Callicebus modestus


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Callicebus modestus
Species Authority: Lönnberg, 1939
Common Name(s):
English Beni Titi Monkey, Rio Beni Titi, Modest Titi, Bolivian Titi, Titi Monkey
Spanish Lucachi, Mono Tití
Taxonomic Notes: Kobayashi and Langguth (1999) and van Roosmalen et al. (2002) recognize five species groups – cupreus, donacophilus, moloch, personatus and torquatus. They place Callicebus modestus in the donacophilus group, along with: Callicebus donacophilus, Callicebus pallescens, Callicebus oenanthe and Callicebus olallae. Tarifa (1996), Anderson (1997) and Felton et al. (2006) suggest that the taxonomic distinctiveness between C. modestus and C. olallae needs further investigation. However, more recent field observations (Martinez and Wallace 2007) and opportunistically collected specimens (R. Wallace pers. obs.) support the taxonomic separation of C. olallae and C. modestus. Preliminary results from a scat-based genetic study show that both are clearly distinct from C. donacophilus and each other (Barreta pers. comm. to R. Wallace 2007).

Assessment Information [top]

Red List Category & Criteria: Endangered B1ab(iii) ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Veiga, L.M., Wallace, R.B. & Martinez, J.
Reviewer(s): Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)
Listed as Endangered as the species is known from a small number of localities in southwestern Beni where its extent of occurrence (excluding savanna) is well below 5,000 km². The range is fragmented, and there is a continuing decline in habitat due to ongoing forest destruction related to agriculture and cattle ranching (likely to accelerate with the forthcoming construction of a major highway).
2003 Vulnerable (IUCN 2003)
2003 Vulnerable

Geographic Range [top]

Range Description: Endemic to Bolivia with very restricted range estimated at 1,800 km² (Martinez and Wallace 2007). It occurs in the upper Río Beni basin, a tributary of the upper Rio Madeira, Beni, Bolivia. van Roosmalen et al. (2002) incorrectly indicated that the species is parapatric with Callicebus dubius along the north bank of the Río Madre de Dios, with Callicebus donacophilus along the east bank of the Río Beni and with Callicebus olallae along the west bank of the upper Río Beni (Hershkovitz 1990). However, Felton et al. (2006) and Martinez and Wallace (in press) demonstrate that the species only occurs to the east of the Río Beni, west to the Manique River in south-western Beni Department. Rowe and Martinez (2003) were unable to confirm its range as proposed by van Roosmalen et al. (2002). The geographical range of Callicebus olallae overlaps with Callicebus modestus, although transitional zones between the two taxa have yet to be confirmed and each seems to specialize on different habitat types (Felton et al. 2006; Martinez and Wallace 2007).
Bolivia, Plurinational States of
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: In 2002, Felton et al. (2006) conducted titi monkey surveys and interviewed local residents at four locations: Puerto Santa Cruz on the Rio Yacuma; La Laguna; Petaca; and Naranjal. Titis were relatively abundant in Naranjal, not encountered at all in Petaca (although local residents claim they occur there), and are no longer present in La Laguna (probably exterminated through hunting). Examination of the holotypes indicates that the Rio Yacuma groups were C. olallae, while two of three groups found in Naranjal were Callicebus modestus (the third appeared to combine characters from both species).

Lopez-Strauss (2007) estimated density for both C. olallae and C. modestus using calling behaviour and an adapted point-count methodology. Conservative density estimates were recorded for C. modestus between 0.9 and 12.4 groups/km² (Lopez-Strauss 2007).
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: This taxon occurs in relatively dry forest patches within a forest-savanna mosaic (Lonnberg 1939; Anderson 1997; Felton et al. 2006; Martinez and Wallace 2007). Two relatively large groups with 5 to 7 members were found in Naranjal. Three groups, each with two members (possibly C. olallae), were encountered at Puerto Santa Cruz, to the north of the Rio Yacuma. Martinez and Wallace (2007) and Lopez-Strauss (2007) detail average group sizes of 3 and 2.64 individuals, respectively.
Systems: Terrestrial

Threats [top]

Major Threat(s): The main threat to this species is forest loss and habitat fragmentation. Groups surveyed by Felton et al. (2006) occurred in fragments surrounded by cattle ranches. A farmer in Naranjal reported seeing groups crossing grassland gaps (300–400 m) between patches of forest (Felton et al. 2006). There is some limited hunting for pets. The proposed major improvement to a regional road will exacerbate deforestation and is likely to increase hunting pressure (Felton et al. 2006).

Conservation Actions [top]

Conservation Actions: A very small part of the range of this species is included within the Beni Biosphere Reserve area (R. Wallace pers. comm.). Conservation programmes in the region include: the Greater Madidi Landscape Conservation Program in northern La Paz and south-western Beni Departments of the Wildlife Conservation Society that has lead research efforts on both Bolivian endemics since 2002; and the Asociación Boliviana para la Conservación and Conservation International who have worked with the Santa Rosa Municipality in the development of a Municipal Reserve in south-western Beni Department.
It is listed on CITES Appendix II.

Citation: Veiga, L.M., Wallace, R.B. & Martinez, J. 2008. Callicebus modestus. The IUCN Red List of Threatened Species. Version 2014.3. <>. Downloaded on 24 November 2014.
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