Scientists Are Learning More About Big Birds From Feathers

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ScienceDaily (July 13, 2009) — Catching adult eagles for research purposes is no easy task, but a Purdue University researcher has found a way around the problem, and, in the process, gathered even more information about the birds without ever laying a hand on one.

"Many birds are small, easy to catch and abundant," said Andrew DeWoody, associate professor of forestry and natural resources. "With eagles, the effort can be 100 to 1,000 times greater than catching chickadees."
Eagles can be hard to find, they often require live bait to attract and, with sharp talons and beaks capable of snapping off human fingers, they pose a risk to their would-be captors.
Instead of catching eagles, DeWoody collects their feathers and uses the small amount of DNA in them to create a tag that corresponds to a particular bird. Those tags can be used to determine population, parentage, roosting patterns and sex ratio.
"In an afternoon, you can go out and pick up hundreds of feathers," DeWoody said, "As field work goes, it's about as easy as it gets."
DeWoody's method is described in a chapter of the Handbook of Nature Conservation: Global and Economic Issues, which was released this week. The chapter is a compilation of his research on the topic.
Most birds are studied by catching them in nets and attaching tracking devices. Researchers can then follow the birds and use radio technology to triangulate their locations.
Eagles and other large birds present several challenges, however, even beyond catching them.
"Eagles will literally fly hundreds of miles in two days," DeWoody said. "They fly in areas where you can't track them in a pickup truck."
Capturing a bird as large as an eagle can often be traumatic to the animal.
"They're wild animals that don't want to be caught," DeWoody said. "They can get hurt as well. Using feathers, you avoid all that."
And costs can be as high as $5,000 for the tracking technology that researchers must attach to eagles, a prohibitive cost if studying more than a few birds.
DeWoody's studies were done in Kazakhstan with imperial eagles, a top predator of international concern because its population is declining.
The feathers give a good picture of recent eagle habits because they do not survive long in Kazakhstan's winters. Any feathers collected after the winter thaw, then, had to have been recently dropped. In one study, DeWoody's team found that an area thought to have about 40 juvenile eagles living in it based on human observation actually had closer to 300.
The work also helped researchers understand more about the roosting habits of some eagles that use a nest for months at a time versus others who float around from roost to roost. Another study showed that DNA could be used to distinguish eagle species from one another, and that imperial, golden and white-tailed eagles often utilized the same roosts at the same time.
The National Geographic Society and the National Birds of Prey Trust funded DeWoody's research.
Journal reference:
Jamie A. Rudnick, Todd E. Katzner and J. Andrew DeWoody. Genetic Analyses of Noninvasively Collected Feathers Can Provide New Insights Into Avian Demography and Behavior. Handbook of Nature Conservation: Global and Economic Issues, 2009
Adapted from materials provided by Purdue University.

Male Seahorses Like Big Mates

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ScienceDaily (July 13, 2009) — Male seahorses have a clear agenda when it comes to selecting a mating partner: to increase their reproductive success. By being choosy and preferring large females, they are likely to have more and bigger eggs, as well as bigger offspring, according to Beat Mattle and Tony Wilson from the Zoological Museum at the University of Zurich in Switzerland.

Seahorses have a unique mode of reproduction: male pregnancy. Male seahorses provide all post-fertilization parental care, yet despite the high levels of paternal investment, they have long been thought to have conventional sex roles, with females choosing mating partners and males competing for their attention. However, clutch, egg and offspring size all increase with female body size in seahorses, suggesting that males may obtain fecundity benefits by mating with large-bodied females.
Mattle and Wilson investigated the mating behavior of the pot-bellied seahorse (Hippocampus abdominalis), concentrating on the importance of partner body size in mate selection. A total of 10 female and 16 male sexually mature seahorses, obtained from a captive breeding facility in
Tasmania, took part in the experiment. Individuals of both sexes were presented with potential mating partners of different sizes. Mating preferences were quantified in terms of time spent courting each potential partner.
Mattle and Wilson found striking differences in courtship behavior between male and female seahorses, with choosy males and indiscriminate females.
Male seahorses were highly active and showed a clear preference for larger partners. In contrast, females were significantly less active and showed ambiguous mating preferences.
The authors conclude: "The strong male preferences for large females demonstrated here suggest that sexual selection may act strongly on female body size in wild populations of H. abdominalis, consistent with predictions on the importance of female body size for reproductive output in this species."
Their findings have just been published online in Springer's journal Behavioral Ecology and Sociobiology.
Adapted from materials provided by Springer Science+Business Media, via AlphaGalileo.

