Geographic Distribution and Habitat
White-tailed titi monkeys—also called red titi monkeys, and not to be confused with coppery titis (Callicebus cupreus) who are also commonly called red titis—are native to the dense rainforests and gallery forests of Ecuador and Peru. A small population can also be found in Colombia.
Size, Weight, and Lifespan
White-tailed titis are small monkeys. Males weigh 1.7–2.5 lb (0.8–1.2 kg) with a height of 11–17 in (30–45 cm); females weigh 1.5–2 lb (0.7–1 kg) with a height of 11–16 in (29–42 cm). Males have a longer tail than females: 14–25 in (39–50 cm) versus 15–19 (39–50 cm).
Their lifespan is approximately 12 years.
What Does It Mean?
Applying or rubbing a substance on oneself.
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The body and tail of white-tailed titis are covered in soft and silky brownish fur with specs of white. Their belly, arms, and side burns are a bright rust color. A band of white hair outlines their forehead. Their small round ears barely protrude from the thick fur on each side of the head. Their face is small and hairless with hazel-brown eyes, a flat nose, and thin lips. The air sac in their larynx allows them to produce very loud calls. Their hands and feet have opposable thumbs and toes.
White-tailed titi monkeys feed mostly on fresh fruit and seeds, which they pick by hand while using their tails for balance. They supplement their nutritional intake by consuming leaves and invertebrates when fruit is not sufficiently abundant. Populations living at the edge of the forest consume many more leaves than other titi monkey groups. This makes sense since fruit is more difficult to find there and the trees at the edge of the forest are exposed to the sun, so their leaves provide more protein than the leaves found in the thick of the forest.
Behavior and Lifestyle
These diurnal monkeys are inconspicuous and difficult to observe while they travel in the canopy. They move between trees and branches by walking on four limbs or by jumping. The only time of day when their presence is easily detectable is early morning when they produce loud duets. These songs are thought to express the bond that links a male and a female and share territorial information with other titi monkeys.
Daily Life and Group Dynamics
White-tailed titi monkeys live in family groups of up to seven members that include one adult male, one adult female, and their offspring. The parents are monogamous and bonded for years. They eat, travel, sleep, and defend their territory together.
Members of the family, especially the bonded pair, spend a lot of their resting hours grooming each other–an activity that reinforces the bonds between them. They also engage in tail entwining: that is, two individuals wrap their tails around each other’s, both during the day and while sleeping. This serves both to reinforce bonds and to balance one another. The pair prefers each other’s company to that of other titi monkeys and show signs of distress if the partners become separated from one another. However, if one partner completely disappears or dies, he or she is replaced by another partner overtime.
The groups sleep in trees. They wake at about 50 minutes before sunrise, relax for a while, and take off to forage just about 2 hours after sunrise. They do not sleep in the same trees they feed from, so foraging for food begins when they depart from their night quarters. Between between January and April, feeding begins earlier than it does during the rest of the year.
Self-anointing has been observed in this species. Individuals have been observed chewing on leaves of flowering shrubs, trees, and vines then rubbing their bodies with the chewed leaves. The significance of this behavior is not known; perhaps some of these plants have insect repellent properties.
The Secoya people, who live near the Aguarico River in Ecuador, believed non-human primates to be the allies of gods and people.
When western naturalists Geoffroy Saint-Hilaire and Deville first discovered white-tailed titi monkeys in 1848, they named them Callicebus discolor. The word callicebus comes from Latin (calli) and Greek (kebos) and means pretty long-tailed monkey.
The species has since been identified as belonging to a different genus and its scientific name was modified to Plecturocebus discolor.
Like other primates, white-tailed titis use a variety of vocalizations to communicate. They produce calls in solos, duets, and choruses that are very specific to the species. In fact, by playing taped duets and waiting for responses from animals belonging to the same species as those in the recordings, scientists are able to identify which titi monkey species are present in the area and how many.
Pairs and/or members of a group produce loud calls in the early morning or after dawn. The atmospheric conditions at that time of day are perfect for carrying the calls far into the forest. Duets are composed of sequences that usually begin with moans and high-pitched syllables, followed by long bellows, and punctuated by a series of rapid syncopated syllables. A male and female join together to sing with such precision that their combined voices sound like they are coming from a single individual. These duets convey to other monkeys that the couple is bonded and the territory is their own. The songs last a few minutes and finish with a series of honk sounds.
Studies indicate that some titi monkey species produce specific alert call sequences that vary in duration and rate depending on the type and location of predators. It is not unreasonable to speculate that white-tailed titi monkeys do the same.
Reproduction and Family
White-tailed titi monkeys breed seasonally. Most births are recorded between September and January. Males maintain close proximity to their mates, especially before the birth of their infant. During the entire pregnancy period, males and females huddle and groom each other more than usual. After a gestation period of 155 days (just over 5 months), a female gives birth to a single infant. The period between births is 14 months, unless the infant dies—in which case the interbirth interval may be shorter. At birth, infants do not have the same coloring at the adults. Their fur color changes overtime.
