Red howler monkey

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Suborder: Haplorrhini
Infraorder: Simiiformes
Family: Atelidae
Subfamily: Alouattinae
Genus: Alouatta
Species: A. macconnelli, A. sara, A. seniculus
Subspecies: A. seniculus arctoidea, A. seniculus juara, A. seniculus seniculus

Other names: A. sara: Bolivian red howler monkey; A. seniculus: red howler monkey, red howling monkey; rode brulaap (Dutch); hurleur roux (French); aullador amazónico, coto rojo, guariba vermelha, mono araguato (Spanish); röd vrålapa (Swedish); A. macconnelli: A. s. insulanus, Guyanan red howler, Trinidad howling monkey; A. s. juara: juruá red howling monkey; guariba vermelha (Spanish); A. s. seniculus: Colombian red howling monkey; guariba vermelha (Spanish).

Conservation status: please search the IUCN Red List.

Life span: 22 years (captive)
Total population: Unknown
Regions: Neotropical South America
Gestation: 191 days
Height: 52.3 to 57 cm (M), 46.8 to 49.7 cm (F)
Weight: 6 to 7.6 kg (M), 4.5 to 6.3 kg (F)

The taxonomy of red howler monkeys is debated. Groves (2001) lists three subspecies of A. seniculus; A. s. arctoidea, A. s. juara, and A. s. seniculus. In their taxonomic review, Rylands et al. describe seven subspecies of the type, A. s. seniculus, A. s. insulanus, A. seniculus ssp. (formerly stramineus), A. s. amazonica, A. s. juara, A. s. puruensis and A. s. arctoidea (2000). Groves subsumes A. s. amazonica and A. s. puruensis under A. s. juara. In addition, he folds both A. s. ssp. (formerly stramineus) and A. s. insulanus into A. macconnelli (Groves 2001) (for a description of the differences in taxonomy see Rylands 2001). Thus, both the Guianan and Trinidad red howler monkeys are listed here as A. macconnelli. Otherwise, Groves’ taxonomy of A. seniculus and its subspecies is followed.


Red howler monkey eating leaves
Alouatta seniculus

Red howlers are a member of the Atelinae, a subfamily of primates that includes the heaviest of the New World Monkeys (Di Fiore & Campbell 2007). (Average weights for males can range between 6 and 7.6 kg (13.2-16.8 lbs) while female weight averages range between 4.5 and 6.3 kg (9.9-13.9 lbs) in the wild (Thorington et al. 1979; Camacho & Defler 1985; Ayres JM 1986 cited in Ford & Davis 1992; Rodríguez & Boher 1988). Head and body length in adults averages 52.3 and 57.0 cm (20.6 and 22.4 in) in males and 46.8 and 49.7 cm (18.4 and 19.6 in) in females (Thorington et al. 1979; Rodríguez & Boher 1988). Sexual dimorphism of weight ranges between populations, but males are larger than females with females averaging between 69 and 95 percent of the body weight of the male (Thornington et al. 1979; Camacho & Defler 1985; Ayres 1986 cited in Smith & Jungers 1997; Rodríguez & Boher 1988; Smith & Jungers 1997). The tail is prehensile and is somewhat longer than the head and body together, averaging 65.5 cm (Thorington et al. 1979; Bergeson 1993; Richard-Hansen et al. 1999). Pelage is predominantly red, red-orange or golden red (Hill 1962; Thorington et al. 1979; Crockett pers. observ. cited in Crockett & Eisenberg 1987). Dorsal surfaces are golden red and the ventral surfaces are darker than the rest of the body, especially in the beard area, ranging from black to brown and maroon (Hill 1962; Crockett pers. observ. cited in Crockett & Eisenberg 1987). The face is blue-black with few hairs (Hill 1962). Variation in the darkness of the red pelage exists between locations and may reflect climatic variables (Thorington et al. 1979). There are no color differences between males and females (Hill 1962).

Bolivian red howlers (Alouatta sara) are brick red, with slightly darker and more reddish limbs, head and base of tail. In addition, their body size is larger than A. seniculus (Groves 2001).

One of the most characteristic features of the red howler, and indeed of the genus Alouatta as a whole, is the large hyoid bone, functioning to deepen the pitch, resonate, and amplify the species’ vocalizations (Thornington et al. 1979; Crockett & Eisenberg 1988). Among the howlers, the hyoid in the red howler is largest and there is significant sexual dimorphism in its size, with male hyoid volume averaging 69.5 ml (2.4 oz) and female hyoids averaging 12.5 ml (0.4 oz) (Sekulic 1981 cited in Crockett & Eisenberg 1987; Crockett & Eisenberg 1987).

Red howlers travel most frequently occurs on tree branches and lianas but can occur arboreally as well as terrestrially (Schön Ybarra 1984; Youlatos & Gasc 2001). The most important mode of movement is clambering, followed by quadrupedal walking and running (Youlatos & Gasc 2001). Travel is mostly slow quadrupedal progression (Fleagle & Mittermeier 1980). Bipedalism and tripedalism are infrequent compared to quadrupedalism (Schön Ybarra 1984). Gap crossing, especially in the upper canopy, is mainly by bridging, in which the monkey maintains contact with supports with at least one of its extremities or its tail at all times (Youlatos 1993; Youlatos & Gasc 2001). Leaping is rarely used to cross gaps (Fleagle & Mittermeier 1980; Schön Ybarra 1984).

One unique form of locomotion is the vertical descent in which the red howler will face the ground and walk quadrupedially down a support with the tail helping to control the descent (Youlatos & Gasc 1994). Suspensory postures are typically seen during feeding and rarely during resting, and normally consist of tail suspension. Red howlers will stand both bipedally as well as quadrupedally, and other postures include reclining and sitting (Schön Ybarra 1984). Red howlers are capable of swimming and are able to cross moving water 200 m (656.2 ft) or greater in width (Hernández-Camacho & Cooper 1976; Soini 1986; Izawa & Lozano 1990b). In addition, the species will also cross savannah and other types of open ground on foot, often during group movements (Neville 1977; Hernández-Camacho & Cooper 1976; Rudran 1979).

In captivity, red howlers have lived past 22 years old (Weigl 2005).


Alouatta macconnelli | Alouatta sara | Alouatta seniculus

Red howlers are found only in neotropical South America. They live in a number of countries including Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, Trinidad and Tobago, and Venezuela ( In general, the red howler range extends from northwest Colombia east and south to the river Amazon in eastern Brazil. In addition, they are found east of the Andes down the western coast of South America from Colombia through Peru and northern Bolivia and east into western Brazil as far as the rivers Purus and Juruá (Napier 1976; Wallace et al. 1998). Within their extensive range however, there are often many areas where they are not found, probably due to ecological factors (Iwanaga & Ferrari 2002). Subspecifically, A. s. seniculus is found in northern Colombia and northwestern Venezuela. A. s. arctoidea is found along the coast of Venezuela in the Rupununi savannah and Paramaraibo. A. s. juara is found mostly in Brazil and likely ranges into Ecuador, northern Peru, Colombia and Venezuela. A. macconnelli are found only in Trinidad and Guyana, and into Brazil north of the eastern parts of the Amazon river (Groves 2001). A. sara are found in the Bolivian Amazon (Cortés-Ortiz et al. 2003). Often there are not discrete demarcations between subspecies (see Crockett 1998a:553 for a map).


