|Scientific Name:||Alouatta arctoidea Cabrera, 1940|
|Taxonomic Notes:||Hill (1962) and Stanyon et al. (1995) listed nine subspecies of the red howler monkey, Alouatta seniculus: A. s. seniculus, A. s. arctoidea, A. s. stramineus, A. s. macconnelli, A. s. insulanus, A. s. amazonica, A. s. juara, A. s. puruensis, A. s. sara.
Alouatta s. arctoidea is here recognized as a full species because Stanyon et al. (1995) concluded that the number of chromosomal differences between A. s. sara and A. s. arctoidea (which resulted in A. s. sara being a considered a full species) was on a similar scale to that found between A. s. sara and A. s. seniculus by Minezawa et al. (1986). Groves (2001, 2005) nevertheless maintains it as a subspecies of A. seniculus.
An undescribed subspecies of A. seniculus north of the Río Orinoco was reported by Bodini and Pérez-Hernández (1987). It may, however, be Mycetes auratus Gray, 1845 and M. laniger Gray, 1845, both from the Orinoco.
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Urbani, B., Boubli, J.-P. & Rylands, A.B.|
|Reviewer(s):||Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)|
This species is listed as Least Concern given its relatively large distribution and lack of any major threats driving a significant range-wide decline.
|Range Description:||Alouatta arctoidea is endemic to Venezuela. Its range, following Hill (1962) and Bodini and Pérez-Hernández (1987), is along the Venezuelan coast, east of Lake Maracaibo from Falcón to the state of Miranda. Bodini and Pérez-Hernández (1987) indicated that the howler monkey north of the Río Orinoco and west through Apure basin north of the Rio Meta, widely distributed throughout the Venezuelan llanos, is a distinct, as yet undescribed, form. Linares (1998), however, considered it to be A. arctoidea. Linares (1998) descibed its range as the Cordillera Oriental, Cordillera Central and the Coro System along northern Venezuela, extending south throughout the llanos to the Río Orinoco, between 10 m and 1,160 m above sea level. To date, the species is known only from Colombia, but it may extend into Colombia in Arauca.|
Native:Venezuela, Bolivarian Republic of (Venezuela (mainland))
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Between 15 to 118 individuals/km² have been recorded in Venezuela (Defler 2003). Rudran and Fernandez-Duque (2003) report on 30 years of demographic data on this species at the Hato Masaguaral, Guarico State, Venezuela. Habitats there include a continous gallery forest along the Río Guarico and forest patches in seasonally inundated grasslands. Populations on the ranch ranged from a peak of 346 in 1989/1990 to 99 in 1999; population densities from 223 to 58 individuals/km². Population increases were found to result in part from increases in group size and in part from increases in the numbers of groups. The authors fojund that density was a good predictor of the size of established and new groups. A gradual increase from 146 in 1970 to 346 in 1989/1990 was partly due to habitat regeneration. The decline in the population from 1990 to 1999 was believed to result from disease and food shortage, the latter resulting in stress, longer distances travelled to find food, less nutritious diets, and increased susceptibilty to botfly infestations. Short-term fluctuations were related to rainfall, drier years reducing population growth. Crockett and Eisenberg (1986) and Crockett (1996) examine particular aspects of demography, habitat and group size in this species.|
|Current Population Trend:||Unknown|
|Habitat and Ecology:||This species is found in the llanos (plains), in deciduous forest patches and gallery forest. Long-term studies of this species have been carried out at Hato Masaguaral, Guarico, in seasonally inundated "bajo llanos". Troth (1979) describes the vegetation on the ranch. It is otherwise known from the biogeographic region of the North coast range (approximately 62ºW to 69ºW), where there are humid rain forest patches, either lowland tropical or pre-montane, resulting from orographic rainfall. Some mountains rise to elevations exceeding 2,000 m and in some ranges there are true montane cloud forests (Eisenberg and Redford 1979). |
The howler monkeys are the large leaf-eaters of the South American primate communities. The molar teeth are particularly adapted for their chewing leaves through shearing. They spend up to 70% of their day lying and sitting about quietly among the branches, fermenting leaves in their enlarged caecums. Like the spider monkeys, they are prehensile-tailed, with a naked patch of skin on the under surface at the tip. Their most characteristic feature is the deep jaw which surrounds the enlarged larynx and hyoid apparatus, a resonating chamber. It is with this enlarged and highly specialized voice box that they produce their howls (grunts, roars and barks). Howling sessions, usually involving the entire group, can be heard particularly in the early morning and are audible at distances of 1-2 km (Drubbel and Gautier 1993).
