February 6, 2008, 5:30 AM CT

Wind as the Force Behind Fish Booms and Busts

The mid-20th century crash of the sardine fishery off California for decades has vexed marine ecologists searching for the root causes of large fluctuations in the sardine population. Before its collapse, the fishery was one of the world's most productive and formed the setting of John Steinbeck's "Cannery Row" in Monterey, Calif.

Researchers at Scripps Institution of Oceanography at UC San Diego have now shed light on the puzzle by proposing a plausible mechanism behind the mystery: wind.

Writing in the online early edition of the Proceedings of the National Academy of Sciences, Scripps scientists Ryan Rykaczewski and David Checkley propose that atmospheric wind forces can determine the availability of microscopic organisms that sardine and anchovy feed upon. When wind causes nutrient-rich waters to rise to the surface, plankton levels increase and sardine populations flourish. On the other hand, sardine numbers crash when plankton become scarce as wind conditions change.

The researchers say their findings may explain the sardine and anchovy booms and busts off California's coast and could explain similar population cycles elsewhere around the world.

"This paper is the first to show a mechanistic relationship between climate variability and the sardine fishery," said Rykaczewski, a Scripps graduate student researcher. "There have been a lot of hypotheses about climate change and sardine and anchovy fisheries, but there has been little scientific support for a mechanism connecting changes in climate to changes in these fish populations"......... Posted by: Kelly      Read more         Source

February 4, 2008, 9:32 PM CT

Gotta have heart!

According tohaps confirmed by their ubiquity on nature cable channels, crocodiles are among natures most fearsome predators. When the opportunity arises, crocodilians will gorge, voluntarily consuming meals weighing 23% of their own body weight. This is analogous to a 130 -pound woman eating, at one sitting, a hamburger weighing 30 pounds. But what to do with all of that food" If they do not digest their meal quickly, crocodilians risk death from within, or if they are young, by predators.

While it has long been known that reptiles have the ability to shunt blood past their lungs, the physiological function of this ability is poorly understood. In a breakthrough article for the March/April 2008 issue of Physiological and Biochemical Zoology, The Right-to-Left Shunt of Crocodilians Serves Digestion, Professor C.G. Farmer and her colleagues at the University of Utah, along with the Utah Artificial Heart Institute, were able to demonstrate through their experiments with American alligators that the bypass function is central in their digestion process, and ultimately, their survival.

After feasting, crocodilians like to find a warm place to lie down while they digest their meal. Eventhough on the outside this behavior seems ordinary, inside their bodies an extraordinary event takes place. During this period of digestion crocodilians divert blood through a special vessel that bypasses the lung, named the left aorta. Humans, other mammals, and birds lack this special vessel, and so all blood pumped by the right side of the heart flows through the pulmonary artery into the lungs, where carbon dioxide (CO2) moves from the blood into the gases of the lungs. Crocodilians can chose not to use the left aorta, in which case their cardiovascular system is very much like the mammalian system. However, when crocodilians are digesting a meal, they chose to shunt and direct CO2-rich blood straight to the stomach where glands make use of the CO2 to form gastric acid and bicarbonate. Consequently this shunt enables crocodilians to secrete gastric acid at a rate that is approximately 10 times the highest rates measured in mammals. If crocodilians are deprived of this ability to sidestep their lungs, their rates of acid secretion drop significantly and their ability to dissolve bone, a regular part of their normal diet, is impaired......... Posted by: Kelly      Read more         Source

February 4, 2008, 8:37 PM CT

Birds and bats hold secrets for aerospace engineers

Natural flyers like birds, bats and insects outperform man-made aircraft in aerobatics and efficiency. University of Michigan engineers are studying these animals as a step toward designing flapping-wing planes with wingspans smaller than a deck of playing cards.

A Blackbird jet flying nearly 2,000 miles per hour covers 32 body lengths per second. But a common pigeon flying at 50 miles per hour covers 75.

The roll rate of the aerobatic A-4 Skyhawk plane is about 720 degrees per second. The roll rate of a barn swallow exceeds 5,000 degrees per second.

Select military aircraft can withstand gravitational forces of 8-10 G. A number of birds routinely experience positive G-forces greater than 10 G and up to 14 G.

"Natural flyers obviously have some highly varied mechanical properties that we really have not incorporated in engineering," said Wei Shyy, chair of the Aerospace Engineering department and an author of the new book "The Aerodynamics of Low Reynolds Number Flyers".