Red howlers can be found in a large variety of habitats within its range. They are found in tropical rain, humid, and dry forests, high terra firma forest, southern forests, mora forests, premontane and lower montane forests, cloud forests (including oak forests), southeast seasonal forests, swamp forests, Igapo forests (seasonally flooded blackwater forest) as well as other seasonally inundated forests, Bajos (floodable lowlands), transition forest, low seasonal forests, semi-deciduous and deciduous seasonal forests, floodplain forests, river terraces, riparian forests, swamp woodlands, eastern Wallaba forests, marsh woodlands and swamps and cacao plantations (Hernández-Camacho & Cooper 1976; Rudran 1979; Braza et al. 1981; Gaulin & Gaulin 1982; Cordero & Boher 1988; Yoneda 1990; Wallace et al. 1998; Youlatos 1998; Palacios & Rodriguez 2001; Lehman 2004).

An example of this widespread use of habitat is in Guyana, where they are found in every forest habitat type in the country (Lehman 2004). The widespread use of forest habitats is seen in Colombian red howlers as well where the species is found at high altitudes, absent only from forests near the alpine treeline (Gaulin & Gaulin 1982). While red howlers are capable of occupying a variety of forest types, in Amazonia, they do not live in habitats more than 1.6-1.8 km (1.0-1.1 mi) inland and they prefer lake and river edge habitat over terra firma forests (Peres 1993; Defler pers. comm. & Peres and Defler pers. comm. cited in Palacios 1998; Palacios 1998).

Red howler monkey climbing branch
Alouatta seniculus

Preferred feeding trees have trunks between 20 and 29 cm (7.9 and 11.4 in) in diameter (Yoneda 1990). Lower strata, including those close to the ground, are sometimes used for feeding but the species is frequently and most often found in higher forest strata. When sympatric with other primates, howlers prefer higher strata than the other species in the habitat (Soini 1986; Yoneda 1988; Peres 1993). Finally, red howlers can live in very small forest patches and secondary growth (Hernández-Camacho & Cooper 1976). The altitudinal limit of the red howler distribution is 3200 m (10498.7 ft) in the central Andes (Hernández-Camacho & Cooper 1976).

Due to its large distribution, different red howler habitats have different temperature and rainfall totals as well as differing in seasonality. In one study in the Andes at an altitude of 2300 m (7545.9 ft) in lower montane wet forest at Finca Merenberg, Colombia, temperatures were recorded to range between 8.5 and 21°C (47.3 and 69.8°F) and to average 12°C (53.6°F). At the same site, annual rainfall was 194.2 cm (76.5 in) with January as the driest month, and March the wettest (Gaulin & Gaulin 1982). At the Estación Biológica Caparú (EBC) in southeastern Colombia in the lowland tropical rain forest, rainfall averages 383.6 cm (151.0 in) yearly, with the lowest rainfall in September with 25.8 cm (10.2 in). There is no discrete dry season at this study site (Defler & Defler 1996). In northern Venezuela in the Barlovento region, mean annual temperature ranges from 25-28°C (77-82.4°F) with between 180 and 240 cm (70.9 and 94.5 in) of rain yearly. Most of the yearly rainfall occurs during the May-January rainy season at this location (Cordero & Boher 1988).


Due to its expansive range, the ecology of the red howler can vary significantly between study sites. Red howlers are, for the most part, herbivores and are predominantly frugivorous and folivorous, consuming mainly fruits and fruit pulp and leaves, supplemented by roots, flowers, epiphytes, seeds, berries, drupes, petioles, leaf buds, bark, wood, vine and liane parts and other plant material (Braza et al. 1983; Soini 1986; Neves & Rylands 1991; Julliot 1996a; de Thoisy & Richard-Hansen 1996; Palacios & Rodriguez 2001; Simmen et al. 2001). Common foods include plants from the genera Ficus, Clarisia, Xylopia, Cecropia, Ogcodeia, and Inga (Soini 1986). In general, red howlers prefer medium or large fruits with juicy pulp and that are bright in color (Julliot 1996a). Of the neotropical primates, they are likely the most folivorous as well, preferring young leaves as opposed to mature leaves (Gaulin & Gaulin 1982; Neves & Rylands 1991; Julliot 1992). The number of plant species eaten can be quite high, with as many as 195 species from 47 families being consumed although relative to usual exploitation; this number is exceptional and probably reflects high biodiversity and food availability at the study site (Julliot 1992; Julliot & Sabatier 1993). The species is also an important seed dispersal mechanism for the plants which it consumes (Andresen 2002).

Fruit availability in red howler habitat is often very seasonal and as a result, its relative importance in the diet varies throughout the year and between study sites. Thus, at some times during the year, the species can be described as predominantly folivorous while at other times they are predominantly frugivorous (for an example see Simmen et al. 2001). In Colombia at Tinigua National Park, red howler diet varies with food availability, but the two main staples are fruits and leaves which range between 10-49% and 43-76% of the diet respectively throughout the year. In the fruit scarcity period at the end of the wet season at this location, between September and November, leaves form a greater percentage of the diet than fruits. Seeds (2-8%), flowers (3-6%) and other foods (1-2%) make up the rest of the diet over the course of the year. Also at Tinigua, fruit abundance goes up during the beginning of the wet season (March-May) and during the dry season (December-February) (Stevenson et al. 2000). In Peru at the Pacaya-Samiria National Reserve, fruit availability is similar to that at Tinigua except for a general scarcity in the dry season. At this study site, feeding time was divided into fruit (72%), leaves (25%) and flowers (3%) and leaves are eaten year-round (Soini 1986). Red howler monkeys do not need to drink water and thus can live in areas away from natural water (Crockett 1998b). Red howlers have also been known to eat soil at natural saltlicks and to eat termite nest material, doing so every two or three days (Izawa & Lozano 1990a). In addition, a solitary male howler was observed catching and consuming green iguanas in French Guiana; however this is the only recorded example of predatory behavior in the species and may be unique to this one individual (de Thoisy & Parc 1999).

Red howler monkey hanging by prehensile tail on a branch
Alouatta seniculus

Red howlers, a diurnal species, show differences in daily activities between the dry and wet seasons. In Venezuela during the dry season, activities on a daily basis consisted of sleeping (37.9%), snoozing (24.0), feeding (19.8%) and locomotion (18.4%). During the rainy season, percentages of daily activities changed to sleeping (43.2%), snoozing (18.2%), feeding (23.8%), and locomotion (14.8%) (Braza et al. 1981). Elsewhere, activity rates are similar, with over half of the time spent resting with feeding and traveling making up the rest of the activities for the day (Schön Ybarra 1984; Neves & Rylands 1991). The predominance of resting activity in the red howler has been proposed to be the result of their highly folivorous diet and the difficulties associated with leaf digestion (Gaulin & Gaulin 1982). In the rainy season, more time is spent feeding than in the dry season and less time is spent resting (Sekulic 1982c). Daily during the dry season, there are two main feeding bouts–one intense bout in the morning and one in the afternoon, a pattern followed in the Andes as well (Sekulic 1982c; Gaulin & Gaulin 1982). In addition, there can be up to three or four smaller feeding bouts throughout the day. A general pattern follows of more fruit being eaten in the earlier hours of the day and more leaves later in the day (Gaulin & Gaulin 1982). Daily activities, especially feeding, often start before the sun rises but stop before nightfall (Soini 1986). Red howlers spend the night in the canopy, huddled in groups (Soini 1986).

