The lion-tailed macaque (Macaca silenus), also known as the wanderoo, is an Old World monkey endemic to the Western Ghats of South India.

Lion-tailed macaques are covered in black fur, and have a striking gray or silver mane that surrounds the face in both sexes.

Lion-tailed macaques are a territorial animal, defending their area first with loud cries and bared teeth towards the invading troops.

[6] Lion-tailed macaques are omnivores, primarily eating indigenous fruits, seeds, flowers, insects, snails, and small vertebrates in virgin forest.

[4] These feeding changes include fruits, seeds, shoots, pith, flowers, cones, mesocarp, and other parts of many non-indigenous and pioneer plants.

[8] While lion-tailed macaques are preyed on by snakes, raptors, and large carnivores, the impact of natural predators on population size does not compare to their largest threat.

The largest threat to the lion-tailed macaque is habitat fragmentation due to large amounts of timber harvesting and exotic plantations, such as tea and coffee.

Their range has become increasingly isolated and fragmented by the spread of agriculture and tea, coffee, teak and cinchona, construction of water reservoirs for irrigation and power generation, and human settlements to support such activities.

From 1977 to 1980, public concern about the endangered status of lion-tailed macaque became the focal point of Save Silent Valley, India's fiercest environmental debate of the decade.

[12] A local census concluded in 2007, conducted in the Theni District of Tamil Nadu, put their numbers at around 250, which was considered encouraging, because until then, no lion-tailed macaques had been reported in that specific area.

[14]) However, it is no longer on ‘The World's 25 Most Endangered Primates’ list, after the international body compiling it determined that the local governments in southern India had acted positively to protect it.