The Endangered Hoolock Gibbon of Bangladesh
Bangladesh is home to one seriously endangered higher primate, the hoolock gibbon. The hoolock is a special primate. It is the only ape in South-Asia. Together with the South-East Asian gibbons, they are called "lesser apes" or "small apes", since they are significantly smaller than the great apes; chimpanzees, orang-utans, gorillas and bonobos.
However, the hoolock is also very different from the other gibbons; the genetic difference between the species is as big as that between humans and chimpanzees. The hoolock have a different chromosome number, their songs are different from other gibbons and they have the poorest survival in captivity of all the gibbons.
Over the past 10-20 years, hoolocks have decreased in numbers with around 70%, according to The World Conservation Union (IUCN). In Bangladesh there are now only 200 individuals left and ¾ of them live in small populations of less than 20 individuals isolated in forest patches, from where it is impossible for them to transfer and mix with other populations. The reason for this dramatic reduction in gibbon numbers is deforestation. Forests are cut down at an ever increasing rate and the patches that remains are small and totally isolated from one another. Just in the last 5 years, hoolock gibbons have disappeared from 8 forest areas in Bangladesh due to the clear-felling of timber.
Lawachara National Park in Sylhet is the biggest remaining gibbon habitat in the country, with a census population of 49 individuals. Together with the adjacent Chautoli and Kalachara forest areas the population reaches 60 individuals in 16 family groups. This seems like a fairly good number, but as illegal logging and other human activities are reducing the number of large trees that the gibbons are depending on for travel and food, there is still a risk that gibbon families become isolated within this forest area. Gibbons are tree-dwellers who feel very vulnerable on the ground and therefore rarely descend from the safety of the canopy to cross open areas. Young juveniles also experience great difficulties in jumping across even small gaps in the canopy, like that over human trails and roads.
However, the most serious problem, which the gibbons are unable to solve even by descending to the ground, is the lack of available fruit trees in small forest patches. Like all other apes, including humans, gibbons can not survive on a fibre rich leaf diet -- they need a variety of ripe fruits throughout the year. In a natural rainforest the number of tree species is high and at any time of the year there will be some trees that bear fruit. Most forests in Bangladesh are not natural, but have been planted with commercially valuable tree species. Although the gibbons can use these trees for food and travel, the limited number of different species means that there are times of the year when no fruits are available. In many remaining gibbon habitats this has led to periodical starvation and a reduction of young gibbons surviving to adulthood.
In contrast to most other local primates, who live in big groups, the gibbons exhibit a completely different social system. Gibbons are monogamous and they live their whole adult lives together with one partner and all the dependent offspring, in a defended territory. Monogamy in itself is limiting the breeding opportunities in fragmented populations, as young gibbons experience difficulties in finding a partner. Gibbons do not reproduce before they have a stable partner and a territory of their own and both males and females in small populations might thus remain "single" their whole lives and contribute nothing to the following generation.
Gibbons also differ from monkeys in that they have a much longer childhood. The gibbon infant's development is as slow as that of a human child during the first years and the baby will cling to its mother and breastfeed for more than 2 years. After this the young animal will remain in his parents care for another 5-6 years, learning from them how to live and survive amongst the tree tops. Like humans, the hoolock will start looking for a partner and a new home upon reaching adulthood, which in gibbons occurs when they are around 8 years old.
The public is now offered a last chance to see how these apes live in their natural habitat in Lawachara National Park. Intimate photographs of the hoolock gibbons and their forest, taken by freelance photographer Sirajul Hossain, are on display at the National Museum Gallery in Dhaka from 26th to 30th of July.
There are still ways to prevent the hoolock from going extinct in Bangladesh if the people and the decision makers are willing to take an interest in the plight of these special apes. Forest areas could be made better protected from illegal logging and from the encroachment by surrounding farmlands. Re-planting of fast growing tree species could be conducted in logging areas as an emergency solution and new plantations should be made to serve as connecting corridors between isolated forest patches. A wide variety of fruit trees should be added and planted in forests to ensure the long term survival of the hoolocks within. The situation in the West-Bhanugah forest area is of the kind that if logging is halted in Chautoli and Kalachara areas, and forest corridors are established through re-forestation programmes here, there is a great possibility that the current population is of a sufficient size to recover without further human assistance. Can Bangladesh afford to let this chance go by?
(R) thedailystar.net 2006