Southern Elephant seals responded rapidly to climate and habitat change.

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ScienceDaily (July 12, 2009) — Southern Elephant seals responded rapidly to climate and habitat change and established a new breeding site thousands of kilometres from existing breeding grounds, according to new research.

An international research team, including post-doctorate Dr Mark de Bruyn and collaborators from the US, South Africa and Italy, led by Professor Rus Hoelzel from the School of Biological and Biomedical Sciences, Durham University, found that when the Antarctic ice sheets of the Ross Sea Embayment retreated in the Holocene period 8,000 years ago, elephant seals, Mirounga leonina, adopted the emergent habitat and established a new population which flourished.
DNA sequences from the ancient remains of seals from the now extinct Antarctic colony showed high levels of genetic diversity, probably due to the very large population size sustained there. The study, published in the academic journal PLoS Genetics, and funded by the US National Science Foundation, shows how environmental change can drive the demographic and evolutionary processes that determine diversity within and among species.
Tracking these processes during periods of change reveals mechanisms for the establishment of populations, and provides predictive data on response to potential future impacts, including those caused by climate change.
Professor Rus Hoelzel said: "In general, this approach of looking to the past to understand what might happen in the future, has good potential for predicting the impact of environmental change in both marine and terrestrial systems.
"We've shown how a highly mobile marine species responded to the gain and loss of new breeding habitat. The new habitat was quickly adopted, probably because seals migrate annually into Antarctic waters to feed. However, when the ice returned and the habitat was lost, only a small proportion returned to the original source population. The Antarctic population crashed and much diversity was lost."
This habitat was released after the retreat of the grounded ice sheet in the Ross Sea Embayment 7,500-8,000 years ago, and is within the range of modern foraging excursions from the Macquarie Island colony. Using ancient mtDNA and evolutionary models, the research team tracked the population dynamics of the now extinct colony and the connectivity between this and modern breeding sites.
The team found clear signs of rapid expansion in the new colony 8,000 years ago. This was followed by directional migration away, coupled with a loss of diversity 1,000 years ago, when the sea ice is thought to have expanded. The data suggest that the new colony seals came initially from Macquarie Island, and that some returned there, but in much smaller numbers, when the new colony habitat was lost 7,000 years later.
In order to understand how biodiversity is generated and maintained over time, the team has set out to understand the process by which the seal populations formed and diverged. They analysed data from ancient DNA to show how elephant seal populations responded when new breeding habitat was gained and then lost over the course of approximately 7,000 years.
Professor Rus Hoelzel said: "Using ancient DNA, we were able to track the dynamics and diversity of a population from its foundation, through to its extinction, in the context of Holocene climate change. We learned that new habitat emerging within the species' migratory range could be quickly taken advantage of, but that the reverse was not true. The movement patterns of seals from this Antarctic breeding site would have been unlikely to take them near other potential breeding sites, and so when their breeding site was lost, their numbers crashed.
"The seals that discovered the new breeding site had things good, because food was abundant and nearby, however when the ice returned, the new colony collapsed and only a few seals made it back to their original home.
"This illustrates the importance of understanding the behaviour and life history of a species, in order to model how it may be able to respond to rapid change."
The key factors in the expansion of the new colony were likely to be the abundant local food resource and extensive physical habitat that allowed rapid expansion after the initial founder event, and a tendency for females to return to annual breeding sites in this species.
When the ice expanded again 1,000 years ago, the seals returned to their origins but in much smaller numbers.
Adapted from materials provided by Durham University, via EurekAlert!, a service of AAAS.

