LAJAS, Puerto Rico - The easy life is over for hundreds of monkeys - some harboring herpes and hepatitis - that have run wild through southwestern Puerto Rico for more than 30 years.

Authorities launched a plan this month to capture and kill the monkeys before they spread across the entire island, threatening agriculture, native wildlife and possibly people. But some animal experts and the farmers who have complained for years about the rhesus and patas monkeys think it may be too late.

"I don't honestly believe they will ever get rid of the patas monkeys in Puerto Rico," said Mark Wilson, director of the Florida International Teaching Zoo, which has helped find zoos willing to take some of the animals. "They may go deep into the forest, but they will never go away. There's just too many of them, and they are too smart."

At least 1,000 monkeys from at least 11 distinct colonies populate the Lajas Valley. After a year of study, rangers began trapping them in steel cages that are about 10 feet long, baited with food and equipped with a trip lever. Two of 16 monkeys were released with radio collars for further tracking. Each of the others was killed with one shot from a .22-caliber rifle.

Officials determined shooting the monkeys was more humane than lethal injection, said Secretary of Natural Resources Javier Velez Arrocho. He said he regrets having to kill the animals but had no choice after 92 organizations rejected them.

Animal treatment is a sensitive topic in Puerto Rico, which was in the spotlight last year after about 80 dogs and cats were seized from a housing project and hurled off a bridge. In May, a veterinarian confirmed that more than 400 racehorses, many in perfect health, are killed by injection in Puerto Rico each year. Both cases sparked widespread criticism.

But the elimination of pesky monkeys has not spawned public protests.

"My personal opinion is that I would rather see them put to sleep than put through horrible experiments," said Sally Figueroa, a board member of the animal-welfare group Pare Este in the eastern city of Fajardo.

The scourge of nonnative animals is particularly acute in Puerto Rico because of its lush climate and lack of predators. Several species of dangerous snakes, crocodiles, caimans and alligators - imported, kept as pets, then released into the wild - now flourish in more than 30 rivers, said Sgt. Angel Atienza, a ranger who specializes in exotic animals.

The Lajas monkeys arrived in the 1960s and '70s after escaping research facilities on small islands just off the mainland. They adapted easily, fueled by plentiful crops, including pineapple, melon and the eggs of wild birds.

The creatures cost about $300,000 in annual damage and more than $1 million in indirect ways, such as forcing farmers to plant less profitable crops that do not attract the animals, according to an analysis by the U.S. Department of Agriculture and other agencies.