The Hoolock Gibbon is the only ape found in India and its distribution in Southeast Asia, spans India, Myanmar, Bangladesh and southern China, between 20° N and 28° N, and 99° E to 98° E. Gibbons typically consist of an adult pair with 0-4 immature offspring with average group size ranging from 2.7 to 4. They are exclusively arboreal and spend 15–25% of their time moving for foraging, feeding, sun basking and resting. They occupy a home range of about 14 to 55 hectares covering a day range of about 600-1200 m (300-1600 m). They are frugivorous in nature and their diet consist of 51-65% fruits followed by 5-23% leaves, 13% buds, 12% flowers, 0.1% animal prey. They are highly social animal and their reproductive strategies are less documented. The duration of the menstrual cycle is 27.83 days ranging from 20 to 33 days for six cycles and of which the gestation period is about 210 days (but may vary from 195– 210 days). Usually a single birth occurs during winter (November-February). The population of gibbons in the wild has declined by more than 90% over the past three decades due to various anthropogenic threats, possibly because of burgeoning human population. Although some socio-cultural values are associated with these attractive and agile forest gymnasts, hoolock gibbons are seriously threatened due to anthropogenic activities like agricultural cultivation, tea plantation, hunting and poaching etc. Therefore there is an urgent need to launch ‘Project Primate’ akin to ‘Project Tiger’ and ‘Project Elephant’ for future survival of the species.
Keywords: Western hoolock gibbon, Eastern hoolock gibbon, population status, distribution, habitat, behavioural ecology, feeding behaviour, food plant, dietary diversity, activity pattern, home range, reproductive behaviour, social behaviours, sun basking, vocalization, grooming, anthropogenic threat, conservation, protected area, importance of gibbon.