As a result, the Raffles' banded langur meets the criteria for being listed as critically endangered by the IUCN.
[6][7][8] William Charles Linnaeus Martin formally described P. femoralis based on material that had been collected by Sir Stamford Raffles in Singapore.
[9][10] Gerrit Smith Miller Jr. resolved the issue in 1934, determining that Singapore was the actual type locality.
[4][10][12] The Raffles' banded langur is diurnal and arboreal, preferring rainforest with trees of the family Dipterocarpaceae.
[11] The Raffles' banded langur appears to have two birth seasons, once between June and July and another between December and January.
"[12] Mammalogist Ronald M. Nowak described the species' alarm call as "a harsh rattle followed by a loud chak-chak-chak-chak."
[6][18] As a result of the small, fragmented population and continuing risk of further deforestation, the species meets the criteria to be listed as critically endangered by IUCN.
[6] The Raffles' banded langur was once common throughout the island of Singapore but that population is now critically endangered with approximately 60 individuals left in the Central Catchment Nature Reserve.
[24] The Singapore population feeds from at least 27 plant species, including Hevea brasiliensis leaves, Adinandra dumosa flowers and Nephelium lappaceum fruits.
[27] The Nee Soon Swamp Forest is the primary area of Central Catchment where the Raffles' banded langur is found.
[33] The government also hopes that eventually when the vegetation matures the Eco-Link@BKE will allow banded leaf monkeys to repopulate Bukit Timah.
[35] In April 2021 a single Raffles' banded langur was observed in Bukit Timah but it is unclear whether it used the Eco-Link@BKE to get there.
[36][37] The National Parks Board staff wrote of the sighting at the website of the Lee Kong Chian Natural History Museum.
[37] Concerns have been raised as to whether construction of the Cross Island MRT line through Central Catchment may adversely impact the Raffles' banded langur population in the area.