Bolivian titi monkeys, Callicebus donacophilus, are primarily found in eastern Bolivia in the upper basins of the Mamore River and the Rio Grande. They may also be found in the extreme southwestern parts of the Brazilian states of Mato Grasso and Rondônia.
Biogeographic Regions: neotropical (Native )
- Ferrari, S., S. Iwanga, M. Messias, E. Ramos, P. Ramos, E. da Cruz Neto, P. Coutinho. 2000. Titi monkeys (Callicebus spp., Atelidae: Platyrrhini) in the Brazilian state of Rondônia. Primates, 41(2): 229-234.
- Hershkovitz, P. 1990. Titis, new world monkeys of the genus Callicebus (Cebidae, Platyrrhini): a preliminary taxonomic review. Fieldiana Zoology, 55: 1-109.
Bolivian titis are small, New World monkeys , averaging about 320 mm in length. Males are only slightly larger than females, weighing on average 991 g while females weigh 909 g. Titis have long tails that are not prehensile. They have very little prognathism and long skulls. Titi monkeys have long hind limbs with an intermembral index of 75.
The chest and belly of Bolivian titi monkeys is completely orange to brown-orange while the dorsal side and extremities range from grey to orange agouti in color. The tail may include black or grey coloring, and they have white tufts on their ears.
The dental formula of Bolivian titis, as with other titi monkeys, is 22.214.171.124/126.96.36.199. Compared to other platyrrhines, the canines of titi monkeys are relatively short and their molars are fairly simple.
Bolivian titi monkeys can be distinguished from closly related speices including Callicebus olallae, Callicebus brunneus, and Callicebus modestus by their well-developed malar stripe and lack of distinct sideburns.
Average mass: Males 991 g; Females 909 g.
Average length: 320 mm.
Sexual Dimorphism: sexes alike
- Fleagle, J. 1999. Primate Adaptation and Evolution. San Diego: Academic Press.
- van Roosmalen, M., T. van Roosmalen, R. Mittermeier. 2002. A taxonomic review of the titi monkeys, genus Callicebus Thomas, 1903, with the description of two new species, Callicebus bernhardi and Callicebus stephennashi, from Brazilian Amazonia. Neotropical Primates, 10: (suppl.).
Habitat and Ecology
The diet of titi monkeys comprises mainly fruit pulp, leaves, insects and seeds. They form small, pair-bonded, territorial groups and are considered monogamous. They have small home (1.5-30 km) and day ranges (0.5-1.5 km). A study on the behavioural ecology and calling behaviour of C. donacophilus is underway at two sites in forest patches in and on the outskirts of Santa Cruz (K. Dingess pers. comm. to R. Wallace, 2007).
Bolivian titi monkeys inhabit riparian zones and gallery forests near swampy grasslands and other open areas.
Habitat Regions: tropical
Terrestrial Biomes: forest ; rainforest
Other Habitat Features: riparian
Bolivian titi monkeys are primarily frugivorous, and it is estimated that their diet consists of over 70% fruit. They also eat leaves, seeds, and insects. Much of the day is spent resting in order to digest their mostly herbivorous diet.
Animal Foods: insects
Plant Foods: leaves; seeds, grains, and nuts; fruit
Primary Diet: herbivore (Frugivore ); omnivore
- Wright, P. 1989. The nocturnal primate niche in the new world. Journal of Human Evolution, 18(7): 635-58.
Titi monkeys, including Bolivian titis, can coexist with many other New World monkeys including marmosets, tamarins, squirrel monkeys, capuchins, owl monkeys, howler monkeys, woolly monkeys, and spider monkeys. However, some of these larger species often chase titi monkeys away from fruit trees and other sources of food. Because titi monkeys prefer to remain isolated within their social group, they attempt to avoid contact with other primates.
Because they are frugivores, Bolivian titi monkeys may play a small role in seed dispersal.
The main parasites found in neotropical primates, including Bolivian titi monkeys, are trypanosomes (Trypanosoma cruzi, Trypanosoma rangeli, Trypanosoma minasense, and Trypanosoma devei), which are a prevalent cause of infection.
Ecosystem Impact: disperses seeds
- Ziccardi, M., R. Lourenço-de-Oliveira, R. Lainson, M. do Carmo de Oliveira Brígido, J. Augusto Pereira Carneiro Muniz. 2000. Trypanosomes of Non-human Primates from the National Centre of Primates, Ananindeua, State of Pará, Brazil. Memórias do Instituto Oswaldo Cruz, 95(2): 157-159. Accessed May 03, 2011 at http://memorias.ioc.fiocruz.br/952/3890.html.