Home range can vary between .03 and 1.82 sq. km (.01 and 0.7 sq. mi), but in most studies, ranges are at the lower end of that variance (Braza et al. 1981; Sekulic 1981; Gaulin & Gaulin 1982; Soini 1986; Izawa 1997b; Kimura 1999; Yumoto et al. 1999; Palacios & Rodriguez 2001). There is some indication that home ranges are stable (Izawa 1997b). Home ranges often have some overlap with those of other troops and thus, the species is not strictly territorial (Sekulic 1981; 1982; Izawa 1997b; Kimura 1999). Sleeping trees are located in exclusive home range areas as well as areas of overlap with the home ranges of other troops (Sekulic 1982c). Daily path averages between 980-1150 m (3215.2-3773.0 ft) per day, but can range between 340 and 2200 m (1115.5 and 7217.8 ft) (Sekulic 1981; Gaulin & Gaulin 1982; Yumoto et al. 1999; Palacios & Rodriguez 2001).

A possible instance of tool use or object manipulation was observed in which a wild male red howler was observed to hit a two-toed sloth (Choloepus didactylus) repeatedly with a stick, however the reason for this behavior is unknown (Richard-Hansen et al. 1998).

Due to its large range and extent of occurrence, the red howler is sympatric with a number of primates. These include members of the genera Callithrix, Saguinus, Saimiri, Aotus, Callicebus, Pithecia, Cacajao, Cebus, Lagothrix, and Ateles (Peres 1997b). Spider monkeys (Ateles paniscus) are displaced by red howlers when encountered in the same fruit tree (Simmen 1992). In addition, white-tailed deer (Odocoileus virginianus) will form feeding associations with red howlers by remaining below the arboreal primates and collecting otherwise inaccessible foods accidentally dropped to the forest floor by the monkeys (Agoramoorthy 1997).

Raptors are predators of red howlers. Harpy eagles (Harpia harpyja) have been observed attacking, killing, and consuming adult howlers and the species is particularly vulnerable in forest edge habitats and open forest (Eason 1989; Peres 1990; Sherman 1991). Other evidence for predators includes strong circumstantial evidence of jaguar (Panthera onca) predation on the species that was not directly observed (Peetz et al. 1992). Potential but unconfirmed predators of red howlers include pumas (Felis concolor), foxes (Cerdocyon thous), ocelots (Leopardus pardalis), spectacled caimans (Caiman crocodiles) and Boa constrictor snakes (Sekulic 1981; Crockett 1996).

Communal defecation is characteristic of red howlers although sometimes individuals will defecate alone (Andresen 2002). Usually the group will simultaneously defecate from the same tree or group of trees, a behavior that usually occurs in the morning after waking up and at midday after the resting period (Braza et al. 1981; Julliot 1986b).

Content last modified: November 26, 2007

Written by Kurt Gron. Reviewed by Carolyn Crockett.

Cite this page as:
Gron KJ. 2007 November 26. Primate Factsheets: Red howler (Alouatta seniculus) Taxonomy, Morphology, & Ecology . <>. Accessed 2020 July 14.


Troop size is variable, but a general trend follows that groups are larger in semideciduous habitats and smaller in evergreen areas. Also, group size variation at a single site over extended periods of time is comparable to that between different habitats (Crockett & Eisenberg 1988). In one thirty-year study, troop size averaged annually between 6 and 10.5 individuals but could be as small as 4 individuals and as large as 18 (Rudran & Fernandez-Duque 2003). The group sizes reported by Rudran & Fernandez-Duque approximate the range of group sizes that are found in the wild between study sites (see Crockett & Eisenberg 1988 and Chapman & Balcomb 1998 for lit reviews).

Three Red howler monkeys vocalizing
Alouatta seniculus

Group composition can be either unimale or multimale up to (rarely) 6 males. Multimale groups are usually larger than unimale groups and average 2.2 adult males however both types of groups have comparable numbers of adult females. Among the adults, there are more females than males in the population and per group there are usually 2 or 3 adult females within a range of 1 to 4 (Soini 1986; Crockett & Eisenberg 1988; Rudran & Fernandez-Duque 2003). All adult males in a group are dominant to all group females (Neville et al. 1988). There are never more than four breeding females in a group (Crockett 1996).

Within multi-male groups there is a hierarchy of males, with an alpha male dominant to the other males in the group as well as being the only male within the group that is able to reproduce (Kimura 1997; Pope 1990; Crockett 2003). The alpha male is usually physically larger than the subordinate group males and challenges of alpha male status by other males can be violent and result in injuries to one or both parties (Rudran personal communication cited in Jones 1983; Izawa 1997a; Kimura 1997). Breeding males will not leave a group voluntarily and only leave if forced by challengers (Pope personal communication cited in Jack 2003). When first established, groups are usually unimale (Crockett 1996; Rudran & Fernandez-Duque 2003).

Both sexes of red howlers emigrate from their natal troops, but in different proportions. Around 70-80% of females will breed outside of their natal group while for males the figure is 98% (Crockett 1996). If a female breeds within a group, she will remain in that group for the rest of her or the group’s life (Pope 2000). Females rarely are able to integrate into established troops and must form new troops while males are usually able to join existing troops, often by challenging resident males with another non-group male (Crockett 1984; Crockett & Pope 1993; Crockett 1996; Crockett 1998b; Pope 2000). Indeed, males are usually not able to join or invade an established group without the help of another male individual, often a relative (Pope 1990; Agoramoorthy & Rudran 1993). Over half of males disperse before or at sexual maturity (Agoramoorthy & Rudran 1993).

Solitary females are actively prevented from joining established groups by group females and as a result, non-troop females have a relatively high rate of physical injuries (Rudran 1979; Sekulic 1982a; Crockett & Pope 1988). As a result, females must emigrate farther than males to establish new groups while males are able to join existing groups, often adjacent to their natal group (Pope 2000). In addition, after emigration from the natal troop, a significant amount of time can be spent solitary (Crockett 1996). Most females emigrate from their natal group between 2-4 years old while males emigrate between 4-6 years old (Crockett & Pope 1993).

Vocalization by a howler group is common in the early mornings and serves to discourage other howlers who are not members of a group from approaching over the course of the day (Sekulic 1982c). If a different group or troop approaches over the course of the day, usually in areas of home range overlap, males will coalesce and begin roaring, joined soon after by the group females (Sekulic 1982d; Crockett 1998b). Both groups will then face one another for a time and roar, but not chase, for a time and then begin to rest (Sekulic 1982d).