Howler groups are usually small, ranging in size from 2-16 animals and averaging 4-10 (Neville et al. 1988). Mean group size in Hato Masaguaral, Guarico State, Venezuela, ranged 7.7 to 10.5 at various times in the period 1969 to 1984 (Crockett and Eisenberg 1984). Mean numbers of adult males per group ranged 1.1 to 1.8, and adult females from 2.3 to 2.9. Group size in another ranch in the llanos, Hato El Frío, was 7.6 (Braza et al. 1981). In the red howlers, there is usually only one dominant male in the group (occasionally two), others being sub-adults, or juveniles, along with a harem of two to five females. Unlike the spider monkeys, and related to the large proportion of leaves in the diet (up to 50% of the annual diet), the howler monkeys generally have quite small and broadly overlapping home ranges, of 5 ha up to 45 ha, depending on the type of habitat (Neville et al. 1988). The large groups of A. palliata may have home ranges extending to 60 ha (Estrada 1982), whereas in the llanos of northern Venezuela, home ranges of A. arctoidea can be as small as 4 ha (Sekulic 1982).
Howlers are the only New World primates which regularly include mature leaves in their diet, although softer, less fibrous, young leaves are preferred when they are available. Their folivory and ability to eat mature leaves is undoubtedly one of the keys to their wide distribution and the wide variety of vegetation types they inhabit. Mature fruit is the other important food item, especially wild figs (Ficus) in many regions, but they also eat leaf petioles, buds, flowers (sometimes seasonally very important), seeds, moss, stems and twigs, and termitaria.
Crockett and Rudran (1987a,b) examined seasonal variation in births in red howlers from northern Venezuela, and found that they were less frequent during the early wet season (weaning would occur at the time of greatest food shortage). Oestrus lasts 2-4 days, with intervals between oestrous periods of about 17 days. Interbirth intervals are generally about 16.6 months, although they may be shortened by the death of an infant to about 10.5 months (Crockett and Sekulic 1984). Crockett and Rudran (1987a,b) reviewed long-term demographic data on births at Hato Masaguaral, examining seasonality and interannual and habitat differences. Mean gestation length is 191 days (range 186-194, n=6) (as for A. seniculus seniculus in Crockett and Sekulic 1982).
As for Alouatta seniculus, Venezuela
Adult male 6.31 kg (n=64) (Rodríguez and Boher 1988)
Adult female 4.67 kg (n=46) (Rodríguez and Boher 1988).
|Major Threat(s):||The main threat to this species is hunting.|
This species occurs in a number of protected areas, including:
El Avila National Park (85,192 ha) (Venezuela, INPARQUES, 1982)
Henri Pittier National Park (107,800 ha) (Venezuela, INPARQUES, 1982)
Aguaro-Guariquito National Park (569,000 ha) (Venezuela, INPARQUES, 1982)
Sierra Nevada National Park (190,000 ha) (Venezuela, INPARQUES, 1982)
Guatopo National Park (92,640 ha) (Venezuela, INPARQUES, 1982)
Macarao National Park (15,000 ha) (Venezuela, INPARQUES, 1982)
El Guacharo National Park (15,500 ha) (Venezuela, INPARQUES, 1982).
This species is listed on Appendix II of CITES (as Alouatta seniculus).
|Citation:||Urbani, B., Boubli, J.-P. & Rylands, A.B. 2008. Alouatta arctoidea. The IUCN Red List of Threatened Species 2008: e.T136486A4298855.Downloaded on 23 April 2018.|
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