Many species of raptors prey on titi monkeys, like Bolivian titi monkeys, including Guianan crested eagles and ornate hawk eagles. Other predators include felids such as jaguars as well as various arboreal snakes. Predation on infants by tufted capuchins has also been observed. Bolivian titis are have a cryptic coloration, helping them to blend in with their surroundings and avoid predation.
- Guianan crested eagles Morphnus guianensis
- ornate hawk eagles Spizaetus ornatus
- jaguars Panthera onca
- tufted capuchins Cebus apella
Anti-predator Adaptations: cryptic
Life History and Behavior
Communication and Perception
Titi monkeys, including Bolivian titis, utilize a variety of vocalizations in order to communicate. These vocalizations are complex and numerous, though they are generally classified into two groups: the higher pitched squeaks, trills, chirps, and grunts; and the lower pitched chirrups, moans, pants, honks, bellows, pumps, and screams. Higher pitched sounds tend to be employed when they are agitated or encounter violence. Lower pitched, louder sounds are often used in intra-group signaling as well as contacting other social groups over a long range. Certain chirrup sounds are believed to reveal information about the age and sex of the calling monkey and can be used to locate group members. Moans can be heard during copulation and greeting.
Titis perform a characteristic bout of vocalizations at the outer boundary of their relatively small range to define and reinforce the boundaries of their home range. This generally occurs in the morning soon after awakening. A male emits loud calls, moans, grunts, and other vocalizations in order to establish the boundaries. If a neighboring group draws near, the groups participate in what is known as "duetting", with both groups calling. As the groups draw together, the intensity of this duetting increases and both males and females participate. If two groups directly confront each other, more physical communication is exhibited included tail-lashing, piloerection, chasing, and further calling.
Titi monkeys also use physical communication, including grooming and tail entwining. Male and female mates show a strong preference for grooming and entwining with each other rather than with other members of their group.
Communication Channels: tactile ; acoustic
Other Communication Modes: duets
Perception Channels: visual ; acoustic
- Moynihan, M. 1966. Communication in the titi monkey, Callicebus. Journal of Zoology, 150: 77-127.
- Müller, A., G. Anzenberger. 2002. Duetting in the Titi Monkey Callicebus cupreus: Structure, Pair Specificity and Development of Duets. Folia Primatologica, 73: 1-12.
- Robinson, J. 1979. Vocal regulation of use of space by groups of titi monkeys Callicebus moloch. Behavioral Ecology and Sociobiology, 5: 1-15.
The oldest Bolivian titi in captivity reached 24.8 years of age. Little information is available regarding the lifespan of this species in the wild. Other members of the genus Callicebus, such as Callicebus moloch, live an average of 25 years.
Status: captivity: 25 years.
- de Magalhaes, J., A. Budovsky, G. Lehmann, J. Costa, Y. Li, V. Fraifeld, G. Church. 2009. The Human Ageing Genomic Resources: online databases and tools for biogerontologists.. Aging Cell, 8(1): 65-72. Accessed May 03, 2011 at http://genomics.senescence.info/species/entry.php?species=Callicebus_donacophilus.
Lifespan, longevity, and ageing
Like all titi monkeys, Bolivian titis are monogamous. A strong bond is formed between male and female partners, which generally mate for life. They remain in close proximity to one another for almost all of their activities and often rest together with hands clasped and tails interwoven in a characteristic manner known as “twining.” They also have been observed grasping feet, nuzzling, and lip-smacking. When apart, they display physical signs of anxiety and distress. Titi monkeys also exhibit “jealous” behavior when approached by a stranger, especially the male, who mounts and tightly grasps his mate in the presence of another individual to prevent “extramarital” relations.
Mating System: monogamous
In captivity, Bolivian titi monkeys breed throughout the year. In the wild, a breeding season is predicted, perhaps in the spring preceding the rainy season in Bolivia. In captivity, female titi monkeys give birth approximately one year after finding a mate. After a gestation period of about 18 weeks, females give birth to a single offspring, though twins are uncommon. Although female Bolivian titi monkeys reach sexual maturity at 2 years of age, the mean age of first birth is 4 years.
Average number of offspring: 1.