A new way of estimating species richness.

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ScienceDaily (July 12, 2009) — Ask biologists how many species live in a pond, a grassland, a mountain range or on the entire planet, and the answers get increasingly vague. Hence the wide range of estimates for the planet's biodiversity, predicted to be between 2 million and 50 million species.

A new way of estimating species richness reported this month in the journal Ecology Letters by University of California, Berkeley, ecologist John Harte and colleagues, will make such estimates more precise for habitats of all sizes and types, from deserts to tropical rainforests.
"We know how to census the number of species in a square-meter plot or within an acre, but a major problem in conservation biology and ecology is estimating the diversity of biota at very large spatial scales, such as in the Amazon," said Harte, UC Berkeley professor of energy and resources. "This theory provides a much more accurate means of doing that."
The method, derived from the field of information theory, will affect not only conservation efforts to save species facing habitat loss, but also estimates of the impact of global warming, Harte said.
"Quantifying the magnitude of the extinction crisis involves estimating the richness of life in different habitats," he said. "The new theory is probably going to reduce the direness of the predictions of species loss under either habitat loss or climate change at the largest spatial scales, but it will increase (the direness) of estimates of loss at smaller scales."
Losing half of a small biome, for example, will have a worse impact than people think, while losing half of a large area would turn out better, he said.
Harte, who spends his summers in the Rocky Mountains studying the impact of climate change on plants, has for decades mulled over the problem of extrapolating from small study plots to large areas. Census takers have mastered this art, profiling the U.S. population by sampling small representative subsets. When biologists try to profile specific animals, plants or microbes of the Amazon, however, the estimates based on a small number of meter- or acre-size plots can vary by a factor of 10.
Ecological estimates of the number of species at large scales come from a hypothetical curve based on fractals, which predicts that the number of species will increase with area, but increase more slowly for larger and larger areas - a power-law rise with the number of species proportional to the ¼ power of the area.
"You can sample an area and count the number of species, and then double the area and find more species, but not twice as many, because the species overlap," Harte said.
He and colleague Jessica Green showed in 2003 that the theory of fractals, which posits that physical patterns such as the distribution of plants look similar on small and large scales, does not explain species richness over large areas. In addition, experimental tests of the species-area relationship showed that the curve has to be tweaked for every class of organisms and habitat studied.
Harte and colleagues Adam Smith of UC Berkeley and David Storch of Charles University in Prague, Czech Republic, decided to approach the problem from the perspective of information theory, which has provided key insights into thermodynamics and statistical mechanics.
In their report, they say that maximizing the information entropy - making full use of what is known from small plots without assuming anything about the unknown, larger areas - "provided a formal and robust derivation of the relationship between number of species and area."
The method not only scales up from measurements in small plots to provide more precise estimates of the number of species over large areas, but provides a universal species-area relationship, Harte emphasized.
"People have been finding different curves when looking at different organisms or in different habitats, but in fact, all these curves are the same," he said. "There really is a universal curve people are sampling, they are just sampling along different parts of the curve depending on the habitat or class of organisms."
Harte, Smith and Storch tested their theory with data from one of the few areas on Earth that has been thoroughly studied on both the small and large scale - the Western Ghats mountain range of India overlooking the Arabian Sea. A "biodiversity hotspot" of nearly 60,000 square kilometers, the Western Ghats are partially protected and have been studied extensively by Indian scientists in small sections - 48 quarter-hectare plots - and through large-scale surveys, Harte said.
While earlier species-area theories predict between 400 and 500 species of trees throughout the range of low hills, Harte's theory estimates around 1,070. To date, Indian scientists have documented more than 900 tree species in the preserve. Because a handful of new species is discovered each year, scientists guess that the Western Ghats contain between 1,000 and 1,100 species in all, Harte said.
"Before our publication, there really was no solidly-based theory that provided a means of making such estimates," he said.
The newly derived relationship between number of species and area is mathematically more complicated, but it does predict that as the area increases, the number of new species found approaches zero. This is more realistic than the previous species-area curve, which theoretically predicts an infinite number of species.
Harte has already received several dozen requests for reprints, and he predicts "it will generate a lot of discussion. I think the debate is going to be interesting."
The study was supported by the National Science Foundation, the Czech Ministry of Education and the Academy of Sciences of the Czech Republic, of which Storch is a member.
Adapted from materials provided by University of California - Berkeley.