"They're not only lighter, but also have much more adaptive structures as well as capabilities of integrating aerodynamics with wing and body shapes, which change all the time," Shyy said. "Natural flyers have outstanding capabilities to remain airborne through wind gusts, rain, and snow." Shyy photographs birds to help him understand their aerodynamics......... Posted by: Kelly      Read more         Source

January 29, 2008, 9:52 PM CT

Insects on coffee plants

Ever since a forward-thinking trio of physicists identified the phenomenon known as self-organized criticality-a mechanism by which complexity arises in nature-researchers have been applying its concepts to everything from economics to avalanches.

Now, scientists at the University of Michigan and the University of Toledo have shown that clusters of ant nests on a coffee farm in Mexico also adhere to the model. Their work, which has implications for controlling coffee pests, appears in the Jan. 24 issue of the journal Nature.

The basic idea of self-organized criticality often is illustrated with a sand pile. As you trickle sand onto the cone-shaped pile, the cone grows and grows until it reaches a "state of criticality" where it stops growing. Add more sand, and the grains just slide down the sides in mini-avalanches.

"What physicists have done-both mathematically and physically-is look at how a number of grains of sand actually fall with each avalanche," said John Vandermeer, the Margaret Davis Collegiate Professor of Ecology and Evolutionary Biology and one of the Nature paper's authors. "What they find is that most avalanches involve one or two sand grains, and relatively few avalanches involve hundreds of sand grains." Such a pattern-with small versions of a phenomenon being more common than big ones-characterizes what's known as a power law, a sort of fingerprint of systems that exhibit self-organized criticality......... Posted by: Kelly      Read more         Source

January 29, 2008, 9:37 PM CT

The Pitter Patter of Little Feet

Building upon several years of research into the gecko's uncanny ability to climb sheer walls, scientists at the University of California, Berkeley, have developed an adhesive that is the first to master the easy attach and easy release of the reptile's padded feet. The material could prove useful for a range of products, from climbing equipment to medical devices.

Unlike duct tape or glue, the new material is crafted from millions of tiny, hard, plastic fibers that establish grip; a mere square two centimeters on a side can support 400 grams (close to a pound). While tape sticks when it presses onto a surface, the new adhesive sticks as it slides on a surface and releases as it lifts -- this is the trick behind a gecko's speedy vertical escapes.

The new study appeared online Jan. 23, 2008, in the Journal of the Royal Society Interface.

There are other synthetic adhesives inspired by gecko feet and they adhere much like conventional tape. In contrast, the new adhesive brushes along a surface to develop traction. While ideal for hanging posters, the characteristic is even more important for any application that requires movement, such as climbing.

"The gecko has a very sophisticated hierarchical structure of compliant toes, microfibers, nanofibers and nanoattachment plates that allows the foot to attach and release with very little effort," said co-author and Berkeley professor Ron Fearing, "The gecko makes it look simple, but the animal needs to control the directions it is moving its toes--correct movement equates to little effort," he said......... Posted by: Kelly      Read more         Source

January 28, 2008, 10:35 PM CT

Lusty voles, mindless of danger, mate like rabbits

Forgetful Casanovas are lucky in love.

At least thats how University of Florida scientists interpret the results of new research on the mating habits and nervous systems of prairie voles. An article about the research, which examined both the voles behavior and their brains, appears in this weeks edition of the Proceedings of the National Academy of Sciences.

Prairie voles, aka Microtus ochrogaster, are common native rodents in the central U.S. and southern Canada. Because they mate for life and are relatively easy to study, the mouse-like creatures have been the subject of much research by researchers probing questions of monogamy and sexual faithfulness among mammals.

Steve Phelps, an assistant professor of zoology and one of the papers three authors, said a number of male voles pick a female partner and settle in a territory often for life. A minority, however, shirks steady partners and home bases, instead ranging across other males turf and mating with other males females.

Alexander Ophir, a postdoctoral associate in zoology at UF, is the papers lead author and conducted the research, which is funded by the National Science Foundation. Ophir, Phelps and Jerry Wolff, a biologist at St. Cloud State University in Minnesota, set out to find out what makes the male wanderers wander behavior all the more puzzling because faithful males enthusiastically defend their partners, lunging at and biting the interlopers......... Posted by: Kelly      Read more         Source

January 28, 2008, 10:32 PM CT

Elephant engineers

It is like the premise of a popular home improvement show: in the before photos, the surroundings are undesirable and in the after shot theres lots of attractive spaces to grab a meal, start a family and relax in seclusion from lifes stresses. The difference here is that the potential new homeowner is a lizard and the renovations come -- not from a sophisticated Manhattan designer -- but instead from a herd of elephants. An examination of the connections between elephants and lizards appears this month in the journal Ecology, where a researcher reports that the elephants eating habits have a strong influence on the lizards habitat choices. The results demonstrate an important and little understood aspect of ecosystem engineering, and may help land managers working on wildlife refuges in Africa.

