The banded leaf monkey is one of four primate species native to Singapore. The CCNR is the only location in Singapore where the nationally critically endangered banded leaf monkeys can be found. Due to rapid urbanisation and habitat loss, the population at Bukit Timah Nature Reserve had died out in 1987. The Central Catchment population had declined to as few as 10–15 monkeys before recovering to about 40 by 2012. Today, they are restricted to a small area within the Central Water Catchment with a population of about 70 by 2022.
