Black-Horned Capuchin, Sapajus nigritus
BLACK-HORNED CAPUCHIN
Sapajus nigritus
Geographic Distribution and Habitat
The black-horned capuchin (Sapajus nigritus), also known as the black capuchin, is native to the South American countries of Argentina and Brazil. This small American monkey is at home in the lowland and montane tropical Atlantic Forest biome, at elevations between 980 and 3,280 feet (300–1000 m) above sea level. Black-horned capuchins are reasonably tolerant of change and disturbance, so they also have done quite well living in disturbed forests and even in pine and eucalyptus plantations. In some cases, they live on the forest edge bordering agricultural fields.
Capuchins are commonly considered to be split into two genera: Sapajus, the tufted capuchins, and Cebus, their un-tufted gracile cousins. Black-horned capuchins share the former genus with seven other species. This arrangement was first proposed in 2012. However, some sources still consider black-horned capuchins to be in the genus Cebus. They may still list black-horned capuchins as a subspecies of the tufted capuchin (S. apella), although they are usually considered to be their own species.
Size, Weight, and Lifespan
The average black-horned capuchin weighs somewhere between 4.4 and 7.3 pounds (2.0–3.3 kg). Their head and body length ranges from 12.6–21.7 inches (32–55 cm), with males on the larger size. Their tail adds another 14–20 inches (35–50 cm) to their overall length. Black-horned capuchins live to an average age of 30 years in the wild but can live up to 50 years in captivity.
Appearance
It’s often quite obvious at first glance how the black-horned capuchin got its name. Two black tufts of hairs jutting out from their temples give these monkeys their devilish silhouette. Otherwise, they have a very similar build to other tufted capuchins: a medium-sized body, long arms and legs, and a prehensile tail that comes in very handy for navigating their forest habitat. A prehensile tail can grasp objects. Their bodies are typically a reddish or gray brown, which darkens into dark brown and black on their arms, legs, and tails. Their eyes are large and expressive, and their face is encircled with a ring of white hair and, further back, black hair. Their “horns” sprout from this area, although on some individuals—perhaps those having a bad hair day—these tufts resemble two amorphous poofs rather than horns. Aside from size, adult females, adult males, and juveniles all look alike. Their coat colors do not vary with age or sex.
Diet
Black-horned capuchins are omnivores in the truest sense of the word—that is, they consume both plants and other animals. This makes for a highly varied diet of fruits, seeds, insects, frogs, nestlings, small mammals, stems, flowers, and leaves, with a rough breakdown of about 50–75% fruits and nuts, 25–35% animals, and 7% other plant parts. During periods of fruit shortages, they compensate by eating more leaves. Tree frogs are a particular favorite food item for black-horned capuchins. They have been known to use tools to access larvae and crack open nuts. Young black-horned capuchins watch the adults using tools and try to mimic them, often to no avail until they are older and more dexterous. Tool use was once believed to be what separates humans from other primates, but we now know that not only do many primates utilize tools, other animals do as well.
Behavior and Lifestyle
Black-horned capuchins are diurnal—awake during the day—and fully arboreal, meaning that they spend just about their entire life in the trees. They move about by swinging and climbing through the trees. They travel about a half mile (750 m) per day during the dry season and about 2 miles (3 km) per day in the wet season. Their home ranges are typically between 200 to 370 acres (80–150 ha). Most of their day—about 70% of their waking hours—is spent foraging, which they do from sunrise to the late evening. During the wet season, when food is abundant, they spend more time resting and less time foraging. At night, black-horned capuchins find tall trees to sleep in. These trees must be tall enough to protect them from ground-dwelling predators, be comfortable to sleep in, and, ideally, have enough space for at least two capuchins, although black-horned capuchins will sleep alone if they have to.
Foraging is a noisy process between the frequent calls to groupmates and noisily banging open nuts, so it can also be perilous, as this noise can attract predators. Because of this threat, black-horned capuchins stick to their groups, where there is strength in numbers. When a predator is spotted, the alpha male lets out a whistle to alert his troop. While they run and hide, the alpha males and other males of the group fend off predators.
Black-horned capuchins are colorblind. While this may seem a hindrance, scientists have found that colorblind monkeys (and humans!) are better at identifying camouflaged objects than their counterparts that see a wider spectrum of colors. In the wild, black-horned capuchins are likely better at spotting camouflaged insects to eat. It is believed that the reduction in color information from being colorblind means that the monkeys are better able to recognize shapes, contours, and contrasts—such as those of a juicy, bark-colored bug on a branch.
