Gibbons once occupied the treetops of mountain rainforests all across Southeast Asia. Their intelligence, agility, and haunting song fixed them in folklore from China to Indonesia, where indigenous people named them “Spirits of the Trees” and “Gentlemen of the Forest.” In Southern China the gibbon, which was a common subject for painters, it was believed they lived for hundreds of years and could change into humans.
In Thailand there are several large national parks that still have thriving groups of four of the species indigenous to the country. Biologist Dr. Tom Terleph and his collaborators have dedicated a few weeks every summer to tracking and recording gibbons in Khao Yai for the last several years, including groups found on the tourist trails.
“The single greatest threat to all gibbon species is habitat loss due to human encroachment,” says Dr. Terleph, commenting on the future of the species. Today gibbons are considered endangered in all of the countries where they are still found in nature.
As gibbons live entirely in trees, catching glimpses of them in the wild is a rare treat but not impossible. Today gibbons exist in Khao Sak, Kaeng Krachan, and Kui Buri parks, but probably the best chance a casual visitor will have to see them in the wild is the country’s most visited park: Khao Yai.
A favorite destination for birders and wildlife photographers, famous for its population of wild elephants, the mountainous Khao Yai is only two hours’ drive north of Bangkok.
Gibbons live high in the canopy of dense jungle and move fast, so they are exceedingly difficult to spot. At Khao Yai, however, some family groups of white-handed gibbons are acclimated enough to people that they can often be seen just at the edge of the public areas.
“Gibbons are mostly monogamous and live in fairly small family groups usually consisting of a breeding couple and its dependent offspring. Unlike other primates, you hardly ever see them engaging in overt aggressive interactions. They spend most of their time either foraging or grooming each other – and of course calling,” Terlaph says.
The most famous gibbon song is the duet, which is usually started by a male’s call, answered by his mate’s “great call,” which pierces the jungle at over 100 decibels. The duet is thought to be a territorial display, and territories can be held by a pair for decades.
“Gibbons don’t build nests like orangutans, they usually pick a sleeping tree in the afternoon and bed down for the night; once that happens they’re difficult to find.”
When gibbons are on the move, swinging and leaping from tree branch to tree branch in looping, arcing feats of acrobatic perfection, they are the fastest non-flying arboreal mammal, moving at up to 35 kilometers an hour and covering distances of up to 50 feet in a single leap.
“Their slight, small bodies which identify them as the so-called ‘lesser apes’ are what allow them to move so fast. Their arms are long and their hands are specialized for gripping and swinging. When they pause on the move they can become completely still, hanging from a limb, using either their hands or feet.”
To see gibbons in Khao Yai visitors should get up as early as possible, at or before dawn, to get to the general area around the back of the Khao Yai National Park Visitor Center. Then, listen. The calls are unmistakable and easy to follow. Keep looking up and listen for movement in the treetops. Once located they can be seen flying through the air or lounging, feeding, and grooming in the trees.
Gibbons stay active for most of the day, but they usually stop calling by noon and after that finding them is much more difficult.
Having a pair of binoculars or a good zoom lens is the best way to catch the gibbons’ loving, family structure. Mothers cuddle and hug their babies, adolescents run amok with their siblings high above the ground, and adults patiently groom one another; then, all at once, they take flight and are out of sight in seconds.
Unfortunately, in Southeast Asia there is still an active trade in gibbons as pets or for their body parts to be used in traditional medicines. The capture and poaching continues to thin the already small numbers of these shy but extraordinary animals.
There are of course other ways to see gibbons; they have always been popular attractions at zoos for their acrobatic antics and expressive faces. There are also gibbon conservation and rehabilitation projects that bring humans and gibbons together, but, once seen in the wild, watching a gibbon in captivity almost feels almost like witnessing a crime. Khao Yai is where they belong.