Rates of allogrooming vary widely between groups and individuals. Allogrooming is infrequent and of short duration and primarily serves social purposes (Sánchez-Villagra et al. 1998).

Rates of physical injuries resulting from aggression among red howlers is high, with over a third of individuals in one study population exhibiting scars and physical injuries from encounters with other red howlers (Crockett & Pope 1988). However, rates of actual aggressive behaviors are quite low, even if they can be quite violent when they do occur (Crockett 1984). Agonistic conflicts between males most often elicit piloerection, throat-rubbing, growling and roaring from those involved (Sekulic 1982d).


Red howlers are best described as having a single or multi-male polygynous breeding system in which in the multi-male troops, the dominant male has almost exclusive breeding access to troop females (Crockett & Rudran 1987b; Pope 1990; Kimura 1992). However, following infanticide and male status changes within a troop, females will mate with several males (Crockett 2003). In addition, extra-group copulations have been observed in which females mate with the dominant male of a neighboring group in addition to the dominant male of their group (Agoramoorthy & Hsu 1999). Often, females must emigrate from their natal groups because of competition between females for breeding position. In fact, only around 20% of females will breed in their natal groups and the others emigrate, either to found new troops, join existing troops, or simply disappear (Crockett 1998b). Females may emigrate because larger female group size may be attractive to infanticidal males (Crockett and Janson 2000).

Solicitation and copulatory behavior can consist of tongue-flicking, genital-sniffing and inspection, and genital and body licking (Izawa & Lozano 1989; Agoramoorthy & Hsu 1999). Copulation is short in duration, and the male mounts the female from behind, as if covering her (Izawa & Lozano 1989). In one study, copulations within a group were common, and occurred on average once every three hours (Sekulic 1982a).

Two red howler monkeys perched on a branch
Alouatta seniculus

Red howler monkeys do not breed in a strictly seasonal fashion; however there are consistent, annual dips and peaks in births. In semi-deciduous habitats in Venezuela, a reduction but not cessation in births is seen early in the wet season and among troops a synchrony of births is sometimes observed (Crockett & Rudran 1987a). Similarly, in evergreen tropical forests in Peru, breeding occurs year-round but with fewer births in June-September and most between October and April (Soini 1986).

Females first give birth at around 4 or 5 years of age while males usually do not father offspring until they are around 7 (Crockett & Rudran unpub cited in Crockett & Eisenberg 1987; Crockett 1998b). Average gestation length in wild red howler monkeys is 191 days (6.3 months) (with an inter-birth interval after a surviving infant of an average of 517.1 days (17.0 months) (Crockett & Sekulic 1982; Crockett & Rudran 1987b). Based on hormonal studies, estrous cycle length is estimated at 29.5 days (.97 months) (Herrick et al. 2000). Estrous is sometimes externally visible in females, although the indications are often only slight and unreliable in addition to being variable between individuals (Crockett & Sekulic 1982; Sekulic 1982a).


Births in red howlers occur at night and during the day and usually it takes only one or two minutes for the mother to give birth. Shortly after parturition, the mother will consume the placenta (Sekulic 1982b). The newborn infant is tiny, and is born with eyes closed and pale hair (Izawa 1997a). In general, group females both adult and immature spend a lot of time near infants, and dominant males spend more time than other group males near new mothers and their infants than other group males (Sekulic 1983b).

Adoption is documented in the species with wild kin, group and non-group females having adopted abandoned infants or the infants of others, and in some cases nursing and raising them until weaning (Izawa 1989; Agoramoorthy & Rudran 1992).

One of the most marked features of red howler ecology is the prevalence of infanticide by males which significantly raises infant mortality in the species. Infanticide occurs in two contexts in the red howler, during invasions of a group by external males and during breeding status changes among resident males (Crockett & Sekulic 1984; Agoramoorthy & Rudran 1995). Infanticide in this and other howler species is proposed to be the result of sexual selection and shortens the inter-birth interval of a female (Crockett 2003). According to Crockett (2003), there is less evidence supporting the hypothesis that infanticide is related to food competition within a group (Agoramoorthy & Rudran 1995). Often, females attempt to resist infanticide but are not usually successful. After the death of an infant, a female will usually conceive 1-3 months later and solicit copulations as soon as one week after the death of a previous infant (Crockett & Sekulic 1984; Agoramoorthhy & Rudran 1995). In one study, overall mortality was about 20% in the first year and more than 44% of infant mortality was attributable to infanticide (Crockett & Rudran 1987a).

Red howler mothers overall give the impression of only vague or passive interest in their infants however they will groom them and actively defend them from threats (Neville 1972b). For the first month after birth, the infant is carried ventrally by the mother, after which, it will ride on the mother’s back (Mack 1979; Soini 1986). During both ventral and dorsal carrying, the infant will wrap its tail around the base of the mother’s tail (Mack 1979; Izawa & Lozano 1992). During group movement until the fourth month, ventral carrying occasionally is still used. Up to four months old, the infant remains within 2 meters (6.6 ft) of the mother but in the fifth and six months, more time is spent away from the mother. During the fifth and six months, the occurrence of carrying is limited to nursing and travel and by the seventh through ninth month; the infant is carried less than a quarter of the time (Mack 1979). In the second month, quadrupedal movement and use of the prehensile tail is first seen and by month four, adult locomotion is attained and the infants will move about on their own (Mack 1979; Soini 1986). Independence, but not weaning, occurs between seven or eight months of age (Izawa & Lozano 1992). Males either never or rarely carry infants (Mack 1979; Soini 1986). Play with adults is also rare and usually occurs between the infant and other infants or juveniles. However, in general, group members, especially females, are very interested in the infant and spend a lot of time near them (Mack 1979; Sekulic 1983b). Most weaning occurs between 10.5 and 14 months (Crockett & Pope 1993). Nursing can persist into the 17th or 18th month of age, especially while resting (Mack 1979).


Red howler monkey howling
Alouatta seniculus

Vocal communication in howler monkeys is highlighted by its loud calls, the “roars” or “howls” from which the genus gains its common name (Drubbel & Gautier 1993). The loud calls are amplified by a large hyoid that resonates vocalizations as part of a specialized vocal apparatus that allows the species to produce single roar emissions for as long as 8 seconds (Sekulic & Chivers 1986; Schön Ybarra 1988). Loud calls have been classified into two general types by different researchers, either “barks” and “roars” or “short” and “long” calls (Schön Ybarra 1986; Drubbel & Gautier 1993). “Barks” are typically short, harsh, and low-pitched vocalizations, often uttered in syllables or rhythms. “Roars” are very loud, low-pitched, long calls which are uttered together with other group members and can be heard up to a kilometer away (Schön Ybarra 1986). While roaring mostly occurs in the morning (timing highly variable, but as early as 169 minutes before dawn), it also occurs during the night and over the course of the day as well (Schön Ybarra 1986; Sekulic 1981; 1982c; 1983a; Sekulic & Chivers 1986). Roaring is usually heard in encounters with non-group individuals, especially when they are visible, and may repel males from other troops that might try to enter the group (Sekulic 1981; 1982d). In addition, roaring is heard in intra-group situations as well (Sekulic 1982d). Experimental evidence hints that female howling serves to incite male competition (Sekulic 1983a). Soft growlings are heard during feeding and play (Crockett pers. comm.)

