Science Digest

Monday, June 15, 2009

Macaw Comeback

The Lear's macaw, a blue parrot found only in northeastern Brazil, is now an endangered species -- and that's a good thing.

The global conservation organization that tracks threatened species downlisted the Lear's macaw last week from "critically endangered," the highest threat category, to "endangered."

"The bottom line is that conservation works," said Steve Holmer, a spokesman for the American Bird Conservancy. "If we can secure the habitat and make it sustainable, it gives the species a chance."

The conservancy estimates the population of Lear's macaws to be 960, up from fewer than 100 in 1989. The group's conservation efforts included buying nearly 4,000 acres of the bird's habitat with its Brazilian partner, FundaƧao Biodiversitas.

The reserve, called the Canudos Biological Station, employs four full-time rangers to protect the birds 24 hours a day. In addition to poachers and illegal bird traders, the macaw is threatened by the destruction through farming of its primary food source, the seeds and fruit of licuri palm trees.

It's far more common for birds to move up, not down, on the Red List of the International Union for the Conservation of Nature and Natural Resources. Currently, 1,227 species, 12 by percent of the world's birds, are threatened with extinction and 192 of those are critically endangered. When the American Bird Conservancy announced the success of the Lear's macaw and a New Zealand petrel, the organization also reported that four birds had been uplisted.

-- Rachel Saslow

Taming Time?

Scientists have identified two genetic regions that make some animals tame and others aggressive. The discovery suggests it might be possible to breed tigers that are as docile as lambs, and vice versa.

The finding grew out of unusual circumstances: In 1972, scientists in the Soviet city of Novosibirsk captured a large number of rats. They divided them into two groups -- tame and aggressive -- and interbred the animals within each group. After more than 60 generations, the rats in the aggressive group became extremely jumpy and aggressive around people; the tame rats had no problem being handled.

Scientists then interbred the animals across the two groups and studied the genetic makeup of more than 700 offspring, along with measuring the physical and behavioral variations among the animals. Two genetic regions appeared to be linked with variations in tameness.

In a study published in the June 2009 issue of Genetics, Frank W. Albert at the Max Planck Institute for Evolutionary Anthropology in Germany said the discovery opens the door to a better understanding of animal husbandry.

"Maybe we'll then be able to domesticate a few of those species where humans have historically not been successful, like the wild African buffalo," Albert said.

-- Shankar Vedantam

Dinosaur Debate

There is compelling evidence that birds are dinosaurs. Both have hollow bones and hard-shelled eggs. Pelvis, wishbone, wrist bone, three-toed hind foot -- they're strikingly similar.

There is also evidence that dinosaurs sat on their eggs, just like birds. Specifically, birds are believed to be descendants of a type of dinosaur known as maniraptoran therapods.

But as with all orthodoxies, there is dissent. Two scientists at Oregon State University have published a paper in the Journal of Morphology arguing that dinosaurs did not have bird-like lungs.

"No known therapod dinosaur could possibly have ventilated a birdlike lung," said zoologist John Ruben, who co-authored the study with colleague Devon Quick.

They researched the skeletal-muscular structure supporting the air sacs that enable a bird to breathe. No such anatomy is known in therapod dinosaurs, Ruben said.

"It's far more like that the two groups share a common ancestor and for at least some period of time evolved in parallel," Ruben said. The birds-are-dinosaurs model is popular because "it allows people to think that somehow velociraptor sprouted feathers and flew off in the sunset and now is flying around your back yard."

But Jack Horner, curator of paleontology at the Museum of the Rockies in Montana, said the criticism is based on a misunderstanding of how we can tell species are related.

"Differences don't matter," Horner said. "It doesn't matter how many differences there are between birds and dinosaurs because there are hundreds of similarities."

There is no other animal in the fossil record more closely related to birds than therapod dinosaurs, he said, and the hypothesis is based on hundreds of characteristics.

-- Joel Achenbach

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