Spending a couple days at the RPPN Feliciano Miguel Abdala, near the town of Caratinga, in the state of Minas Gerais was one of the most fun experiences of my life. It was just Mrs. Angus and me in the reserve (there was also a research team headed by Prof. Karen Strier from the Univ. of Wisconsin, but we only saw them briefly).
The Muriqui (which is an indian word meaning "happy men of the forest") are endangered but their population in the reserve is steadily growing.
We also saw some capuchin and howler monkeys!
Here is a slideshow: