Identification of the Cat Ba Langur
As indicated by this species former name (the Golden-headed langur), head and neck down to the shoulders are bright golden to yellowish-white, with the head and the crest being most brightly coloured. The rump and the extremities of adult males and females of the Cat Ba langur are covered by dark chocolate brown, almost black fur. A grey band runs from the thighs to the back, forming a V-shape above the tail root and long hair of the back forms a shoulder cape. Another prominent feature of all Trachypithecus langurs is their long tail. Its length clearly exceeds head-body length.
The only difference in the colouration between the sexes is a white pubic patch on the female. The infant coat colouration of the Cat Ba langur as well as of the other Trachypithecus species in Vietnam is a flamboyant orange.
Distribution of the Cat Ba Langur and Ecology
The only known locality of where this langur occurs is the island of Cat Ba. There is no evidence that the Cat Ba langur ever inhabited the mainland. Immigration of this species onto Cat Ba Island might have taken place long before the sea level rose due to a melting of glacial ice. The last time this melting happened was some 10,000 years ago and it turned the former mountainous Ha Long Bay into a huge Archipelago.
The Cat Ba langur along with two of its close relatives, the Francois’ langur (Northern Vietnam and Southern China) and the White-headed (Southern China), are closely associated with limestone areas. These langur species prefer Karst and forest on limestone as habitat and regularly sleep in caves throughout the year. Scientists suggest that caves and cracks are important as shelter against unfavourable weather conditions. One langur group usually has several (up to 12) different resting caves. The group spends only 1-2 nights in the same cave before moving on to other feeding and sleeping places.
A significant proportion of a langurs’ daily life is devoted to foraging and resting. The diet of the Cat Ba langur mainly consists of leaves, but also includes fresh shoots, flowers, bark and some fruits that are not palatable to human beings. Most of the langur’s food has very high concentration of fibre and tannic acids, and often contains substances that would be poisonous to other animals, including human beings.
Threat Status
The World Conservation Union (IUCN) lists the Cat Ba langur as one of the most critically endangered primate species of the World, due to its small population size and restricted range. Only 65 langurs currently survive in the wild whilst an additional two live in the Endangered Primate Rescue Centre at Cuc Phuong National Park.
In the past, poaching constituted the primary threat to langur survival and resulted in a population decline from estimated 2,500-2,800 individuals in the 1960s, to a mere 53 individuals by 2000.
As a result of this steep decline in numbers, the remaining langur population is now highly fragmented and low reproductive output threatens their future survival. The population of the Cat Ba langur is subdivided into seven isolated sub-populations. Some of these include all-female groups and are therefore non-reproducing social units. Langurs were mainly poached for the preparation of traditional medicine, referred to as “monkey balm”, and only rarely for use as food, as their meat has a very unpleasant smell.
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