Literature modestus

Lönnberg, 1939

Callicebus modestus

Locality: The Stockholm Museum has 2 specimens form El Consuelo, Rio Beni, Bolivia.

Description: In spite of some difference in age both specimens are quite alike. The appearance resembles generally to a certain degree that of some member of the cupreus group as it presents a similar grizzled brown colour. This is affected by the outer half of the hairs being annulated with alternating buffish and blackish brown rings. The lower side of the body is rufous, not annulated, which increases the likeness mentioned, but the limbs are not rufous as in cupreus but annulated as the back. The upper parts of the head are looking somewhat more brightly rufous in consequence of the tips of the hairs being more vividly coloured. The extreme frontal edge is somewhat blackish produced by the basal parts of the hairs. The face is beset with short, adpressed whitish hairs. The whiskers are not well developed, tipped with rufous. The hairs of the ears are white. The hairs of the arms are annulated with rufous and black all the way to the black hands. The hairs of the upper or outer side of the fingers are also black, but on the sides between them are also seen some whitish hairs. The hind legs are also annulated as the back, although somewhat brighter rufous, but towards the feet the black becomes dominating, and the upper side of the toes is pure black. The tail is speckled blackish and greyish white. In the older specimen the black is dominating in the middle for about two thirds. The fur of the back is long, generally from 4,5 to somewhat more than 5 cm, and the under wool is also very dense, but the long hairs are not so silky soft as in C. olallae.

Collectors’ measurements: Male: total length 715mm; tail 400mm; hind foot 90mm.

Skull: measurements and description of 2 individuals in publication.

Remarks: Although the specimens of C. modestus and C. olallae have been collected at not very distant places, they appear to be so different that they certainly must be considered as representing two different species. This is also further proved by a comparison of the skulls of the fully adult male specimens.

Both these western species differ by having white hairs on their ears from the species of titi monkeys, C. toppini and C. rutteri described by Thomas from Peru, which both have red hairs on their ears. The latter of these has also a whitish frontal band. The absence of such a band distinguish these new species also from several other western titi monkeys, at the same time as they also differ from them in other respects, so much that a direct comparison is not needed.

Thomas, O. (1928a). The Godman-Thomas Expedition to Peru. – VII. The mammals of the Rio Ucayali.  Annals and Magazine of Natural History (10) 2: 253-254.

Cabrera, 1958

Callicebus moloch donacophilus

Synonyms: Callithrix donacophilus (D’Orbigny, 1835 and 1847); Saguinus personatus variation B (Lesson, 1840); Callithrix cinerascens (Forbes, 1894 – part); Callicebus donacophilus (Thomas, 1908); Callicebus geoffroyi? Miranda Ribeiro, 1914 = nom nud.); Callicebus modestus (Lönnberg, 1939).

Distribution: Central and northern Bolivia, and west of the Brazilian state of Mato Grosso.

Cabrera, A. (1958). Catálogo de los mamíferos de América del Sur. Instituto Nacional de Investigacion de la Ciencias Naturales, Ciencia Zoologica, 4 (1): 137-142.

Hill, 1960

Callicebus cupreus modestus

Synonym: Callicebus modestus (Lönnberg, 1939).

Type locality: El Consuelo, Rio Beni, Bolivia. Type in Stockholm Museum.

Distribution: Known only from the type locality.

Description: Closely resembling several other members of the cupreus group, with which it agrees in general grizzled brownish upper parts, the distal half of each hair being annulated with alternating zones of buff and blackish-brown; also in the under parts being rufous without annulation of individual hairs. Differing in the absence of red from the limbs, which are clothed with annulated hairs like those of the back. Forehead with thin line of black superciliary hairs, but Lönnberg says “the extreme frontal edge is somewhat blackish produced by basal parts of the hairs”; no white frontal band present. Whiskers not well developed, rufous tipped; ear hairs white; crown more brightly rufous than back from more vivid colouration of hair-tips. Fore-limbs with hairs annulated with black and reddish down to wrists, the hands quite black, fingers black above, but whitish at sides. Hind-limbs similarly coloured to back, but rufous tinge brighter, the black becoming predominant distally, especially on feet; upper surface of toes pure black. Tail grizzled blackish and greyish-white, the black dominant in the middle.

