During his famous 5 year-long expedition to Latin America (1799-1804), Alexander von Humboldt collected,  together with his naturalist partner, Aimé Bonpland, around 60,000 plant specimens and an unknown number of animal specimens that we can safely assume to be in the thousands. Some of these specimens were being shown and described to the scientific world for the first time, including the peculiar yellow-tailed woolly monkey.

© Eduard Ender

However, the monkey specimens weren’t caught by Humboldt or Bonpland. They were the flat skins used by Peruvian muleteers as saddle covers, and which came into the possession of our naturalists in 1802. Humboldt unfortunately never had the chance of seeing the monkey alive, but he still managed to determine that it belonged to a whole new species.

Be that as it may, all that was known about the yellow-tailed woolly monkey for over 125 years after Humboldt officially described the species in 1812 was: 1) that it was traditionally used as saddle covers by Peruvian muleteers; 2) it had yellow stripes on its tail and yellow pubic tufts; and 3) that, based on Humboldt’s examinations, it was a howler monkey. Howler monkeys, like the name suggests, howl, a lot. Woolly monkeys don’t. In fact, this particular woolly monkey doesn’t howl at all. It barks, like a dog. But in all fairness to Humboldt, it was impossible to tell what sound came out of those woolly monkeys with only the skins.

In 1925 and 1926, two professional animal collectors captured five specimens of the yellow-tailed woolly monkey which was by then considered likely extinct but did not realise what they had rediscovered. These specimens resulted in a decade-long argument between naturalists which ended up in the specimen being considered as part of a different species for decades. Nothing else, other than the specimens left hanging in some museum cabinet, was known about the species which disappeared back into oblivion. As far as the world was concerned, the species had gone extinct, again.

Mission (almost) impossible

© Elemaki

The year was 1974. The day was the 26th of April. A team of biologists was setting off to Peru to attempt a seemingly impossible feat: the rediscovery of the lost yellow-tailed woolly monkey, a species that, in the eyes of many, had already undergone “extinction” twice.

Russell Mittermeier and his team of biologists from both Peru and Colombia went on a 12-day expedition to the Peruvian Amazon where the professional collectors had obtained the only known specimens of the species some 50 years prior. The search was somewhat successful, with the team finding more skins, this time ‘fresh’ ones. A hunter that crossed paths with them happened to be carrying a skin and skull of an adult male he had killed only days before. He also had more skins and skulls at his place. Despite these findings, nothing new had been uncovered and still no sight of a live animal.

It wasn’t until the 11th hour, in this case, the team’s 11th day, that luck finally struck. Local children directed the team to the house of a soldier who kept a juvenile yellow-tailed woolly monkey as a pet. It wasn’t in its natural habitat, but it was a live specimen.

The discovery made the headlines of several newspapers, particularly in Peru. This was a media stunt to raise awareness for one of the largest endemic mammal species of Peru, then thought to be on the verge of disappearing if nothing was done.

On the (yellow) tail of the woolly monkey

© Magali Courtade

Roughly 42 years later, in 2016, I found myself hiking through treacherous paths and over muddy hills in the middle of the Amazon jungle. I was there, with the help of Neotropic Primate Conservation, a local NGO, that did research and conservation on all three of Peru’s endemic monkeys, to achieve what Mittermeier and his team hadn’t, finally seeing the yellow-tailed woolly monkey roaming free in the wild.

After following the monkey’s calls for a while, we discovered the primate, thought extinct twice in two centuries, in its natural habitat. Right there, looking through the branches above our heads were the yellow-tailed woolly monkeys. They stood still, looking in our direction and right into our souls for a few seconds as if trying to understand what we were doing and why. I could see the monkeys in their full glory. How beautiful they were with their lustrous and velvety furs. A smile automatically formed on my lips. There’s something special about seeing these creatures in the wild, roaming free through the forest.

The monkeys eventually got used to our presence and decided not only to resume their activities, but to turn it into a performance, showing us, what they were capable of. I observed, not only the monkeys, but everything that surrounded me, trying to absorb as much of it as possible. The forest had a raw and misty feeling to it, with the grey sky and the occasional pouring clouds contributing to this; the monkeys were sublime, having a majestic appearance to them, certainly knowing how to carry those impressive tails of them; and the people following them, studying them, and admiring them, being grateful to be able to share such personal moments with those creatures. I counted myself in one of those people blessed by the opportunity. It was strange to imagine that such imposing creatures that appeared to reign on the canopy of the forest were struggling to stay afloat.

© Andrew Walmsley/NPC

Five hours had passed from the moment I had first sank in the mud that day to start looking for monkeys. I was standing together with one of the guides, who was there to make sure no ill fortune would fall upon me or the monkeys. I stood right underneath another family of monkeys. They were jumping back and forth so high up in the canopy that all we could make out was their flying black silhouette against the grey sky. Everybody else had returned to the house, but I wanted some more alone time with these animals, observing their acrobatic moves for one last time.

More than two centuries after being discovered by western science, those incredible monkeys are still facing the same threats. Mittermeier in fact recently stated that he doesn’t believe the species will survive another two decades. He didn’t see, however, the tremendous efforts that foreign conservationists but also local people are doing in order to save this animal from oblivion. This small group of people whose strength and dedication equal that of an army are devoting their lives to this cause, and they’re moving mountains and muddy hills to actively preserve the monkeys and to change people’s perceptions towards some of the rarest mammals in the world. The monkeys might have a fighting chance after all.


Henrique Bravo Gouveia is a biologist focusing on the communication of science and conservation of all things endangered. He co-founded an NGO named ‘Lonely Creatures’ with the purpose of telling the stories behind threatened species, showing their uniqueness and importance. He is currently doing research on mangroves in Hong Kong.