COMMON SQUIRREL MONKEY: CHARACTERISTICS, HABITAT, FEEDING, BEHAVIOR - BIOLOGY - 2025

The common squirrel monkey (Saimiri sciureus) is a placental mammal belonging to the Cebidae family. Its body is slim and is covered by short, gray fur. This hue contrasts with its legs, which are bright yellow.

When this species is young, the tail is prehensile, but in the adult it loses the ability to grasp and hold objects. However, it is very versatile and the animal uses it as a balancing element and sometimes as a lever.

Common squirrel monkey. Source: I, Luc Viatour

In relation to teeth, the common squirrel monkey has 36. The cheek teeth have large cusps, which help to grind the fruits and insects that make up their diet. Both sexes have canines, but in the male they are longer.

As for the trunk, it is long and the forelimbs are shorter than the hindquarters. On the legs, this primate has nails instead of claws.

The Saimiri sciureus is distributed in the tropical forests, alluvial plains and primary and secondary forests of much of South America

characteristics

- Coloring

The coat of the common squirrel monkey ranges from greenish-gray to brown. On the tail, the color progressively darkens until it ends in a dark, almost black tone. This species is characterized by having yellow or orange legs and forearms.

The face is white, while around the mouth, which includes the nostrils, it has a black or dark brown spot. In relation to the ears, they are white. The dark hair on her head forms a deep "V" between her eyes.

- Size

The average weight of the male ranges from 554 to 1150 grams, while that of the female is between 651 and 1250 grams. In relation to the length of the body, it can vary from 31.6 to 31.8 centimeters, with a tail that measures around 40.6 centimeters.

- Seasonal sexual dimorphism

This species exhibits seasonal sexual dimorphism. The male squirrel monkey shows a great variation in its body mass, increasing up to 20% of its weight months before the reproductive season.

Thus, it adopts a more robust appearance, due to the fat and water that the animal stores between the muscle and skin of the shoulders, head, ribs and upper arms. This makes him look more attractive to the female, which can help him when mating.

Studies

Much is known about the physiology of this male fattening, however, recently research has been done on this sexually dimorphic trait, to find out if it is associated with natural selection.

In these investigations the sexual behaviors of lean males were compared with that of robust males. They spent more time with the females in heat and less time alone. In addition, they were for long periods involved in various socio-sexual activities, thus reducing the duration of feeding activities.

This suggests a trade-off between reproductive behaviors and maintenance. On the other hand, 62% of the antagonistic behaviors between males occurred during the mating stage, which implies a male-male confrontation for the female.

However, the winning male does not force the female to mate, and may even be rejected by it. This pattern of behavior suggests the choice of the male, by the female. Due to this, probably, the fattening of the male of Saimiri sciureus is the product of intra and intersex selection.

- Locomotion

This primate is quadruped, moving in this way through the forest. When it needs to move between branches, it does so by jumping. Its habit is generally arboreal, occasionally descending to the ground to forage or to play with the other members of its group.

- Vision

The squirrel monkey sees objects in color; however, each animal has one of six different types of color vision. This variation is the product of the presence of 3 cone-length pigments, which have a medium to long wave range.

According to research, these structures are related to three alleles, located at the same locus of the X chromosome.

- Communication

To express itself, this mammal uses vocalizations, olfactory signals and complex behaviors, such as postural displays, among others.

An example of chemical communication is known as "urine washing." In this, both the male and the female, urinate on their legs, and then clean them on the arms, shoulders and legs.

In this way, the animal marks the route through which it moves, for other squirrel monkeys to follow. In addition, the male can use this olfactory signal to show his dominance to the group.

Vocalizations

The Saimiri sciureus emits a large number of calls, which present intra and inter-group variations. These can be organized according to their function, in addition to having notable differences in terms of their acoustic structure.

Thus, the vocal behavior of the adult female includes 21% of "caretaker" type vocalizations. These calls are used by the mother while breastfeeding and to indicate to her young where she is.

Taxonomy and subspecies

-Animal Kingdom.

-Subreino: Bilateria, -Filum: Cordate.

-Subfilum: Vertebrate.

-Infrafilum: Gnathostomata.

-Superclass: Tetrapoda.

-Class: Mammal.

-Subclass: Theria.

-Infraclass: Eutheria.

-Order: Primates.

-Suborder: Haplorrhini.

-Infraorder: Simiiformes.

-Family: Cebidae.

-Subfamily: Saimiriinae.

-Gender: Saimiri.

-Species: Saimiri sciureus.

There are different positions regarding the recognition of the existence of subspecies. However, various investigations and international organizations, such as the IUCN, recognize at least four subspecies of Samiri sciureus. These are: Saimiri sciureus sciureus, Saimiri sciureus albigena, Saimiri sciureus cassiquiarensis and Saimiri sciureus macrodon.

Habitat and distribution

Squirrel monkeys live in the rainforests of South America. Thus, it is distributed in Bolivia, Colombia, Brazil, Ecuador, Guyana, Suriname, French Guiana, Peru and Venezuela.