Measurements: had and body 315mm; tail 400mm; foot 90mm.

Skull: see measurements in publication.

Hill, W.C.O. (1960). Primates. Comparative anatomy and taxonomy  4 (A): 98-147.

Hershkovitz, 1963

Callicebus moloch brunneus

Synonyms: Callithrix brunnea (Wagner, 1842); Callithrix brunnea (Wagner, 1848); Callithrix castaneoventris (Gray, 1866), Callicebus toppini (Thomas, 1914); Callicebus olallae (Lönnberg, 1939); Callicebus modestus (Lönnberg, 1939); Callicebus cupreus acreanus (Vieira, 1952); Callithrix cuprea (Goeldi and Hagman, 1904); Callicebus caligatus (Osgood – not Wagner -, 1916).

Remarks: the original description of castaneoventris, toppini, olallae, modestus and acreanus, all from the same general area, are based on vague comparisons with cupreus only. No mention was made of other related forms although Lönnberg did attempt to distinguish his modestus from his olallae described in the same paper. It is not surprising therefore, that all should prove equally distinct from cupreus and equal to each other, or brunneus, the oldest available name.

The original characterization of the subadult and adult cotypes of Callicebus modestus from higher up the Rio Beni, points to complete intergradation between brunneus and donacophilus. Geographically, modestus could be assigned to either race. The hands and feet of both specimens are black as in brunneus. The tail is described as “speckled blackish and greyish white”, but with the black “dominating in the middle for about two thirds” in the adult. If this means that the tail is dominantly blackish for two thirds its length, then the older cotype of modestus is more like brunneus, in this respect. On the other hand, the ears of modestus (and the type of olallae) are said to be tufted with white, a feature which is more conspicuously developed in donacophilus than in any other race. Cabrera (1958) treats modestus as a synonym of modestus. The original description of modestus, however, suggests a darker animal than any now identified with donacophilus.


Hershkovitz, 1988

Callicebus modestus

Only member of the modestus group.

Remarks: the species is known only from the adult type skin and skull, and those of a subadult syntype; one of the smalles species of the genus; externally most similar to members of the C. moloch group; cranially most distinctive and probably most primitive of living higher primates (Haplorhini); braincase volume smallest for cebids.

The Bolivian highland Callicebus modestus and Callicebus olallae known only from their individual type localities hardly 50km apart in the upper Yaruma-Mamoré basin, differ widely from each other and all others. In the absence of contrary evidence, each may also be regarded as an isolated relic species despite the geographic proximity to each other and to other populations of C. brunneus and C. donacophilus. Their geographic position may be analogous to that of the Peruvian Callicebus oenanthe and perhaps should be classified with it as essentially insular.

Distribution of C. olallae, C. modestus, C. brunneus and C. donacophilus donacophilus, correlate with Brown’s single postulated refuge 22 (yungas). Present geographic distribution of prototypes of the most primitive living species C. olallae, C. modestus, C. oenanthe, C. donacophilus, and the hypothetical prototype of the C. moloch group is rooted in the southwestern portion of the generic range, well beyond the Río Solimoes Amazons flood plain.

The most primitive living species, the Bolivian C. modestus, may be nearest the common ancestral stock.

Herskovitz, P. (1988) Origin, Speciation, and Distribution of South American Titi Monkeys, Genus Callicebus (Family Cebidae, Platyrrhini), by Philip Hershkovitz . Proceedings of the Academy of Natural Sciences of Philadelphia 140 (1): 240-272.

Hershkovitz, 1990

Callicebus modestus

Member of the modestus Group.

Synonym: Callicebus modestus (Lönnberg, 1939).

Type locality: El Consuelo, Rio Beni, Beni, Bolivia; altitude, 196 m above sea level. Lectotype in Royal Natural History Museum, Stockholm.

Distribution: Known only from the upper Rio Beni basin in the upper Rio Madeira watershed, Beni, Bolivia.