Except for howling, the species is surprisingly silent, but the species does have a canon of other vocalizations (Defler 2004). Aggressive vocalizations include the “incipient roar”, the “roar accompaniment” and the “oodel.” The “male woof”, “female woof” or “bark”, “incipient woof”and the “whimper” are heard when disturbed. Infant vocalizations are the “eh”, the “squeeking hinge”, the “infant bark”, and the “purr” (Defler 2004). Other vocalizations include the “nGot”, heard before howling in a threatening sense and the “ngut”, a tense vocalization (Izawa 1997a).

Throat-rubbing has been observed in wild red howlers. This is apparently scent-marking and is usually performed on a large branch or tree trunk in which the animal moves its throat back and forth for several minutes. Male red howler monkeys throat-rub at higher rates than females and in most cases, the behavior is associated with hostility with other red howlers and sometimes is accompanied by howling and piloerection (Sekulic & Eisenberg 1983). There are throat glands in both sexes which points to a scent-marking role in muzzle and chin rubbing (Epple & Lorenz 1967 cited in Neville et al. 1988). Other marking activities include the rubbing of the anus on a branch after defecation, the rubbing of the muzzle and the beard on branches, back rubbing, and communal defecation (Braza et al. 1981; Defler 2004).

Red howlers use several visual signals. Sexual signals are tongue flicking and lip smacking. Aggressive and agonistic signals are back-arching, lip-pursing, and genital displays. When alarmed, they will branch-shake and yawn. To show submission, red howlers crouch (Defler 2004).

Content last modified: November 26, 2007

Written by Kurt Gron. Reviewed by Carolyn Crockett.

Cite this page as:
Gron KJ. 2007 November 26. Primate Factsheets: Red howler (Alouatta seniculus) Behavior . <>. Accessed 2020 July 14.


For individual primate species conservation status, please search the IUCN Red List.
Also search the current scientific literature for primate conservation status (overall as well as for individual species), and visit CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora).

Conservation information last updated in 2007 follows, for comparison:

Red howler monkey perched on a branch
Alouatta seniculus

Red howler monkeys are adaptable and are capable of living in small patches of forest (Phillips & Abercrombie 2003). A population can live in 1 sq. km (0.4 sq. mi) forest fragments, one group can survive in a 0.1 sq. km (.04 sq. mi) fragment and a 0.01 sq. km (.004 sq. mi) forest fragment can possibly support red howlers if they are able to alter their ecology somewhat (Gilbert 2003). In addition, because of their ability to disperse, they are resilient in areas where other primates have disappeared from a particular habitat (Hernández-Camacho & Cooper 1976; Defler 2004).


Threat: Human-Induced Habitat Loss and Degradation

The most pressing threat to the red howler, like other primates is habitat destruction (Defler 2004). Because seasonally flooded forests are inhabited by red howlers, they have the potential to be adversely affected by both the damming of rivers as well as logging along the edges of rivers (Ayres 1982).

In Trinidad, where A. macconnelli populations are considered vulnerable by the IUCN Red List, the main threats to the habitats of the species are illegal logging, forest clearance for agriculture and destruction resulting from oil exploration (Hsu & Agoramoorthy 1996).

The building of hydroelectric dams can also profoundly alter red howler habitat. In one case of a dam in Venezuela, howlers formerly inhabiting both sides of a river are now restricted to islands in a catchment lake for the dam resulting in their isolation from other populations and the disappearance of some groups (Norconk 1997).

Threat: Harvesting (hunting/gathering)

Howler monkeys are one of the most widely hunted primate taxa in the neotropics and are choice prey items even in areas which are only marginally under hunting pressure (Peres 2000). However, the degree of hunting of red howlers is variable between locations (Hernández-Camacho & Cooper 1976; Defler 2004). In habitats in the western Brazilian Amazonian seasonally flooded forests, red howlers are a preferred subsistence prey during high water, because fishing is precluded by the floods (Peres 1997a).

In Trinidad, hunting is a significant threat to red howlers even though it is illegal. In areas around wildlife sanctuaries on the island, up to 85% of individuals interviewed admitted to eating or hunting monkeys for meat (Hsu & Agoramoorthy 1996).

In Colombia, red howlers are also sometimes killed and taken for their enlarged hyoid, which is used as a drinking vessel to treat goiters. A minor hunting threat to the red howler is killing for its skin, but this occurs only occasionally (Hernández-Camacho & Cooper 1976).

Threat: Pollution

Oil pollution has the potential to threaten red howler populations on Trinidad, as pipelines and allocation wells leak into the local water supply. Large mammals drink from the water supply and thus red howlers might potentially affected by such leaks (Hsu & Agoramoorthy 1996).

Threat: Intrinsic Factors

Red howlers are susceptible to a number of intestinal parasites, including those of the genera Strongyloides, Trichuris, Chilomastix, Blastocystis and Iodamoeba which have the potential to cause parasitic infections and potentially represent a threat to members of the species (Phillips et al. 2004). They are also susceptible to a number of other maladies in their natural habitat (de Thoisy et al. 2001).




Content last modified: November 26, 2007

Written by Kurt Gron. Reviewed by Carolyn Crockett.

Cite this page as:
Gron KJ. 2007 November 26. Primate Factsheets: Red howler (Alouatta seniculus) Conservation . <>. Accessed 2020 July 14.

The following references were used in the writing of this factsheet. To find current references for Alouatta seniculus, search PrimateLit.


Agoramoorthy G, Rudran R. 1992. Adoption in free-ranging red howler monkeys, Alouatta seniculus of Venezuela. Primates 33(4):551-5.

Agoramoorthy G. 1997. Apparent feeding associations between Alouatta seniculus and Odocoileus virginianus in Venezuela. Mammalia 61(2):271-3.

Agoramoorthy G, Hsu MJ. 1999. Extragroup copulation among wild red howler monkeys in Venezuela. Folia Primatol 71(3):147-51.

Red howler monkey artwork
Alouatta seniculus

Agoramoorthy G, Rudran R. 1995. Infanticide by adult and subadult males in free-ranging red howler monkeys, Alouatta seniculus, in Venezuela. Ethology 99(1):75-88.

Agoramoorthy G, Rudran R. 1993. Male dispersal among free-ranging red howler monkeys (Alouatta seniculus) in Venezuela. Folia Primatol 61(2):92-6.

Andresen E. 2002. Primary seed dispersal by red howler monkeys and the effect of defecation patterns on the fate of dispersed seeds. Biotropica 34(2):261-72.

Ayres JM. 1982. Conservation of primates in Brazilian Amazonia: problems and strategies. In: Harper D, editor. Conservation of primates and their habitats. Leicester (UK): U Leicester. p2-33.

