The woolly spider monkey, or muriqui, is one of the most threatened primate species in the world. Because of deforestation in their natural habitat--the Atlantic coastal forests of southeastern Brazil--the muriquis are confined to less than 3 percent of their original range. As of 1987, there were only a dozen forest fragments known to support a total muriqui population of about 500. As of 1998, at least 20 forests are known to support at least...