimedia Commons)

Sep. 17, 2013 — Birds originated from a group of small, meat-eating theropod dinosaurs called maniraptorans sometime around 150 million years ago. Recent findings from around the world show that many maniraptorans were very bird-like, with feathers, hollow bones, small body sizes and high metabolic rates.

But the question remains, at what point did forelimbs evolve into wings -- making it possible to fly?
McGill University professor Hans Larsson and a former graduate student, Alexander Dececchi, set out to answer that question by examining fossil data, greatly expanded in recent years, from the period marking the origin of birds.

In a study published in the September issue of Evolution, Larsson and Dececchi find that throughout most of the history of carnivorous dinosaurs, limb lengths showed a relatively stable scaling relationship to body size. This is despite a 5000-fold difference in mass between Tyrannosaurus rex and the smallest feathered theropods from China. This limb scaling changed, however, at the origin of birds, when both the forelimbs and hind limbs underwent a dramatic decoupling from body size. This change may have been critical in allowing early birds to evolve flight, and then to exploit the forest canopy, the authors conclude.

As forelimbs lengthened, they became long enough to serve as an airfoil, allowing for the evolution of powered flight. When coupled with the shrinking of the hind limbs, this helped refine flight control and efficiency in early birds. Shorter legs would have aided in reducing drag during flight -- the reason modern birds tuck their legs as they fly -- and also in perching and moving about on small branches in trees. This combination of better wings with more compact legs would have been critical for the survival of birds in a time when another group of flying reptiles, the pterosaurs, dominated the skies and competed for food.

"Our findings suggest that birds underwent an abrupt change in their developmental mechanisms, such that their forelimbs and hind limbs became subject to different length controls," says Larsson, Canada Research Chair in Macroevolution at McGill's Redpath Museum. Deviations from the rules of how an animal's limbs scale with changes in body size -- another example is the relatively long legs and short arms of humans -- usually indicate some major shift in function or behaviour. "This decoupling may be fundamental to the success of birds, the most diverse class of land vertebrates on Earth today."

"The origin of birds and powered flight is a classic major evolutionary transition," says Dececchi, now a postdoctoral researcher at the University of South Dakota. "Our findings suggest that the limb lengths of birds had to be dissociated from general body size before they could radiate so successfully. It may be that this fact is what allowed them to become more than just another lineage of maniraptorans and led them to expand to the wide range of limb shapes and sizes present in today's birds."

"This work, coupled with our previous findings that the ancestors of birds were not tree dwellers, does much to illuminate the ecology of bird antecedents." says Dr. Dececchi. "Knowing where birds came from, and how they got to where they are now, is crucial for understanding how the modern world came to look the way it is."

Funding for the research was provided by the Fonds de recherche du Québec -- Nature et technologies, the Canada Research Chairs program, and the National Sciences and Engineering Research Council of Canada.

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Story Source:

The above story is based on materials provided by McGill University.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

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Journal Reference:

1. T. Alexander Dececchi, Hans C. E. Larsson. Body and Limb Size Dissociation at the Origin of Birds: Uncoupling Allometric Constraints Across a Macroevolutionary Transition. Evolution, 2013; 67 (9): 2741 DOI: 10.1111/evo.12150

McGill University (2013, September 17). How birds got their wings: Fossil data show scaling of limbs altered as birds originated from dinosaurs. ScienceDaily. Retrieved September 18, 2013, from http://www.sciencedaily.com­ /releases/2013/09/130917123613.htm