For months they've run on the periphery of the debate over the plan to shoot deer at Valley Forge national park:

Coyotes.

A small number have taken residence inside the park, among the "urban coyotes" that dwell in places from New York to Chicago to Beverly Hills, Calif.

Now, animal-rights advocates are arguing that the number of coyotes in Valley Forge should be encouraged to grow, as a way to provide a predatory check on the deer and eliminate any cause for gunfire.

"It would serve as a natural form of population control," said Matthew McLaughlin, director of the Pennsylvania chapter of Friends of Animals.

Park officials say it wouldn't work - certainly not fast enough to help a forest that's being devoured by deer. Next month, park managers intend to proceed with a plan to eliminate 86 percent of the deer during the next four years.

To some people, the idea of using coyotes to reduce the herd seems far-fetched, if not risky, given how many people jog and hike in the park:

If you and your jogging partner should be approached by a coyote, is it possible to outrun the beast? Answer: You don't need to outrun the coyote. You only have to outrun your jogging partner.

Seriously, coyotes tend to be timid around people, and attacks are extremely rare. And plainly the fate of the deer is no laughing matter, as evidenced by the controversy surrounding the park plan for "lethal reduction." Officials intend to cull the herd from an estimated 1,277 to between 165 and 185.

Sharpshooters are to kill 500 deer this winter, 500 the next, and between 250 and 300 in each of the third and fourth years. Animal-rights activists say the killings are unnecessary and will be dangerous to people who live or travel near the park.

No one has suggested bringing more coyotes into Valley Forge.

Instead, the Pennsylvania chapter of Friends of Animals has begun a campaign called the Coyote Coexistence Initiative, an outgrowth of a lawsuit the group filed last year to try to stop the deer shoots. That suit, still active, helped delay the first kill for a year.

One of the Friends' arguments is that park officials did not fully consider the role of natural predators - specifically coyotes - in maintaining a stable deer population. The initiative seeks to promote respect for coyotes as important players in the environment and to reduce what has been a dramatic increase in the number of coyotes killed in Pennsylvania.

Friends leaders say the park does not exist in isolation - it must be evaluated as part of the larger biosystem. If coyotes were allowed to increase statewide, the animals would likely also increase inside the park, helping to limit the deer, they said.

"We can't look at the coyotes in a five-mile park as in a vacuum," said Lee Hall, vice president of legal affairs for the Friends.

She acknowledged it would take time for coyotes to affect the deer population, but asked, "What's the emergency this year?" The group plans to seek a court injunction to stop next month's shoot.

Park officials say, however, that time is slipping away. Because of the herd's appetite, the forest has not generated new growth since 1995, and "we simply cannot withstand another 20 years of that," said Kristina Heister, the park spokeswoman and natural-resource manager.

Officials evaluated the possibility of using coyotes to reduce the herd, she said, but found it would require large numbers - well beyond the few coyotes sometimes glimpsed or photographed.

"There's no scientific evidence to suggest that at the population density [of deer] that we have, that the reintroduction of predators would be effective," she said.

Other opinions were more direct.

"It's a laughable idea," said Bruce Davis, who lives at the edge of the park in Tredyffrin Township. "We have pets and small children in that neighborhood. And plenty of adults who would be frightened by coyotes. . . . Even if they're only interested in the deer, there's 10 deer in my yard every night."

Mark O'Neill of Bryn Mawr, who regularly visits the park and deplores the damage done by deer, wondered if coyotes would even bother with deer, given the smorgasbord of nearby household pets. "Fifi the dog and Fluffy the cat are much easier to eat," he said.

There is evidence, though, that coyotes can significantly reduce deer, particularly by taking the young. A study in South Carolina, while not claiming a causal relationship, found that a statewide decrease in deer followed an increase in coyotes. An Alabama study found coyotes were the leading cause of a 67 percent mortality rate among fawns in a herd in Auburn.

To biologists, the coyote is a social, doglike animal, colored like a German shepherd. Here in the East, an adult male weighs 45 to 55 pounds.

To American Indians, the coyote is the trickster of lore, always out for a laugh. To the producers of Looney Tunes cartoons, he's the perfect comic foil - Wile E. Coyote, forever chasing the Roadrunner.

In popular culture, "coyotes" is the slang term for Mexican smugglers and the name of the pro ice-hockey team in Phoenix.

Historically, the coyote has been seen as a nuisance, a danger to livestock. But as cities have spread and suburbs expanded into what was wilderness, coyotes have survived and thrived in St. Louis, Boston, Detroit, and Washington. In Chicago, a three-year study found coyotes living near the airport and in subdivisions.

Coyotes can be found across Pennsylvania, and deer are a main meal - not surprising, given their density in many areas and the numbers killed on highways, according to the state Game Commission.

But coyotes are prey as well as predators.

Coyotes can be hunted or trapped virtually all year in Pennsylvania, the tally growing from 1,810 in 1990, to 10,160 in 2000, to 23,699 in 2008.

Attacks on humans are unusual - about four a year in the United States. By comparison, dogs bite 4.7 million people a year.

But when incidents occur, they make news, as in July when two girls were attacked by coyotes within nine days of each other in suburban New York. Neither girl was seriously injured.

Attacks on pets are more common, and pertinent to Valley Forge, a 5.3-square-mile park surrounded by houses, hotels, and the King of Prussia mall.

This month in North Jersey, a woman in Kinnelon told police that a coyote snatched her 20-pound pug. In nearby Sparta, a coyote killed a 20-pound miniature pinscher in August.

McLaughlin, of Friends of Animals, does not underestimate that risk. Some states that treat coyotes gently also educate people about keeping a closer eye on pets and children. Part of the coexistence initiative involves exactly that.

But at Valley Forge, he said he believed coyotes could help manage the herd. "They could put a dent in it," he said.

Contact staff writer Jeff Gammage at 215-854-2415 or jgammage@phillynews.com.