Scientists consider the Manu Biosphere Reserve to be one of the most biodiverse places on earth, and much of its vast wilderness has barely been studied, since it is still home to uncontacted indigenous groups. Straddling the boundary of the Madre de Dios and Cusco provinces, the reserve is Peru's second largest protected area, encompassing more than 4½ million acres of pristine tropical forests. Its extraordinary biological diversity is in part due to its precipitous
terrain, which ranges in altitude from 3,450 meters (12,000 feet) down to 300 meters (less than 1,000 feet). This geographical diversity results in varied ecosystems: from high-altitude puna grasslands, to luxuriant cloud forest, to seemingly endless lowland rain forest, which in turn shelter a stunning range of flora and fauna. To top it off, a near total absence of humans means that the animals here are less skittish and more easily observed.
Whereas Manu's cloud forest is home to dozens of hummingbird species, the spectacular cock of the rock and the andean bear (a.k.a. spectacled bear), the reserve's rain forest holds most of its more than 200 mammal species, including 13 species of monkeys, which scrutinize visitors with the same curiosity they elicit. White caimans sun themselves on sandy riverbanks, whereas the larger black caimans lurk in the oxbow lakes. With luck, you may see a tapir, giant river otter, or one of the region's elusive cats (jaguars and ocelots among them). You are bound to see a sampling of the avian life that has made Manu world famous. The area counts more than 1,000 bird species, fully one-ninth of those known to science. Those birds include several species of macaws, toucans, jacamars, cocoi herons, harpy eagles, razor-billed currasows, blue-headed parrots, and horned screamers. Manu is also home to hundreds of colorful butterfly species, and array of ants, beetles and spiders, as well as millions of mosquitoes, so be sure to take an ample supply of insect repellent.
A UNESCO World Heritage Site, the Biosphere Reserve is divided into three distinct zones. The smallest, and most accessible, is what's known as the "cultural zone," home to several indigenous groups and the majority of the jungle lodges. Access is permitted to all—even independent travelers, in theory— though it would be extremely difficult to visit it on your own. About three times the size of the cultural zone, Manu's "reserved zone" contains several remote nature lodges, which can only be visited with a guide from one of the 10 agencies authorized to take people into the area, as this is a controlled scientific research area. The western 80% of Manu is designated a national park. Only authorized researchers and indigenous peoples who reside there are permitted in this zone.