Black-Crowned Central American Squirrel Monkey, Saimiri oerstedii
BLACK-CROWNED CENTRAL AMERICAN SQUIRREL MONKEY
Saimiri oerstedii
Geographic Distribution and Habitat
Black-crowned Central American squirrel monkeys are native to the Pacific coast of Costa Rica and inland Panama. Their territory is large but heavily fragmented. It starts at the Río Tulín in the north Herradura and Dota mountains, stretches along the coast of the Golfo Dulce and the Burica Peninsula, and extends to the western part of the Chiriquí Province and the Archipelago of the Golfo de Chiriquí, in Panama.
Black-crowned Central American squirrel monkeys live in seasonally inundated forests, river edge forests, floodplains, and secondary forests. Historically, they were found at altitudes up to 1,650 feet (500 m), but recent sightings indicate some populations are now also present at altitudes between 1,960 and 2,600 feet (600 and 800 m) and up to 3,900 feet (1,200 m) above sea level.
The climate in Costa Rica and Panama is tropical with two seasons: dry and rainy. The rainy season on the Pacific coast lasts from May to mid-December, with the most rain in June and October. The forest is the greenest and most lush in July and August. Temperatures all year round average 80°F (26° C).
Squirrel monkeys belong in the genus Saimiri. For some time, quite a few squirrel monkey species were grouped as one species in what was referred to as the “common squirrel monkey”. With the benefit of molecular studies, the consensus today is that the Saimiri genus includes up to seven species and seven subspecies throughout Central and northern South America. All display varied morphological (physical) characteristics, including dental variations.
These species differences are thought to have diverged between 12 and 20 million years ago due to ecological factors, such as the formation of rivers, the movement of tectonic plates, and varied climate events. Some studies suggest that the ancestors of the black-crowned Central American squirrel monkey, S. oerstedii, appeared 2.3 million years ago.
Size, Weight, and Lifespan
Adult males average 1.8 pounds (829 g) with some individuals weighing as little as 1.6 pounds (750 g) and others as much as 2 pounds (950 g). Adult females are smaller with an average weight of 1.5 pounds (695 g), with variations between 1.3 and 1.7 pounds (600-800 g). Their body measures between 8.8 and 11.6 inches (22.3–29.4 cm) in length. Their tails add 14–18 inches (35.5–45.7 cm).
The lifespan of squirrel monkeys in the wild ranges from 15 to 20 years, whereas in captivity, they can live up to 25 years.
Appearance
Black-crowned Central American monkeys are covered in a dense pelage that appears soft yet thick enough to keep them dry when exposed to the rain. Their long tail is covered in gray fur and ends with a black tip. Their back and limbs are a creamy reddish-caramel color with some gray on the shoulders and thighs. Their belly and throat are white. Their face is expressive, with white fur framing and forming semi-circles above their almond-shaped eyes. Their ears are large, compared to the size of the face, and fuzzy. The skin around the mouth is a medium gray, matching perfectly the gray of the fur on the crown of the head. Their body is slender. They have long and bare pinkish digits that end with fingernails. Their thumbs and big toes are semi-opposable.
Squirrel monkeys are distinguished by the shape of the pigmented arch on the eyebrows. The black-crowned Central American squirrel monkey sports what is referred to as a Gothic arch that is defined by the high arch of white hair around the eyes, and the darker hair on their heads forms a deep “V” shape between their eyes.
Diet
These primates are frugivore-insectivores, which means they mostly consume fruit, seeds, flowers, invertebrates, and small vertebrates. During the dry season, when fruit is not as abundant as in the rainy season, they rely on animal prey, such as invertebrates and occasionally fruit bats.
They spend most of their waking hours (75-80%) foraging in the lower canopy and understory of the forest. According to some studies, females may spend more time looking for food and eating than males do because males have to spend time controlling the group and keeping everyone safe from predators. Members of the group also spread out more while foraging than when they rest or travel together.
Behavior and Lifestyle
Black-crowned Central American squirrel monkeys are arboreal (tree-dwelling) and diurnal (active during daylight hours). They travel in the canopy by walking and running using their hands and feet to grasp onto branches (quadrupedal locomotion). Their tail is not prehensile, but they can wrap it around a branch to keep their balance when they’re not moving, or hold it high up and move it left or right to keep their balance while traveling around. They can also leap from branch to branch.
The members of the troop forage together in the morning and late afternoon. The rest of the time, they sleep, groom, and play. Studies indicate that they rest a lot less during the rainy season because they have to travel more to find food, and that they travel a lot less during the mating season.
When several troops share the same environment, members of these troops tend to avoid each other, so there is little to no conflict, except when they are competing for large invertebrates and small vertebrates or bird eggs.
The brains of primates that eat fruit have more convolutions than the brains of primates that feed exclusively on foliage. This may be because of the cognitive challenge of identifying when fruit is ripe and where to find it. This is the case for squirrel monkeys.
Squirrel monkeys are very social and live in large troops that typically include 25-70 (sometimes up to 100) individuals. Larger troops have been observed when several troops temporarily merge. There is little or no feeding competition between groups.
The troops are composed of multiple males, females, and offspring.
Males are in charge of safety; they are vigilant at all times, alerting the group members if they spot a predator so everyone can run for shelter.
Males remain within their native troop, whereas females transfer to a different troop when they reach maturity and before the mating season. Contrary to what occurs in some other primate species, black-crowned Central American squirrel monkey females do not form coalitions mainly because they leave their natal group when they reach maturity. Females are also more likely to move to a different troop if their infant dies, so long-term relationships with other females are not formed, nor are they advantageous.
