Spider Monkey

Species: Ateles spp and Brachyteles arachnoides

Physical Description: Ht.- 18-25 in. Wt.- Ateles 10-19lbs. Brachyteles 26-33lbs. (Due to the relative absence of sexual dimorphism male and female dimensions are roughly equivalent) Coat- pale gray to brown in most, some black Skin- last 4 in. of the tail lack fur. Brain size- NA. Locomotion- 1. Quadrupedal crossed extension pattern (52% of the time) 2. bipedal walk or run 3. leaping 4. brachiation (25% of the time) Longevity- 12-25 years

Geographic Location: Mexico south to Paraguay, N. Argentina, and S. Brazil.

Ecology: Habitat- tropical and subtropical evergreen forests from sea level to 1000m.

Home range: 100 to 389 Ha Day Range- .5 to 5 km Population Density- 15-18 per km Day activity- 30% of time feeding, 44% resting, 25% moving.

Diet: Ateles-80% fruit, 20% leaves Brachyteles- 51% leaves, 35% flowers, 14% flowers.Techniques used to get food - use prehensile tail for suspension under branches while feeding on leaves and fruit.

Social Organization: Group size - 15-25 Composition - approximately 3 females to every male Mating system- estrous females actively choose their mating partners, some females from consortships with specific males that last up to 3 days, they have also been observed to mate with a number of males on a single day, sexual activity and face-to-face copulation may last up to 25 minutes.

Male/female transfer: Females often visit neighboring groups especially when they are carrying newborn infants and young females may emigrate permanently. Whether males emigrate or remain in their natal groups is unknown.

Male/female dominance: males are dominant to females, and are ranked, males sometimes form coalitions against females, but are seldomly aggressive.

Kinship: matrilineal-females show little aggression towards dependent offspring and are more tolerant to older juveniles, males are also seldomly aggressive towards their potential offspring Territoriality-males are more territorial than females, they move and interact in male subgroups Foraging parties- groups of 2-8 Aggression - males exhibit more aggressive behavior than females, but even then aggression is relatively low.

Intelligence: they are considerably intelligent, have limited color vision, use their prehensile tail to pick up fruit, eat only ripe fruit, and have a complex system of vocalization

Reproduction: Birth seasonality - entire year Age of maturity - 5yrs. for male and female. Gestation length - 226-232 days Estrous swellings - no, but actively approach males when in estrous, males appear sensitive to smell of urine of female in estrous. Litter size - 1 Interberth interval- 17-50 months Infant wt. - NA Infant mortality - NA. Parental Care - Infants are dependent on the mother for their first 3 years. Mothers have approximately one birth every 3 to 4 years. Females do not begin cycling until they are done weaning, or their infant has died. Sons are weaned longer than daughters. Most interaction is between the mother and the youngest of her offspring.

Topics of Special Interest: Ateles- extensive system of vocalizations, 15 separate calls with distinct meanings and several others which have not been defined. many sounds are used in conjunction with others, and some sounds may be used to identify individuals of the group Brachyteles - the largest and most ape-like of the New World monkeys, it is also the most endagered neo-tropical primate species. it is found in the Atlantic forest region of Southeastern Brasil, only 200-250 remain dispersed among 7 small remnant forest areas. It is very vulnerable because of its slow maturation, low reproductive rate and dependence on mature rain forest. Many are shot for food when they are close to population centers. In some populations urine cleansing has been observed, they wet the tail, hand, and foot. The stimulus for this in females has not been determined, in males it is associated with the presence of a sexually receptive female or copulative activity.

Bibliographical Sources

Baxter, Fedigan. Sex differences and social organization of free-ranging spider monkeys (Ateles geoffri). Primates 1984 vol. 25 : 279-294.

Primate Societies. Capuchins, Squirrel monkeys, and Atelines 1987 7: 69-82.

Eisenberg, J.F. The Behavior of Ateles Geoffroyi and Related Species. 1966 Smithsonian Institute.

Milton, K. Urine washing behavior in the woolly spider monkey. Zeitschrift-fur-Tiersychologie. 1985 vol. 67: 156-160.

Milton, K. Mating paterns of woolly spider monkeys, Brachyteles arachnoides. Behavioral-Ecology and Sociobiology. 1985 vol. 17:53-59.

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