Geographic Distribution and Habitat
The masked titi monkey, also known as the Atlantic titi, is a New World primate native to Brazil. Found nowhere else in the world, this species occupies the country’s Atlantic coastal rainforests east of the Andes mountains in the states of Bahia, Espírito Santo, northwestern Minas Gerais, northern Rio de Janeiro, and Sao Paulo. Dwelling mostly in thickets and vine tangles of the lower forest canopy, masked titis have also been observed living in banana tree groves.
With a range that overlaps that of other monkeys—including other titis, lion tamarins, and spider monkeys—some of Brazil’s most densely populated human settlements now infringe into the living space of masked titi populations, disturbing their habitat and forcing the monkeys to “share” their living space with these encroaching human primates.
Size, Weight, and Lifespan
About the size of a bunny rabbit, the male of the species is only slightly larger than the female.
Head-to-body length in males is between 14 and 16.5 in (35 to 42 cm). Tail length adds another 18.5 to 21.65 in (47 to 55 cm). Male masked titis weigh between 2.4 and 4 lb (1.1 to 1.7 kg).
Head-to-body length in females is between 12 and 16 in (31 to 40 cm). Tail length adds another 16.5 to 22.05 in (42 to 56 cm). Female masked titis weigh between 2.2 and 3.5 lb (1.0 to 1.6 kg).
Lifespan of wild masked titi monkeys is undocumented. However, the lifespan of the closely related dusky titi monkey (callicebus moloch) is 25 years, in captive populations, leading scientists to speculate a similar longevity for masked titis.
Masked titis possess a startling beauty. A black forehead and sideburns give the appearance of a furry, dark mask, indicative of the species’ name. Brown-orange eyes appear to jump out from this darkness and take in the world through centered apertures, the monkey’s pupils, giving the impression that the monkey is staring at you intently. A somewhat flattened snout sits nonchalantly in place. Covering the monkey’s body is a thick orange coat with a blend of yellow, gray, or buff-colored undertones. The furry nonprehensile tail, which is incapable of grasping objects, is tinged with black. Hands and feet are black.
Although they eat primarily fruit, masked titi monkeys are considered opportunistic feeders; that is, they will eat whatever is abundant and readily available, adapting their diet to the season and environment. They aren’t terribly fussy eaters, either. Besides fleshy fruits, they will munch on seeds, leaves, bird eggs, insects, and even small animals. Human food, whether as an intentional handout or stealthily stolen, is also up for grabs in areas where both titis and humans are found.
And sometimes, these monkeys eat dirt. Scientifically, this consumption of soil is known as “geophagy.” Masked titis have been observed eating soil from termite and ant mounds—less frequently, they have been observed engaging in geophagy from the forest floor and from decomposed tree trunks. So why are masked titis dirt-eaters? Scientific speculation suggests the practice of geophagy as a dietary mineral supplementation, an adjustment of the pH balance in the stomach (acting as an antacid), absorption of plant toxins, relief from internal parasite infestation, or simply a feel-good tactile sensation in the mouth. However, no conclusive findings have been reached.
Behavior and Lifestyle
Titis move through the forest “quadrupedally”; that is, by walking on all fours. Hunching their body and rotating their hind limbs outward, they leap forward with outstretched arms and advance by grasping from branch to branch. When resting (a favored pastime!), they sit in a hunched position with their tail hanging down vertically.
Rarely do masked titis descend from their treed habitat. Scientific speculation suggests that the monkeys remain high in the trees to avoid being eaten by the snakes who slither on the forest floor below. On the occasions that they have been sighted on the ground, however, scientists observed that these monkeys quickly bound across the terrain, leaping as high as 3 feet (1 m) off of the ground.
Titi monkeys are called “zogui zogui” in Spanish.
Masked titis are represented by five subspecies, each identified by distinct color patterns. This color differentiation occurs when certain segments of the population are genetically isolated from one another due to an ecological barrier, such as a river.