Description: All upper and outer parts brownish or reddish agouti except whitish ear tufts, forehead reddish brown agouti, like crown, the thin blackish superciliary fringe excepted; outer surface of limbs reddish brown agouti; hands, toes blackish or mixed blackish and reddish; sideburns not contrasting in coloration with forehead and crown; whitish malar stripe absent, whitish ear tufts present; tail dominantly blackish agouti, darker than dorsum.

Skull: elongate, comparatively low-slung, greatest height perpendicular to Frankfurt plane about 51% greatest skull length; condylobasal length about 86% greatest skull length; braincase extremely narrow, greatest width about 48% greatest skull length (50%-59% in other species); postorbital constriction about 41% greatest skull length (43%-53% in other species); posterior palatal border behind posterior plane of m33 ; superior temporal ridges extremely approximated, distance between them at frontoparietal sutures about 50% greatest braincase width, about 22% at lambdoidal crest between parieto-occipital sutures; hamular process of pterygoid plate least reduced, the interpterygoid fossa widest and deepest of genus.

Measurements: See publication.

Comparisons: Distinguished from Callicebus brunneus by generally paler coloration, forehead reddish brown agouti, ear tufts whitish, outer surface of limbs not blackish; from C. caligatus by sideburns not sharply defined from coloration of crown, forehead, and crown agouti, ear tufts whitish, tail dominantly blackish throughout; from C. cupreus discolor and C. c. ornatus by absence of pale frontal blaze, dominantly brownish outer surface of limbs; from C. oenanthe by forehead-like crown, facial border blackish; from all other species of Callicebus by one or more of above characters and most cranial characters detailed above.

Specimens examined: Total 2. Bolivia – Beni: El Consuelo, Rio Beni.

Hershkovitz, P. (1990). Titis, New World Monkeys of the genus Callicebus: A Preliminary Taxonomic Review. Fieldiana Zoology 55: 1-109.

Kobayashi, 1995

Callicebus modestus

Based on cranial measurements, the genus can be divided in five groups:

  • the donacophilus group (including modestus, olallae, d. donacophilus and d. pallescens)
  • the cupreus group (including caligatus, c. cupreus, c. discolor and c. ornatus)
  • the moloch group (including brunneus, h. hoffmannsi, h. baptista, moloch and cinerascens)
  • the personatus group (including p. personatus, p. nigrifrons, p. melanochir)
  • the torquatus group (including t. lucifer, t. lugens, t. medemi, t. regulus, t. purinus and t. torquatus).

The group position of C. dubius remains uncertain; C. oenanthe and C. barbarabrownae were not examined.

Kobayashi, S. (1995). A phylogenetic study of Titi Monkeys, Genus Callicebus, based on cranial measurements: 1. Phyletic groups of Callicebus. Primates 36(1): 101-120.

Anderson, 1997

Callicebus modestus

Synonyms: Callicebus modestus (Lonnberg, 1939; Hershkovitz, 1988; Kobayashi, 1990; Groves, 1993; Anderson, 1993); Callicebus moloch brunneus (Hershkovitz, 1963); Callicebus moloch modestus (Emmons and Feer, 1990).

Locality: Beni, El Consuelo.

Remarks: The specific status of both Callicebus modestus and C. olallae needs further study. Hershkovitz
(1990) published photographs of the skull of the holotype and noted its elongation. He wrote that Callicebus modestus differs from C. brunneus “by generally paler coloration, forehead reddish brown agouti, ear tufts whitish, outer surface of limbs not blackish.” If a series of Callicebus from the Beni River
valley could be obtained and studied, a betterunderstanding of variability would be gained and the present hypothesis of specific distinctness of C. modestus and C. olallae could be tested more rigorously.

Anderson, S. (1997). Mammals of Bolivia, Taxonomy and Distribution. Bulletin of the American Museum of Natural History 231: 1-652.

Groves, 2001

Callicebus modestus

Synonyms: Callicebus modestus (Lönnberg, 1939).

Distribution: Known only from the type region.

