Endangered Animals – Black Spider Monkey

spider monkey shockedBlack spider monkeys have long, glossy black hair covering their entire bodies except for their faces. Their long hair immediately distinguishes them from other species of spider monkeys, but there are other defining characteristics (Newland 1994). Adults have red or pink-skinned faces which are bare except for a very few short white hairs on their muzzles (Konstant et al. 1985; Groves 2001). Infants do not have pinkish faces like adults but rather dark skin on their faces which lightens as they age (Rowe 1996). Spider monkeys are among the largest of the New World monkeys and are long-limbed and somewhat gangly in their appearance especially in contrast to their characteristic pot bellies; the spidery appearance of their long arms, legs, and tails is indicated by the common name (Groves 1989; Sussman 2000).

Of all the species of spider monkeys, black spider monkeys are the largest (van Roosmalen & Klein 1988). In general, spider monkeys are not characterized by a high degree of sexual dimorphism; the average weight for wild black spider monkey males is 10.8 kg (23.8 lb) while females weigh 9.66 kg (21.3 lb) on average (Youlatos 1994; Di Fiore & Campbell 2007). The height of male spider monkey averages 557 mm (1.83 ft) while females average 552 mm (1.81 ft) (Youlatos 1994).

a family of spider monkey

The body structure and several other morphological characteristics of black spider monkeys are adaptations to their completely arboreal lifestyle. First, their elongated arms allow them to move in a specialized manner through the trees using a hand-over-hand motion. This type of locomotion, called brachiation, is also seen in the lesser apes (Schmitt et al. 2005). In addition to their elongated arms, black spider monkeys have especially hook-like hands with elongated fingers which allow them to swing over branches with ease. Unlike most other primates, spider monkeys lack an external thumb, but this is not because they are less evolved than other primates (Erikson 1963; Fleagle 1988). The abbreviated thumb is really a specialized adaptation; their ancestor had an opposable thumb, but over time, it has shrunk in size relative to other bones of the hand due to lack of use in their arboreal environment (Groves 1989; Tague 1997). Another morphological adaptation seen in black spider monkeys is the presence of a long, specialized tail.

An adaptive trait seen only in some New World monkeys is the presence of a prehensile tail, which allows arboreal animals to move through the canopy with additional ease, security, and efficiency. Black spider monkeys have a ‘third hand’ to grasp branches while moving through the canopy, preventing side-to-side swinging motion that could lead to inefficiency and increased effort in locomotion (Schmitt et al. 2005). On the underside of the very tip of the tail there is a patch of skin with distinct pattern of lines like a fingerprint. This patch of skin, or friction pad, at the tip is functionally important because it helps the tail grip onto surfaces, much like fingers on a hand (Groves 1989; Newland 1994; Lemelin 1995). Additionally, the presence of a prehensile tail is important in suspensory feeding: the tail supports the entire weight of the monkey while both hands are free to forage (Mittermeier 1978). The prehensile tail seen in black spider monkeys is relatively longer than the nonprehensile tail of other primates and has more vertebrae which are smaller relative to overall tail length than non-specialized tails seen in other primates. This anatomical feature is significant because the presence of additional, but smaller vertebrae allows for increased flexibility and extension in the prehensile tail compared to nonprehensile tails (Schmitt et al. 2005). In addition to brachiation, black spider monkeys move through the environment through quadrupedal walking and running and through clambering movement which utilizes numerous supports in no particular order or pattern (Mittermeier 1978; Youlatos 2002).

The maximum recorded longevity for black spider monkeys is 33 years, but without long-term field research, it is difficult to draw conclusions from one measurement (Ross 1991).

Black spider monkeys are found in eastern South America in Brazil, French Guiana, Guyana, Surinam, and possibly in Venezuela (Konstant et al. 1985; Rylands et al. 1995). In Brazil, they are isolated to Para State, in the northeastern part of the country, north of the Amazon River and east of the Rio Branco. Their range extends north into French Guiana, Surinam, and eastern Guyana but they are restricted to the forests east of the Guianan Highlands in these countries (Collins & Dubach 2000; Groves 2001). If they are present in Venezuela, it is at the very eastern tip of the country. While their presence has not been confirmed, it is possible because there are neither habitat nor geographic barriers precluding black spider monkeys from living in forests on the Venezuelan-Guyanan border (Konstant et al. 1985).

