Doubts About Woodpecker

An expert on the ivory-billed woodpecker is questioning evidence that the rare bird, once thought to be extinct, is alive in the swamps of southeast Arkansas.

Jerome A. Jackson, a zoologist at Florida Gulf Coast University, is challenging a blurry video cited by other scientists as showing a clip of one bird, saying the four-second image does "no more than suggest the possibility" the bird still exists.

"I am certainly not saying that ivory-billed woodpeckers are not out there," Jackson said yesterday in an e-mail. "I truly hope that the birds do exist in Arkansas."

Cornell University researchers said in April that they had spotted the bird, previously thought to have died out. The findings were reported in the journal Science.

Jackson, author of the book "In Search of the Ivory-Billed Woodpecker," has written a paper with two other biologists questioning the discovery, but he would not identify the journal in which it will appear or discuss details until the research is published.

Life on Mars Called Unlikely

Four billion years of freezing temperatures make it unlikely that any life that formed in Mars's early, warmer years would have survived, a study said.

Researchers examined three meteorites from Mars that were found on Earth, measuring the amount of argon gas in the rocks to determine their temperature history, according to the study in today's issue of the journal Science.

NASA's Mars Exploration Rovers have detected minerals suggesting that rocks have been immersed in water. Still, the research shows that temperatures probably have not risen much above the current average daily reading of about minus-72 degrees Fahrenheit for most of the planet's 4.5 billion years, co-author Benjamin Weiss said.

"It is hard to imagine that life could evolve in a situation where water is almost always frozen and temperatures are almost always subzero," said Weiss, an assistant professor at the Massachusetts Institute of Technology.

The study is being published as NASA is preparing to launch the Mars Reconnaissance Orbiter to search the planet's surface for evidence of past water.

Spider-Like Caterpillars

Tiny, snail-eating caterpillars found in Hawaiian rain forests tie up their prey with sticky silk and then snack at leisure, surprised scientists said.

It was the first time that caterpillars that eat snails or any other mollusk have been found, the researchers reported in Science. And although caterpillars of all kinds spin silk to make cocoons, this is the first time one has been seen using it to capture prey, as spiders do.

"Although all caterpillars have silk glands, this predatory caterpillar uses silk in a spider-like fashion to capture and immobilize prey," Daniel Z. Rubinoff and William Haines of the University of Hawaii said. The caterpillars of the new species, Hyposmocoma molluscivora, are small -- about a third of an inch long.

-- From News Services