Average gestation period: 18 weeks.
Range age at sexual or reproductive maturity (female): 2 (low) years.
Average age at sexual or reproductive maturity (female): 4 years.
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); viviparous
Male Bolivian titi monkeys play a dominant role in the care of their young. Although females nurse their offspring, males are the principal carriers and protectors of their young. During the first week of life, mother Bolivian titi monkeys carry their infants only 20% of the time, and after the first month, maternal contact is scarce. Infants experience more stress and elevated heart rates when separated from their father than from their mother, with few exceptions. Bollivian titi monkeys experience a stronger bond with their mate than with their offspring.
Parental Investment: male parental care ; female parental care ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Male)
- Anzenberger, G., S. Mendoza, W. Mason. 1986. Comparative studies of social behavior in Callicebus and Saimiri: behavioral and physiological responses of established pairs to unfamiliar pairs. American Journal of Primatology, 11: 37-51.
- Gron, K. 2007. "Primate Factsheets: Dusky titi (Callicebus moloch) Taxonomy, Morphology, & Ecology" (On-line). Accessed April 18, 2011 at http://pin.primate.wisc.edu/factsheets/entry/dusky_titi/taxon.
- Mendoza, S., W. Mason. 1986. Contrasting responses to intruders and to involuntary separation by monogamous and polygynous new world monkeys. Physiology and Behavior, 38: 795-801.
- Mendoza, S., D. Reeder, W. Mason. 2002. Nature of Proximate Mechanisms Underlying Primate Social Systems: Simplicity and Redundancy. Evolutionary Anthropology, 11: 112-116.
- Valeggia, C., S. Mendoza, E. Fernandez-Duque, W. Mason, B. Lasley. 1999. Reproductive biology of female titi monkeys (Callicebus moloch) in captivity. American Journal of Primatology, 47: 183-195.
Molecular Biology and Genetics
Barcode data: Callicebus donacophilus
There is 1 barcode sequence available from BOLD and GenBank. Below is the sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species. See the BOLD taxonomy browser for more complete information about this specimen. Other sequences that do not yet meet barcode criteria may also be available.
-- end --
Download FASTA File
Statistics of barcoding coverage: Callicebus donacophilus
Public Records: 1
Specimens with Barcodes: 1
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2003Least Concern(IUCN 2003)
- 1996Lower Risk/least concern
Although populations are declining, Bolivian titi monkeys are listed by the IUCN as a species of least concern. They have a relatively wide range and a slowly declining population. Bolivian titi monkeys have proven fairly adaptable, and they have a low number of natural predators. Their main threat is attributed to habitat loss due to agriculture. Bolivian titi monkeys are one of three primate species that survive within and around the borders of cities and rural human establishments in this region.
CITES: appendix ii
IUCN Red List of Threatened Species: least concern
- Veiga, L., R. Wallace, S. Ferrari. 2008. "Callicebus donacophilus" (On-line). In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. Accessed April 25, 2011 at http://www.iucnredlist.org/apps/redlist/details/41548/0.
It is listed on CITES Appendix II.
Relevance to Humans and Ecosystems
Economic Importance for Humans: Negative
There are no known adverse effects of Bolivian titi monkeys on humans.
Economic Importance for Humans: Positive
Bolivian titi monkeys may play a part in drawing tourists to forested areas of Bolivia.
The white-eared titi (Callicebus donacophilus), also known as the Bolivian titi or Bolivian gray titi, is a species of titi, a type of New World monkey, from eastern Bolivia and a small area of Brazil. The species has a range that extends east from the Manique River in Beni Department, Bolivia to southern Rondônia in Brazil. The southern end of its range includes forests around the city of Santa Cruz de la Sierra.
It is a medium-sized monkey with a grey back, orange underside and distinctive white ear tufts. It has an omnivorous diet, eating fruits, other plant materials and invertebrates. It is predated upon primarily by raptors, though felids and other monkey species have been known to attack the species. It is a monogamous species and lives in small groups of two to seven members consisting of the pair and their offspring. The family group has a home range of 0.005 to 0.14 square kilometres (0.0019 to 0.054 sq mi) and the adults have a complex vocal repertoire to maintain their territory. It is also known for its characteristic twining of tails when groups are sitting together. White-eared titis can live for more than 25 years in captivity.
