Science briefs: Tortoises born once more in the wild in the Galapagaos

An expedition in 1970 found only 19 adult tortoises on the archipelago's Pinzon island, averaging 70 years old, so scientists removed them to start a captive breeding program on Santa Cruz island. The program produced juveniles that were transplanted back to the island, which is the only place the species is found.

Danny Rueda, who is in charge of conservation and restoration of ecosystems in the Galapagos, said that in December six infant Pinzons were found to have been born on the island. He said there are now 650 juvenile and adult tortoises on Pinzon.

Rueda said the reintroduction of the tortoise was helped by the 2012 campaign to eradicate rats that infested Pinzon and other islands in the archipelago after being introduced long ago by passing ships. The rats prevented the reproduction by tortoises and other species.

"Finding the six baby tortoises tells us that the process of eradicating rats succeeded," he said. "We have begun to see that the ecosystem has begun to restore itself."

About 2,000 snow geese migrating from Mexico to their Alaskan nesting grounds were found dead in Idaho, the state's Department of Fish and Game announced Monday. Although testing is still in progress, officials believe that the deaths are consistent with avian cholera.

The suddenness in which the birds died is part of the reason that experts suspect avian cholera, which kills acute sufferers in as little as six hours. "Basically, they just fell out of the sky," said Fish and Game spokesman Gregg Losinski.

To prevent any other wildlife from picking up the disease, officials have collected and burned the carcasses, all found in the Mud Lake and Market Lake Wildlife Management Areas in the southeast region of the state. While local wildlife populations are potentially at risk from avian cholera, humans are at a low risk of picking up an infection from the bacteria that causes the disease, officials said.

Some studies have indicated that their palm-size hatchlings orient themselves to Earth's magnetic field. A study published in the Proceedings of the Royal Society B finds that the turtles may use the field to navigate in adulthood, too.

Scientists at the National Oceanic and Atmospheric Administration tracked 15 leatherback turtles with GPS tags from August 2007 to September 2009. The turtles swam from their feeding grounds off Massachusetts to the western Atlantic subtropical gyre, a great swirl of ocean currents circulating from the equator almost to Iceland and from the East Coast to Europe and Africa.

The researchers found that despite being in the currents, the turtles were able to keep moving south.

"They were able to maintain their orientation during day and night," said Kara Dodge, an NOAA marine biologist in Woods Hole, Mass., and an author of the new paper. "This suggests they are using the Earth's magnetic field." Dodge conducted the research as a doctoral student at the University of Massachusetts Amherst.

Adult leatherbacks do not survive in captivity. But research on the sensory systems of turtles that fare better in the lab, like loggerheads and green sea turtles, may reveal more about their navigational skills.