RED-BELLIED TITI

Plecturocebus moloch

Geographic Distribution and Habitat
The red-bellied titi (Plectorocebus moloch), also known as the dusky titi, is a species of New World monkey living in the forests south of the Amazon River. Restricted by the Paraguay and Pilcomayo rivers, this species’ range extends as far south as Paraguay. To the west, its range is confined by the towering Andes mountains while it stretches east as far as the Brazilian cerrado, or “grasslands.”

Red-bellied titis live in a variety of habitats. Lush evergreen neotropical terra firma rainforests, floodplain forests, and freshwater swamp forests are rich with all that they need. But as members of a rather adaptable and hardy species, they can also survive at forest and swamp edges as well as within disturbed forests. 

Generally, anyplace wet, where vegetation grows dense, is suitable for red-bellied titis, and they prefer the tangled and thorny underbrush where they keep quiet and out-of-sight of predators and other monkeys.

TAXONOMY IN TRANSITION

Red-bellied titis were classed under the name Callicebus until 2016 when their genus was changed to Plectorocebus following new genetic research. As such, much of the literature to date names them as the former.

Red-bellied titi range, IUCN 2020

Size, Weight, and Lifespan
Red-bellied titis are small monkeys. Males and females are roughly the same size, ranging between 10.5 and 17 inches (27.2–43.4 cm) in length. Their long tails, stretching 14–21.5 inches (35.0–54.6 cm) more than double their lengths.

Males can weigh between 1.8 and 2.6 pounds (850–1200 g). This is only slightly more on average than females who can weigh between 1.5 and 2.2 pounds (700–1020 g).

Titi monkeys have been known to live up to 25 years in the wild.

Appearance
Red-bellied titis are small and furry monkeys. They sport long tails that are gray at their base and white at their tip. The fur on their backs and outer surfaces of their limbs is a brownish gray hue, while their chests, bellies, and inner parts of their limbs are distinctly orange. The same orange-colored fur surrounds their small black faces like a beard and also covers the upper surfaces of their hands and feet. The crown of their head is a grayish brown color, slightly darker than that found on their backs.

Sitting still on a branch, red-bellied titis like to scrunch their small, round, furry bodies up into a ball. From any angle other than the front, they typically look more like a ball of fur than any monkey. Their naturally amorphous shape may be further obscured by their habit of sitting close to others—often with their tails entwined—making them essentially indistinguishable from one another.

Photo credit: © Sidnei Dantas/iNaturalist/Creative Commons

Diet
While the diet of the red-bellied titi is not well researched at this time, other titi species are often described as frugivorous. Their diet is a bit more complex than just fruit, however. They also eat leaves and some other plant parts, as well as some invertebrates like moths, butterflies, cocoons, spiders, and ants.

Some titi species are known to eat up to 100 species of fruits. In general, they prefer to eat the fruit of smaller trees, possibly because they are easier for these smaller-sized monkeys to exploit efficiently.

Leaves do make up a significant portion of titis’ diets—especially in the dry season when fruit is less available. In general, they only eat leaf buds or young leaves, both of which provide more protein than mature leaves while also being much easier to digest.

Insects act as another reliable source of protein also eaten more often during the dry season than the wet. Researchers have noticed that lactating mothers tend to eat insects the most, probably because the extra protein aids the production of milk.

What Does It Mean?

Arboreal:
Physically adapted to living primarily or exclusively in trees.

Crypsis:
In ecology, the ability of an animal to avoid observation or detection by other animals through methods such as camouflage, nocturnality, subterranean lifestyle, and mimicry.

Dominance hierarchy:
A type of social hierarchy that arises when members of a social group interact, often aggressively, to create a ranking system. In social living groups, member are likely to compete for access to limited resources and mating opportunities. 

Frugivorous:
Having a diet that consists of fruits.

Gene flow:
The transfer of genes from one population into another through breeding.

Genetic bottleneck:
When a species’ population is reduced in size (i.e. by a cataclysmic event, habitat fragmentation, etc.) limiting the genetic diversity of the species.