Diagnosis: (after Hershkovitz, 1990) Brown- or red-agouti, with whitish ear tufts; forehead and crown red-brown agouti, with a thin black brow fringe; toes with black hairs; sideburns not contrasting; tail blackish agouti.

Remarks: Externally resembling the C. moloch group, but cranially primitive according to Hershkovitz (1990).


Roosmalen et al., 2002

Callicebus modestus

Type locality: El Consuelo, Río Beni, Beni, Bolivia. The lectotype is an adult male, skin and skull at Royal Natural History Museum, Stockholm, Sweden, no. A612105, collected under no. 135 by A. M. Olalla in 1937; lectoparatype a sub-adult male, skin and skull deposited in the same museum (RNHMS), collected under no. 136 by A. M. Ollalla in 1937.

Distribution: As far as is known, it occurs only in the upper Río Beni basin, a tributary of the upper Rio Madeira, Beni, Bolivia. 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.

Description: Upper and outer parts of body light brownish or reddish agouti except or white to whitish ear tufts, reddish brown agouti forehead and crown, and thin blackish superciliary fringe; outer surface of limbs reddish brown agouti; hands and feet blackish or blackish mixed with reddish; sideburns same colour as forehead and crown; tail blackish agouti, darker than dorsum. Distinguished from Callicebus brunneus by paler coloration, whitish ear tufts, and dominantly blackish tail; from Callicebus olallae by overall light brownish or reddish agouti instead of orange coloration, and face not framed with blackish fur; from Callicebus donacophilus by upper and outer parts of body light brownish or reddish agouti instead of buffy to orange agouti, and dominantly blackish agouti tail and cheiridia instead of buffy mixed with blackish.

van Roosmalen, G.M.; van Roosmalen, T. and  Mittermeier, R.A. (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.): 1-52.

Felton et al., 2006

Callicebus modestus

Locality: Naranjal (14º05′S, 66º56′W)

Description: Monkeys of Groups 4 –5 had a grey-brown-red agouti back and upper limbs; light red-brown forehead, sideburns and beard; well-developed white ear tufts; dark hands with sparse whitish fur; reddish under parts and chest; a greyish, uniformly coloured non-tapering tail, darker than dorsum. The fur appeared dense and frizzy. There were whitish hairs above the nose and eyebrows and on the muzzle. An examination of the holotypes suggests that Groups 4 and 5 were C. modestus.
The pelage colour of most of the individuals of Group 6 was similar to that of Groups 1–3 (C. olallae) in that they had a rufous non-agouti back and chest, creamy under-parts, and a pale throat, although they resembled Groups 4 –5 (C. modestus) by having conspicuous white ear tufts and pale hands. One distinctly coloured individual in this group appeared lighter and possibly had grey-red agouti fur on the back. All individuals of Group 6 also had a denser layer of white hairs on the face and a whitish anterior base of the tail.
Although we can be confident that we have found individuals that are representative of the two species originally classified by Lönnberg in 1939, this does not imply that we are certain of the taxonomic distinctiveness of C. modestus and C. olallae. The identification of individuals that possessed characteristics in keeping with both C. modestus and C. olallae certainly raises questions regarding their taxonomy. There is also reason to question previous views that these species are parapatric (Hershkovitz, 1988), as no rivers or watersheds separate the populations observed in this study. It is our opinion that the proximity of the original collection site for C. olallae, and the current known distribution of C. modestus, suggests that they share at least part of their respective geographic ranges. Nevertheless, further investigation is needed to establish whether these species may be genetically isolated by stretches of open grasslands. Similarly, variations in the composition and structure of vegetation across forest patches should be determined in order to assess possible differences in habitat preferences between the two. We concur with Anderson (1997) that further information is needed to determine the taxonomic distinctiveness of C. modestus and C. olallae.

Felton, A., Felton, A.M., Wallace, R.B. and Gómez, H. (2006). Identification, Behavioural Observations, and Notes on the Distribution of the Titi Monkeys Callicebus modestus Lönnberg, 1939 and Callicebus olallae, Lönnberg 1939. Primate Conservation 20: 41-46.