Black-horned capuchins live in groups, called troops, of sizes varying from about 10 to 30 individuals, with females outnumbering males. An alpha male leads and protects the group, deciding where to go, what to eat, and who is allowed to join the group. Males disperse from their natal groups upon reaching maturity, while females tend to stay with the group they were born into. However, females may switch groups when the alpha male changes or if a group splits into two. Both sexes have their own hierarchies, with the top-ranking male dominant to the top-ranking female. Social grooming is used as an equalizer that helps group members to bond, regardless of their rank.
Black-horned capuchin home ranges overlap by about a third, meaning that groups find themselves in close contact relatively frequently. While these interactions can be peaceful—multiple groups have been observed foraging in close proximity without conflict—it can sometimes cause issues. If tensions arise, the alpha males attempt to drive each other’s groups away by throwing rocks, screaming, and even directly fighting one another.
Black-horned capuchins are known to make a large variety of vocalizations, from the purring of an amorous female towards her intended mate, to the screaming of alpha males as they protect their group. Whistling and barking are commonly heard among black-horned capuchins while they forage. Whistling is often used as an alarm call—though, curiously, false alarm calls are often made for no obvious reason. Black-horned capuchins also make a wide array of facial expressions that help them communicate with their group mates.
Mating among black-horned capuchins is initiated by the female. While it can occur at any time of the year, most mating occurs between December and April. A male signals his intent to breed by marking his own hair with urine. When a female is receptive, she chooses a male and signals her intent by following him around, making faces like smiles and eyebrow wiggles, purring in his general direction, and poking him and abruptly running away, to encourage him to chase her. This behavior can go on for several days. When the male notices and if he chooses to, he will then mate with her.
After 150 days, about 5 months, the female gives birth to a single infant. This baby will take up much of her attention for the next several years, until fully independent. For the baby’s first year, he is carried on his mother’s chest. During much of his second year, he is usually carried on her back. Two years after giving birth, the mother can breed again. Young reach their full size at about three years of age, but are still at least somewhat reliant on their mother until about four years of age for females and up to eight years for males. While the mother provides all the baby’s direct care, males protect the group’s territory and hunt for food.
Black-horned capuchins serve a role as seed dispersers when foraging, as they drop seed-laden fruit to the forest floor, and disperse seeds in their droppings. They act as predators to the many amphibians, birds, and other small animals that they eat. Black-horned capuchins are in turn predated on by animals such as jaguars, harpy eagles, cougars, and pythons.
The International Union for Conservation of Nature lists the black-horned capuchin as Near Threatened (IUCN, 2015), appearing on the IUCN’s Red List of Threatened Species. It is predicted that they will undergo a 30% reduction in their population over the next half-century, or about three generations. They face threats from habitat loss and forest fragmentation and hunting. It is unknown what their current population is, and estimates of their population densities have ranged from 9 to 244 individuals per square mile (3.5 to 94 individuals per square km), depending on where the survey was completed.
Black-horned capuchins are hunted by humans for food, for fur, for trophies, and as crop pests. They are also sometimes taken from the wild for the pet trade. However, the major threat against black-horned capuchins, as is the case for most primates, is habitat loss. Five hundred years ago, the Brazilian Atlantic Forest covered an area twice the size of Texas—about 330 million acres (1.3 million square km). Over 85% of the forest has since been cleared, and what remains is extremely fragmented. In contrast to the Brazilian Amazon, the Atlantic Forest has borne the brunt of Brazil’s surge in population, as it includes about 70% of all Brazilian residents, and hosts several huge cities, such as Rio de Janeiro and São Paulo. Despite the rampant deforestation and the immense pressure from human development, the Atlantic Forest hosts 60% of all of Brazil’s threatened species and is home to 26 of Brazil’s 77 primate species. Conserving what remains of the Atlantic Forest is a high priority for conservationists. This will become all the more challenging as the Atlantic Forest is expected to face extreme climate changes in the coming decades. In fact, climate scientists predict that it will change more in the next 50 years than it has since the last ice age. It is difficult—impossible, really—to predict all of the ecological impacts that these climate changes will have, but ecologists are sure that it will be an uphill battle for the many species that rely on the forest.
Black-horned capuchins are listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival. Black-horned capuchins live in a number of protected areas, the largest of which is the Iguazu National Park in Argentina and Brazil.
Research into human-wildlife conflict issues has also been conducted to learn more about the impacts black-horned capuchins can have on agriculture. One study, for example, examined the reasons behind why black-horned capuchins strip bark on pine plantations, and determined that it was related to seasonal fruit scarcity. This research could be applicable to forest management, and some potential solutions include planting less-preferred pine species and enriching native forests with fruit-producing trees.
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Written by K. Clare Quinlan, February 2023