Sapajus libidinosus

Both sexes are the same height, about 37 cm, but show a strong sex difference in weight, with males weighing about 3.5 kg and females weighing about 2.1 kg. They also show sex difference in canine length, with males averaging 1.5 cm and females only 1 cm. Male weight is related to social status; when males become alpha males, they gain about 20% more weight. When they lose dominance, they also lose extra weight.
They look very similar to other capuchin species. Their fur ranges from golden to dark brown, with darker hair on the head, tail, and around the arms and legs. When they reach sexual maturity, they grow two small tufts of black hair on their heads and have black "sideburns" running down the sides of their faces. Their faces can vary in shade, with the hair around the mouth and lower face tending to be lighter, which explains why they are called "bearded capuchins" (Bearded capuchins). They also have strong, prehensile tails that allow them to hang from br

The bearded monkey is distributed in Brazil (Bahia, Piauí, Rio Grande do Norte, Mato Grosso, Minas Gerais, São Paulo, Mato Grosso do Sul, Pernambuco, Alagoas, Pará, Ceará, Maranhão, Goiás, Paraíba) and in the Tocantins River Basin of Brazil.
The bearded monkey is found in a wide range of habitats, such as dry deciduous forests, mangroves, forests and scrublands in the Caatinga of northeastern Brazil, gallery forests and dry forests in the scrub savanna of central Brazil. The species is highly resistant to human disturbance and can survive in disturbed habitat areas. A family group of 135 hectares was observed in Serra da Capivara.

Bearded Capuchin (scientific name: Sapajus libidinosus) English Bearded Capuchin, Black-striped Capuchin, German Rückenstreifen-Kapuzineraffe, Portuguese Macaco-prego, Macaco-prego-amarelo, no subspecies.

The bearded monkey is a New World monkey, a member of the family Capuchinidae, which also includes capuchins and squirrel monkeys. Until the past few decades, the bearded monkey was considered a subspecies of the black-capped monkey, but has been accepted as a separate species over time. Even within the bearded capuchin species, more taxonomic debate is seen, as the southern population is sometimes considered a separate species, called Azaras's capuchin.

Bearded capuchins live in mixed-sex groups. Small groups of 8-20 individuals are very cohesive. Females are kin-oriented and remain in their natal group as adults, while males migrate to a new group, which usually contains more females, usually about two females for every male. Males form dominance hierarchies, with one adult male dominating all members of the group. The alpha male is the centerpiece of the group's social network, and females show a preference for grooming the alpha male, although they will groom each other as well. Females also establish vertical dominance hierarchies and form alliances with other females during conflicts. Subordinate males, unlike alpha males, are often marginalized from the group.

Bearded capuchins are diurnal animals, most active during the day and sleeping in trees at night. They spend most of their day foraging and wandering, especially during the dry season when fruit is less abundant. These savanna-dwelling capuchins spend a higher percentage of their time on the ground compared to capuchins living in rainforests. They usually walk on all fours, however, they are also said to walk bipedally when carrying heavy stones in their arms to crack nuts. In this case, they use their thick tails for balance.

Adults of both sexes showed a high tolerance for young infants, allowing them to observe how nuts are cracked up close and even allowing infants to take cracked nut fragments from their hands. It takes several years for young bearded capuchins to learn how to crack nuts, and this high level of tolerance and associated foraging may help infants learn this skill. This social learning allows nut cracking skills to be passed down from generation to generation and may form the evolutionary basis of culture seen in humans. This species can even do what is known as "adopting" another bearded monkey's baby, a behavior that is extremely rare among primates. Bearded monkeys use a wide variety of facial expressions to communicate, including lifting their scalp, smacking their lips, and threatening with an open mouth. Facial expressions are used not only in courtship rituals, but also in other intimate and aggressive encounters as well as gestures, vocalizations, and body postures. Bearded monkeys make many types of vocalizations, including alarm calls when they see a predator, such as birds, snakes, or dogs.

Bearded monkeys have a wide range of food resources, including a variety of fruits, seeds, arthropods, frogs, nestlings, and even small mammals. Fruits make up about 50% of the diet, with invertebrates also making up a large proportion, and other plant parts such as stems, flowers, and leaves are also consumed. The species is able to use tools while foraging, an unusual behavior among Neotropical primates. The bearded monkey is famous for its nut-cracking behavior. They use stone tools to crack the hard shell of palm nuts so they can eat the kernel inside. This is done by placing the nut on a boulder or hard surface and then using both hands to lift a rock and hit the nut to crack the shell.

The bearded monkey performs a number of interesting and unusual courtship rituals. When females are ready to mate, they will follow the male around trying to get his attention. This may even involve the female throwing rocks or sticks at the male. Males tend to be either uninterested or aggressive towards the female initially. This is followed by "touch and run" behavior, where the female touches the male and then runs away before the male can attack the female. Eventually the male returns the female's estrus and mating takes place. Females will usually first try to get the attention of the monkey king, who fathers most of the babies in the group. Females reach sexual maturity around 5 years of age and give birth approximately every two years, usually to a single infant. The infant is initially carried on the mother's belly and later on her back. The infant is gradually weaned but forages independently at 2 years of age. Males typically reach adulthood around 5 years of age, but do not reach average adult weight until around 10 years of age.

The bearded monkey population is declining due to continued habitat loss. As of 2012, the Caatinga and Cerrado biomes, where the species is found, had lost almost 50% of their suitable habitat due to continued deforestation. The species is heavily hunted and collected in the wild for the illegal pet trade. The severity of hunting pressure is evidenced by the large number of individuals seized from the illegal trade by wildlife screening centers. Most of these captured individuals cannot be returned to the wild due to physical and behavioral impairments caused by captivity. Other threats are the impact of hybrids or exotic species intentionally released from captivity on the bearded monkey. Most bearded monkeys in the Caatinga Biome are isolated in hilly and mountainous areas, often destroying or feeding on crops from nearby farms, causing conflicts with farmers and often leading to their killing.

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