lips and beckons us in the direction of the calls. Five minutes
later we spot them – a black male and tan female. They
perch a couple of metres apart, their characteristic long
forearms holding onto the branches above, while their baby
crouches below munching leaves.
India has two species of gibbon, but Hollongapar is home
to just the western hoolock (Hoolock hoolock). The eastern
hoolock gibbon H. leuconedys, which varies slightly in
colour and has a narrower gap between its bushy brows, is
found close to the Tibetan border in Arunachal Pradesh.CALL OF THE WILD
The duet we’re hearing is territorial, Borah explains, but
hoolock gibbons also have specific calls for mating, food and
danger. If one family calls another will sometimes reply. The
morning song – which in Hollongapar occurs every two
to four days – can last up to half an hour, and identifies the
singer’s species, sex and identity.
Today the song bout climaxes after 15 minutes, and
the family disappears. Gibbons get around using a lanky
yet powerful alternate-arm-swinging technique called
brachiation, which propels them at up to 55km/h, as they
hurl themselves across gaps in the forest canopy as wide as
6m.
Knowing that we’re unlikely to catch up with the super-
athletic gibbon family, we make our way back to the track.
Deben points out an all-male group of capped langurs above
us. Unlike gibbons, which are monogamous and live in small
family groups based around a breeding pair, these monkeys
form social groups of up to 15 individuals.
Hollongapar offers a refuge to seven of India’s 11 primate
species, and is one of the last strongholds of the rare stump-
tailed macaque, considered Vulnerable by the IUCN. Though
the sanctuary has the highest primate biomass in India, the
abundance of food means there is little competition. The
gibbons are frugivorous and frequent the treetops, whereas
Hollongapar’s other primates live in the middle and lower
canopies. Living at the top of the canopy is not
without problems, however. Gibbons are threatenedhen Kumud Ghosh wakes in his village amid the tea
plantations of Assam he’s greeted by a spine-tingling
sound somewhere between the hoot of an owland the howl of a wolf. As Ghosh leaves his home a second,
lower-pitched voice joins in, and by the time he’s walked the
2km stretch to Hollongapar Gibbon Sanctuary, the duet has
reached a magnificent crescendo.
“When I hear the western hoolock gibbons sing, freshness
comes to my body,” explains Ghosh, who has studied the
species for 15 years. “For me, it is like listening to classical
music.” Ghosh is one of the rangers at this 21km^2 forest reserve
in north-east India. Upgraded to a wildlife sanctuary in 1997,
Hollongapar is home to hoolock gibbons, the only wild apes in
the country. However, unlike Assam’s Kaziranga National Park,
which is famed for its one-horned (Indian) rhinos, the reserve
receives few visitors.
As we step through the thick shrubs of the subtropical
deciduous forest, my pulse quickens when I hear what
sounds like a fire alarm. The noise is high-pitched and
intermittent, accompanied by what could pass for the
whoops greeting a best man’s speech at a wedding.
Forest guard Deben Borah smiles, puts his finger to his
W
MAIN: A western
hoolock gibbon
carries her one-
month-old babyRIGHT: Tea
plantations (top)
have replaced the
species’ crucial
forest habitat – in
contrast Hollongapar
(bottom) offers tall
trees with a suitable
canopyHOOLOCK: BERNARD CASTELEIN/NATUREPL.COM; TEA: ALI WOOD; HOLLONGAPAR: NHPA/PHOTOSHOT