Callicebus personatus

Geographic Distribution and Habitat

The masked titi (Callicebus personatus), also called the northern masked titi or Atlantic titi, is endemic to one of the most biodiverse rainforests of Latin America: the Brazilian Atlantic Forest. Located east of the Andes Mountains, this coastal stretch of woods hosts a variety of neotropical trees, vines, ferns, mosses, and epiphytes (air plants). It is here that the masked titi dwells, traversing the low forest canopies throughout the states of Bahia, Espírito Santo, Minas Gerais, Rio de Janeiro, and São Paulo. They live in sympatry (coexistence with other species) with other titis, tamarins, and spider monkeys.

All is not perfect in this seemingly tropical paradise, however. Fragmentation and disturbed forests occur at high frequencies as human settlements continue to grow, thereby prompting the masked titi to showcase one of its excellent skills: adaptation. Not to be discouraged by the company of humans, masked titis are able to reside in disturbed forests and even co-exist with people, so long as food availability is substantial.  

Maked titi geographic range. Map: IUCN, 2008 (click to enlarge)

Size, Weight, and Lifespan

Masked titis are relatively compact and small in stature, averaging 14–16.5 inches (35–42 cm) in size and 1.7–2.86 pounds (.8–1.3 kg) in weight.

Males grow between 14 and 16.5 inches (35–42 cm) and weigh between 2.4 and 4 pounds (1.1–1.7 kg); females are 12–16 inches (31–40 cm) in length and weigh 2.2–3.5 pounds (1.0–1.6 kg).

Their slight sexual dimorphism is often difficult to detect during observations and studies; so is determining their lifespan. Unable to verify this information, scientists look to close relatives for a hypothesis. The dusky titi monkey (Callicebus moloch), which lives up 25 years in captivity, may offer insight to their longevity.


Titi monkeys have several commonalities in their appearance: dense, fluffy bodies, long hind legs, swooping, non-prehensile tails, and squashy snouts. The masked titi does not stray from these shared traits. Their specific features include a black forehead, sideburns, and throat, which creates a “mask” that surrounds their dark, hairless face. They have watchful, brown eyes and petite mouths, often portraying an expression of keen interest or fascination. The color of their head and face is contrasted against their ochre-colored bodies, which range from blonde to deep orange and sometimes gray. (Southern populations are predominantly buffy-colored, while northern populations are a striking golden, tawny.) Photographs often capture them hunched over, positioned on low tree branches, with their tails draped beside them. They have black hands and feet, and their tails sometimes contain flecks of black.


A diet of fleshy fruits, fruit pulp, flowers, leaves, and seeds are the masked titi’s primary nosh. Occasionally, they consume insects, bird eggs, and small animals. A diverse diet allows these opportunistic eaters to alter their home range based on food availability. Whether they’re in disturbed or undisturbed forests, they forage for what is accessible.

In addition, these monkeys can also be geophagic—or soil eaters. Researchers have not reached a consensus as to why they do this; some suggest to achieve tactile sensations in their mouths, or to combat intestinal parasites. Others speculate the soil helps absorb plant toxins—although sufficient studies have not been conducted on this matter.

Since masked titis rarely feel safe foraging on the ground, the soil they consume is typically sourced from ant or termite mounds. It is assumed that it is quicker and easier to procure this loose, aggregate soil compared to the densely packed ground soil. For an unknown reason, they prefer termite mound soil to ant soil. Overall, the supplementation is quite a puzzling mystery.

Behavior and Lifestyle

Masked titis are diurnal (active during the day) and live in lower levels of the canopy, about 16 feet (5m) high. They spend 99% of their day traversing branches and vines, presumably to avoid predation from below and above; lurking ocelots and boas traverse the ground floor while owls and falcons patrol the skies and upper canopies. Their home range is relatively small, averaging roughly .05 square miles (10.7–12.3 ha). About 18–19% of their range is shared with nearby groups.

When on the move, these quadrupeds slightly arch their back as they walk on all fours with their limbs rotated outward. They leap from branch to branch, extending their long arms to grasp the next nearby support. They have a vertical leap of 3 feet (1 m).

Fun Facts
  • Masked titis are geophagic, meaning they eat dirt. Scientists once hypothesized that this may have been to supplement sodium in their diet. However, tests indicate that the soil they consume has very low sodium levels. As a result, this notion was dismissed. Studies are still ongoing to determine the reason.
  • Bonded pairs sleep together, cuddled against one another with their tails intertwined.
Daily Life and Group Dynamics

Like many titis and marmosets, masked titis are monogamous, meaning they have only one mate. They live in territorial groups of 2–7, consisting of a bonded mating pair and their offspring. These monkeys start their day at dawn when families slowly stir from their sleeping boughs. The adult male is almost always the last to rouse. Upon arising, they relieve themselves in their sleeping tree before the group moves to a fruiting tree, where they begin foraging for breakfast. “Dawn calls” are commonplace duets sung by the male and female during this time.

