Long thought to be harmless, SIV—the source of HIV—may lead to a lethal, AIDS-like illness in chimps, after all. Though a blow to conservationists, the discovery may hold insights for human medicine.

From the limestone caves to the world's tallest waterfall—"the eyes of the planet" are on the finalists from which the seven natural wonders of the world will be chosen.

For the first time, Florida is allowing select hunters to kill pythons in the wild. The non-native snakes are believed to number in the tens of thousands and are killing endangered species, experts say. Video.

Developing ultrasound blasts to disrupt enemy sonar may sound more like a submarine arms race than animal evolution. But some moths seem to have done just that.

A white tiger dives into the blue, Google goes three-wheeling at Stonehenge, a conservator "camps" at Westminster Abbey, and more in the week's best news pictures.

Vampire bats in Peru are increasingly biting people, and a National Geographic researcher is trying to find ways to stem the resulting spread of deadly rabies. Video.

Don't let the foot-long claws fool you. Unlike the X-men's most popular pugilist, this newfound dinosaur species was no predator, scientists say.

The discovery of the world's oldest known dinosaur burrow suggests that when the going got tough, some polar dinosaurs started digging.

Basking sharks, the world's second biggest fish, usually die at sea. So why did a 20-foot giant beach itself on New York's Long Island on Tuesday?

Warning: disturbing images. Asian demand for whole-pangolin-fetus soup, pangolin-scale "medicines," and other concoctions is driving these scaly anteaters to the edge of extinction, a new report says.

Jumbo squid were found flapping on a California beach Saturday after an earthquake, but experts think the timing is coincidental. So what did strand the ocean giants? With video.

Bloody and incomplete, their horns hacked away by poachers, rhinoceros carcasses are appearing in greater numbers, due to growing Asian demand and international trade, groups say.

A favorite of divers in Australia, the blue groper grows to about three feet (one meter) long and can change its own sex. But its numbers are diving, and researchers are trying to throw the groper a lifeline. Video.

Hungry house cats use an annoying but irresistible combination of sounds when they want to be fed, a new study has found. With video.

In the first goring death at Spain's running of the bulls since 1995, a 27-year-old was killed Friday after a bull became separated from the pack. Video.