Ayres JM. 1986. Uakaris and Amazonian flooded forest. PhD dissertation, University of Cambridge, Cambridge (UK).

Bergeson D. 1993. Preliminary data on prehensile tail use in two cebid species. AAZPA Reg Conf Proceed 1993:753-9.

Braza F, Alvarez F, Azcarate T. 1981. Behaviour of the red howler monkey (Alouatta seniculus) in the llanos of Venezuela. Primates 22(4):459-73.

Braza F, Alvarez F, Azcarate T. 1983. Feeding habits of the red howler monkeys (Alouatta seniculus) in the llanos of Venezuela. Mammalia 47(2):205-14.

Camacho JH, Defler TR. 1985. Some aspects of the conservation of non-human primates in Colombia. Prim Conserv 6:42-50.

Chapman CA, Balcomb SR. 1998. Population characteristics of howlers: ecological conditions or group history. Intl J Primatol 19(3):385-403.

Cordero Rodríguez GAC, Boher BS. 1988. Notes on the biology of Cebus nigrivittatus and Alouatta seniculus in northern Venezuela. Prim Conserv 9:61-5.

Cortés-Ortiz L, Bermingham E, Rico C, Rodríguez-Luna E, Sampaio I, Ruiz-García M. 2003. Molecular systematics and biogeography of the neotropical monkey genus, Alouatta. Mol Phylog Evol 26:64-81.

Crockett CM, Pope TR. 1993. Consequences of sex differences in dispersal for juvenile red howler monkeys. In: Pereira ME, Fairbanks LA, editors. Juvenile primates: life history, development, and behavior. New York: Oxford U Pr. p104-18.

Crockett CM. 1998a. Conservation biology of the genus Alouatta. Int J Primatol 19(3): 549-78.

Crockett CM. 1984. Emigration by female red howler monkeys and the case for female competition. In: Small, MF, editor. Female primates: studies by women primatologists. New York: Alan R. Liss. p159-73.

Crockett CM. 1998b. Family feuds. In: Ciochon RL, Nisbett RA, editors. The primate anthology: essays on primate behavior, ecology, and conservation from Natural History. Upper Saddle River(NJ): Prentice Hall. p28-35.

Crockett CM, Sekulic R. 1982. Gestation length in red howler monkeys. Am J Primatol 3(1-4):291-4.

Crockett CM, Eisenberg JF. 1987. Howlers: variations in group size and demography. In: Smuts BB, Cheney DL, Seyfarth RM, Wrangham RW, Struhsaker TT, editors. Primate societies. Chicago: U Chicago Pr. p54-68.

Crockett CM, Sekulic R. 1984. Infanticide in red howler monkeys (Alouatta seniculus). In: Hausfater G, Hrdy SB, editors. Infanticide: comparative and evolutionary perspectives. New York: Aldine Pub Co. p173-91.

Crockett CM, Janson CH. 2000. Infanticide in red howlers: female group size, male membership, and a possible link to folivory. In: van Schaik CP, Janson CH, editors. Infanticide by males and its implications. Cambridge (UK): Cambridge U Pr. p75-98.

Crockett CM, Pope T. 1988. Inferring patterns of aggression from red howler monkey injuries. Am J Primatol 15(4):289-308.

Crockett CM, Rudran R. 1987a. Red howler monkey birth data I: seasonal variation. Am J Primatol 13(4):347-68.

Crockett CM, Rudran R. 1987b. Red howler monkey birth data II: interannual, habitat, and sex comparisons. Am J Primatol 13(4):369-84.

Crockett CM. 2003. Re-evaluating the sexual selection hypothesis for infanticide by Alouatta males. In: Jones CB, editor. Sexual selection and reproductive competition in primates: new perspectives and directions. Norman(OK): Am Soc Primatol. p327-65.

Crockett CM. 1996. The relation between red howler monkey (Alouatta seniculus) troop size and population growth in two habitats. In: Norconk MA, Rosenberger AL, Garber PA, editors. Adaptive radiations of neotropical primates. New York: Plenum Pr. p489-510.

Defler TR, Defler SB. 1996. Diet of a group of Lagothrix lagothricha lagothricha in southeastern Colombia. Intl J Primatol 17(2):161-90.

Defler TR. 2004. Primates of Colombia. Bogotá: Cons Intl. 550 p.

Di Fiore A, Campbell CJ. 2007. The Atelines: variation in ecology, behavior, and social organization. In: Campbell CJ, Fuentes A, MacKinnon KC, Panger M, Bearder SK, editors. Primates in perspective. New York: Oxford U Pr. p 155-85.

Drubbel RV, Gautier J-P. 1993. On the occurrence of nocturnal and diurnal loud calls, differing in structure and duration, in red howlers (Alouatta seniculus) of French Guyana. Folia Primatol 60(4):195-209.

Eason P. 1989. Harpy eagle attempts predation on adult howler monkey. Condor 91(2):469-70.

Epple G, Lorenz R. 1967. Vorkommen, morphologie und function der sternaldrüsse bei den Platyrrhini. Folia Primatol 7:98-126.

Fleagle JG, Mittermeier RA. 1980. Locomotor behavior, body size, and comparative ecology of seven Surinam monkeys. Am J Phys Anth 52:301-14.

Ford SM, Davis LC. 1992. Systematics and body size: implications for feeding adaptations in new world monkeys. Am J Phys Anth 88(4):415-468.

Gaulin SJC, Gaulin CK. 1982. Behavioral ecology of Alouatta seniculus in Andean cloud forest. Intl J Primatol 3(1):1-32.

Gilbert KA. 2003. Primates and fragmentation of the Amazon forest. In: Marsh LK, editor. Primates in fragments: ecology in conservation. New York: Kluwer Acad/ Plenum Pub p145-57.

Groves C. 2001. Primate taxonomy. Washington DC: Smithsonian Inst Pr. 350p.

Hernández-Camacho J, Cooper RW. 1976. The nonhuman primates of Colombia. In: Thorington Jr RW, Heltne PG, editors. Neotropical primates: field studies and conservation. Washington, D.C.: Nat Acad Sci p35-69.

Herrick JR, Agoramoorthy G, Rudran R, Harder JD. 2000. Urinary progesterone in free-ranging red howler monkeys (Alouatta seniculus): preliminary observation of the estrous cycle and gestation. Am J Primatol 51(4):257-63.

Hill WCO. 1962. Primates: comparative anatomy and taxonomy. V. Cebidae, Part B, a monograph. Edinburgh (UK): Edinburgh U Pr. 537p.

Iwanaga S, Ferrari SF. 2002. Geographic distribution of red howlers (Alouatta seniculus) in southwestern Brazilian Amazonia, with notes on Alouatta caraya. Intl J Primatol 23(6):1245-56.

Izawa K. 1989. The adoption of an infant observed in a wild group of red howler monkeys (Alouatta seniculus). Field Stud New World Monk, La Macarena, Colombia 2:33-6.