The white-eared titi population has a declining trend. The decline is believed to be mainly caused by human-induced habitat loss and degradation. Despite this, the International Union for Conservation of Nature (IUCN) classified the species as Least Concern in 2008 as it has shown adaptability to habitat disturbance and is found over a wide range.
The white-eared titi belongs to the New World monkey family Pitheciidae, which contains the titis (Callicebus), saki monkeys (Pithecia), bearded sakis (Chiropotes), and uakaris (Cacajao). It is a member of the subfamily Callicebinae, of which the only extant genus is Callicebus, containing all of the titi monkeys.
Although the exact position of species within the Callicebus genus is debated, the white-eared titi has been placed within the subgenus Callicebus in the C. donacophilus group with the Rio Beni titi (C. modestus), Rio Mayo titi (C. oenanthe), Ollala Brothers' titi (C. olallae), and white-coated titi (C. pallescens). The white-coated titi has sometimes been considered a subspecies of the white-eared titi, but they are treated as separate species in the latest edition of Mammal Species of the World.
The white-eared titi is a medium-sized primate with grey to orange pelage. The species does not exhibit sexual dimorphism; the male's head and body length averages 311 millimetres (12.2 in) while females average 340 millimetres (13 in). The white-eared titi's fluffy tail is longer than the length of its head and body together. It typically has thick fur, with a dorsal side and limbs that vary in colour from grey agouti to orange agouti, with an orange underside and white ear tufts.
Body weight ranges from around 800 to 1,200 grams (1.8 to 2.6 lb), with the female generally a little lighter. It has the dental formula , meaning that on each side of the jaw it has two incisors, one canine tooth, three premolars, and three molar teeth. The canine teeth are relatively short when compared with other New World monkeys. In captivity, the white-eared titi has been known to live for over 25 years.
The white-eared titi is cryptic, diurnal and known to live in small family groups. It is a monogamous species that is thought to mate for life and lives in groups that usually consist of two to seven members; an adult pair and up to five young. Multi-male groups have also been recorded. Offspring are carried by the male, and are always with them, except when feeding. Between the ages of two to four years, offspring will disperse from the natal group, with females leaving earlier than the males.
There is a strong bond between the adult mating pair, they stay close and carry out activities together. Either member of the pair may follow the other and leadership changes through the day. Evidence of the strength of the pair bond is shown by grooming, huddling together with their tails twined, nuzzling, and gentle grasping. Titi monkeys are highly territorial and when confronted with another family group, both will respond with threatening behaviour, males showing increased agitation towards intruding males. When not close together, the pair show a significant amount of distress and agitation.
Titi monkeys are well known for their vocal communication, and have a complex repertoire of calls. The calls can be divided into two categories: high-pitched quiet calls and low-pitched loud calls. Vocalisations are often combined and repeated to form sequences that are used to indicate distress, conflict, play, bonding, disturbance, and to strengthen territory. The high-pitched quiet calls are mostly used when the monkeys are disturbed, but may also be used before or after group calling, while foraging, or to find other members of the group. The loud low-pitched calls are mostly used in long distance group calling. Their function is to ensure adequate spacing between the home ranges of different family groups. These vocalisations are known as duets, and generally involve the male and female. If a neighbouring group is within earshot of these calls they will respond with their own duetting.
The white-eared titi is arboreal, spending most of its time in the lower strata of the forest. It may enter the main canopy when travelling longer distances and may also cross small areas of open ground, though the latter is rare. During normal movement through its environment it is quadrupedal and mostly walks, clambers and leaps, but it can also bound and climb. It leaps small distances, no more than a few body lengths, between trees where vegetation is not thick enough to support its primary forms of locomotion. When travelling on the ground it is said to use a "bounding movement" whereby it leaps more than 1 metre (3.3 ft) off the ground. The titi monkey prefers branches which are less than 5 centimetres (2.0 in) in diameter and its tail never touches the support it is on.
There is relatively little known about the ecology of the white-eared titi or even titi monkeys in general, and few studies have focused on the white-eared titi. It is diurnal, commencing activity around sunrise and continuing until sunset. Food availability may influence activity times; if there is an abundance of food in the warmer months when plants are fruiting titi monkeys may start earlier, or if there is a lack of food, titi monkeys may remain at the feeding tree into the evening. The titi monkey usually rests during the middle of the day and has two main feeding periods, in the morning and in the afternoon. It has an increased period of feeding towards the end of the day. In total, the titi monkey is active for an average of 11.5 hours, 2.7 hours of which is spent feeding. Titi monkeys sleep on branches at least 15 metres (49 ft) above the ground. In the same manner as resting during the day, titi monkeys huddle together and twine tails to sleep.
