Its diet consists mainly of fruits, occasionally also eating different plant parts, bird eggs, insects and small vertebrates.

[11] One male gibbon will produce warning calls and attract attention to himself while other members of his group make their escape.

[11] Kloss's gibbons also exhibit less aggregate behavior like grooming and playing, possibly to reduce their visibility and stay hidden from hunters.

[7] Native peoples of the Mentawai Islands kill Kloss's gibbon and other endemic primates for subsistence, and also participate in poaching activities.

[6] Globalization and industrialization in the Mentawai Islands are contributing toward the degradation of high quality habitat needed by Kloss's gibbon.

[13] Road development and the adoption of air rifles are allowing natives to kill Kloss's gibbon easier and at higher rates.

[13] Kloss's gibbon spends the majority of its time in the tree canopy, and as a result, this species requires undisturbed, old-growth forest habitats to sustain itself.

[6] Fragments of habitat need to be connected to allow movement without risk of exposure in highly modified areas.

[6] Local government has been cooperating with global organizations such as UNESCO to raise awareness as well as increase the amount of protected land in the Mentawai Islands.