SCIENCE

Notebook

William Osler, the legendary first physician-in-chief of Johns Hopkins Hospital in the late 1800s, once opined: "The desire to take medicine is perhaps the greatest feature which distinguishes man from other animals."

Since then, however, many scientists have observed what appears to be self-medication by animals. With seeming intentionality, chimpanzees swallow leaves, which help them expel parasites. Other animals, including birds and apes, sometimes eat soil rich in clay, a substance known to sop up bacteria and toxins, in apparent efforts to get relief from gastrointestinal illness.

But almost all observations have been in nature, where it is difficult to know why an animal is making choices. Was it really sick? Did the "medicine" really help?

Scientists at Utah State University have done what they call the first definitive test. Juan J. Villalba and colleagues created three distinct sheep feeds, each spiked with a substance that caused a different kind of discomfort -- acid stomach, poor digestion with gut sores, and a toxic syndrome accompanied by low calcium levels. They also created three other blends, each with a single antidote for one of those toxic foods.

In experiments involving 20 sheep kept in pens, described in the May issue of the journal Animal Behaviour, the team showed that the animals quickly had a preference for the food with the proper antidote -- and made the right choice again five months later, indicating the animals remembered which food would cure what they had.

Much remains to be learned, the scientists say, about how animals learn medical associations in nature and to what extent that knowledge is shared communally.

-- Rick Weiss

New Hammerhead Shark Found

Scientists have discovered a species of hammerhead shark off the South Carolina coast, making it the ninth known species of the distinctively shaped predators. The shark, which the researchers are calling the "cryptic species," is thought to be at risk of extinction because it may exist only off the South Carolina coast. University of South Carolina biologist Joe Quattro, along with Jim Grady of the University of New Orleans and Trey Driggers at the National Marine Fisheries Service, discovered the species.

While studying scalloped hammerheads, Quattro noticed that genes in the cryptic sharks' mitochondrial DNA differed from those of other sharks that appeared to be otherwise the same. Further studies revealed another genetic marker that differentiated the two groups of scalloped hammerheads. In the summer, Quattro will tag the sharks to determine where they go once they leave South Carolina waters.

"Protecting this prime nursery habitat is vital to the survival of the cryptic species," said Quattro, who published his findings in the journal Marine Biology.

Sylvia Earle, a shark and marine expert at the advocacy group Conservation International, said the discovery highlights the need to continue exploring the seas: "It's another indication of how much we have to learn about the ocean."

-- Juliet Eilperin