One of the first long-term field studies of black spider monkeys was conducted by Marc van Roosmalen at Raleighvallen-Voltzberg Nature Reserve in central Surinam, and research has continued in the reserve since this pioneering study. Wild black spider monkeys have been studied in French Guiana by Dionisios Youlatos and in Guyana by Shawn Lehman. Most of the ecological and social data in published literature comes from studies conducted in Surinam black spider monkeys.

Black spider monkeys are found in moist tropical evergreen forests and prefer undisturbed primary rainforests (Kinzey 1997). Throughout their range, black spider monkeys are found in high densities in high rainforest- areas which are not affected by seasonal flooding of rivers- and in high mountain savanna forest, as well as occasionally in swamp or marsh forests along creeks, and occasionally in high mountain savanna forest (van Roosmalen & Klein 1988; Kinzey & Norconk 1990; Trolle 2003). These high mountain savanna forests are found on the interior of Surinam and are present because of large, granite rock formations which limit the growth of emergent rainforest trees but which allow for smaller, savanna-like species to grow (Mittermeier & van Roosmalen 1981).

In Guyana, the tropical climate translates into high average daily temperatures, large amounts of annual rainfall, and distinct wet and dry seasons. The average daily temperature is 25.7°C (78.3°F), but the warmest months of the year are September and October while the coldest months are December and January (Lehman 2000). The mean annual rainfall is between 2000 and 3400 mm (6.56 and 11.2 ft) and is distributed across two wet seasons. The summer rainy season lasts from May to August and another wet season spans November to January. There are two dry seasons as well, the longer lasting from mid-August to November or December and the shorter lasting from February to April (Lehman 2000). Black spider monkeys in Guyana are found primarily in lowland evergreen rainforests in the interior forest region of the country and are not found in swamp forests or woodlands (Lehman 2004a; 2004b). In neighboring Surinam, black spider monkeys are almost entirely restricted to the interior forests of the country, which begin about 60 miles from the coast. The climate of Surinam’s tropical forests is comparable to those of Guyana. The mean annual temperature is 26.1°C (78.9°F) and the monthly average temperature only varies by about two degrees during the year. The warmest months are September and October while the coolest months are January and February (van Roosmalen 1985). The annual rainfall in Surinam is between 2000 and 2400 mm (6.569 and 7.87 ft) and is concentrated during certain times of the year. The long rainy season lasts from mid-April to mid-July, with peak rainfall occurring in May and is followed by a long dry season lasting from August until mid-November. From December to April, the rainfall varies greatly, but there is usually a short rainy season followed by a short dry season within this time period (van Roosmalen 1985).

baby spider monkey

Where black spider monkeys occur in French Guiana, the average annual temperature is 26.1°C (78.9°F) and annual rainfall varies from 3000 to 3250 mm (9.84 to 10.7 ft) (Youlatos 2002). Similar to other range countries, French Guiana experiences seasonal variation in rainfall with the dry season lasting from mid-August to mid-November and a long rainy season for the rest of the year. The rainy season is punctuated by a short dry season lasting briefly during February and March (Zhang 1995).

In one field study conducted north of Manaus, Brazil, black spider monkeys were found in terra firma rainforests with seasonal precipitation. In the Adolfo Ducke Forest Reserve, annual precipitation ranges between 2170 and 2900 mm (7.11 and 9.51 ft). Rainfall is concentrated during the wet season which lasts from December to May and which is followed by a dry season lasting from June to October or November (Rylands & Keuroghlian 1988).

The population density estimate for black spider monkeys in Suriname is 7.1 individuals per square kilometer (4.41 individuals per mi²); this is compared to a density of 8.57 individuals per square kilometer (5.33 individuals per mi²) in another study site in French Guiana (van Roosmalen 1985; Kessler 1998). Groups of spider monkeys protect a territory or core area, but in other species of spider monkeys, there is some amount of range overlap between groups (van Roosmalen & Klein 1988).

Compared to other New World primates, spider monkeys are large-bodied and are less susceptible to predation, but there are a number of potential predators within their range (Di Fiore 2002). Some potential predators include multiple species of raptors, felids such as jaguars and pumas, as well as large snakes (Di Fiore 2002). Generally speaking, the observation of predation events is rare and most evidence of predation is circumstantial. In one instance, though, a crested eagle (Morphnus guianensis) was seen capturing and killing a juvenile black spider monkey in French Guiana (Julliot 1994). While these events are unlikely to be witnessed, the presence of large predators combined with observational evidence leads to the conclusion that predators can threaten black spider monkeys (Di Fiore 2002).

Source: Cawthon Lang KA. 2007 April 10. Primate Factsheets: Black spider monkey (Ateles paniscus) Taxonomy, Morphology, & Ecology . .

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