Izawa K, Lozano MH. 1990a. Frequency of soil-eating by a group of wild howler monkeys (Alouatta seniculus) in La Macarena, Colombia. Field Stud New World Monk, La Macarena, Colombia 4:47-56.

Izawa K, Lozano MH. 1990b. River crossing by a wild howler monkey (Alouatta seniculus). Field Stud New World Monk, La Macarena, Colombia 3:29-33.

Izawa K, Lozano MH. 1992. Social changes within a group of red howler monkeys (Alouatta seniculus), IV. Field Stud New World Monk, La Macarena, Colombia 7:15-27.

Izawa K. 1997a. Social changes within a group of red howler monkeys, VI. Field Stud Fauna Flora, La Macarena, Colombia 11:19-34.

Izawa K, Lozano MH. 1989. Social changes within a group and reproduction of wild howler monkeys (Alouatta seniculus) in Colombia. Field Stud New World Monk, La Macarena, Colombia 2:1-6.

Izawa K. 1997b. Stability of the home range of red howler monkeys. Field Stud Fauna Flora, La Macarena, Colombia 11:41-6.

Jack K. 2003. Males on the move: evolutionary explanations of secondary dispersal by male primates. Prim Rep 67:61-83.

Jones CB. 1983. Social organization of captive black howler monkeys (Alouatta caraya): “social competition” and the use of non-damaging behavior. Primates 24(1):25-39.

Julliot C. 1992. Diet diversity and habitat of howler monkeys. In:Thierry B, Anderson JR, Roeder JJ, Herrenschmidt N, editors. Current Primatology, Volume I: ecology and evolution. Strasbourg (FR): Univ Louis Pasteur. p67-78.

Julliot C, Sabatier D. 1993. Diet of the red howler monkey (Alouatta seniculus) in French Guiana. Intl J Primatol 14(4):527-50.

Julliot C. 1996a. Fruit choice by red howler monkeys (Alouatta seniculus) in a tropical rain forest. Am J Primatol 40(3):261-82.

Julliot C. 1996b. Seed dispersal by red howling monkeys (Alouatta seniculus) in the tropical rain forest of French Guiana. Intl J Primatol 17(2):239-258.

Kimura K. 1992. Demographic approach to the social group of wild red howler monkeys (Alouatta seniculus). Field Stud New World Monk, La Macarena, Colombia 7:29-34.

Kimura K. 1999. Home ranges and inter-group relations among the wild red howler monkeys. Field Stud Fauna Flora, La Macarena, Colombia. 13:19-24.

Kimura K. 1997. Males’ life history and their social relations of wild red howler monkeys. Field Stud Fauna Flora, La Macarena, Colombia 11:35-40.

Lehman SM. 2004. Biogeography of the primates of Guyana: effects of habitat use and diet on geographic distribution. Intl J Primatol 25(6):1225-42.

Mack D. 1979. Growth and development of infant red howling monkeys (Alouatta seniculus) in a free ranging population. In: Eisenberg JF, editor. Vertebrate ecology in the northern neotropics. Washington D.C.: Smithsonian Inst Pr. p127-36.

Napier PH. 1976. Catalogue of primates in the British museum (natural history). Part I: families callitrichidae and cebidae. London: British Museum (Natural History). 121 p.

Neville MK. 1972a. The population structure of red howler monkeys (Alouatta seniculus) in Trinidad and Venezuela. Folia Primatol 17:56-86.

Neville MK. 1972b. Social relations within troops of red howler monkeys (Alouatta seniculus). Folia Primatol 18:47-77.

Neves AMS, Rylands AB. 1991. Diet of a group of howling monkeys, Alouatta seniculus, in an isolated forest patch in central Amazonia. A Primatol no Brasil 3:263-74.

Neville MK, Glander KE, Braza F, Rylands AB. 1988. The howling monkeys, genus Alouatta. In: Mittermeier RA, Rylands AB, Coimbra-Filho A, Fonseca GAB, editors. Ecology and behavior of neotropical primates: volume 2. Washington D.C.:WWF. p349-453.

Norconk MA. 1997. Primate conservation in the wake of a hydroelectric plant. AZA Reg Conf Proc (1997):570-6.

Palacios E. 1998. Ecological bases for lake- and river-side habitat use of Alouatta seniculus in Colombian Amazonia. ASP Bull 22(3):8.

Palacios E, Rodriguez A. 2001. Ranging pattern and use of space in a group of red howler monkeys (Alouatta seniculus) in a southeastern Colombian rainforest. Am J Primatol 55(4):233-51.

Peetz A, Norconk MA, Kinzey WG. 1992. Predation by jaguar on howler monkeys (Alouatta seniculus) in Venezuela. Am J Primatol 28:223-8.

Peres CA. 2000. Evaluating the impact and sustainability of subsistence hunting at multiple Amazonian forest sites. In: Robinson JG, Bennett EL, editors. Hunting for sustainability in tropical forests. New York: Colombia U Pr. p31-54.

Peres CA. 1990. A harpy eagle successfully captures an adult male red howler monkey. Wilson Bull 102(3):560-1.

Peres CA. 1997a. Effects of habitat quality and hunting pressure on arboreal folivore densities in neotropical forests: a case study of howler monkeys (Alouatta spp.). Folia Primatol 68(3-5):199-222.

Peres CA. 1997b. Primate community structure at twenty western Amazonian flooded and unflooded forests. J Trop Ecol 13(3):381-405.

Peres CA. 1993. Structure and spatial organization of an Amazonian terra firme forest primate community. J Trop Ecol 9(3):259-76.

Phillips KA, Abercrombie CL. 2003. Distribution and conservation status of the primates of Trinidad. Prim Conserv 19:19-22.

Phillips KA, Haas ME, Grafton BW, Yrivarren M. 2004. Survey of the gastrointestinal parasites of the primate community at Tambopata National Reserve, Peru. J Zool Lond 264(2):149-51.

Pope TR. 2000. The evolution of male philopatry in neotropical monkeys. In: Kappeler PM, editor. Primate males: causes and consequences of variation in group composition. Cambridge (UK): Cambridge U Pr. p219-35.

Pope TR. 1990. The reproductive consequences of male cooperation in the red howler monkey: paternity exclusion in multi-male and single-male troops using genetic markers. Behav Ecol Sociobiol 27(6):439-46.

Richard-Hansen C, Vié J-C, Vidal N, Kéravec J. 1999. Body measurements on 40 species of mammals from French Guiana. J Zool Lond 247(4):419-28.

Richard-Hansen, Bello N, Vié J-C. 1998. Tool use by a red howler monkey (Alouatta seniculus) towards a two-toed sloth (Choloepus didactylus). Primates 39(4):545-8.

Rudran R, Fernandez-Duque E. 2003. Demographic changes over thirty years in a red howler population in Venezuela. Intl J Primatol 24(5):925-47.

Rudran R. 1979. The demography and social mobility of a red howler (Alouatta seniculus) population in Venezuela. In: Eisenberg JF, editor. Vertebrate ecology in the northern neotropics. Washington D.C.: Smithsonian Inst Pr. p107-26.

