Fiddler crabs take carefully calibrated steps to find their way home, according to a new study in Current Biology [subscription required]. Scientists testing the tiny crustaceans’ homing skills found that both the length and number of their strides were guided by some sort of internal mileage counter. This allows them to plot a direct path back to their sandy burrows even if the burrows are out of sight. “We were able to measure every step by every leg of every animal in this experiment, and since these are eight-legged animals, that’s a lot,” [Scientific American] says co-author John E. Layne.
Many animals appear to have built-in GPS systems, although exactly how they function is not well-understood. Birds and sea turtles may use the position of the stars and the earth’s magnetic field to navigate. The honeybee has been shown to use the flow of the passing landscape across its field of vision. Some other animals may be able to gauge linear acceleration and use that to determine distance [The New York Times]. The way animals keep track of their movements and the distance they’ve traveled is known as path integration.
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Don’t let their fierce looks fool you: Some male carnivorous dinosaurs were actually devoted dads, researchers say. A new study examined the bones of three species of dinosaurs found sitting on fossilized egg clutches and declared that in these species, it was the males who sat on the nests and cared for the young. The three types of dinosaurs, Troodon, Oviraptor and Citipati, lived roughly 75 million years ago and were theropods — the primarily meat-eating group that also includes monstrous beasts like Tyrannosaurus rex and Giganotosaurus [Reuters].
The new findings upend some notions of dinosaur family life, and also suggest that birds, which are believed to have evolved from small, feathered dinosaurs, may have inherited this behavioral trait. Study coauthor Frankie Jackson says the study “sheds light on the origins of parental care systems in birds.” … Males protect or support offspring in more than 90 percent of bird species — a distinctly rare attribute in the animal world. In mammals, males provide parental care in 5 percent of species, and it’s even rarer in reptiles [Washington Post].
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Flu season is taking a toll on chicken farms across Asia, where new bird flu outbreaks are cropping up from China to India, leading to massive poultry slaughters. Health officials say the chickens are infected with the deadly bird flu strain known as H5N1, but thus far there have been only a few cases of human infection. Two human cases have been reported in Indonesia, one in Cambodia, and in Egypt a 16-year-old girl died of the virus. Yi Guan, a Hong Kong microbiology professor, says the recent spate of cases across the region may not be completely isolated and would likely get worse as winter sets in, when the risks of influenza tend to peak [The Wall Street Journal].
In China, more than 370,000 chickens were culled after an outbreak was announced in the eastern province of Jiangsu. The usual precautions have been imposed: birds have been slaughtered in the surrounding area, farms quarantined and disinfected, and the transport of fowl banned. But no information has been released about the scale of the outbreak – how many birds were found to be carrying the H5N1 strain of the virus and how many of them died [BBC News]. Chinese authorities say migrating birds probably brought the virus to local farms.
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The roots of mammalian hair go far back into evolutionary history, according to a new study. Hair, which provides insulation and protection, is seen as one of the main evolutionary innovations that led to the rise of mammals. But the origins of hair date back to an unknown reptile ancestor that lived more than 300 million years ago, in the Paleozoic era, the new study says [National Geographic News].
Previously, biologists had considered the possibility that hair evolved from scales or feathers, but the paucity of fossils showing the evolution from reptiles to mammals has made the question a hard one to examine. So in this new study, published in the Proceedings of the National Academy of Sciences [subscription required], researchers ignored the fossil record and looked instead to the genetic record of living animals: namely, a chicken and an anole lizard.
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Warmer winters in Norway seem to be causing a decline in lemming populations, according to a new study, and researchers say the decline of the rodent is having a cascading effect. Lemming predators, like foxes and owls, have been forced to hunt different prey in what researchers call a clear-cut example of how global warming can have a disruptive impact on entire ecosystems.
Lemming populations throughout Scandinavia tend to explode naturally every three to five years, causing huge numbers to go in search of food. Occasionally this leads the rodents to jump into water and swim to new pastures new—the origin of the myth that lemmings commit mass suicide. When lemmings boom, they’re hard to miss. Norwegians have had to use snowplows to clear the squashed rodents off the roads [National Geographic News]. But the study of lemming populations during the last four decades found no population explosions since 1994.
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The chicken industry has been remarkably effective in breeding efficient egg-layers and plump-breasted broilers, but a new study says that focus has created a chicken population that lacks genetic diversity, leaving the birds more vulnerable to diseases. The study found that industrial chickens have lost about half of the genetic variations once found in the wild chicken populations, and some have lost 90 percent of those genes.
This means most of the world’s chickens lack characteristics that evolved when they lived in the wild, and may be useful again to help them face stress and disease as livestock. Scientists want to breed DNA for traits such as disease resistance, or “animal well-being”, back into commercial birds without introducing undesirable traits at the same time [New Scientist]. Researchers say the biggest concern is that if commerical chickens are nearly identical genetically they’ll all be susceptible to the same infectious diseases, and an outbreak of of a ailment like avian flu could devastate the entire industry.