Masked titis are tree-dwelling monkeys (making them “arboreal”) who live in groups of two to seven individuals, usually consisting of a monogamous breeding pair and the pair’s offspring. They are active during daylight hours (making them “diurnal”) and spend at least half of their day resting, 2 to 3 hours feeding, and less than 20 percent of the day traveling. At night, they choose a bough of a tall tree to their liking, 82 to 131 ft (25 to 40 m) above the forest canopy, and sleep huddled together, tails intertwined while resting their heads upon their folded hands. Come morning, adult males are the last to rise, lingering in their bedtime nest.
With overlapping home ranges, bumping into other masked titi groups when traveling is not uncommon. Encounters can be aggressive, and these territorial primates will do what they can to intimidate members of another masked titi group.
Communication among masked titi monkeys includes vocalizations, posturing, and tactile activities.
When encountering another group of masked titis in their travels, adult males will give a territorial cry known as a “loud call” that sounds like “chirrup-pump.” Loud calls consist of short sequences of noises given either as a single burst or as a series of short bursts, lasting from a few seconds to two minutes. While sounding a loud call, adult males may aggressively chase members of an “outsider” masked titi group from the area.
Like all titi monkeys, masked titis engage in “dawn calls” each morning. A male and female couple typically “sings” these notes together as a duet. (One might conjecture, however, that the dawn call is not an effective alarm call for those adult males who like to linger in their bedtime nest!)
Social bonds are developed and strengthened through group grooming and through the monkeys’ nightly “sleep huddle.”
Scientists have reported tool usage by a captive masked titi. Using pieces of straw, the monkey was able to pry cockroaches (snacks!) out of crevices. This captive masked titi also relocated his sleeping box, to better access the cockroaches hiding beneath, scientists conjecture.
Information about the mating rituals (“courtship”) of masked titi monkeys is unknown, perhaps hindered, in part, by the similar outward appearances of the two sexes. Not much information is available about this species’ reproduction, either. Scientists speculate that the female’s gestation period may be five to six months, similar to the dusky titi monkey. Births occur between August and October, with females giving birth to a single offspring.
Infants are born helpless. Although they are nursed by their mothers (in dusky titi monkeys, the young are weaned at 12 to 16 weeks), it’s the fathers who become the primary caregivers when masked titi infants are just one-week old. Dad, not mom, is the parent who carries his baby around.
Masked titi monkeys disperse seeds of the fruits they eat through their feces, helping to nourish the ecosystem in which they live. They also serve their ecosystem (unwittingly) as prey to larger natural predators, including large snakes, such as pit vipers and tree boas; big cat species, and raptors.
The masked titi is classified as Vulnerable by the International Union for Conservation of Nature (IUCN, 2015), appearing on the IUCN Red Lists of Threatened Species. Vulnerable means that the species faces a threat of extinction in the wild.
Brazil’s Atlantic Forest has been cut down to 5 percent of its original state (razed for agricultural use, cattle ranching, lumber, charcoal production, and urban development) with only 2 percent of undisturbed forest remaining. Therefore, survival of masked titi monkeys is totally dependent on their ability to successfully reside in disturbed forests, alongside or within human settlements.
Although the species is not hunted as intensively as capuchins and marmosets, who also make their home in Brazil’s eastern Atlantic rainforest, the masked titi population has nevertheless decreased by 30 percent in the last 24 years because of continued habitat loss. And as masked titi groups become increasingly isolated from one another, the risk of inbreeding increases, leading to diluted genetic diversity and potential health maladies.
Masked titis are 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. However, as is often the case with endangered species, laws created to protect them are largely ignored and difficult to enforce.
The largest remaining groups of masked titi monkeys reside within the Reserva Biològica de Sooretama and the Reserva Natural de Linhares, in the Brazilian state of Espírito Santo. Total population of the species is unknown.
No known direct conservation programs are in place for the protection of this species. However, some conservationists see these charismatic monkeys as potential ecotourism ambassadors who can bring attention to the dire ramifications of increasingly endangered habitats.
Written by Kathleen Downey, June 2017. Conservation status updated December 2020.