Though there is little published research on the diet of the white-eared titi, titi monkeys in general are omnivores that eat fruit, leaves, insects, and seeds. They mostly eat leaves, especially protein-rich young leaves and leaf buds, so a significant period of the day is spent resting to digest the cellulose. They consume more than 100 different species of plants and fruit. Titi monkeys will also eat small insects (ants, moths, butterflies, and their cocoons), spiders, and can catch flying prey if it comes close to them. During the dry season there is an increased feeding time on leaves, and during lactation it is thought insect consumption increases to augment the protein content of the diet.
The titi monkey may travel between 425 and 1,152 m (1,394 and 3,780 ft) during the day, and can maintain a home range of 0.005 to 0.14 km2 (0.0019 to 0.054 sq mi). During the dry season there is less fruit available and therefore less need to travel large distances, so the day range may only be a third of the usual distance. Its home range is often shared with other primate species including marmosets, squirrel monkeys, capuchins, owl monkeys, howler monkeys, and spider monkeys. It is sometimes chased from feeding sites by larger species, and will generally try to avoid other primates.
Habitat and distribution
The white-eared titi is found in tropical humid forests, preferring drier regions to more humid ones. It is found in riparian zones and gallery forests and is clearly associated with open habitats like grasslands and swampy grasslands. It is found in areas with dense vegetation, often choosing to inhabit the thickest parts of the forest. The species seems to be quite tolerant of habitat disturbance. In Bolivia, the white-eared titi is found in the upper parts of the Mamoré, Grande, and San Miguel river basins, east of the Manique River in Beni and in the forests surrounding the city of Santa Cruz de la Sierra. Its range extends north to southern Rondônia in Brazil.
The white-eared titi is considered "Least Concern" on the International Union for Conservation of Nature (IUCN) Red List. The species is not considered threatened due to its adaptability and abundance over a relatively wide range, and despite having a decreasing population trend the decline is not rapid enough to be placed in a threatened category. The species is also listed on CITES Appendix II.
The white-eared titi's main threat is deforestation and habitat loss due to agriculture. The area of greatest habitat loss is around the city of Santa Cruz de la Sierra, but it still survives within the city limits and on the edges of many rural establishments. It has few natural predators and is proven to be adaptable to habitat disturbance. Farmland may surround and isolate areas of titi habitat which occasionally has positive benefits to the monkey. Farmers may prevent hunters on the land, thereby inadvertently protecting the species. It also appears that the titi monkey can cross open ground between forest fragments, and some groups can thrive in disturbed habitats near human activities. However, the fragmented habitats may prevent the establishment of new territories and decrease reproductive opportunities. Forest corridors to connect fragmented forests have been proposed as an effective means to help ensure the survival of the titi monkey. The white-eared titi is found in the Beni Biological Station Biosphere Reserve and the Amboro National Park in Bolivia and benefits from the protection these reserves provide.
- Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M. eds. Mammal Species of the World (3rd ed.). Baltimore: Johns Hopkins University Press. pp. 143. OCLC 62265494. ISBN 0-801-88221-4. http://www.bucknell.edu/msw3/browse.asp?id=12100329.
- "Callicebus donacophilus". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=572965. Retrieved 2006-11-28.
- Veiga, L. M., Wallace, R. B. & Ferrari, S. F. (2008). Callicebus donacophilus. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 2009-01-03.
- van Roosmalen, M. G. M.; van Roosmalen, T; Mittermeier, R. A. (June 2002). "A taxonomic review of the titi monkeys, genus Callicebus Thomas, 1903, with the description of two new species, Callicebus bernhardi and Callicebus stephennashi, from Brazilian Amazonia". Neotropical Primates 10: 1–52. doi:10.1.1.177.4220.
- Ferrari, S.; Iwanga, S.; Messias, M.; Ramos, E.; Ramos, P.; da Cruz Neto, E.; Coutinho, P. (2000). "Titi monkeys (Callicebus spp., Atelidae: Platyrrhini) in the Brazilian state of Rondônia". Primates 41 (2): 229–234. doi:10.1007/BF02557805.
