One of the smallest primates, the cotton-top tamarin is easily recognized by the long, white sagittal crest extending from its forehead to its shoulders.

Up to 40,000 cotton-top tamarins are thought to have been caught and exported for use in biomedical research before 1976, when CITES gave them the highest level of protection and all international commercial trade was prohibited.

Now, the species is at risk due to large-scale habitat destruction, as the lowland forest in northwestern Colombia where the cotton-top tamarin is found has been reduced to 5% of its previous area.

)[8] In 1977, Philip Hershkovitz performed a taxonomic analysis of the species based on fur coloration patterns, cranial and mandibular morphology, and ear size.

[9] Subsequent analyses by Hernández-Camacho and Cooper (1976),[10] Russell Mittermeier and Coimbra-Filho (1981),[9] and later Grooves (2001)[11] consider the S. oedipus and S. geoffroyi types to be separate species.

At that time, the area was covered by a sea, which created a geographic barrier that caused the species to diverge through the process of allopatric speciation.

[2] The cotton-top tamarin has fur covering all of the body except the palms of the hands and feet, the eyelids, the borders of the nostrils, the nipples, the anus, and the penis.

Historically, the entire area was suitable for the cotton-top tamarin, but due to habitat loss through deforestation, it survives in fragmented parks and reserves.

One of the most important areas for the cotton-top is the Paramillo National Park, which consists of 460,000 hectares (1,800 sq mi) of primary and secondary forests.

Insectivory is common in the cotton-top and the species hunts for insects using a variety of methods: stealth, pouncing, chasing, exploring holes, and turning over leaves.

[5][16] The species is thought to rise late and increases the speed of its foraging and travelling before dusk to avoid crepuscular and nocturnal predators.

[2][16][19] These small familial groups tend to fluctuate in size and in composition of individuals and a clear dominance hierarchy is always present within a party.

[26] Males may invest additional support in rearing offspring as a form of courtship to win the favor of the group's dominant female.

[28] While caregiving by males appears to be altruistic, particularly in cotton-top sires, the costs of infant care may in fact be tolerated for selfish reasons.

Namely, the costs to male weight and foraging ability may, in turn, promote consecutive pregnancies in dominant females, thereby providing more offspring bearing the sire's genes.

[30] The cooperative breeding hypothesis predicts that cotton-top tamarins engage with this young-rearing paradigm, and in turn, naturally embrace patterns of prosocial behavior.

[21] These monkeys engage in such behavior by acting altruistically within their groups in caring for infants, vocalizing alarm calls, and in sharing food.

[32] Despite an expansive array of altruistic behaviors, cotton-top tamarins engage in great bouts of spite through negative reciprocity and punishment.

Based on this, researchers believe that repeated interactions in a cooperative society like that of the cotton-top tamarin can heighten the chances that an individual will designate behavioral punishments to others in its group.

Females typically employ scent-marking intruder response tactics, whereas males are more prone to vocalizing threats, physical aggression, and piloerection.

They concluded that it uses a simple grammar consisting of eight phonetic variations of short, frequency-modulated "chirps"—each representing varying messages—and five longer constant frequency "whistles".

[38] Using this range of vocalizations, the adults may be able to communicate with one another about intention, thought processes, and emotion, including curiosity, fear, dismay, playfulness, warnings, joy, and calls to young.

This indicates that verbal perception is a quickly acquired skill for offspring, followed closely by auditory comprehension, and later by proper vocal producibility.

[39] To confirm the notion that language acquisition occurs as a progression of comprehension before production, Castro and Snowdon (2000) showed that infants respond behaviorally to vocalizing adults in a fashion that indicates they can comprehend auditory inputs.

[20] Early observations by Patricia Neyman even showed that cotton-tops produce diverse sets of alarm calls that can discriminate the presence of birds of prey versus ground-based predators.

Researchers have argued that long calls exhibit individual differences, thus can carry information sufficient for recipients to determine caller identity.

Since tamarins can discriminate between predatory threats using varying vocalizations, recipients of an AC are thought to extract various complex signals from this form of communication.

While this may appear to be a result of a very primitive form of communication, Roush and Snowdon (2005) maintain that the food-calling behavior confers some mentally representable information about food to recipient tamarins.

This land is then used for large-scale agricultural production (i.e. cattle) and farming, logging, oil palm plantations, and hydroelectric projects that fragment the cotton-top tamarin's natural range.

While biomedical studies have recently limited their use of this species, illegal capture for the pet trade still plays a major role in endangering the cotton-top.