Subspecies

There are four subspecies, which are located in different regions. The Saimiri sciureus sciureus is distributed to the east and northeast of the Amazon. In this way, it extends into Amapá and the Guianas. It is also located in the Brazilian Amazon, south of the Amazon River and east of the Xingú River, as well as east of the Negro and Deminí rivers.

As for the Saimiri sciureus albigena, it lives in the gallery of forests of the eastern Colombian plains, encompassing the eastern area of ​​the Eastern Cordillera of the departments of Casanare, Arauca, Boyacá, Meta, Cundinamarca and Guaviare. In addition, it is sighted in the Magdalena River.

The Saimiri sciureus cassiquiarensis is geographically located in the upper areas of the Amazon. In Venezuela, it lives in the Amazon state, from the Solimões River and the Negro and Demini rivers, to the Casiquiare-Orinoco basin. In Colombia, it is between the Inírida and Apaporis rivers.

Regarding the Saimiri sciureus macrodon, it extends through Brazil, in the upper part of the Amazon, in the state of Amazonas, between the Japurá and Juruá rivers. It is also in the Apaporis River in Colombia and in the eastern region of the Ecuadorian Amazon to the Andes.

In Peru, this subspecies lives south, reaching the Marañón and Amazon rivers, and west of the Huallaga to the Andes region.

Habitat

The common squirrel monkey has a very wide geographic range. However, it prefers tropical rainforests, primary and secondary forests, and gallery forests. In these ecosystems, the primate prefers the middle levels, between the branches of the trees, although it could go down to the ground or go up to the canopy.

Other habitats where Saimiri sciureus can be found are seasonally flooded forests, alluvial plains, forested slopes, and riverside forests.

Feeding

The common squirrel monkey is both frugivorous and insectivorous, so it bases its diet on fruits and some varieties of insects. However, it occasionally consumes seeds, flowers, leaves, arachnids, and some small vertebrates.

During the early hours of the morning, the mammal begins its search for fruits, thus traveling through all levels of the canopy. After this routine, spend the rest of the day hunting spiders and insects.

Food is influenced by the seasons. Tropical forests are characterized by marked temporal and spatial variation in productivity, and many primates face foraging problems associated with seasonal changes in fruit availability.

Thus, in the summer season, fruitful trees are scarce, so fruits constitute approximately 20% of the diet, while insects represent 80%.

In the winter season, the number of trees increases markedly and the availability of insects and arthropods decreases. Due to this, the common squirrel monkey feeds mainly on fruits, reaching a percentage of 79.9%.

Research

The specialists conducted a study in the eastern region of the Amazon. The results indicate that the animal spends most of the time feeding, particularly arthropods.

Also, the investigative work reviews the hunting and subsequent consumption of a small bat. However, the search for Chiroptera is not reflected as a habitual feeding behavior.

Reproduction

The male of the Saimiri sciureus is sexually mature when it is between 3.5 and 4 years of age, while the female can reproduce at 2.5 years. This species has a promiscuous mating system, however, generally one or two males can copulate many more times than any other male in the group.

Mating

Females have a preference for those sexually mature males that have a more corpulent appearance, a product of weight gain months before mating.

Thus, while the larger males monopolize the copulation, the young females, who are in their first or second reproductive season, join the less stocky males.

To find out if the female is receptive, the male chases and grabs a female, holding her in such a way as to allow him to inspect her genitalia. The researchers state that the male probably uses olfactory signals to let the female know his reproductive status.

The basis of this signaling is found in the behavior assumed by the male, since he remains close to the female until she shows interest in him.

The squirrel monkey is a seasonal breeder. It mates between the months of September and November, and the young are born in February and April. This ensures that offspring are born in the rainy season, when food resources are abundant.

Breeding

After 160 to 170 days have elapsed, the calf is born. The mother is responsible for almost everything related to the care of the young. Regarding this aspect, pregnant mothers are synchronized at birth, which makes it easier for the group to have greater vigilance of all newborns, since they are highly vulnerable to predation.

During the entire first month, the calf remains constantly in physical contact with its mother. Generally, it is carried on the mother's back. When he is between 5 and 7 weeks, he begins to move away from the mother, to explore the environment on his own.

Young people become independent between the second and fourth month of life, interacting much of their time with the other juveniles in the group.

Behavior

The common squirrel monkey is a diurnal animal, so it is most active during the day and at night it rests. The vast majority of activities are carried out in the trees near a water source.

Social

The groups where S. sciureus lives are smaller than those of the other species of the genus Saimirí. Thus, between 15 and 30 primates can be formed. Said groupings, multi-female and multi-male, are integrated.

Thus, both sexes form a single linear hierarchy, with the majority of males being dominant for females.

Aggressive behaviors are very rare among females, however, they do not form alliances. However, temporarily, relationships can be established between the mother and the calf and between the young and another female, different from its mother.

In contrast, the males form very close bonds and have very aggressive behaviors. Common squirrel monkeys are often scarred from fierce fighting within the group.

In addition, the males are vigilant of the community where they live, with the intention of defending it from predators. On the other hand, both sexes migrate from their birth groups. The female changes groups several times, while the male spends a large part of her life alone or on the periphery of the group.

References

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