Squirrel monkeys do not groom each other; their social bonds are maintained by how close they are to each other. At night, for example, they sleep huddling together on branches with their tails intertwined. Juveniles and infants develop social skills and bond by playing together.
Like most primates, the way black-crowned Central American squirrel monkeys communicate is varied. They use scent, visual cues, and vocalizations. Males, for instance, know if a female is receptive during mating season through scent, and females recognize their infants by their odor. Males and females also commonly use urine-washing by peeing on their hands and feet and spreading the urine all over their body. This unusual custom helps squirrel monkeys scent mark their territory, advertise their reproductive status, assert dominance, but also helps them control their body temperature and makes the branches on which they travel less slippery.
Squirrel monkeys use visual displays to convey many messages to other animals in their group. Facial expressions can be indicative of fear or submission; staring at another monkey or showing one’s private parts are signs of dominance and can lead to aggressive behavior.
Infants vocalize through grumbles, cackling, purrs, chucks, and peeps. Adults use many calls (25 to 30), each with different meanings — some are calls to get the troop to travel, others, like howls, are alerting that a predator is approaching, and everyone should run to a safe place. A study conducted several years ago found that, to communicate with group members, either single or double clicks were used depending on how spread out they were while foraging.
Female black-crowned Central American squirrel monkeys become mature at about one year of age, while males take much longer and mature between the ages of four and six. Mating season occurs during the rainy season, at which time males gain more than 20% of their body weight to assert themselves and gang up to mob females. All females are receptive around the same time for about two days, and only every two years.
Females give birth to one offspring between February and April, after a gestation of approximately 147 days.
Mothers carry their baby on their backs and are in constant contact with it for the first thirty days. They nurse them for approximately 20 days, at which point babies start taking solid food but are not completely weaned until they reach the age of five or six months. At the end of their first month, babies start exploring their environment, grabbing and manipulating green and dead leaves, bark, or other items. Like human babies, at that stage of life, they put everything into their mouths. For the first three months, mothers work together to ensure their offspring are protected from predators, however, they resist having other females carry or touch their young. Males have limited or no interactions with the little ones, but they remain vigilant and protect them if there is danger.
From the fourth month to the seventh month of life, physical contact between mothers and offspring is negligible. The youngsters learn to become independent by play-fighting with each other during their first year of life.
Squirrel monkeys play a key ecological role by spreading seeds, either by dropping them or excreting them, from the fruit they consume and thereby promote forest regeneration.
The International Union for Conservation of Nature lists the black-crowned Central American squirrel monkey as Endangered (IUCN, 2020), appearing on the IUCN Red List of Threatened Species.
Black-crowned Central American squirrel monkey populations have declined by about 60% in fewer than 30 years due to habitat loss and forest fragmentation, mainly caused by deforestation for human activities. Farming, cattle ranching, timber (especially teak, which is highly prized for export), and palm oil plantations are the main culprits. The expansion of hydropower plants has also had a toll on the Amazon forest of Panama.
Other threats include the capture of squirrel monkeys for the illegal pet trade, mostly at the border of Panama. These primates are also killed by wild dogs or by farmers who view them as pests, especially after incidents involving monkeys raiding crops of maize, bananas, or lychees. Some monkeys are electrocuted when they come in contact with electric wires that they don’t know to identify as dangerous.
Habitat fragmentation prevents troops from moving freely and can restrict the gene pool available for reproduction.
Although not everyone agrees, the number of individuals in the wild is estimated at 3,000 in Costa Rica and over 4,700 in Panama.
Natural predators include, among others, jaguars, coatis, capuchin monkeys, collared forest falcons, crested eagles, and boas.
Central American squirrel monkeys are listed on the Convention on International Trade in Endangered Species (CITES) Appendix I and occur in numerous protected areas in Costa Rica and Panama.
For many years, Costa Rica was considered an environmental and sustainability leader. After losing almost half of its forest coverage by 1987, the government instituted a system by which local communities would be paid to help protect nature, thereby reversing deforestation. However, in 2024, a series of new policies put the ecological achievements of the country at risk and may well reverse progress to protect and promote biodiversity.
Some new initiatives offer hope for the future, such as the Forest Landscape Restoration project, which aims to restore over 61,000 acres (25,000 hectares) of degraded land in Panama.
- IUCN redlist 2020
- The Tico Times – Is Costa Rica Losing Its Green Edge? Report Warns of Policy Shift
- www.earth.org How Costa Rica Reversed Deforestation and Became an Environmental Model – Carol Konyn
- https://vetexplainspets.com/how-long-do-squirrel-monkeys-live/#
- The ontogeny of foraging in squirrel monkeys, Saimiri oerstedi – S. Boinski and D.M. Fragaszy
- https://primatecare.com/primate-care-sheets/squirrel-monkeys/reproduction/
- Animal behavior of the Saimiri oerstedii in the Osa Peninsula: eating, sleeping and traveling patterns – Cody Compton
- https://olaw.nih.gov/sites/default/files/Squirrel_Monkeys.pdf – Squirrel Monkeys (Saimiri) – A. Michele Schuler, D.V.M., Ph.D
- https://www.saczoo.org/squirrel-monkey
- https://palotoaamazontravel.com/squirrel-monkey-a-star-of-the-amazon-rainforest/
- Behavioral Biology of Squirrel Monkeys – Anita L. Stone; Lawrence Williams
- Squirrel Monkey Behavior in Research – Lawrence Williams, Martha Glasgow
Written by Sylvie Abrams, May 2025