Mystery Of Bat With An Extraordinary Nose Solved

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ScienceDaily (July 7, 2009) — A research paper co-written by a Virginia Tech faculty member explains a 60-year mystery behind a rare bat's nose that is unusually large for its species.

The article, "Acoustic effects accurately predict an extreme case of biological morphology," by Z. Zhang, R. Müller, and S.N. Truong, details the adult Bourret's horseshoe bat (known scientifically as the "Rhinolophus paradoxolophus," meaning paradoxical crest), and it's roughly 9 millimeters in length nose. The typical horseshoe bat's nose is half that long, said Rolf Mueller, an associate professor with the Virginia Tech mechanical engineering department and director for the Bio-inspired Technology (BIT) Laboratory in Danville, Va. "This nose is so much larger than anything else," among other bats of the region, he said.
Mueller's findings show that the bat uses its elongated nose to create a highly focused sonar beam. Bats detect their environment through ultrasonic beams, or sonar, emitted from their mouths -- or noses, as in the case of the paradoxolophus bat. The echoes of the sound wave convey a wealth of information on objects in the bat's environment. This bat from the remote rainforests of South East Asia received its name 58 years ago because of its mysterious trait.
Much like a flashlight with an adjuster that can create an intense but small beam of light, the bat's nose can create a small but intense sonar beam. Mueller and his team used computer animation to compare varying sizes of bat noses, from small noses on other bats to the large nose of the paradoxolophus bat. In what Mueller calls a perfect mark of evolution, he says his computer modeling shows the length of the paradoxolophus bat's nose stops at the exact point the sonar beam's focal point would become ineffective.
"By predicting the width of the ultrasonic beam for each of these nose lengths with a computational method, we found that the natural nose length has a special value: All shortened noses provided less focus of the ultrasonic beam, whereas artificially elongated noses provided only negligible additional benefits," Mueller said. "Hence, this unusual case of a biological shape can be predicted accurately from its physical function alone."
The findings with the paradoxolophus bat are part of a larger study of approximately 120 different bat species and how they use sonar to perceive their environment. Set to finish in February 2010, it is hoped the study's focus on wave-based sensing and communication in bats will help spur groundwork for innovations in cell phone and satellite communications, as well as naval surveillance technology.
Mueller worked on the study with engineers and scientists from China's Shandong University, where he held a professorship when the research project began, and the Vietnamese Academy of Sciences. The article will appear in Physical Review Letters' print edition on July 17 and on the Web site on July 14.
Adapted from materials provided by Virginia Tech, via EurekAlert!, a service of AAAS.

Mangrove-dependent Animals Globally Threatened

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ScienceDaily (July 7, 2009) — Substantial numbers of terrestrial vertebrates are restricted to mangrove forests. Many of these specialized species are listed as threatened by the International Union for the Conservation of Nature. Prospects for mangrove-restricted animals are bleak, because more than two percent of mangrove forests are lost each year.

