The deadly H5N1 strain of bird flu has evolved into several distinct sublineages—potentially complicating efforts to develop effective vaccines.

Marmoset and tamarin monkey dads gain an average of 10 percent of their body weight by the time their mates give birth, new research shows.

Drug traffickers implanted heroin packets in purebred dogs, according to the U.S. Drug Enforcement Agency, which seized the puppies in a raid.

Rats can locate the direction of a stench's source in a single sniff, new research shows. The find provides insight into the spatial dimension of smell and the speed at which the brain operates.

Related Video: Rat Smelling in Stereo

Score one for the Swiss-Army-knife theory. A new study hints that brains are made up of distinct parts dedicated to distinct tasks, including recognizing faces.

Fur, wool, or down—don't shed your winter coat anytime soon. Weather-forecasting rodent Punxsutawney Phil "predicts" six more weeks of winter.

Watch how the regal horned lizard of Mexico's Sonoran desert uses an unusual defense tactic to repulse a hungry coyote.

Human activity is directly responsible for the rapid, large-scale decline of orangutan populations in parts of Asia, according to a new gene study.

In a bid to study and protect great hammerhead sharks, a marine scientist hopes to attach satellite-tracking tags to the 500-pound (230-kilogram) predators—by hand.

A teenage girl who died two weeks ago tested positive yesterday for the H5N1 strain of the virus, making her the first bird flu victim in the war-torn nation.

A cross between a horse and a rhinoceros—with 14 toes? Learn eight amazing facts about the endangered Baird's tapir, whose animal ancestors date back 35 million years.

Crammed into trunks and pockets, puppies too sick or young to survive on their own are being sold for up to a thousand dollars each in California parking lots.

It may be tiny, but this fish has sparked a debate that's big—though nowhere near as ugly.

To follow the movements of cougars in remote areas of western North America, a team of biologists has found a different kind of tracking device: a virus that's the feline equivalent of HIV.

By cracking the bird-flu genetic code, scientists have added to the arsenal against the virus—and uncovered a secret of its deadliness.