Invertebrate:
An animal without a backbone (spine), including arthropods, mollusks, myriapods (such as earthworms, leeches, millipedes, and centipedes), sea anemones, and corals.

Monogamous:
Having only one sexual partner. ​

Natal group:
The group into which an animal is born.

​Neotropic: 
Relating to, or constituting the tropical New World biogeographic region that extends south, east, and west from the central plateau of Mexico.

New World monkey:
Monkeys native to Central and South America.

Swamp forest:
Peat swamp forests are tropical moist forests that grow in permanently water-logged areas with mineral-deficient water; the waterlogged soil prevents dead leaves and wood from fully decomposing, over time creating a thick layer of acidic peat. Peat swamp forests are typically surrounded by lowland rainforests on better-drained soils, and by brackish or salt-water mangrove forests near the coast. 

Visit the Glossary for more definitions

Behavior and Lifestyle
Titi monkeys are arboreal and prefer to spend their time in tangled underbrush, where they spend their days searching for food or resting. They move about on all-fours, make acrobatic leaps between branches, and effortlessly scurry up trees. Their compact bodies make them nimble, and their long tails give them exceptional balance.

Like all primates, titis are social. Uniquely, however, they do not seem constrained by any social hierarchy. They are friendly with all members of their in-group.

Titis are territorial, however, and protect their small home ranges from possible intruders. The smallness of their worlds may be why they tend to be a bit cautious in new situations.

Each morning, the group ventures to the edge of their territory where they make loud calls, warning other titi monkeys to keep away. More often than not, another group meets them at the boundary. While it’s rare for titi monkeys to display physically violent behavior, even toward strangers, the groups’ exchanges usually grow noisy and chaotic. Eventually, the two groups retreat back to the centers of their respective home territories, where they happily go about their days.

Within their groups, titis show a tendency to be overwhelmingly pro-social. In fact, they are well known for their displays of affection, especially mating pairs. The male and female of such a pair spend almost all of their time near one another, frequently stopping their other activities in order to nuzzle and groom. Often, they sit on a branch together, holding hands or feet. Sometimes they wrap their long tails around one another as they dangle toward the ground. 

Titi monkeys are quite emotional monkeys. If their physical displays of affection aren’t enough to convince you, mating pairs’ close bonds become most evident when they are unexpectedly separated. Both partners immediately drop whatever they are doing and begin to look for each other, making frantic and emotional calls as they do.

Male titi monkeys are even known to become jealous. At the sight of another male, the male half of a pair quickly positions himself between his mate and the intruder. If their intruder is not convinced to leave, the male shows a sudden increase in affection toward his female mate. The female half of a pair usually displays the opposite behavior, however, and saves her displays of affection for when she is alone with her mate.

At this time, behaviors unique to red-bellied titis are not well researched.

Fun Facts

Red-bellied titis are coordinated enough to catch flying insects, like butterflies, out of the air.

Titis sometimes greet each other by making mouth-to-mouth contact, showing that they come in peace.

Titis rarely venture beyond the boundaries of their home range, doing so only to disperse and found a new group. 

Daily Life and Group Dynamics 
Red-bellied titis live in small familial groups composed of a mating pair and their offspring. At any given time, a group may consist of two to seven members. Members are typically warm and affectionate with one another, especially the mating pair.

A group wakes just after sunrise and travels to the edge of its territory, where they make loud intimidating calls, warning other titi groups to stay away. Frequently, they meet other titi groups who have come to the edge of their adjacent territory to do the same. The groups call to each other and make intimidating displays from afar. While the scene quickly grows noisy and chaotic, their exchanges rarely devolve into physical violence. Eventually, the two groups retreat to the centers of their home ranges and go about their days.

Within a titi group, there is no dominance hierarchy. Both the male or female halves of the mating pair can lead a group’s daily activities. Perhaps the female remembers an ideal feeding spot they have been neglecting recently. She leads them there without any flack from the male. It may be more accurate to say that a pair coordinates their group’s activities together.