Martinez and Wallace, 2007

Callicebus modestus

Distribution: According to our observations, C. olallae is largely restricted to riverine habitats on the Yacuma River, although one group occurred 5 km east of the Maniqui River but in similar habitat. A partial preference for drier forest patches is noticeable for C. modestus, which occurred on the eastern and western sides of the Yacuma River. One C. modestus group occurred just 100 meters east of the Maniqui River, but this area was a higher and drier forest area. Overall, these data give preliminary support to the hypothesis that C. olallae is found in relatively humid and riverine forest in this patchily forested landscape; whereas C. modestus is found in relatively drier forest patches. We determined the Beni River as the distributional western barrier for both Bolivian endemics.
During 2005, WCS researchers recovered a titi monkey skin from a hunted individual from forest immediately adjacent to the Beni River on the western side. This specimen represents Callicebus aureipalatii, the new species recently described from the Madidi protected area and registered only on the western side of the Beni River (Wallace et al., 2006).
In June 2005, we observed C. modestus groups in forest immediately adjacent and on the eastern side of the Beni River. However, it is important to note that the C. modestus location around the San Marcos community was in a noticeably drier beltof forest than the majority of the relatively humid forest found immediately adjacent to the Beni River. Indeed, on several previous visits to the community we failed to register Callicebus in the more humid sectors of this forest. The southern and southwestern limits for the two endemics occur in two broad 10 km swaths on either side of the Yucumo – Rurrenabaque road, an area characterized by lack of primary forest and low densities of wildlife related to several human settlements. Colonists who settled in these areas almost ten years ago do not report titi monkeys. In addition, no confirmed records exist for Callicebus in the Pilón Lajas Biosphere Reserve and Indigenous Territory, and indigenous people indicate that titi monkeys are not present within the reserve. These negative reports together with areas of humid forest located to the south (as observed in satellite images) suggest that these larger blocks of more humid forest represent a southern limit for the distribution of both endemic species.
We extended the known distributional limits (Hershkovitz, 1990; Anderson, 1997) for both C. olallae and C. modestus. We found groups of C. modestus between Yacuma and Maniqui Rivers, and groups of both species in the riverine forests of the Maniqui River. Subsequently we investigated reports of the presence of C. modestus to the east of the Mamoré River (M. Herrera, pers. comm. to R. Wallace), but instead were able to verify the presence of Callicebus donacophilus at this location. Additional observations of C. donacophilus east of the Maniqui and Mamoré Rivers suggest that neither C. modestus nor C. olallae occur further east of the Maniqui River. Indeed, the San Borja region is the current known eastern distributional limit for both species.
To determine the northern limit, we extended our surveys to the relatively tall and humid Amazonian forests located south of Riberalta. Here we observed Callicebus groups that resembled species within the C. cupreus species group (van Roosmalen et al., 2002). Unfortunately, due to observation conditions, we were unable to assign species level identification to these groups. Nevertheless, we are certain that these observations do not represent either of the endemic species. We suggest that the southern limit of this more humid forest probably represents a northern boundary for C. modestus and perhaps C. olallae although further field confirmation is recommended.
In the highly fragmented forests between Santa Rosa del Yacuma and San Borja and northeast of Trinidad on the eastern side of the Mamoré River we failed to register Callicebus, and people here report not to have ever seen or heard these monkeys. Forest vegetation in these areas was very scarce and highly patchy, with relatively small and rather scattered stands of forest. In addition, forests did not have abundant canopy vines—a feature that characterized Callicebus localities in the broader southwestern Beni region.
The key result for both C. olallae and C. modestus is the extension of the eastern limit from the previously known distributional area in the Beni and Yacuma Rivers (Anderson, 1997; Felton et al., 2006). Our results also offer a preliminary northern distributional limit for both species although further work is required to establish how this limit varies for each species. Our results show that C. olallae is restricted to riverine forests along the Yacuma and Manique Rivers, whereas C. modestus seems to occupy patches of forest in a larger area between the Beni and Maniqui Rivers. We therefore suggest that C. olallae has an extremely restricted distribution with groups almost entirely concentrated on the Yacuma River, and so far just one group registered along the Maniqui River. Nevertheless, the habitat preferences of both species need further study, particularly given that both species are absent from smaller forest patches in the region.