Travel takes up a significant portion of their day. Masked titis are diligent foragers but are not picky or highly selective. Each feeding period (up to three per day) lasts for 2–3 hours, making up 20% of their total activity. They relax into extensive rest periods between each meal, only to be broken by the need to travel for new foraging opportunities. Although they share overlaps with neighboring groups, they are highly territorial. To ward off challengers or foes, they use loud intergroup vocalizations to defend their terrain.

At night, they huddle close together in an endearing display. Males and females will intertwine their tails together as they drift off to sleep, surrounded by their family until the next day breaks.


Masked titis are predominantly known for their “dawn calls”—a shared serenade performed by the male and female of the group each morning. Whether this is used for territorial reasons is not known. 

Territorial, defensive, and sometimes aggressive towards other groups, they use loud vocalizations to warn and intimidate those who tread too close to their home. This may also be used to ward off predators. While researchers continue to study masked titi communications, we can look to their close cousins, Coimbra-Filho’s titis, to speculate further. They emit long, high-pitched alarm calls for similar reason. These whistle-like warnings can be heard throughout the canopy. Additionally, they are also known for their canary-like chirps that they use for intragroup exchanges.

Reproduction and Family

Not much is known about the reproduction, mating rituals, or infant care of masked titis. Some suggest this is due to the lack of sexual dimorphism between male and females. Looking again at the Coimbra-Filho’s titi, who has a gestation period of five months, one could hypothesize a similar time frame for the masked titi. It is known that between September and October, a single infant is born. 

Fathers are the primary caretakers and carry their offspring. While observations of infant care are scant, other male species of titi are known to be incredibly caring and attentive while mom—who is only involved for nursing purposes—is away. It is dad’s responsibility to transport, groom, play, socialize, and prepare the youngster for adulthood. On average, independence for other titis is achieved between 3–4 months of age.

Ecological Role

As frugivorous eaters, masked titis provide an imperative contribution to their ecosystem: seed dispersal. Their stools contain valuable seeds to help spread and rejuvenate new plant species growth. Although this contribution is bestowed by all species that consume and defecate seed remnants, it’s not something to be overlooked; the truth is that scattered fecal matter is precious.

Today, conserving the Brazilian Atlantic Forest is a top global priority. This ecosystem contains some of the highest biological diversity on the planet, with over 2,200 species of birds, mammals, reptiles, and amphibians, compared to the Amazon. Once twice the size of Texas, its size has unfortunately been reduced by 85%, as it has been subjected to the onslaught of wildfires, deforestation, and agricultural conversion.

Studies have shown that animal mediated seed dispersal is one of the most impactful ways to distribute future plant growth in tropical forests—more than any variation of wind, water, or other abiotic processes. No role is too small, and when it comes to the masked titi, their poop plays a part.

Conservation Status and Threats

The International Union for Conservation of Nature lists the masked titi as Vulnerable (IUCN, 2015). 

Over the past 24 years, or three generations, the masked titi has suffered a population loss exceeding 30%—that’s only covering the span of three generations of families. With a relatively tight geographic range, masked titis reside in the most densely populated area of Brazil, which has previously endured the longest occupation of European colonization. These factors have contributed to an exhaustive elapse of deforestation, agricultural conversion, cattle ranching, and urbanization, often motivated by government and economic interest. The result has rendered significant fragmentation, which not only diminishes the masked titi’s habitat, but subjects them to genetic diversity loss due to smaller, isolated populations. Only 5–10% of their original habitat remains intact.

On a positive note, the masked titi isn’t a target of poaching or illegal trade. Given their size, hunters do not considered them  “desirable” pets or food sources.

Conservation Efforts

The masked titi is 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. Included in international legislation, they are subject to management and trade controls. However, habitat loss is often a complex killer—without further protective measures, the masked titi’s best chance for survival is its ability to inhabit disturbed forests.

As of now, the Reserva Biológica de Sooretama in Brazil hosts the largest population of the masked titi, as well as the Reserva Natural de Linhares.

  • Heiduck, S. (2002). The use of disturbed and undisturbed forest by masked titi monkeys Callicebus personatus melanochir is proportional to food availability. Oryx, 36(2), 133–139.
  • Kinzey, W. G., & Becker, M. (1983). Activity pattern of the masked titi monkey,Callicebus personatus. Primates, 24(3), 337–343.
  • Tabarelli, M., & Peres, C. A. (2002). Abiotic and vertebrate seed dispersal in the Brazilian Atlantic forest: implications for forest regeneration. Biological Conservation, 106(2), 165–176.

Written by Dana Esp, January 2024