After their morning meal, a group settles down to rest. Titis’ plant-heavy diets often mean that they need long stretches of downtime to digest. During this time, the group takes to socializing. The mating pair might groom each other or their offspring. Infants groom the father. This is also the perfect time for juveniles to play together. Occasionally, subadults and even the mating pair themselves may join in.

By the afternoon, a group is hungry again and goes in search of more food. Afterward, they take another rest. The last hours of the day are often spent stuffing their bellies full of leaves.

Come sunset, a group settles into a sleeping spot for the night. Titis prefer sleeping spots within dense vine tangles at least 50 feet (15 meters) off the ground. Sites are usually near the center of their home range and may be reused over and over again. Group members huddle closely together and often entwine their tails with other group members.

The daily lives of titi groups seem to be affected by the seasons. In warmer months, groups tend to rise earlier—perhaps because tasty fruit is more abundant and they are eager to chow down on it—than in colder months. In colder months, groups may remain at their sleeping sites for up to four hours after the sun rises—perhaps because they are more keen to enjoy each other’s warmth than to set off in search of food less satisfying than fruit.

Many species of titi have overlapping ranges with a number of other primates, including a variety of capuchins, howler monkeys, marmosets, owl monkeys, spider monkeys, squirrel monkeys, tamarins, and woolly monkeys. It is not uncommon for titis to be chased from feeding sites by other, larger monkeys. For this reason, titis mostly avoid contact with other monkeys altogether, using the same cryptic strategies with which they hide from predators.

Communication
Titi monkeys are known to have large and complex vocal repertoires that help individuals communicate information about the surrounding world or their own emotional inner states. In fact, their vocalizing behaviors are so complex that some researchers have claimed they represent “the maximum elaboration and complexity which can be attained by a species specific language.”

Titi vocalizations fall into two general categories. High-pitched quiet calls are squeaks, whistles, trills, chirps, grunts, and “sneezes” that are often used specifically for in-group communication. In many cases, they may raise the alarm about a potential threat, like an approaching predator or unwelcome intruder. But similar sounding calls can carry very different meanings depending on the context. For instance, titis like to make whistle calls during pro-social interactions like intense grooming sessions or when juveniles play wrestle. But an adult female who is resisting unwanted advances from a male, is also likely to whistle—as are individuals who become separated from their group.

The other vocalizations titis make are known as low-pitched loud calls. These are often used during interactions with foreign groups of titis. Raucous chirrups, grunts, moans, pants, honks, bellows, and pumps are combined with physical displays like swaying, looking around, putting one’s head down, or head scratching in order to intimidate any intruders who venture too close.

Additionally, infants might make a buzzing sound, or let out a little chirp, if a parent has refused to carry them. When carried by a group member other than a parent, infants might purr to show its apprehension and discomfort with the situation. These sorts of sounds may also help such young and impressionable monkeys to self-soothe when they are experiencing stress.

Titi monkeys use a large variety of physical displays to communicate affection and nurture their bonds. Mating pairs become distressed when unexpectedly separated and often sit together on a branch holding hands, grasping feet, nuzzling, or grooming. Titis also enjoy sitting next to other group members and wrapping their tails around one another’s. Adults make mouth-to-mouth contact with infants and other adults as a greeting or to signal that they come in peace.

Many primates use olfactory methods of communications—titi monkeys included. Titis often sniff the genital region of other group members shortly after approaching them. They also have glands just below their chests that secrete a special chemical. They may rub this gland directly on leaves or branches or apply the chemical indirectly using their hand, leaving behind their scent. Scent-marking can have a variety of uses for primates but is most often used to communicate the boundary of a group’s territory or to aid in navigation.

Currently, the unique ways that red-bellied titis communicate are not well researched.

Reproduction and Family
Titi monkeys form lifelong mating pairs. While females are occasionally known to mate with other males during confrontations with other titi groups, the pair is essentially monogamous. The two rarely separate, and they routinely communicate their strong emotional bond with overt displays of affection, like hand holding or entwining their tails.

