Northern muriqui

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Northern muriqui (Brachyteles hypoxanthus) are one of two muriqui species. They’re also known as woolly spider monkeys because of their fluffy fur and long prehensile tails. They are the largest New World monkeys, growing up to about 1.3 meters long and weighing around 7–10 kilograms.

Where they live
- Endemic to the Atlantic Forest in Brazil, in the states of Rio de Janeiro, Espírito Santo, Minas Gerais and Bahia.

Conservation status
- Critically Endangered. There are fewer than 1,000 mature individuals in the wild. Main threats are habitat destruction and hunting. Only the Caratinga population is considered viable for the next century.

What they look like
- Males and females are similar in size. They have vestigial thumbs, and can be identified by fur color and facial markings.

Diet and movement
- They eat mainly fruit and leaves, but also seeds, flowers, nectar, bark, twigs and even soil.
- Diet changes with the seasons: more fruit in the wet season, more leaves in the dry season.
- They travel through the forest canopy using all four limbs and their tail (brachiation). They sometimes come down to drink water or eat fallen fruit.

Social life and reproduction
- They live in egalitarian, flexible social groups that split and join as needed.
- Females typically leave their birth group around age six; males stay with their mothers longer.
- Groups overlap, but individuals use different levels of the forest to avoid conflicts.
- Infants are born mainly in the dry season. Gestation is about seven months. Females can mate with several partners.
- Infants are easy to spot within a week of birth. Lifespan can exceed 30 years.

Why they matter
- Northern muriquis are mostly arboreal and very peaceful, with low levels of aggression between groups and sexes.
- Their social structure and cooperative relationships provide important clues about human evolution and family life. Their survival relies on protecting their forest habitat and maintaining genetic diversity.