Every night, as darkness descends over the District, thousands of furry prowlers slip out of hiding and take to the city's back yards and neighborhood streets in search of food. And, invariably, they find it in rich supply.

Naturalists have long suspected that raccoons love Washington and everything life here provides. Now a new study suggests that these animals may be more numerous here than in any other city on earth.

And they are everywhere.

"I'm sure they cross the White House grounds now and then," said John J. Hadidian, one of the world's few experts on urban raccoons. He and a team of scientists at the Urban Ecology Center near Georgetown Reservoir have been studying Washington raccoons for seven years.

Urban raccoons inhabit most American cities. They even have been spotted in midtown Manhattan.

But Hadidian said Washington's raccoon population today is the densest ever recorded anywhere: as many as 17,000 may be living inside the city limits. That's one for every 2.35 acres; one for every 35 residents.

In outlying rural areas, raccoon density is about one for every 12 acres. They don't particularly care for suburban living.

"I can't think of a habitat that would be less attractive to a raccoon than a ranch house surrounded with two acres of grass, a few skinny maples and a big dog in the back yard," Hadidian said.

The District's raccoon population has attracted Great Britain's largest television studio. BBC camera crews arrive this week to begin shooting a half-hour special about urban raccoons, a follow-up to a popular special about badgers in English cities.

What Washington offers raccoons is a standard of a living much higher than most places. A smorgasbord of tasty leftovers are set out in city garbage cans each night. And the ornamental shrubs in many yards just happen to be varieties that bear the favorite fruit and berries of raccoons and ripen in one long, continuous harvest season.

The abundant food supply could mean there's room in town for even more raccoons. "I see plenty of food that goes unutilized," said Hadidian, although he said he sees no evidence that the raccoon population is growing.

Housing is even easier to come by. Raccoons den in the hollow of the city's many large trees -- especially the oaks and poplars in Washington's many parks and older neighborhoods. They also like to sleep in chimneys and crawl spaces of old houses.

One study a few years ago by Hadidian showed that almost a quarter of the denning sites were in buildings, most of them residential. Passages for safe travel from one yard to the next are provided by the city's network of storm sewers.

No hunting is allowed in the city, and dogs, a raccoon's biggest threat, must by city law be leashed or penned.

"We have created an ideal habitat for raccoons," Hadidian said.

The result is healthier than normal raccoons that grow bigger than most -- often as large as 20 pounds. There are indications they may even live longer than their country cousins.

The good life seems to make for a more gregarious raccoon. City raccoons, like city people, are more sociable than their country counterparts, who lead solitary lives except when they are mating or nursing their young. In the city, sister raccoons often share a tree hollow during the day; brothers frequently forage together at night.

How does Hadidian know?

For seven years, he and his colleagues have kept in touch with about 700 raccoons by shortwave collar radios that send a signal unique to each raccoon. Using a directional antenna, the team follows the signals each night, in and out of Rock Creek Park and up and down neighborhood streets and alleys.

The animals' positions are noted on a map each hour with a colored dot, a different color for each raccoon. Later, dots of the same color are connected to show where each raccoon traveled that night.

The mapping shows that the raccoons travel everywhere, in back yards, front yards, trees, houses, garages, streets and alleys.

Hadidian's most recent study group, 22 raccoons in the Northwest neighborhood of Barnaby Woods, shows that raccoons are not intimidated by humans. Many raccoons slept and even gave birth in trees just feet away from homes or noisy traffic. They regularly crossed busy streets such as as Military Road.

Typically they roamed about a half mile or more each night, holing up in a different den each day. That's why, Hadidian said, it does no good to trap raccoons and move them elsewhere.

"If something in your yard is attractive to one raccoon, it will certainly attract another," Hadidian said. It's more effective to alter the attraction; for example, wait for raccoons to leave a chimney, then install wire mesh to prevent others from getting in.

Maryland prohibits releasing raccoons, and so do several Virginia jurisdictions. But raccoons sometimes do their own interjurisdictional traveling. One was tracked 30 miles from Rock Creek Park to Silver Spring and over to Rosslyn before returning to the park three months later.

"We don't know how he crossed the river, whether he swam or crossed a bridge," Hadidian said.

Raccoons are apt to be anywhere in the city, although people seldom see them. "They are very good at staying out of our way," he said.

They also are neat scavengers and rarely leave a trail. "They usually open a small hole in a plastic {bag} and carefully pick out what they want, right in the can," Hadidian said.

But raccoons can spread rabies, a fact Hadidian believes people are quick to forget.

The rabies epidemic that spread through Washington's raccoon population during the mid-1980s has moved north to Pennsylvania and New Jersey, subsiding to about a quarter of its former strength, said Kristina Harper, chief of the city's Animal Control Division. But many raccoons are infected, and often they behave no differently than healthy ones.

Humans apparently do not get rabies from raccoons -- at least there are no documented cases. But the disease has spread from raccoons to pets, then to humans.

The best ways to guard against rabies, Harper said, is to vaccinate any pet that goes outside and to avoid handling any wild animals, even those that appear to need help. "You could expose your whole family by meaning well," Harper said.

Fear of rabies was the reason research began on urban raccoons. Little was known about these animals in urban settings before Hadidian's work began. Much has been learned about their habits that will help control the disease. But soon the work will end.

In July, the last study in the series will be complete and the Barnaby Woods gang will become just another group of street corner raccoons. They will be trapped, checked, their collars removed and released where they were found.

But Hadidian is satisfied. "What we've learned will lead to better human-raccoon relations," he said. "That's what's important."