Female titis do not menstruate, nor do they exhibit sexual swellings that communicate their readiness to mate. Though there is evidence that births peak in the rainy season when fruit is most abundant, mating occurs throughout the year. The male half of a pair usually initiates mating by smelling or licking the female’s genitals. Or he might physically manipulate her into a mating position.

After mating, it takes around four months for the fetus to gestate. While titi mothers do occasionally give birth to twins, a single infant is more than likely. Newborns are distinguishable as titi monkeys except that their fur is short and dense, and their ears folded. By two months of age, however, their ears are fully unfolded and their fur coats more closely resemble an adult’s.

Titis have a parenting arrangement quite unique for primates. Once born, infants have limited contact with their mothers. In fact, mother titi monkeys tend to show less interest in their newborns the more pregnancies they have experienced in their lives. Instead, fathers take almost full responsibility for their offspring, carrying them around, providing protection and—once old enough—sharing food with them. 

Until they are old enough to be weaned, however, young titis have to rely on their mothers for nursing. When it is time to nurse, a mother simply raises her arm, alerting the father that she is ready. The father then carries the infant over to her so that their infant can safely climb onto her body.

Though they may occasionally spend time grooming their infants, mother titis tend to spend less and less time providing this kind of care as their offspring age. By the time infants are a month old, nursing is the only contact they have with their mothers. Still, in the event of a real emergency—a fall or an approaching predator—both parents show concern and take action.

Due to their unique parenting arrangement, infant titi monkeys become strongly bonded to their fathers and grow highly stressed when separated from them. For the first several months of an infant’s life, even their contact with older siblings is quite limited. They do not play together at all until a newborn is fifteen weeks old. This is also around the time they learn to run, leap, and climb. Older siblings also carry their younger brothers and sisters more and more as they age. This not only takes stress off the father, but provides them with great practice for when they become parents themselves.

Prior to this being able to play with siblings, infant titi monkeys spend a surprising amount of time alone. At two months of age, even their fathers’ spend less than half their time with them. The male and female pair spend significantly more time nurturing their own bond than those they have with any of their offspring. Thus, infants learn to navigate their habitat mostly on their own, through observation and practice.

By four or five months of age, a titi is mostly an adult. Though they still have much to learn, their interactions with other group members begin to look less juvenile. For instance, instead of sitting on top of their father or siblings, they choose to sit next to them. Furthermore, they can competently navigate the tangled underbrush and feed themselves.

At some point in their lives, the mating pair’s offspring take leave of their natal group. In some species, male titis may join temporary bachelor bands until they find a mate. Females are more likely to leave the group at the moment they find a mate. Once they have dispersed, however, they are no longer considered part of their natal group. Any attempt on their part to return will be met with aggression.

Due to a lack of research, the unique mating habits of red-bellied titis are not known at this time.

Photo credit: ©NINA WENÓLI/iNaturalist/Creative Commons

Ecological Role
The role that red-bellied titis play in their ecosystems is not well known at this time. While their diets are rich in fruit, their small home ranges likely limit their roles as seed dispersers. They do prefer the fruits of small trees, which they are able to exploit more efficiently and with less competition from other—bigger—monkey species.

Being rather small monkeys, titis are often prey for large raptors like the Guianan crested eagle and the ornate hawk-eagle. They may also be hunted by big cats and snakes but capture by these predators is rare. Red-bellied titis use cryptic strategies to avoid predation. They stick to dense foliage where raptors and big cats can’t navigate their larger bodies, and the coloring and patterning of their fur helps them to blend in with their environment.

Conservation Status and Threats
The red-bellied titi is classified as Least Concern by the International Union for Conservation of Nature (IUCN, 2020), appearing on the IUCN Red List of Threatened Species. However, current data about this species’ wild populations is not complete.

Like the majority of primates, titi monkeys’ habitats are at great risk. Deforestation, forest degradation, and forest fragmentation spurred by human activities in regions where they live make their futures precarious. Damming and mining projects not only destroy their habitats, they interrupt their natural ecosystems as well. Large infrastructural projects, like the Trans-American highway, runs through the middle of their natural range, fragmenting the landscape and limiting titis’ movements. The construction of the Santarém-Cuiabá highway has compounded this issue even further.