Rylands AB, Schneider H, Langguth A, Mittermeier RA, Groves CP, Rodríguez-Luna E. 2000. An assessment of the diversity of new world primates. Neotrop Prim 8(2):61-93.

Rylands AB. 2001. Two taxonomies of the new world primates-a comparison of Rylands et al. (2000) and Groves (2001). Neotrop Prim 9(3):121-4.

Sánchez-Villagra MR, Pope TR, Salas V. 1998. Relation of intergroup variation in allogrooming to group social structure and ecoparasite loads in red howler (Alouatta seniculus). Intl J Primatol 19(3):473-91.

Schön Ybarra MA. 1984. Locomotion and postures of red howlers in a deciduous forest-savanna interface. Am J Phys Anth 63(1):65-76.

Schön Ybarra MA. 1986. Loud calls of adult male red howling monkeys (Alouatta seniculus). Folia Primatol 47(4):204-16.

Schön Ybrra MA. 1988. Morphological adaptations for loud phonations in the vocal organ of howling monkeys. Prim Rep 22:19-24.

Sekulic R. 1982a. Behavior and ranging patterns of a solitary female red howler (Alouatta seniculus). Folia Primatol 38(3-4):217-32.

Sekulic R. 1982b. Birth in free-ranging howler monkeys Alouatta seniculus. Primates 23(4):580-2.

Sekulic R. 1982c. Daily and seasonal patterns of roaring and spacing in four red howler Alouatta seniculus troops. Folia Primatol 39(1-2):22-48.

Sekulic R. 1982d. The function of howling in red howler monkeys (Alouatta seniculus). Behaviour 81(1):38-54.

Sekulic R, Chivers DJ. 1986. The significance of call duration in howler monkeys. Intl J Primatol 7(2):183-90.

Sekulic R. 1981. The significance of howling in the red howler monkey (Alouatta seniculus). PhD dissertation, University of Maryland, College Park, MD.

Sekulic R. 1983a. The effect of female call on male howling in red howler monkeys (Alouatta seniculus). Intl J Primatol 4(3):291-305.

Sekulic R. 1983b. Spatial relationships between recent mothers and other troop members in red howler monkeys (Alouatta seniculus). Primates 24(4): 475-85.

Sekulic R, Eisenberg JF. 1983. Throat-rubbing in red howler monkeys (Alouatta seniculus). In: Müller-Schwarze D, Silverstein RM, editors. Chemical signals in vertebrates 3. New York: Plenum Pr. p347-50.

Sherman PT. 1991. Harpy eagle predation on a red howler monkey. Folia Primatol 56(1):53-6.

Simmen B. 1992. Competitive utilization of Bagassa fruits by sympatric howler and spider monkeys. Folia Primatol 58(3):155-60.

Simmen B, Julliot C, Bayart F, Pagès-Feuillade E. 2001. Diet and population densities of the primate community in relation to fruit supplies. In: Bongers F, Charles-Dominique P, Forget P-M, Théry, editors. Nouragues: dynamics and plant-animal interactions in a neotropical rainforest. Dordrecht (NL): Kluwer Acad Pub. p89-101.

Smith RJ, Jungers WL. 1997. Body mass in comparative primatology. J Hum Evol 32(6):523-59.

Soini P. 1986. A synecological study of a primate community in the Pacaya-Samiria national reserve, Peru. Prim Conserv 7:63-71.

Stevenson PR, Quiñones MJ, Ahumada JA. 2000. Influence of fruit availability on ecological overlap among four neotropical primates at Tinigua national park, Colombia. Biotropica 32(3):533-44.

de Thoisy, Richard-Hansen C. 1996. Diet and social behaviour changes in a red howler monkey (Alouatta seniculus) troop in a highly degraded rain forest. Folia Primatol 68(6):357-61.

de Thoisy B, Vogel I, Reynes J-M, Pouliquen J-F, Carme B, Kazanji M, Vié J-C. 2001. Health evaluation of translocated free-ranging primates in French Guiana. Am J Primatol 54(1):1-16.

de Thoisy B, Parc T. 1999. Predatory behaviour by a red howler monkey (Alouatta seniculus) on green iguanas (Iguana iguana). Neotrop Prim 7(2):46-7.

Thorington Jr. RW, Rudran R, Mack D. 1979. Sexual dimorphism of Alouatta seniculus and observations of capture techniques. In: Eisenberg JF, editor. Vertebrate ecology in the northern neotropics. Washington D.C.: Smithsonian Inst Pr. p97-106.

Wallace RB, Painter RLE, Taber AB. 1998. Primate diversity, habitat preferences, and population density estimates in Noel Kempff Mercado national park, Santa Cruz department, Bolivia. Am J Primatol 46(3):197-211.

Weigl R. 2005. Longevity of mammals in captivity; from the living collections of the world. Stuttgart (DE): E. Schweizerbartsche. 214p.

Yoneda M. 1990. The difference of tree size used by five cebid monkeys in Macarena Colombia. Field Stud New World Monk, La Macarena, Colombia 3:13-18.

Yoneda M. 1988. Habitat utilization of six species of monkeys in Rio Duda, Colombia. Field Stud New World Monk, La Macarena, Colombia 1:39-45.

Youlatos D, Gasc JP. 2001. Comparative positional behaviour of five primates. In: Bongers F, Charles-Dominique P, Forget P-M, Théry, editors. Nouragues: dynamics and plant-animal interactions in a neotropical rainforest. Dordrecht (NL): Kluwer Acad Pub. p103-14.

Youlatos D. 1993. Passages within a discontinuous canopy: bridging in the red howler monkey (Alouatta seniculus). Folia Primatol 61(3):144-7.

Youlatos D, Gasc JP. 1994. A preliminary study of head-first descent of lianas in the red howler monkey, Alouatta seniculus, in a primary rain forest in French Guiana. In: Thierry B, Anderson JR, Roeder JJ, Herrenschmidt N, editors. Current Primatology, Vol. I: ecology and evolution. Strasbourg (FR): Univ Louis Pasteur. p203-10.

Youlatos D. 1998. Seasonal variation in the positional behavior of red howling monkeys (Alouatta seniculus). Primates 39(4):449-57.

Yumoto T, Kimura K, Nishimura A. 1999. Estimation of the retention times and distances of seed dispersed by two monkey species, Alouatta seniculus and Lagothrix lagothricha, in a Colombian forest. Ecol Res 14(2):179-91.

Content last modified: November 26, 2007


Alouatta seniculus
Photo: Luiz Claudio Marigo
Alouatta seniculus
Photo: Luiz Claudio Marigo
Alouatta seniculus
Photo: Luiz Claudio Marigo
Alouatta seniculus
Photo: Primates in Art & Illustration Collection
Alouatta seniculus
Photo: Roy Fontaine
Alouatta seniculus
Photo: Roy Fontaine
Alouatta seniculus
Photo: Roy Fontaine
Alouatta seniculus
Photo: Roy Fontaine
Alouatta seniculus
Photo: Roy Fontaine
Alouatta seniculus
Photo: Roy Fontaine
Alouatta seniculus
Photo: Roy Fontaine

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