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Researchers have found a “bizarre” feathered dinosaur with a hodgepodge of characteristics, including four long tail feathers that researchers say may have evolved for display purposes–perhaps to attract a mate or scare off a rival. The well-preserved fossil of the new species, named Epidexipteryx hui, shows that the beast was covered in short, fluffy feathers but lacked the “contour feathers” that help modern birds fly; researchers say Epidexipteryx must have been flightless.
Paleontologist expert Angela Milner commented that the find “shows that feathers were likely being used for ornamentation for many millions of years before they were modified for flight. It provides fascinating evidence of evolutionary experiments with feathers that were going on before small dinosaurs finally took to the air and became birds” [BBC News].
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This summer, hundreds of Magellanic penguins washed ashore on Brazilian beaches, almost 2,000 miles away from their home in Patagonia. While a few penguins are typically discovered on Brazil’s coast each summer, scientists have been perplexed and worried over the mysteriously high number of drifters this year, and say they still don’t have an answer to what brought the birds so far north. In response to the crisis, an animal rescue group staged a dramatic air lift to bring the birds back home.
Like some maritime dust-bowl migration, more than 1,000 of these penguins have floated ashore in Brazil, nearly as far north as the equator. By the time their webbed feet touch sand, many are gaunt and exhausted, often having lost three-quarters of their body weight. Even more have died. “This year is completely anomalous,” said Lauro Barcellos, 51, an oceanographer who founded a rehabilitation center for penguins in southern Brazil. “. . . I’ve worked in this field for 35 years, and I have never seen anything like this” [Washington Post].
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A 33-foot long, carnivorous dinosaur that lived 85 million years ago had a breathing system similar to that used by modern birds, and researchers say the finding is further evidence of the evolutionary link between dinosaurs and birds. A fossil found in a riverbank in Argentina shows evidence of efficient air sacs that pumped air into the dinosaur’s lungs.
Lead researcher Paul Sereno named the new dinosaur Aerosteon riocoloradensis, which means “air bones from the Rio Colorado.” Instead of lungs that expand and contract, Sereno thinks this beast had air sacs that worked like a bellows, blowing air into the beast’s stiff lungs, much like modern birds…. Most paleontologists believe birds evolved from small, feathered meat-eating dinosaurs, and the earliest known birds were strikingly similar to these dinosaurs [Reuters].
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When a hummingbird or a hawk moth sups on the sweet nectar of a wild tobacco plant, they’re not just getting a tasty meal in exchange for their services in spreading the plant’s pollen. Instead, a new study shows that the nectar may be a complex chemical cocktail that simultaneously attracts and repels pollinators in order to optimize the amount of time they spend at each flower, and the attention they pay to flowers on different plants. “This paper shows just how sophisticated a plant can be in using chemistry to get what it wants,” [The Scientist] says lead researcher Ian Baldwin.
The researchers had already analyzed the chemical composition of tobacco plants’ nectar; they found that the compound benzyl acetone is the primary attractant, and that the plants “spike” their nectar with nicotine, presumably as a poisonous deterrent to insects. But in a clever experiment, the research team created genetically modified plants with different levels of these two chemicals. In greenhouse and field experiments, the scientists were surprised to find that not only did nicotine deter nectar robbers and plant nibblers, but the right dose prevented pollinators from lingering too long at any one flower, increasing the number of flowers visited [Science News].
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Some clever magpies can recognize themselves in a mirror, leading researchers to include them among the ranks of self-aware animals—an elite group that is generally thought to include only humans, great apes, bottlenose dolphins, and elephants. This new study suggests that a brain capable of surprisingly sophisticated intelligence developed in a few birds long after they split from the mammalian evolutionary tree, about 300 million years ago.
Says lead researcher Helmut Prior: “It shows that the line leading to humans is not as special as many thought…. After finding this kind of intelligence in apes, many people thought it had developed once in one evolutionary line with humans at the end. The bird studies show it has developed at least twice”[Reuters].
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A new study of fossilized bird feathers from 100 million years ago has determined that the broad stripes visible on the feathers do indicate the color of that ancient bird’s plumage. Researchers say the discovery may allow them to reconstruct the colors of other prehistoric birds and even feathered dinosaurs.
The fossil feathers had an obvious striped pattern but its origin had long been debated, according to Professor [Mike] Benton. “The banding looks so life-like that it can’t be geological in origin – it has to be biological,” he said. “But then how do you square that with the well-known fact that the majority of organic molecules decay in thousands of years?” [BBC News].
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An extensive study of bird genetics has revealed so many surprises about avian evolution that researchers say textbooks and field guides will have to be rewritten. After comparing the genetic codes of 169 species researchers realized that many assumptions about bird evolution are wrong; for example, they found that falcons are not closely related to hawks and eagles, and that flamingos didn’t evolve from other waterbirds.
“With this study, we learned two major things,” said Sushma Reddy, lead author and a fellow at The Field Museum in Chicago, Illinois. “First, appearances can be deceiving. Birds that look or act similar are not necessarily related. Second, much of bird classification and conventional wisdom on the evolutionary relationships of birds is wrong” [AFP].
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