Snowy Owl

The ghostlike snowy owl has unmistakable white plumage that echoes its Arctic origins.

These large owls breed on the Arctic tundra, where females lay a clutch of 3 to 11 eggs. Clutch size depends upon the availability of food, and in particularly lean times a usually monogamous pair of owls may not breed at all. Parents are territorial and will defend their nests against all comers—even wolves.

Young owls, especially males, get whiter as they get older. Females are darker than males, with dusky spotting, and never become totally white. Some elderly males do become completely white, though many retain small flecks of dusky plumage.

The snowy owl is a patient hunter that perches and waits to identify its prey before soaring off in pursuit. Snowy owls have keen eyesight and great hearing, which can help them find prey that is invisible under thick vegetation or snowcover. The owls deftly snatch their quarry with their sharp talons.

A snowy owl's preferred meal is lemmings—many lemmings. An adult may eat more than 1,600 lemmings a year, or three to five every day. The birds supplement their diet with rabbits, rodents, birds, and fish.

World's Biggest Cave Found in Vietnam

James Owen

A massive cave recently uncovered in a remote Vietnamese jungle is the largest single cave passage yet found, a new survey shows.

At 262-by-262 feet (80-by-80 meters) in most places, the Son Doong cave beats out the previous world-record holder, Deer Cave in the Malaysian section of the island of Borneo.

Deer Cave is no less than 300-by-300 feet (91-by-91 meters), but it's only about a mile (1.6 kilometers) long.

By contrast, explorers walked 2.8 miles (4.5 kilometers) into Son Doong, in Phong Nha-Ke Bang National Park, before being blocked by seasonal floodwaters—and they think that the passage is even longer.

In addition, for a couple of miles Son Doong reaches more than 460-by-460 feet (140-by-140 meters), said Adam Spillane, a member of the British Cave Research Association expedition that explored the massive cavern.

Spillane was in the first of two groups to enter the cave. His team followed the passage as far as a 46-foot-high (14-meter-high) wall.

"The second team that went in got flooded out," he said. "We're going back next year to climb that wall and explore the cave further."