Biologist Finds New Genus of Giant Rat

WASHINGTON -- The giant rat was already dead when Louise Emmons found it.

She'd been hunting for just such an oddity in the frosty Peruvian cloud forest, but a weasel had nabbed it first, with a cunning bite through the head.

The rat was still warm, and she loved it immediately, although love is the kind of imprecise word that a rigorous field biologist like Emmons would scorn.

"It was sort of cuddly," she said.

What truly thrilled her was the recognition that she had discovered not just a new species of tree rat, but a whole new genus. Later, she learned her rodent was a relative of the mysterious Incan tomb rats whose bones lay alongside human remains in the ancient Peruvian city of Machu Picchu.

A researcher affiliated with the Smithsonian Institution, Emmons is one of the world's most respected experts on tropical forest mammals.

For the past 10 years, between doing her own research, Emmons has tramped the world for the Washington-based Conservation International, part of a team of biological guerrillas charged with cataloging species living in some of the most remote places on the globe.

Emmons and her colleagues helicopter into a region, set up subsistence camps, eat rice and lentils for days, slog through muck and brush, and emerge after a few weeks with a quick-and-dirty inventory of flora and fauna. This information aids advocates seeking to preserve ecosystems and stave off oil and foresting conglomerates. The team's work in Bolivia led to the creation of the Madidi National Park.

It's dangerous work. Since CI founded its Rapid Assessment Program 10 years ago, three noted scientists have died, two in a plane crash in Ecuador and one in a boat accident in Peru. Emmons has caught bubonic plague from rodents in Borneo and a potentially fatal parasitic infection from flies in Peru. "You have to be driven to do it," said Emmons, 56. But "it's never dull. You never know when you're going to meet a jaguar."

Or a new rat.

The rat is huge, about 30 centimeters long from snout to rump, with almost 20 centimeters of thick, furry tail and prominent fangs for shredding plant life. It has 18 sharp claws for climbing trees, four on each front foot, five on each of the back. It has fetching, almost cartoonlike long whiskers and an endearing white stripe on its head, which contrasts handsomely with its dove-gray fur.

And it may be as shy as Emmons herself, since it had revealed itself to no scientist until that day in 1997 when she happened upon it on the trail in the Vilcabamba, in south central Peru.

There are about 5,000 known species of mammals on Earth, and researchers are finding more at the rate of about 14 a year, which far exceeds the extinction rate of about 120 species over the past 500 years, Emmons said. But it's rare to find such a big one as Cuscomys ashaninka, which Emmons named it for the city of Cuzco, Peru and the Ashaninka people who live nearby.

It's even rarer to discover a new genus - an entire branch on the family tree of rodents.

"She carried it back into camp in her arms, and she was very excited," said Monica Romo, a bat expert from Peru who was on the trip.

Emmons skinned the rat, stuffed the skin with cotton and put it in a box with mothballs. The bones were cleaned and dried; the remainder of the rat went into a vat filled with preservative. (The giant rat, stuffed and mounted, now resides in Peru's national museum in Lima.)

Emmons is fond of rats and quick to defend them. For a species, "success is measured in population and diversity," she said. "And as the largest order of mammals, rats are very successful."

Back in the States, Emmons speculated that her tree rat might be related to rodents whose bones were found in 16th-century Incan tombs and began the long, painstaking process necessary for scientific certitude.

Anthropologists determined in 1916, when they excavated graves at Machu Picchu, that the rodents and other mammals had been placed with the dead. But the biologist on that expedition could not find any similar rats in the Peruvian wilds and concluded they were extinct.

After examining the cranial structure, Emmons went to Yale University's Peabody Museum and compared it with the skulls of the rats exhumed from the tombs. She determined that the tomb rats, n?e Abrocoma oblativa and Cuscomys, belong in the same genus. And she suspects that both species are thriving in the mountains of Peru.

Her discovery may shed some light on a mystery that has puzzled anthropologists. Why did the Incans bury rats with humans?

In a recently published paper, Emmons writes: "Because Cuscomys ashaninka is so large and attractive, the question arises whether C. oblativus may have been kept as a pet, or even domesticated for food or amusement. One complete animal had been placed in a ceramic pot beside the human body."