[13] As all members of the Trachypithecus francoisi species group, this social, diurnal monkey is found in limestone forests.

The topography is of limestone that has been worn away through erosion, which later formed ridges, towers, fissures, sinkholes and other types of landforms.

[3] The Cat Ba Langur are diurnal animals, adapted to living in limestone habitat.

The sleeping caves, ledges, and overhangs used by the langurs are thought to be used as protection from predators and extreme weather.

[2] The Cat Ba langur lives in a moist tropical rain forest on limestone hills, a type of habitat used by 6–7 other genera of the T. francoisi group found elsewhere in Vietnam.

Because there are no rivers and streams and no permanent freshwater ponds on the Cat Ba Island, the langurs take their moisture from rainwater caught in rock pockets and contained in vegetation.

Temporary surface streams form briefly during rainy season, rapidly receding into caves and subterranean passages.

[2] The Cat Ba langur is considered to be one of "The World's 25 Most Endangered Primates[3] and is assumed to have declined by 80% over the last three generations.

The Cat Ba langur's distribution range was declared a National Park in 1986, however that did not stop the poaching and decline of the population.

There is a strictly protected sanctuary, a peninsula on the eastern coast of Cat Ba Island, in the National Park and supports about 40% of the population.

Local citizens, especially fishermen, were informed and rangers were given permission to remove people and take away any poaching equipment they found.

[8] The greatest populations of the Cat Ba Langur are expected to recover with the appropriate conservation of the limestone habitats.

There are currently 3 Cat Ba Langurs held at the Endangered Primate Center in Cuc Phuong National Park, Vietnam.

Cat Ba langurs were used to make a "monkey balm" believed to help with erectile dysfunction and other health issues.

[15] To accommodate all the new tourists, the town of Cat Ba is building a new road that will connect the town to a small village on the northern edge of the island where a ferry will be to take tourists to another popular destination: Ha Long Bay.