Spectacled langurs are primates living in the evergreen forest of southern Thailand. Their existing population have been so severely depleted by habitat destruction and human disturbance so that the present threatened populations will become extinct in the near future unless certain appropriate protective measures are taken on time. The study on ecology and behaviors of this langur was conducted from May 1991 to February 1992 in Mu Koh Ang Thong Marine National Park to reveal their way of life in a limited, isolated habitat. The obtained data well be hopefully incorporated into scientifically-sound and effective management and conservation plans. This study showed that the preferred habitats of the Spectacled langurs comprising plains, foothills and steep limestone cliffs, all luxuriantly covered with evergreen forest, thus providing suitable covers from the only predator, the Reticulated python, and abundant food sources all the year round. Their relationship with man in the area was of mutual benefit. The habitat constraint has induced the declining social structure with abnormal sexual ratio favoring more males than females. All members of the troop, except the infants, performed the guarding and danger-warning duties. Those langurs living in close proximity to human habitation tended to show more tameness than those living in faraway places. Main daily activities were foraging, resting and sleeping

of which the foraging tended to commence in late mornings on cloudy days. After being satiated, they took a rest and then slept in thick foliage. Troop relationship was maintained through constant body touch. In order to prevent unnecessary disturbances to langurs, human activities within the Park should be limited by proper zoning and those langurs living away from human habitation should be enhanced to retain their wild trait of high alertness to danger.