Kloss's gibbon has black fur and long arms. It lives in the canopy of the Mentawai Islands west of Sumatra.
It has no tail, a slender body and long arms. A throat sac beneath the chin helps amplify its calls.
At Bojakan Resort on Siberut Island, West Sumatra, researchers used line transects to survey Kloss's gibbons from November 2018 to January 2019. They recorded 77 individuals in 25 groups, with estimated densities of 12.8 individuals and 4.2 groups per square kilometre. This was one survey site inside Siberut National Park.
Average group size was 3.08 individuals, and groups with offspring were recorded. The researchers observed ground travel and foraging in savannah and reported disturbance from human activity. The counts and group composition provide local records for Kloss's gibbons in the Bojakan forest.
An extinction-risk assessment has not been added yet.
At Bojakan Resort, the survey recorded 77 Kloss's gibbons in 25 groups and reported disturbance from human activity. The authors recommend National Park monitoring and patrols for this area.