- Hershkovitz, P. (1990). "Titis, new world monkeys of the genus Callicebus (Cebidae, Platyrrhini): a preliminary taxonomic review". Fieldiana Zoology 55: 1–109.
- Gron, K. J. (2007-12-19). "Primate Factsheets: Dusky titi (Callicebus moloch) Taxonomy, Morphology, & Ecology". Primate Info Net. http://pin.primate.wisc.edu/factsheets/entry/dusky_titi/taxon. Retrieved 2010-04-10.
- Ankel-Simons, F. (2000). Primate anatomy. Academic Press. ISBN 9780120586707.
- Fleagle, J. (1998). Primate Adaption and Evolution (Second ed.). Academic Press. pp. 145–147. ISBN 0122603419.
- Weigl, R. (2005). Longevity of mammals in captivity; from the living collections of the world. Stuttgart: E. Schweizerbartsche. pp. 54. ISBN 9783510613793.
- Kinzey, W. G. (1981). "The titi monkeys, genus Callicebus: I. description of the species". Ecology and behavior of neotropical primates. Volume 1. Rio de Janeiro: Academia Brasileira de Ciências. pp. 241–276.
- Eisenberg, J. F; Redford, K. H. (1999). Mammals of the Neotropics, Volume 3: Ecuador, Bolivia, Brazil. Chicago: University of Chicago Press. ISBN 9780226195421.
- Wright, P. C. (1984). "Ecological correlates of monogamy in Aotus and Callicebus". Primate ecology and conservation. Cambridge: Cambridge University Press. pp. 159–167.
- Mason, W. A.; Mendoza, S. P. (1993). Contrasting life modes in cebidae: titi monkeys (Callicebus) and squirrel monkeys (Saimiri). AAZPA Regional Conference Proceedings. pp. 715–722.
- Kinzey, W. G. (1997). "Synopsis of the new world primates: Callicebus". In Kinzey, W. G.. New world primates: ecology, evolution, and behavior. New York: Aldine De Gruyter. pp. 213–221.
- Bossuyt, F. (2002). Natal dispersal of titi monkeys (Callicebus moloch) at Cocha Cashu, Manu national park, Peru. 34. American Journal of Physical Anthropology. pp. 47.
- Bicca-Marques, J. C.; Garber, P. A.; Azevedo-Lopes, M. A. O. (2002). Evidence of three resident adult male group members in a species of monogamous primate, the red titi monkey (Callicebus cupreus). 66. Mammalia. pp. 138–142.
- Mason, W. A. (1966). "Social organization of the South American monkey, Callicebus moloch: a preliminary report". Tulane Studies in Zoology and Botany 13: 23–28.
- Wright, P. C. (1985). The costs and benefits of nocturnality for Aotus trivirgatus (the night monkey). PhD dissertation. City University of New York. pp. 315.
- Cubicciotti, D. D.; Mason, W. A. (1978). "Comparative studies of social behavior in Callicebus and Saimiri: heterosexual jealousy behavior". Behavioral Ecology and Sociobiology 3: 311–322. doi:10.1007/BF00296316.
- Anzenberger, G.; Mendoza, S. P.; Mason, W. A. (1986). "Comparative studies of social behavior in Callicebus and Saimiri: behavioral and physiological responses of established pairs to unfamiliar pairs". American Journal of Primatology 11 (1): 37–51. doi:10.1002/ajp.1350110105.
- Mendoza, S. P.; Reeder, D. M.; Mason, W. A. (2002). "Nature of proximate mechanisms underlying primate social systems: simplicity and redundancy". Evolutionary Anthropology 11 (1): 112–116. doi:10.1002/evan.10071.
- Mendoza, S. P.; Mason, W. A. (1986). "Contrasting responses to intruders and to involuntary separation by monogamous and polygynous new world monkeys". Physiological Behavior 38 (6): 795–801. doi:10.1016/0031-9384(86)90045-4.
- Mason, W. A. (1968). "Use of space by Callicebus". In Jay, P. C.. Primates: studies in adaptation and variability. New York: Holt, Rinehart and Winston. pp. 200–216.
- Fernandez-Duque, E.; Mason, W. A.; Mendoza, S. P. (1997). "Effects of duration of separation on responses to mates and strangers in the monogamous titi monkey (Callicebus moloch)". American Journal of Primatology 43 (3): 225–237. doi:10.1002/(SICI)1098-2345(1997)43:3<225::AID-AJP3>3.0.CO;2-Z. PMID 9359966.
