Before working for Conservation International, he spent 11 years at the World Wildlife Fund in the United States, starting as Director of their Primate Program and ending up as Vice-President for Science.

In the late 1970s, Mittermeier undertook one of the first studies of the critically endangered northern muriqui woolly spider monkeys in what would become the Caratinga Biological Station.

The lizard, Anolis williamsmittermeierorum, is named in honor of Mittermeier and American herpetologist Ernest E.

(summa cum laude, Phi Beta Kappa) from Dartmouth college and Ph.D. from Harvard University in biological anthropology for a thesis entitled, "Distribution, Synecology, and Conservation of Suriname Monkeys" in 1977.

[citation needed] Among his books are The Trilogy Megadiversity (1997), Hotspots (2000) and Wilderness Areas (2002), Wildlife Spectacles (2003), Hotspots Revisited (2004), Transboundary Conservation (2005), Lemurs of Madagascar (1994; 2006; 2010), Pantanal: South America's Wetland Jewel (2005), A Climate for Life (2008), The Wealth of Nature: Ecosystems, Biodiversity and Human Well-Being (2009), Freshwater: The Essence of Life (2010), Oceans: Heart of our Blue Planet (2011) and The Handbook of the Mammals of the World (Vol.