For many primates, habitat fragmentation can severely limit their chances of mating with other groups, causing their gene pools to grow less and less diverse with each succeeding generation. Such genetic bottlenecks tend to make offspring vulnerable to all kinds of birth defects, diseases, and parasites that lessen their chances of successfully mating before they perish. This kind of situation can easily spell the end of a species unless it’s quickly and adequately remedied.

Unlike some primates, titis are willing to descend to the ground in order to move between forest fragments. However, crossing busy roads and highways is hazardous for these small monkeys. They are not only vulnerable to on-coming traffic, their cryptic strategies for avoiding predators become useless as well. Furthermore, though titi’s home ranges are notably small, habitat fragmentation impacts the ability of dispersing monkeys to establish their own home ranges. This is a significant problem for such territorial monkeys.

Meanwhile, the addition of smaller roads—while they may not lead to significant forest fragmentation—make once-remote regions suddenly accessible, making new human settlements possible that, in turn, encourage further habitat destruction. Farmers readily clear forests in order to farm soybeans and rice. Coffee growers use slash-and-burn techniques to reduce living forests to ash and cinders, inundating the jungle’s infertile soil with the nutrients required to grow their demanding coffee crops. Villages destroy habitat to collect building materials and fuel or to have space for villagers to graze their animals.

The overwhelming presence of illegal coca farms in titi habitats causes all these same issues and then some. Coca farmers often prefer to spray their crops with dangerous chemicals, like pesticides, that harm the surrounding environment. Furthermore, the illegality of their enterprise makes enforcement of environmental legislation all the more risky and difficult. In general, the possibility for civil unrest in these or nearby regions tends to put the wild animal populations living there at greater risk.

In some cases, titis are hunted by local peoples. Some titi populations are even known to have been wiped out due to extreme hunting pressure combined with lack of regulation enforcement.

Small New World monkeys like titis, marmosets, and tamarins are often traded indiscriminately as pets—a practice detrimental to them as individuals and species. Though there is no indication that red-bellied titis are of unique concern in this regard, it should be noted that titis—and primates in general—do not make good pets.

Primates who end up as pets, either as a result of poaching or captive breeding, are doomed to suffer a miserable life lacking proper upbringing, socialization, and nutritional needs. This often causes irreparable damage to them emotionally, mentally, and physically.

Primates raised as pets cannot return to the wild without proper rehabilitation. Even then, mortality rates are high. Depending on the species and the individual, it can take years before they are ready to be released—if they are ever ready at all.

Conservation Efforts
For now, red-bellied titis are well protected. They are listed on the Convention on International Trade in Endangered Species (CITES) Appendix II and occur in several large and protected areas, such as the Tapirapé Biological Reserve.

Though there are no conservation efforts currently underway to protect this species, a number of more general environmental protection projects are likely to help their cause—if only indirectly.

Eliciting the participation of local peoples will be important to conserving red-bellied titis and their habitats. Local or national governments in the regions where red-bellied titis are found could help to promote forest conservation by subsidizing land or offering locals rewards for not clearing forests. The establishment of new conservation projects in these areas might curb locals’ financial interests away from farming and other destructive practices towards ecotourism and wildlife protection. Similar ventures have been successful in other parts of the world.

The details of red-bellied titis’ unique behaviors and ways of life—as well as completed data on their population status in the wild—are all paramount for their successful conservation. The knowledge that this species has already disappeared before in certain areas, such as the Caxiuanã National Forests, could suggest that this species is in a more precarious situation than what current surveys suggest.

References:

  • ​https://www.iucnredlist.org/fr/species/41556/192452656
  • https://frontiersinzoology.biomedcentral.com/track/pdf/10.1186/s12983-016-0142-4.pdf
  • https://www.sciencedirect.com/science/article/pii/S1055790318304433
  • https://primate.wisc.edu/primate-info-net/pin-factsheets/pin-factsheet-dusty-titi-monkey/​​
  • alltheworldsprimates.org

Written by Zachary Lussier, October 2021