Black-handed spider monkey (Ateles geoffroyi)Black-handed spider monkey baby

Spider monkeys have fully prehensile tails, which are extremely muscular. The lower part of the tail is hairless on the underside, and furnished with sweat glands and nerve tips. This means they can use them like a fifth limb when climbing or to comfortably hang by their tails for extended periods of time, even asleep! They can also use the tail to pick up objects or tickle each other.

Physical description: Black-handed spider monkeys' fur can be anywhere from blonde to pitch black, although a dark coat and lighter coloured belly is rather common. Infants are always black, as are hands and feet (though there are some exceptions, like with most things in life!). Adults weigh between 6-8kg and when standing upright they are about 30-70cm tall. However, their strong tail more than doubles their body length, so they may look much larger when climbing through the trees with all five limbs.

Habitat: Black-handed spider monkeys live in forests and mangroves in Central America, ranging from southern Mexico to Panama. Other species of spider monkey live in South American tropical forest areas of Colombia, Brazil and Bolivia. Spiders like to live in the higher canopy, where they make full use of their prehensile grasping tail and brachiating ability. In other words, they travel through the tops of trees suspended by arms and tail. They also walk on all fours, and sometime walk two legs along branches and occasionally on the ground. This is particularly comical to watch, since their long arms and tail usually flail rhythmically above their heads to keep them out of the way!

Diet: In the wild, spider monkeys mainly eat fruit, but they also like seeds, flowers, leaves, bark and a small amount of insects. Tarzan and Jane, two of the spiders at Monkeyland, were raised with more of a human diet, as can be seen from their big bellies. This unfortunate pair grew up in a South African backyard zoo, in a small cage located right beside a fast food restaurant. They were fed lots of junkfood and weighed around 15kg each when they arrived at Monkeyland, although the average spider monkey weighs only half of that. Even now, Tarzan's favourite pastime is trying to steal carrot cake from our restaurant; although he rarely gets very far… his triumphant squeak usually gives him away and rapidly turns into a disappointed squeal!

Life history: After a gestation period of 7-8 months, spider monkeys give birth to a single offspring. Infants stay with their mother for the first two years of life and they reach sexual maturity at the age of 4-5 years. They normally have their first offspring at the age of 5-7 years, with a birth interval of 2-3 years. The average life expectancy of spiders is 27 years.

Associations: In the wild, black-handed spider monkeys associate with white-throated capuchins. At Monkeyland, there is not much interest between the spiders and our brown capuchins. However, numerous friendships have been observed with squirrel monkeys, and both Tarzan and Jane can be found playing with or grooming the squirrels. There have even been numerous sightings of grooming between spider monkeys and gibbons here. This would not happen in the wild since gibbons come from South East Asia, so these two species would not normally meet.

Social structure: Spider monkeys live in fission-fusion societies, which means they live in large, stable communities who defend their territorial boundaries together, but they usually divide up into smaller subgroups and often change who they are hanging out with. The maximum group size observed in the wild was 35 individuals, although subgroups typically consist of around four individuals. There are naturally about twice as many females as males in a community. Spider monkeys are known to be extremely relaxed and non-aggressive. However, serious aggression and even killings have been witnessed in wild situations where the ratio of males to females was skew.

Territorial marking: Females have a long, pendulous clitoris that can be quite confusing to the untrained eye since it looks very much like a penis. This skin flap may be used to scent mark by collecting urine that is gradually spread over the monkey's territory. Male spider monkeys have a scent gland located on the chest. They mix the oily secretions from this gland with saliva and rub the smelly mixture onto surfaces to scent mark their territory during marking rituals that can last up to an hour at a time.

Vocalisations: Spiders make various vocalisations, mainly consisting of the bark (threat or complaint), whinny (quick squeak to vocalise contentment) and scream (almost like a human scream and used if very agitated). In the wild, males are reported to make long calls used for long-distance communication (up to 500m), but we have not heard these long calls from either of the males at Monkeyland. Here, the predominant spider vocalisation is the whinny, which sounds like a squeaky giggle. It begins with a short low-pitched growling sound, followed by a repetitive high pitch squeak and it is mainly heard as a greeting to familiar humans or favourite foods.

Mating: The menstrual cycle of spider females is around 26 days and they are non-seasonal breeders. Spiders are promiscuous, though occasionally pairs have been observed to stay together for several days. Copulation occurs with the male sitting down and the female sitting on top of him, either facing him or away from him. Males often lock the females into position by crossing their legs over hers. Male spider monkeys are not generally aggressive during mating and females often initiate sex.

Other behaviour: Spider monkeys are very cuddly animals and spend much time enthusiastically grooming each other or curling up with their arms or tails draped around one another. One study of ex-pet spider monkeys showed that if they are too humanised, they become less interested in grooming and social interactions with other spider monkeys. This seems to be the case with all three spider monkeys at Monkeyland, who were all hand-reared at petting zoos and show practically no interest in each other, even though Tarzan and Jane spent their entire lives together.

Conservation: Spider monkeys were classed as vulnerable to extinction by the IUCN, but were recently reclassified as lower risk/least concern. The IUCN estimates that black-handed spider monkeys have suffered a significant historical habitat loss of 71%. Deforestation of their natural habitat is the greatest threat to their survival. They are often also the first to be hunted for consumption, due to their large size compared to most other South American primates. Unfortunately, spider monkeys are also popular pets, although no non-human primate should ever be kept as such. Spider monkeys make particularly bad pets since they are very strong and can be extremely destructive.

Did you know? Spider monkeys don't have thumbs! They swing through the canopy effortlessly by hooking their hands from branch to branch and a thumb could easily get in the way.

References:

Anaya-Huertas and Mondragón-Ceballos (1998) Social behaviour of black-handed spider monkeys (Ateles geoffroyi) reared as home pets. International Journal of Primatology, 19(4), 767-784.

Cuarón, A.D., de Grammont, P.C., Cortés-Ortiz, L. Wong, G. & Silva, J.C.S. 2003. Ateles geoffroyi. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. www.iucnredlist.org. Downloaded on 16 July 2006.

Chapman, C.A. and Lefebvre, L. (1990) Manipulating foraging group size: spider monkey food calls at fruiting trees. Animal Behaviour, 39, 891-896.

Valero, A., Schaffner, C.M., Vick, L.G., Aureli, F. and Ramos-Fernandes, G. (2006) Intragroup lethal aggression in wild spider monkeys. American Journal of Primatology, 68, 732-737

www.birdsofeden.co.za Information supplied by:
Lara Mostert

www.monkeyland.co.za
www.birdsofeden.co.za

South Africa WILD ANIMAL CLUBS, ORGANISATIONS AND ASSOCIATIONS