Last month a family of monkeys was moved from its home at Brookfield Zoo to a patch of Brazilian jungle that had not resounded with monkey screech and chatter for many years.
Within hours of landing in Brazil, the golden lion tamarins were being outfitted with radio monitoring collars. A day later, the former zoo denizens were in their new, wild home, free to roam as they pleased but also exposed for the first time in their lives to being hunted and eaten by ocelots and hawks.
Four-year-old Bert, 8-year-old Gemma and their four youngsters thus became the latest recruits in a series of risky but tentatively successful experiments in resupplying nature with endangered species that have been bred and raised in the safety of zoos.
For the golden lion tamarins, the importance of repatriation efforts recently became clear when the population of native tamarins mysteriously decreased by more than a third. That means zoo-born tamarins and their descendants now are the largest group living in the wild and provide a crucial buffer against extinction.
Once mostly interested in collecting wild animals for display, zoos now are eagerly joining programs aimed at returning them to their native habitats. As wild animal populations worldwide continue to diminish, zoos and conservationists also are shifting their focus to saving not just individual species but the entire ecosystem those species need to survive.
In the past two decades, zoos have learned how to breed and care for all kinds of endangered species, from red and Mexican wolves, Wyoming toads and Attwater’s prairie chickens to insects such as Karner blue butterflies and the last 2,000 American burying beetles.
The golden lion tamarin project, pioneered almost 20 years ago, represents one of the first international efforts to shore up a disappearing species through captive-bred reintroductions. It also illustrates how–despite the best efforts of modern science–the experiments could still crash and burn, condemning these species to extinction after all.
“We got into the game so late, when the numbers of so many of these animals had plunged so low,” said Jim Dietz, a University of Maryland conservation biologist who with his wife, Lou Ann, helped launch the effort to save the tamarins. “We’re only at the stage of just trying to learn the rules of the game. We may lose some of these species before we can figure out all the rules.”
In 1982, an estimated 390 golden lion tamarins were living in Brazilian forests, plus about 70 in zoos. Since then, the populations have increased to about 500 in the wild and 500 in captivity. Still, survival of the species is in doubt.
Even as Bert and Gemma were getting settled last month in a 2.5-acre fragment of former rain forest along Brazil’s northeast coast, officials were alarmed to discover the population of native golden lion tamarins in another preserve had dropped to about 200 from 330 in a matter of months.
Dietz and other scientists are fairly certain they know why: The tamarins are being eaten by medium-size predators–ocelots, certain snakes and weasel-like creatures called tayras–whose numbers are no longer being checked by top predators.
“The big predators that used to live there–the jaguars, pumas and eagles–are gone,” Dietz said, mostly killed off by farmers and ranchers who moved into the area and thought the animals were a danger to their livestock.
If Dietz’s suspicions are true, wildlife experts will have to figure out a way to control the predator populations or end up watching the extinction of the tamarins they have worked so hard to save.
Despite the precarious nature of the work, conservation experts have achieved some preliminary successes in increasing the wild populations of once-decimated species.
In 1987, for example, wildlife officials captured the last of 27 surviving California condors to breed them in captivity. Now there are 170 of the big birds, and 53 young descendants of the original group live back in the wild.
In a similar undertaking from 1985 to 1987, officials captured the last 18 black-footed ferrets from a wild Wyoming prairie. From those few, more than 3,000 ferrets have been bred, with 240 remaining in captivity. Of many hundreds reintroduced to the wild, roughly 300 survive in a world made precarious by disease and lack of wilderness.
More Top Picks Best Red Light Bulbs For Sleep
And with just 200 wild tamarins left, the 300 reintroduced zoo animals and their offspring now make up the largest group living in the wild.
Golden lion tamarins, probably the most striking members of a family of long-tailed monkeys known as marmosets, once teemed in a huge swath of the formerly vast and flourishing Atlantic Forest of Brazil. But modern farming, ranching and highways have decimated the coastal forest, with only 7 percent remaining by 1982–and less than 1 percent of the portion inhabited by golden lion tamarins.
About 8 to 13 inches long and weighing 1 to 2 pounds, the animals are popular as pets, which also has contributed to their disappearance from the wild.
Concerned biologists decided to leave the few surviving wild tamarins undisturbed and concentrate on breeding captive monkeys so that zoo animals could be reintroduced to the wild, deepening the population’s genetic pool.
The campaign to breed the almost impossibly cute golden lion tamarins proved to be an easy sell to zoos, which in the 1970s and 1980s advertised themselves as stationary arks and refuges for endangered species. The number of zoos breeding the tamarins quickly rose to 142, which now care for 500 of the monkeys, the maximum number project directors want in captivity.
“We don’t need more than 500 to meet our long-term genetic objectives,” said John Ballou, a population biologist at the National Zoo in Washington, who oversees the tamarin breeding project.
Brookfield Zoo, one of the first to join the program, soon became a “pipeline” zoo, receiving monkey families from other zoos and preparing them for reintroduction to the wild. Part of that preparation has been a monkey “boot camp” on the Brookfield campus where the animals are allowed to live unfettered in the trees.
The zoo has shipped out several monkey families in the past 15 years to be released in what remains of their former habitat. That end of the project has been successful too.
“The zoo breeding program has done the job in filling the forests with tamarins,” said Ballou, adding that the six Brookfield monkeys sent to Brazil last month will be the only zoo animals added to the wild this year. “The growth of the introduced populations in the wild is such that we don’t need more bodies down there, though we still need to reintroduce some zoo animals for genetic reasons from time to time.”
If the experience of past introductions holds true, Bert and Gemma, will have the hardest time adapting to the wild. Adults have only a 30 percent survival rate.
Their offspring, two males and two females ranging from 6 months to 1 year old, probably will fare better, more easily adapting to finding food and avoiding predators. Babies born in the jungle when the offspring reach sexual maturity in the next year or two will be, for all intents and purposes, wild, with a 70 percent survival rate.
The small group will have to be lucky, however, to avoid the calamities that can befall tiny populations living in small areas. A disease could kill them all in a matter of days, or an unforeseen shift in the environment could wipe them out.
Other endangered species also face an uphill battle.
“The main problem is finding remote areas where the condors can stay away from reaches of man both directly or indirectly,” said Sean Farry, manager of a wild reintroduction program for California condors in the Grand Canyon. “They’ll roost on power lines and get electrocuted. One bird died of lead poisoning after eating carcasses that had been shot by hunters, ingesting bullet or shotgun pellet fragments.
“They’ve died from drinking toxic antifreeze in roadside puddles, and we’ve had a couple killed by hunters. They’re dying too quickly to sustain their population.”
Similarly, though it is easy to breed black-footed ferrets, very few wildernesses are left that can support them in the wild. They need to live within communities of prairie dogs, which they hunt and eat. Ranchers, however, hate prairie dogs and still regularly poison and hunt them.
Efforts to save a single species usually result in a domino effect, said Lou Ann Dietz, a conservationist working for the World Wildlife Fund’s endangered spaces program.
“You don’t just save the golden lion tamarins,” she said. “You save their forest, which happens to be home to an incredible number of species that can only be found in this part of Brazil and nowhere else in the world.
“There are at least three species of birds you won’t see anywhere else, a butterfly, a certain kind of brown howler monkeys, some endemic mice species and a maned sloth, just to list a few. So if we save the habitat for tamarins, we’re saving it for a whole lot of other animals as well.”