- Robinson, J. G. (1977). Vocal regulation of spacing in the titi monkey (Callicebus moloch). PhD dissertation. University of North Carolina-Chapel Hill.
- Robinson, J. G. (1979). "An analysis of the organization of vocal communication in the titi monkey Callicebus moloch". Zeitschrift Fur Tierzuchtung und Zuchtungsbiologie 49: 381–405.
- Gron, K. J. (2007-12-19). "Primate Factsheets: Dusky titi (Callicebus moloch) Behaviour". Primate Info Net. http://pin.primate.wisc.edu/factsheets/entry/dusky_titi/behav. Retrieved 2010-04-10.
- Moynihan, M. (1966). "Communication in the titi monkey, Callicebus". Journal of Zoology 150: 77–127.
- Lawler, R. R.; Ford, S. M.; Wright, P. C.; Easley, S. P. (2006). "The locomotor behavior of Callicebus brunneus and Callicebus torquatus". Folia Primatologica 77 (3): 228–239. doi:10.1159/000091232.
- Youlatos, D. (1999). "Comparative locomotion of six sympatric primates in Ecuador". Annales Des Sciences Naturelles 20 (4): 161–168.
- Fragaszy, D. M. (1979). "Titi and squirrel monkeys in a novel environment". Captivity and behavior: Primates in breeding colonies, laboratories, and zoos. New York: Van Nostrand Reinhold. pp. 172–216. ISBN 9780442223298.
- Welker, C.; Jantschke, B.; Klaiber-Schuh, A. (1998). "Behavioural data on the titi monkey Callicebus cupreus and the owl monkey Aotus azarae boliviensis. A contribution to the discussion on the correct systematic classification of these species. Part I: introduction and behavioural differences". Primate Report 51: 3–18.
- Kinzey, W. G. (1978). "Feeding behaviour and molar features in two species of titi monkey". Recent advances in primatology. 1: Behaviour. London: Academic Press. pp. 373–385.
- Wright, P. C. (1989). "The nocturnal primate niche in the new world". Journal of Human Evolution 18 (7): 635–658.
- Robinson, J. G. (1979). "Vocal regulation of use of space by groups of titi monkeys Callicebus moloch". Behavioral Ecology and Sociobiology 5: 1–15.
- Izawa, K.; Yoneda, M. (1981). "Habitat utilization of nonhuman primates in a forest of the western pando, Bolivia". Kyoto University Overseas Research Reports of New World Monkeys 2: 13–22.
- Terborgh, J. (1985). "The ecology of Amazonian primates". Key environments: Amazonia. Oxford: Pergamon Press. pp. 284–304.
- Crandlemire-Sacco, J. (1988). "An ecological comparison of two sympatric primates: Saguinus fuscicollis and Callicebus moloch of Amazonian Peru". Primates 29 (4): 465–475.
- Meritt Jr., D. A. (1980). "Captive reproduction and husbandry of the douroucouli Aotus trivirgatus and the titi monkey Callicebus spp.". International Zoo Yearbook 20: 52–59.
- Lawrence, J. M. (2007). Understanding the pair bond in brown titi monkeys (Callicebus brunneus): male and female reproductive interests. PhD dissertation. Columbia University.
- Tirado Herrera, E. R.; Heymann, E. W. (2004). "Does mom need more protein? Preliminary observations on differences in diet composition in a pair of red titi monkeys, Callicebus cupreus". Folia Primatologica 75: 150–153. doi:10.1159/000078304.
- Wright, P. C. (1996). "The neotropical primate adaption to nocturnality: feeding in the night (Aotus nigriceps and A. azarae)". Adaptive radiations of neotropical primates. New York: Plenum Press. pp. 369–382.
- Felton, A.; Felton, A. M.; Wallace, R. B.; Gómez, H. (2006). "Identification, behavioral observations, and notes on the distribution of the titi monkeys Callicebus modestus Lönnberg, 1939 and Callicebus olallae, Lönnberg 1939". Primate Conservation 20: 41–46.
- DeLuycker, A. M. (2006). "Preliminary report and conservation status of the Río Mayo titi monkey, Callicebus oenanthe Thomas, 1924, in the Alto Mayo valley, northeastern Peru". Primate Conservation 21: 33–39.
|Wikispecies has information related to: White-eared titi|
|Wikimedia Commons has media related to: Callicebus donacophilus|