Squirrel Monkey

The Guianan squirrel monkey is a species of squirrel monkey from Guiana, Venezuela and Brazil. It has a pink face, black muzzle and white arches over the eyes, an olive or olive-gray crown, a white belly and yellow-orange arms. It often feeds and moves in mixed groups with capuchin monkeys, and its varied diet includes insects, seeds, fruit, young leaves, flowers, gum, nectar, spiders, lizards and bird eggs. Breeding is synchronized within each group, and after a gestation of about five months the infants in a group are typically all born within a week of each other, in January or February. Males provide no parental care, and the species can live more than 20 years.

About the squirrel monkey

The squirrel monkey is a small New World monkey of the genus Saimiri, the only genus in the subfamily Saimiriinae. The name Saimiri sciureus once covered a single "common squirrel monkey" across the Amazon; today it means the Guianan squirrel monkey of northern Brazil and the Guianas, a fast, fruit- and insect-eating canopy primate.

Genetic studies in 2009 and 2015 split the old common squirrel monkey into several species. Humboldt's squirrel monkey (S. cassiquiarensis) of Colombia, Peru and Ecuador and Collins' squirrel monkey (S. collinsi) of northeastern Brazil are now separate. The same work found that the Guianan squirrel monkey's closest relative is the Central American squirrel monkey of Costa Rica and Panama, despite the gap between their ranges.

These are small, slender monkeys. Guianan males measure 25–37 cm (9.8–14.6 in) in the body with a 36–40 cm (14–16 in) tail; females are 25–34 cm (9.8–13.4 in) with a tail of 36–47 cm (14–19 in). Males weigh 550–1,400 g (19–49 oz) and females 550–1,200 g (19–42 oz). Animal Diversity Web calls them the smallest members of the primate family Cebidae.

The face is the giveaway: pink skin, a black muzzle and white arches over the eyes, under an olive or olive-gray crown. The back can be gray, olive or orange, the belly white, and the arms and legs a bright yellow-orange. That black-and-white face earned the genus the name "death's head monkey" in German, Swedish and Dutch. Squirrel monkeys have nails rather than claws, and males carry large upper canines.

The long tail is not prehensile in adults. Instead it serves as a balancing pole as the monkey runs along branches, and it often curls over a shoulder when the animal rests. Infants have slightly prehensile tails.

Behavior and diet

Squirrel monkeys are diurnal and arboreal, spending most of their time in the middle canopy but sometimes climbing high or dropping to the ground. They move fast through the branches. Troops usually number 12 to 100, and groups of up to 500 have been seen in undisturbed forest.

Society is built around the adult females and their young, who form the core of the troop. Males are generally dominant to females, but females hold high status and can form coalitions against dominant males. All males leave their birth group once mature, then live alone, trail another troop at a distance, join a new mixed-sex troop, or even travel with other monkey species. Guianan squirrel monkeys regularly feed and move with capuchin monkeys.

The diet is mainly fruit and insects. A troop spends roughly the first hour of the day collecting fruit, then spreads out through every level of the canopy hunting spiders and insects. The Guianan squirrel monkey also eats seeds, young leaves, flowers, gum, shoots, nectar, lizards and bird eggs, and has been seen eating a bat at least once. Most of its water comes from food, topped up from tree holes and puddles, and when fruit is scarce it turns to nectar.

Heat is a real problem for an animal this small in a humid forest. Squirrel monkeys can sweat only through their palms and soles, so they seek shade, shift posture, and practice "urine washing": they urinate on their hands and rub it onto their feet, where it evaporates and cools them. They also rub urine on their tail and skin to mark territory.

Squirrel monkeys are usually quiet but cry out loudly when alarmed, with calls described as caws, bawls and shrieks. Their call types are inherited: monkeys raised in isolation, and even one deaf from birth, produced the same calls as others. Warning calls help protect the troop from large falcons; snakes and wild cats are also predators.

Breeding is seasonal and synchronized. Before mating season, males gain weight in the upper body, a hormone-driven change, and become more aggressive. After a gestation of about five months, all infants in a group are typically born within a week of each other during the rainy season. Fathers give no care, but other females help as "aunts." Infants are weaned at about six months; females mature at about 2.5 years and males at four to five.

Range and habitat

The genus lives in the tropical forests of Central and South America. Most species occupy neighboring ranges across the Amazon, while the Central American squirrel monkey lives apart in Costa Rica and Panama. Since the taxonomic split, Saimiri sciureus itself is limited to Brazil and the Guianas.

Within that range, squirrel monkeys use many forest types: primary and secondary forest, gallery forest along rivers and forest edges. They favor vegetation that gives good cover from birds of prey, including rainforest, savanna, mangroves and marshland, and their daily activity tends to center on a source of water.

They have also turned up where they don't belong. At least five populations of escaped or released common squirrel monkeys have existed in Florida since the 1960s, including at Silver Springs and in Broward and Polk counties. In Brazil, free-ranging squirrel monkeys appeared in Rio de Janeiro's Tijuca Forest in 2009, and by 2010 they were considered invasive in the Atlantic rainforest, with concern about them eating the eggs of endangered birds.

Squirrel monkey vs black-capped squirrel monkey

Two groups of squirrel monkeys are recognized, and the quickest way to tell them apart is the white patch above the eyes.

Conservation status

The Guianan squirrel monkey, Saimiri sciureus, is listed as Least Concern on the IUCN Red List, most recently assessed in 2021. Before the split, the common squirrel monkey was also rated Least Concern, though considered vulnerable to deforestation.

The main threats are habitat destruction, illegal hunting, and capture for the pet trade and medical research, for which squirrel monkeys have been taken extensively. Not every squirrel monkey is so secure: the Central American squirrel monkey and the black squirrel monkey are listed as Vulnerable.