Uakari

Lore & Background

Uakari are unusual among New World monkeys because their tail length (15–18 cm) is substantially less than their head and body length (40–45 cm). Their bodies are covered with long, loose hair, but their heads are bald. They have almost no subcutaneous fat, so their bald faces appear almost skull-like. Like their closest relatives the saki monkeys, they have projecting lower incisors. These monkeys have the most striking red facial skin of any primate. Females choose their mates based on how red the male's face is, and evidence suggests that the red facial coloration reflects the health of the primate. The four species of uakari currently recognized are all found in the north-western Amazon basin. The bald uakari, remarkable for its brilliant scarlet complexion, is found north of the Amazon River and south of the Japurá River in the Mamirauá Sustainable Development Reserve. The black-headed uakari is found north of the Amazon and south of the Rio Negro. The Neblina uakari is found north of the Rio Negro, west of the Rio Marauiá and east of the Casiquiare canal. The Aracá uakari is currently known only from the Rio Curuduri basin. They have been observed both in small groups and in larger troops of up to 100. When traveling through the forest they move in the lower branches of the trees, though when foraging they also go up to the canopy. They mostly eat fruit, and unlike other Neotropical frugivores will consume a large amount of unripe fruit for which they have specialised dentition. They also eat flowers, seeds, invertebrates, buds and leaves.

Reader's Guide

Uakari are significant as a distinctive genus of New World monkeys that illustrate the diversity of Amazonian primates. Their unusual morphology—short tails, bald heads, and vivid red faces—makes them a subject of interest for studies on sexual selection and health signaling. The red facial coloration, which females use to choose mates, is thought to reflect the primate's health, providing a clear example of honest signaling in the wild. Their specialized dentition for eating unripe fruit also highlights their ecological niche in Amazon flooded forests. The genus has a deep evolutionary history, with a concestor dating to 1.7 million years ago in the Solimões River, from which they spread and diversified following intermittent river rearrangements. Their presence in protected areas like the Mamirauá Sustainable Development Reserve underscores conservation relevance.

Did You Know?

• Uakari have the most striking red facial skin of any primate, and females choose mates based on how red the male's face is.
• Their tail length (15–18 cm) is substantially less than their head and body length (40–45 cm), unusual among New World monkeys.
• They consume a large amount of unripe fruit, for which they have specialised dentition, unlike other Neotropical frugivores.
• A phylogeographic reconstruction found that the concestor of living uakari dates to 1.7 million years ago in the Solimões River.