Working at the Mpala Research Center in Kenya between 2004 and 2007, the author of the report, Robert M. Pringle of Stanford University, observed that Kenya dwarf geckos (Lygodactylus keniensis) showed a strong preference for trees which had been damaged by browsing elephants (Loxodontia africana). In fact, the local lizard population increased proportionally with the number of damaged trees. By contrast, lizards were virtually absent from undamaged trees in the same study area......... Posted by: Kelly      Read more         Source

January 28, 2008, 10:15 PM CT

Race against time to save Tasmanian devils

A delegation of Tasmanian government officials traveled halfway around the world to visit Cold Spring Harbor Laboratory (CSHL), to lend their support and extend their gratitude for research aimed at understanding a unique transmissible and rapidly spreading cancer that threatens the very existence of Tasmanian devils. To combat this especially aggressive disease, a CSHL research team in collaboration with 454 Lifesciences is committing resources to sequence parts of the devils genome in an effort to increase the odds of saving them from extinction.

In 1996 researchers first discovered the facial tumors on Tasmanian devils. Subsequent research revealed that the cancer is transmitted from one devil to another when tumor cells are transplanted through fighting, biting, and other physical contact. Once afflicted with the cancer, aggressive tumors begin to appear on the face and neck of the devils, restricting their ability to eat. Within approximately three months, the devils succumb to the disease and often die of starvation. The disease has decimated the devil population by nearly 90 percent in certain geographical areas of Tasmania, and officials project that within twenty years the entire species could become extinct.

The process by which the disease spreads among the devils has only been seen once before and represents a new field in cancer biology. Inbreeding in wild populations may prevent the devils immune system from recognizing the cancer as foreign, allowing the cancer to be transmitted. To provide an alternate fate for the devils, the Tasmanian government will have an insurance population of more than two hundred devils in quarantined facilities before the end of 2008......... Posted by: Kelly      Read more         Source

January 24, 2008, 10:58 PM CT

When accounting for the global nitrogen budget, don't forget fish

Like bank accounts, the nutrient cycles that influence the natural world are regulated by inputs and outputs. If a routine withdrawal is overlooked, balance sheets become inaccurate. Over time, overlooked deductions can undermine our ability to understand and manage ecological systems.

Recent research by the Universite de Montreal (Canada) and the Cary Institute of Ecosystem Studies (Millbrook, New York) has revealed an important, but seldom accounted for, withdrawal in the global nitrogen cycle: commercial fisheries. Results, published as the cover story in the recent issue of Nature Geoscience, highlight the role that fisheries play in removing nitrogen from coastal oceans.

Nitrogen is essential to plant and animal life; however, it is possible to have too much of a good thing. During the past century, a range of human activities have increased nitrogen inputs to coastal waters. Fertilizer run-off is the best documented and most significant source of terrestrial nitrogen pollution. Nitrogen-rich fertilizer applied to farmland eventually makes its way into coastal waters via a network of streams and rivers.

Research spearheaded by Roxane Maranger (Universite de Montreal) and Nina Caraco (Cary Institute) demonstrates that commercial fisheries play an important but declining role in removing terrestrial nitrogen from coastal waters. Accounting for this withdrawal is crucial; terrestrial-derived nitrogen can stimulate coastal phytoplankton growth, leading to eutrophication. Typically eutrophic waters are characterized by reduced dissolved oxygen, decreased biodiversity, and species composition shifts......... Posted by: Kelly      Read more         Source

January 21, 2008, 9:11 PM CT

Captive carnivores not up to wild living

A study by the University of Exeter has highlighted the problems of reintroducing animals to the wild for conservation projects. Published online in the journal Biological Conservation, the research highlights the low survival rates of captive carnivores that are released into their natural habitats. On average only one in three captive-born carnivores survives in the wild, with most deaths correlation to human activities.

Recent high-profile conservation projects have involved reintroducing wolves into the Scottish Highlands, bringing red kites back to England and reintroducing golden lion tamarins to Brazil. Most of these animals were born in captivity, with zoos playing a major role in such projects, while other schemes involve moving wild animals to new areas.

This study evaluated 45 case studies, involving 17 carnivore species, and observed that only 30% of captive animals released survived. Over half the deaths were caused by humans in incidents such as shootings and car accidents. The animals were also more susceptible to starvation and disease than their wild counterparts and less able to form successful social groups.

Kristen Jule, lead author on the paper and University of Exeter PhD student, says: Animals in captivity do not commonly have the natural behaviours needed for success in the wild. Their lack of hunting skills and their lack of fear towards humans, for example, are major disadvantages. We have suspected for some time that captive born animals fared less well than wild animals, but here it is finally quantified, and the extent of the problem is critical......... Posted by: Kelly      Read more         Source