Adult tamarin
Image: JESSE COHEN, National Zoological Park
LITTLE LIONS. Prized as pets and their habitat destroyed, tamarins are now threatened with extinction.Researchers estimate that only 500 of these diminuitive tamarin monkeys can be found today in the wild.
The squeaky trills and clucks of the Golden Lion Tamarin are sounds that Benjamin Beck of the U.S. National Zoological Park in Washington D.C. and his colleagues with the Golden Lion Tamarin Conservation Program hope to hear more of in the future. Their efforts were featured last week on an episode of the television show, Scientific American Frontiers.

For more than two decades, the Golden Lion Tamarin Conservation Program--coordinated by the National Zoological Park and the Smithsonian Institution in collaboration with Instituto Brasileiro de Meio Ambiente e dos Recursos Naturais (IBAMA), Golden Lion Tamarin International Research and Management Committee, Centro de Primatologia do Rio de Janeiro, University of Maryland and the World Wildlife Fund--has reintroduced hundreds of zoo-born tamarins back into the coastal forests of Brazil. Only 10 to 20 percent of these relocated monkeys have survived--and then only with human help. But the scientists are hopeful. Because the offspring do quite well, compared with other conservation programs, this one is considered a huge success.

Reintroducing animals to the wild is not a new strategy, but in recent years such programs have changed their goals. Success had been measured by how many reintroduced animals survived, and for how long. By that definition, Beck notes that only 12 percent of the 145 reintroduction programs documented since 1900 have been effective. And so today, success is defined differently. Researchers now view reintroduced species as a means to promote ecosystem education and habitat preservation, even if they don't ultimately reestablish a sustainable population in the wild.

It will be difficult to reestablish large numbers of Golden Lion Tamarins (Leontopithecus rosalia). The population began to decline during the 1960s as agricultural and industrial development in Brazil decimated their native habitat, the Atlantic Coastal rain forest. Also, until the late 1960s, the fiery-gold monkeys--which weigh only 500 to 600 grams (about one pound)--were prized as household pets. By 1975, their numbers had dropped so dramatically that they were listed on CITES, an international treaty that recognizes and protects endangered species from trade.

Tamarin family
Image: GOLDEN LION TAMARIN CONSERVATION PROGRAM

TAMARIN KIN. Families of tamarin live in the rain forest's tree canopy and eat insects, fruit and small animals found there.

Collaborators in Brazil and at the National Zoo in Washington D.C. began developing the Golden Lion Tamarin Conservation Program as early as the 1960s. And in 1984, they reintroduced the first captive tamarins back into a thin strip of protected forest spanning 5,300 hectares (slightly smaller than the island of Manhattan).

The monkeys didn't feel at home. The scientists tried to train the tamarins to live in tree canopies, as they normally would, and to search for food, including insects, fruits and other small animals. But the trained animals fared no better than those reintroduced with no training. Today more relocated monkeys survive, but only because they are constantly supplied with whatever they need. The scientists that monitor the populations offer food, shelter, rehabilitation and navigation assistance for tamarins that wander off the protected land.

But even though animals born in captivity cannot survive independently, their offspring apparently can. Second-generation zoo emigrants have a 65 percent chance of surviving in the wild--odds that are two to three times greater than their parent's chances. Thus, it is this generation that scientists hope will become fully reacclimated in the wild. In 1996, only 7 captive-born tamarins were reintroduced, but they successfully produced 38 offspring, which are now living on their own, without the aid of humans. Beck estimates that the total population of reintroduced tamarins plus their offspring is anywhere between 220 and 240.

It is an impressive total, given that there are only 500 Golden Lion Tamarins surviving in the wild. Even so, the program estimates that to establish a sustainable population of tamarins will require a minimum of 2,000 individuals by the year 2025. Otherwise, the animals will be vulnerable to inbreeding, disease, natural disaster and human interference.

So too, conservationists guess that the population will need at least 23,000 hectares of habitat. Collaborators have obtained another 3,000 hectares of protected forest since the program began, and local Brazilians have agreed not to destroy forests where the tamarins live. But saving these rare creatures from extinction is--at this point--far from certain.