India, Jan. 10 -- Ever seen a monkey with glasses? Visit the forests of Northeast India, and you might catch a glimpse. The Phayre's leaf monkey stands out among India's primates for its striking facial markings-a dark face framed by white rings around the eyes and lips, giving it a bespectacled look. Even among local communities in the forests of Tripura, Mizoram and southern Assam, where the monkey is found, the primate is known as chasma bandor (in Bengali) and chasma-chakuwa bandar (in Assamese).

The primate's other physical features also pique fascination. Its thick bluish-grey coat turns slightly brownish on the body and limbs, while a slender, long tail-often longer than the body-helps it balance as it moves among treetops. Adults...