The East Javan langur moves through trees with its long tail and mainly eats young leaves. Its coat occurs in black and reddish forms.
The coat occurs in black and reddish forms. Newborns of the nominate subspecies described by Krakow Zoo have bright orange fur.
Researchers studied Javan lutungs in Baluran National Park, Indonesia, during 2017–2018. Six groups contained 8–20 animals; they traveled through savannah and were seen foraging on the ground. The park includes forest, savannah and shrubland. Estimated density was 14.91 animals per km², with a population estimate of 3,727. The respective 95% confidence intervals were 7.91–28.08 animals per km² and 1,979–7,019 animals.
Long-tailed macaques were within 50 m and five minutes of the lutungs in more than 90% of morning and late-afternoon follows. Both species were recorded near one another in 15 of 64 line-transect encounters, a co-occurrence rate of 24%. Researchers also observed shared sleeping sites and responses to each other’s calls.
An extinction-risk assessment has not been added yet.
In Baluran National Park, Javan lutungs traveled through savannah and foraged on the ground. The authors recommend including dry habitats beyond forest in habitat assessments; long-tailed macaques occurred nearby in 15 of 64 transect encounters (24%).