Overfishing Drives African Bushmeat Appetite and Other Stories
Overfishing Drives African Bushmeat Appetite
In years when fish catches are low, people in the West African state of Ghana turn to bushmeat to fill their stomachs. The new study, by Justin Brashears of the University of California, Berkeley, and colleagues, is based on 30 years of data collected on the trade in wildlife meat and marine fish catches. The researchers report in the journal Science that months when ocean fish are expensive and scarce see a rise in the amount of bushmeat for sale in local markets, especially in coastal communities. Park rangers also report higher rates of poaching in times of low fish catches. And populations of 41 species of wild mammals in six nature reserves also dipped more sharply in years when seafood was scarce. By contrast, the weather, oil prices, and other political factors bore little relationship to bushmeat hunting. The trade in bushmeat is threatening populations of many African species, including hyenas, leopards, monkeys, hippos, and elephants. The scientists say that foreign fishing boats plying West African waters, most of which are from the European Union, are accelerating the decline of both African fish stocks and land-based wildlife.
Body Language Is A Fear Factor
A fearful pose can be just as alarming to the brain as an anguished face, according to a new study. The research, by Beatrice de Gelder of Harvard Medical School, helps explain how panic can spread quickly through a crowd. de Gelder filmed actors doing mundane tasks such as pouring water and in dramatic situations such as finding a robber outside a door. She reduced the images to silhouettes, and blacked out the actors' faces. She then showed the photos to four men and three women hooked up to a magnetic resonance imaging machine, or MRI. In response to photos of neutral activities, areas of the brain linked to visual image processing to become active. But the photos of fearful postures triggered activity in the brain's visual, emotional, and motor action areas. The study, reported in the Proceedings of the National Academy of Sciences, demonstrates that emotions can be telegraphed nonverbally, and that body language indicating danger is enough to prime the human nervous system to respond with flight or physical action.
Extinction Rates Reach Frightening New Heights
Species are disappearing at record-breaking rates, according to a grim new report by the World Conservation Union (IUCN). The group's 2004 Red List, which tracks the status of the planet's rarest species, cites 15,589 known species at risk of extinction. If anything, the list is an underestimate; it misses millions of as-yet-undescribed species as well as most marine creatures, whose population status is largely unknown. Vulnerable species include one in three amphibians, one in four mammals, and one in eight birds. This year, the Hawaiian thrush, the Costa Rican golden toad, and the St. Helena olive tree were among those species officially declared extinct. Interestingly, mainland extinction rates were equal in severity to those on islands, which are considered more ecologically fragile. Scientists now say the current extinction rate is 100 to 1,000 times greater than is natural. Responsibility for virtually all the listings can be laid at humanity's doorstep. Habitat destruction, hunting, fishing, species invasions and human-accelerated climate change are the worst culprits.
Brown Bears Beat Glaciers In Ancient Migration
The story of grizzly migration into North America has long puzzled scientists. Fossil remains show that the relatives of southern Canada's brown bears first slouched into eastern Alaska from Asia more than 35,000 years ago. Then glaciers blocked the path south from 23,000 to 13,000 years ago. But the bears didn't seem to have spread south until after the path reopened; all southern grizzly fossils found were younger than 13,000 years old. But genetic studies didn't gibe with this information. DNA studies suggest southern grizzlies are more closely related to one another than to bears from northern Canada and Alaska. But the remains of these southern bears' 35,000-year-old relatives have also been found along the land bridge route. Now Paul Matheus of the University of Alaska, Fairbanks, and colleagues have solved the paradox. Matheus found a grizzly jaw in a Canadian museum that had been collected in southern Canada but was also 23,000 years old. He reports in the journal Science ancient brown bears therefore did expand farther south before ice slammed the route shut. This first wave of bears gave rise to modern southern grizzlies, while a second wave of brown bears began recolonizing Alaska and the Yukon later, about 21,000 years ago.
Titan Shows No Shimmering Waves
Mirrorlike reflections from lakes and seas are absent from the latest images of Saturn's moon Titan. Snapped by the spacecraft Cassini, the images all but rule out the existence of lifegiving liquids on the moon's surface. Astronomers had long believed cloud-shrouded Titan had surface oceans made of hydrocarbons such as ethane. They hoped these strange lakes might carry either the precursors to life-giving molecules or early forms of life itself. Their hopes had been bolstered by Earth-based radar observations taken as recently as 2003, which indicated up to 75 percent of the moon's surface might be liquid. But Cassini's photos of Titan were taken from just 1,200 kilometers away, and the dark areas thought to be liquid appear too varied in hue to be pools or oceans. Nevertheless, some scientists are holding out hope that smaller bodies of liquid will be found elsewhere on the frigid planet. They also believe a distinctive, pancake-shaped dome on its surface may be the result of slumping ice rather than molten rock.
Moas On Decline Prior To Humans' Arrival
New Zealand's flightless moas may have numbered in the millions shortly before they went extinct, new genetic studies suggest. The finding cast doubt on theories that human hunters were solely responsible for their demise. Neil Gemmel of the University of Canterbury, New Zealand, and colleagues analyzed mitochondrial DNA sequences from 58 birds belonging to the largest species of moa, Dinornis. The amount of diversity in the birds' genes, the researchers report in the journal Biology Letters, suggests there were about 300,000 to 1.4 million Dinornis a few thousand years before human contact, and between 3 to 12 million moas of all species. Previous studies estimated total moa populations at about 159,000 animals when people first arrived about 1,000 years ago. The new study indicates moas must have been declining before humans arrived. Even the intensive hunting and grassland burning that ended in the giant birds' extinction probably could not have wiped out so many moas in such a short time. The scientists now suspect massive eruptions from an ancient volcano may have coated the moas' habitat with ash, or that new, fatal diseases that could have been introduced by migrating birds.
Bats Owe Wings To Finger Gene
A fortuitous mutation in a single gene launched the ancestors of bats into the sky. The discovery, by Karen Sears of the University of Colorado, Denver, helps explain why no primitive bats have been found in the fossil record. Bat wings consist of skin stretched between extra-long finger bones. In the study, Sears compared the finger growth of both bat and mouse embryos. The digits of both species lengthen from an area known as the hypertrophic zone located at the ends of the finger bones. This zone is far larger in the digits of bats than in mice. The difference is caused by a change in a mammalian limb growth gene known as BMP2. When Sears applied the protein produced from bat BMP2 to the digits of embryonic mice, their fingers elongated to batlike proportions. The mutation would have allowed the first bats to fly almost immediately. A new life in the air would have greatly favored animals with echolocation abilities and aerobatic wings, so that any transitional bat species would have evolved quickly into more advanced forms. Sears reported the finding at a meeting of the Society of Vertebrate Paleontology in Denver.
Overfishing Drives African Bushmeat Appetite: BBC / New Scientist
Body Language Is A Fear Factor: MSNBC (Associated Press) / National Geographic
Extinction Rates Reach Frightening New Heights: Scientifc American / Discovery.com (Agence France Presse) / BBC
Brown Bears Beat Glaciers In Ancient Migration: Los Angeles Times (Associated Press) / National Geographic / BBC
Titan Shows No Shimmering Waves: New Scientist
Moas On Decline Prior To Humans' Arrival: New Scientist
Bats Owe Wings To Finger Gene: New Scientist
Source: California Academy of Sciences