From upper left to lower right: binturong, masked palm civet, common palm civet, and small-toothed palm civet. These four species share similar ecology such as nocturnal, semi-arboreal, and frugivory.

We lurched along an unpaved road in the night, walls of trees and knotted vines on either side. In the darkness lurked some of the world’s most unusual mammals, and I had come to Borneo to fulfill a ...