Males actively participate in the care of their offspring. They carry them around (or rather the baby clings to her dad’s back). They groom them, play with them, and protect them against predators and other threats. Mothers nurse their infants, but they do not groom or play with the little ones. The babies nurse until they are 5 months old, when they begin eating solid foods. When foraging, males do share all food items with their offspring. The exception is when they’re eating leaves, flowers, insects, or seeds. Youngsters are responsible for staying close to the adults while moving from place to place, which may explain mortality rates. Of all infants born, roughly 88% survive to become juveniles and 53% make it to adulthood.
White-tailed titi monkeys are fully grown at 1 year of age. Both males and females leave their natal groups between the ages of 2 and 5 to start their own families. In some instances, groups of more than one adult pair have been observed. Perhaps this occurs when the forest is so fragmented, it does not offer dispersal opportunities. Therefore the offspring would have been forced to remain in their natal group and wait for an outside adult male or female to join them. However, it is difficult to ascertain because there is not enough data.
As fruit and seed consumers, white-tailed titi monkeys help keep the forest healthy by dispersing seeds.
Conservation Status and Threats
The International Union for Conservation of Nature lists white-tailed titi monkeys as Least Concern (IUCN, 2015). Although their habitat is threatened by deforestation due to land conversion and logging, they have a relatively large range and they adapt to life in secondary forests as well as disrupted and fragmented forests.
In Ecuador, the white-tailed titi is considered Near Threatened due to the high rates of deforestation and forest fragmentation in large areas of its range. There are no major threats throughout most of its range in Peru, however much of the western margins of their range suffers from high levels of deforestation. In addition, white-tailed titis suffer from the illegal pet trade in northern Peru.
White-tailed titis are considered Vulnerable in Colombia, where its range is restricted and the region is subject to petroleum exploration, coca plantations, and herbicides, making conservation activities difficult.
Natural predators include the harpy eagle and the tayra, a mammal in the weasel family.
The white-tailed titi monkey is listed on the Convention on International Trade in Endangered Species (CITES)–a multilateral treaty to protect endangered plants and animals—Appendix II, which includes species not necessarily threatened with extinction, but in which trade must be controlled in order to avoid utilization incompatible with their survival.
The species occurs in several national forests and ecological reserves in Ecuador and Peru, such as the Cuyabeno Wildlife Reserve, the Yasuni National Park or the Cordillera Azul and Gûeppi-Sekime National Parks. Efforts to protect forests and limit logging in these two countries therefore contribute to the conservation of the white-tailed titi monkey.
The species is not found in any protected areas in Colombia and there is no concrete data available on conservation of the white-tailed titi monkeys in that part of the world.
- Initiation of feeding by four sympatric Neotropical primates (Ateles belzebuth, Lagothrix lagotricha poepigii, Plecturocebus (Callicebus) discolor, and Pithecia aequatorialis) in Amazonian Ecuador: Relationships to photic and ecological factors – D. Max Snodderly, Kelsey M. Ellis, Sarina R. Lieberman, Andrés Link, Eduardo Fernandez-Duque, Anthony Di Fiore
- Self-anointing behavior in captive titi monkeys (Callicebus sp) – Joâo Pedro Souza-Alves, Natasha M Albuquerque, Luana Vinhas, Thayane S Cardoso, Raone Beltrâo-Mendes, Leandro Jerusalinsky
- Past, Present, and Future of Secoya Ethnoprimatology in the Ecuadorian Amazonia – Stella de la Torre, Pablo Yépez, Alfredo Payaguaje.
- IUCN Red List
- Duetting Patterns of Titi Monkeys (Primates, Pitheciidae: Callicebinae) and Relationships with Phylogey – Patrice Adret, Kimberly A Dingess, Christini B Caselli, Jan Vermeer, Jesus Martínez, Jossy C Luna Amancio, Silvy M van Kuijk, Lucero M Hernani Lineros, Robert B Wallace, Eduardo Fernandez-Duque and Anthony Di Fiore
- Demography and Life History of Wild Red Titi Monkeys (Callicebus discolor) and Equatorial Sakis (Pithecia aequatorialis) in Amazonian Ecuador: A 12-year Study – Sarie Van Belle, Eduardo Fernandez-Duque and Anthony Di Fiore
- Social monogamy, male-female relationships, and biparental care in wild titi monkeys (Callicebus discolor) – Andrea Spence-Aizenberg, Anthony Di Fiore, Eduardo Fernandez-Duque
- Titi monkey call sequences vary with predator location and type – Cristiane Câsar, Klaus Zuberbûhler, Robert J Young, Richard W Byrne.
Written by Sylvie Abrams, September 2020