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Wildlife of Borneo

Southern grey gibbon

Hylobates muelleri

The southern grey gibbon lives in southeastern Indonesian Borneo, including the Kutai forest landscape.

EndangeredEndemic to Borneo
Species details & taxonomy
Species
Hylobates muelleri
Genus
Hylobates
Family
Hylobatidae
Order
Primates
Class
Mammalia
Southern grey gibbon — Hylobates muelleri
Southern grey gibbon (Hylobates muelleri).Seno Nur Rohman · Wikimedia Commons · CC BY-SA 4.0 · Original

Range and habitat

The southern grey gibbon lives in southeastern Indonesian Borneo, including the Kutai forest landscape. The western grey gibbon and northern grey gibbon are separate relatives in other parts of the island. It is therefore a Borneo endemic with a regional range rather than an island-wide species.

Sources & references · 2American Society of Mammalogists, MDD v2.5 · Hylobates muelleri: taxonomyJapanese Ministry of Environment, Biodiversity Center · Hylobates muelleri: ecology with Kutai references

Threats and conservation

The southern grey gibbon is globally Endangered. Forest conversion, fragmentation and damaging logging reduce connected canopy. Dawn and morning offer opportunities to listen for forest gibbons, while visual encounters depend on where the animals are travelling and feeding.

Sources & references · 2American Society of Mammalogists, MDD v2.5 · Hylobates muelleri: taxonomyJapanese Ministry of Environment, Biodiversity Center · Hylobates muelleri: ecology with Kutai references

Forests and observation

In Kutai, gibbons use forest ranges that contain feeding and sleeping trees. They favour sweet fruit but also eat young leaves and insects. Their day is spent in trees, so the arrangement of crowns matters alongside the quantity of food. Selectively logged forest can retain habitat, although removing important trees and breaking canopy connections reduces its value.

Sources & references · 1Japanese Ministry of Environment, Biodiversity Center · Hylobates muelleri: ecology with Kutai references

Where gibbon ranges meet

At Rekut in the Barito Ulu landscape, southern grey gibbons meet Bornean white-bearded gibbons, and hybrids have been studied. This contact zone shows that the boundaries between forest primates can be biologically active. Conservation needs to preserve the landscape and its natural connections, including populations that do not fit a simple visual label.

Sources & references · 1Borneo Nature Foundation · Searching for the hybrid

Pairs and territorial song

Adult pairs occupy forest ranges and exchange coordinated duets. In Kutai playback experiments, approaches and vocal responses varied with the location of the simulated caller: intrusions near the centre provoked stronger responses than calls at the boundary or beyond it. Male songs also help neighbouring groups maintain spacing in the forest.

Sources & references · 2American Journal of Primatology · My life among the apesZeitschrift für Tierpsychologie · Location-specific responses of gibbons (Hylobates muelleri) to male songs

Where to look

A recorded occurrence does not guarantee a sighting or visitor access. Read the area and experience guides for habitat, responsible observation, guiding and current access before choosing a trip. Keep wildlife at a distance and follow local restrictions.

Places with documented occurrence

Related discoveries

Nature areas

Walking infrastructure in Bontang Mangrove Park, Kutai National Park; current access must be checked separately.
Nature areas

Kutai National Park

Kutai National Park protects a mosaic of lowland rainforest, swamp, heath and coastal habitats in East Kalimantan. Orangutans and large ironwood trees are important parts of its identity, but neither represents every corner of the park. Visitors need to choose a named visitor sector: a river approach to Prevab is different from a forest walk at Sangkima. The park is not one attraction reached from a single central marker. Current park information describes guided facilities at Prevab, while route conditions and entry arrangements still need confirmation for your dates. Use nearby local access towns for the final approach rather than treating a hotel in Balikpapan or Samarinda as accommodation inside the forest.

Gunawan gtp · Wikimedia Commons · CC BY-SA 4.0 · Cropped · Original

Destinations

Primary rainforest in Danum Valley.
Destinations

Borneo

Borneo rewards a journey built around a few contrasting places: a river city, a forest stay, a highland community or an island coast. Indonesia, Malaysia and Brunei share the island, but each part has its own gateways, languages and travel arrangements. Start by choosing the landscapes and experiences that matter most to you; the country and regional guides below turn that choice into a workable route. Sabah combines mountain, forest and sea journeys, Sarawak connects river towns with caves and living heritage, Kalimantan opens five very different provinces, and Brunei offers a compact capital-and-rainforest combination. You can enjoy a substantial first trip within just one of these regions. Seeing the whole island is a much larger undertaking.

Gido (gidovd) · Wikimedia Commons · CC BY 2.0 · Cropped · Original

Sources & references

Borneo Nature Foundation · Searching for the hybridAccessed: 2026-10-04

American Society of Mammalogists, MDD v2.5 · Hylobates muelleri: taxonomyAccessed: 2026-10-04

American Journal of Primatology · My life among the apesAccessed: 2026-10-04

Zeitschrift für Tierpsychologie · Location-specific responses of gibbons (Hylobates muelleri) to male songsAccessed: 2026-10-04

Japanese Ministry of Environment, Biodiversity Center · Hylobates muelleri: ecology with Kutai referencesAccessed: 2026-10-04

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