Description: During this study, we encountered 66 groups of Callicebus at 20 localities. Of these, 14 groups were Callicebus olallae, 31 were Callicebus modestus, 16 were Callicebus donacophilus, and for five groups we were unable to assign a species identification. These new records have dramatically increased the number of observations for the endemic species. For each species, we have identified diagnostic morphological characteristics helpful to distinguish the species in field. These features relate mainly to pelage coloration patterns.
Callicebus olallae has rather long, brown reddish body pelage. Under good light conditions, a wide orange band along each hair is visible, with the tip of the hair appearing brown. The tail is more grayish but the color does not contrast strongly with the coloration of the body fur; the base of the tail is lighter both dorsally and ventrally. White ear tufts are very conspicuous. Narrow rims of black hair that reach the ears are distinguishable around the faces of some individuals. Hands and feet are black with some white hairs visible. Another important feature is the vertically elongated form of the head with a clearly prominent and oval-shaped mouth especially noticeable in adult males. Body fur color appears more intensely red when individuals are in direct sunlight.
Callicebus modestus has a non-uniform orange-brownish fur color caused by the presence of alternate bands of orange and dark brown hair, known as agouti pelage. The tail does not have the conspicuous lighter basal zone, and the grayish color of the tail is very noticeable and highly contrasting with the rest of the body fur. Conspicuous white ear tufts are present as in C. olallae. Hands and feet are also black with light hairs visible, though not as light as in C. olallae. However, this last trait is not easily distinguishable. Contrasting with C. olallae, the head of adult male C. modestus is wider laterally with a not too prominent pentagon shaped mouth area apparently due to a more prominent nasal area not observed in C. olallae. The tail appears black if exposed directly to sunlight, and appears lighter if backlit.
Direct and prolonged observations allowed us to determine critical diagnostic phenotypic traits for both C. olallae and C. modestus under a variety of lighting and weather conditions. Pelage coloration is the clearest characteristic that allows species identification in the field. For C. olallae for at least some animals we confirmed the black ring around the face originally described by Lönnberg (1939), contrasting with observations of the same species by Felton et al. (2006). The contrast between the color of the tail and body pelage is another important difference, with the basal zone conspicuously lighter in C. olallae. The longer and shaggier pelage of C. olallae was another recognizable trait. Differences in the density of white hair on the ear tufts were not considered diagnostic because observations suggested variability across phenotypes in the same groups, although this may be related to observation conditions that did not allow for the distinction of subtle features. We also noticed some distinctions in the head shape of adult males that concur with cranial measurements reported by Kobayashi (1995).

Martinez, J. and Wallace, R.B. (2007). Further Notes on the Distribution of Endemic Bolivian Titi Monkeys, Callicebus modestus and Callicebus olallae. Neotropical Primates 14(2): 47-54.

Mercado and Wallace, 2010

Callicebus modestus

Distribution: in the west of the Beni Department, limited on the eastern margin of the Beni River.

Mercado, N.I. and Wallace, R.B. (2010). Distribución de primates en Bolivia y áreas prioritarias para su conservación. Tropical Conservation Science 3 (2):200-217.

Martinez and Wallace, 2013

Callicebus modestus

Distribution: our field observations in Porvenir zone suggest that this gallery forest area may not be suitable for Callicebus due to low vine densities, and as such this zone may constitute a barrier separating C. modestus from the unidentified Callicebus species.
This survey also provides us with a more complete picture of the general distribution of the Bolivian endemic titi monkeys, Callicebus olallae and C. modestus. With no new northern localities found for these endemic primates, we can confirm the zone of El Candado community as the northern limit for C. modestus (Martínez and Wallace 2007).

Martínez, J. and Wallace, R.B. (2013). New information about the distribution of Callicebus (Pithecidae, Primates) in northern Beni Department, Bolivia. Ecología en Bolivia 48(1): 57-62.