Wild Predators Pose Little Threat to Livestock and Other Stories
Wild Predators Pose Little Threat to Livestock
Wolves and lions, bears and leopards have long been mortal enemies of ranchers. In an attempt to protect their livestock, human herders have hunted many big predators to the brink of extinction.
Now a new study of livestock predation around the world suggests these carnivore hunts may be a bloody waste of time. According to Kate Graham of the University of Stirling, United Kingdom, big carnivores are responsible for no more than 3 percent of livestock deaths. For example, lions killed about 2.4 percent of the cattle in Kenya each year, while a range of predators annualy killed about 2 percent of cattle in Zimbabwe.
And eradicating local predators isn't a long-lasting solution, sending kill rates down for less than a year. Evidence suggests the most visible carnivores are receiving an unwarranted amount of blame. For example, the endangered red kite is threatened in Spain because it hunts rabbits, yet 28 other predators eat rabbits also. The research is to be published in a book due out in 2005.
DNA Could Help Stop Elephant Poachers
DNA found in elephant tusks can be used as a tool to pinpoint the regional source of the ivory. The information could help governments crack down on elephant poaching, which has decimated populations throughout much of the continent.
Biologist Sam Wasser of the University of Washington, Seattle, and colleagues extracted DNA from elephant dung and tissue samples from 28 locations in Africa. They then analyzed how several DNA markers varied from region to region. The researchers found they could tell apart elephants from different forests and savannas with near-perfect accuracy. The result: a map of the likely genetic variation of elephants throughout Africa. Interpol already uses the map to trace the origins of poached ivory.
The technique could also help resolve a current dilemma in elephant conservation. After banning international trade in ivory in 1989, the Convention on International Trade in Endangered Species (CITES) has allowed some southern African nations with healthy elephant populations to sell some ivory stockpiles. However, it's been impossible to tell which tusks are legal to sell and which have been poached and imported from other parts of Africa. Now DNA fingerprinting should help keep the trade in ivory honest.
Voles Follow Their Noses for Mating Strategy
Fidelity is a bad word among female meadow voles. They prefer to play the field, mating with many neighbors instead of sticking to just one guy. As a result, their sperm compete inside the female to determine litter paternity.
Now scientists report in the journal Nature that male voles can sniff out the presence of a previous suitor's sperm and alter their mating tactics accordingly. In the study, Javier delBarco-Trillo of the University of Memphis, Tennessee, and colleagues put male and female voles together in cages. Half the cages contained the testosterone-based odor of other male voles; half were scent-free.
Each of the ten males in scented cages sniffed the area painted with the smell before mating. The researchers found males in scented cages produced an average of 169 million sperm per ejaculation, compared to 98 million sperm in the unscented containers. This scheme is likely designed to swamp out the semen of previous mates, making males with discerning noses more likely to father pups.
Bar Coding with DNA
Most consumers are familiar with the zebra-striped bar codes that identify products at stores and markets. Now a similar approach can be used to distinguish new species fast, sidestepping the painstaking anatomical studies employed in traditional taxonomy.
Paul Hebert of the University of Guelph, Canada, and colleagues sequenced the cytochrome c oxidase 1 gene which codes for a critical metabolic enzyme in DNA from 260 museum specimens of North American birds. They report in the Proceedings of the National Academy of Sciences that each species of bird possessed a unique sequence for this gene, while birds belonging to the same species had nearly identical versions. Based on this barcode information, the scientists say they may have identified four new bird species.
Hebert's team also collaborated with Daniel Janzen of the University of Pennsylvania, Philadelphia, to analyze 480 blue skipper butterflies from Costa Rica. As caterpillars, many had appeared somewhat different, but all metamorphosed into nearly identical adult butterflies. The barcoding research, reported in the journal PLoS Biology, suggests the butterflies belong to at least 10 different groups. The splits coincided with caterpillar types. The technique works best on species that diverged long ago and have had time to evolve unique barcode sequences. If accepted by the scientific community, barcoding could add a new dimension to the definition of species.
Wild Predators Pose Little Threat To Livestock: New Scientist
Voles Follow Their Noses for Mating Strategy: National Geographic
Source: California Academy of Sciences