The macaque's meat is prized by the ethnic Minahasan people, a largely Christian group in the world's most populous Muslim-majority country, who have no reservation about eating exotic animals, unlike Indonesia's Islamic communities.
"I like the taste, hot and spicy, it is similar to wild boar or dog," Nita, a 32-year-old local Minahasan who gave only her first name, told AFP.
At a market in Tomohon city, a stomach-churning array of burnt, mutilated animals were on offer.
Black crested macaques — flame-roasted and whole, with pained grimaces etched on their faces — were on tables for sale alongside piles of sliced-open pythons, burnt bats and dogs.
The macaques and some other animals at the market are protected by Indonesian law and officials have in the past raided the site, leading to violent clashes with vendors.
But the trade in exotic creatures was still booming during a recent visit, with some local travel agents even offering tours to adventurous foreign travellers.
The demand for the meat has prompted Minahasan hunters to go far and wide in search of the macaque, heading in pickups to remote parts of the island.
'Nail in coffin'
The population of Macaca nigra in its natural habitat on Sulawesi has dropped more than 80 percent in four decades, from an estimated 300 per square kilometer (0.4 square miles) in 1980 to just 45 per square kilometer in 2011, researchers say.
The International Union for Conservation of Nature classifies the monkey as critically endangered. As well as being threatened by their status as a local delicacy, the monkey's natural habitat is being destroyed by expansion of settlements and agricultural lands.
As the population has fallen, the local wildlife protection agency and activists have started campaigning to save them.
Tents manned by activists explaining that the monkey is protected have been set up at local markets, while billboards have been put up by roadsides to warn people that they face up to five years in jail if they hunt the creatures.
NGOs and the local government have pushed schools to include lessons on conservation, including about the Macaca nigra, in their curriculum.
Campaigners have also reached out to churches in the mainly Christian area to urge priests to preach that humans are the guardians of Earth and must protect endangered creatures like the monkeys, said activist Siwi.
They are also seeking to highlight the macaques' key role in supporting biodiversity. As they swing through the jungle canopy, the macaques disperse seeds and encourage growth of some trees, according to Stephan Lentey of the Macaca Nigra Project NGO.
But campaigners warn that villagers' hunger for the meat heaps extra pressure on a creature already threatened by habitat loss.
Hunting the animals for food "is the final nail in the coffin for a dwindling population," said Simon Purser of the Sulawesi-based Tasikoki wildlife rescue center.