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A creaking and rustling sound came from the branches and leaves in the canopy above, breaking the silence of the forest and stopping the Post-Release Monitoring (PRM) team members in their tracks. Curiosity made them look up to see which creature of the Juq Kehje Swen Forest they would encounter on this occasion.

Just then, they spotted a group of small apes - Müller's gibbons, known locally as owa kalawat - jumping about in the canopy. The owa kalawat (Hylobates muelleri), is a primate that inhabits the Juq Kehje Swen Forest, alongside orangutans and long-tailed macaques. This small ape, from the Hylobatidae family, is endemic to Kalimantan.

The owa kalawat lives in small family groups that retain their territory through the use of distinctive calls. Its vocalisations are so loud and strong, they can be heard up to a distance of 2 km away. This ensures that other gibbons hear and understand the territory is occupied and claimed. Vocalisations are also used by the males of the species to attract females. The owa kalawat is monogamous, choosing one mate to stay with for life.

Hylobates muelleri by Rofinus

Hylobates muelleri by Nurbayati

This arboreal animal is quite active during the day and has incredibly strong legs and hands, making it easy to grip and move from tree to tree without falling to the ground. These gibbons also play a significant role in distributing seeds of plants and forest fruits, thus contributing to forest propagation.

Unfortunately, this unique primate is classified by the International Union for the Conservation of Nature (IUCN) as an ‘Endangered’ species, largely due to deforestation and myths surrounding their use in traditional medicine. Therefore, more protective measures need to be put in place to combat the threats driving the population decline of this species. When we protect wildlife like the owa kalawat, we also help preserve the forests in which they inhabit.

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