More than 40 percent of a sample of amphibians, reptiles, mammals, and birds that are restricted to mangrove ecosystems are globally threatened with extinction, according to an assessment published in the July/August issue of BioScience. The study, by David A. Luther of the University of Maryland and Russell Greenberg of the Smithsonian Migratory Bird Center, was based on an extensive literature search and expert consultations.
The conclusions emphasize the vulnerability of animals that are dependent on a habitat rapidly being lost or degraded through coastal development, overexploitation, pollution, and changes in sea level and salinity.
Mangroves, which are salt-tolerant woody plants concentrated along coastal margins, generally in warm regions, have long been known to support many species of animals. Hundreds of vertebrates are sometimes found in mangroves, but Luther and Greenberg concentrated on the 69 terrestrial vertebrate species and subspecies that seem restricted to mangroves: 48 birds, 14 reptiles, 6 mammals, and 1 amphibian. These include several species with striking adaptations, such as specialized glands to excrete salt. The ground foragers among them feed primarily on crabs, but many of the birds feed on insects. For unclear reasons, mangrove-restricted species and subspecies are concentrated in Asia and Australia.
Between the early 1980s and 2001, between 19 and 35 percent of the world's mangrove forest area was lost. At this rate of loss--about 2 percent each year--mangroves could be extinct in 100 years. Only 27 of the terrestrial vertebrates that are dependent on mangroves have been assessed by the IUCN (International Union for the Conservation of Nature), and 13 of those are classified as threatened on the IUCN Red List, Luther and Greenberg report. They urge research aimed at predicting how continuing changes to mangrove forests are likely to affect the species found there: such information could guide attempts to conserve these specialized ecosystems.
Journal reference:
David A. Luther and Russell Greenberg. Mangroves: A Global Perspective on the Evolution and Conservation of Their Terrestrial Vertebrates. BioScience, July/August
Adapted from materials provided by American Institute of Biological Sciences, via EurekAlert!, a service of AAAS.

New Monkey Discovered In Brazil -- Threatened By Proposed Dams And Other Development In Region

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ScienceDaily (July 7, 2009) — The Wildlife Conservation Society (WCS) announced on July 7 the discovery of a new monkey in a remote region of the Amazon in Brazil.

The monkey is related to saddleback tamarins, which include several species of monkeys known for their distinctively marked backs. The newly described distinct subspecies was first seen by scientists on a 2007 expedition into the state of Amazonas in northwestern Brazil.
The discovery was published in the June online edition of the International Journal of Primatology. Authors of the study include Fabio Röhe of the Wildlife Conservation Society, José de Sousa e Silva Jr. of Museu Paraense Emílio Goeldi, Ricardo Sampaio of the Instituto Nacional de Parquisas de Amaozônia, and Anthony B. Rylands of Conservation International.
Researchers have dubbed the monkey Mura's saddleback tamarin (Saguinus fuscicollis mura) named after the Mura Indians, the ethnic group of Amerindians of the Purus and Madeira river basins where the monkey occurs. Historically this tribe was spread through the largest territory of any of the Amazonian Indigenous peoples, extending from the Peruvian frontier today (Rio Yavari) east to the Rio Trombetas.
The monkey is mostly gray and dark brown in color, with a distinctly mottled "saddle." It weighs 213 grams (less than ¾ of a pound) and is 240 millimeters (9 inches tall) with a 320 millimeter (12.6 inch) tail.
"The Wildlife Conservation Society is extremely proud to be part of this exciting discovery in the Amazon," said Dr. Avecita Chicchon, Director of WCS's Latin America Programs. "We hope that the discovery will draw attention to conservation in this very fragile but biodiverse region."
According to the study's authors, the monkey is threatened by several planned development projects in the region, particularly a major highway cutting through the Amazon that is currently being paved. Conservationists fear the highway could fuel wider deforestation in the Amazon over the next two decades. Other threats to the region include a proposed gas pipeline and two hydroelectric dams currently in the beginning stages of construction.
"This newly described monkey shows that even today there are still major wildlife discoveries to be made," said the study's lead author, Fabio Röhe of the Wildlife Conservation Society. "This discovery should serve as a wake-up call that there is still so much to learn from the world's wild places, yet humans continue to threaten these areas with destruction."
Journal reference:
Fabio Röhe, José de Sousa e Silva, Ricardo Sampaio and Anthony B. Rylands. A New Subspecies of Saguinus fuscicollis (Primates, Callitrichidae). International Journal of Primatology, 2009; DOI: 10.1007/s10764-009-9358-x
Adapted from materials provided by Wildlife Conservation Society, via EurekAlert!, a service of AAAS.