Spider monkeys have a tail with fingerprints and a brain built for fruit maps
A spider monkey's tail can reach 89 centimetres, and its bare tip carries skin ridges like fingerprints, letting it work as a fifth hand. Its brain, at 107 grams, is twice the size of a howler monkey's of the same body weight, probably because remembering where and when over 150 kinds of trees bear ripe fruit takes serious memory.
Spider monkeys, genus Ateles, live in the high canopy of tropical forests from southern Mexico to Brazil, foraging 25 to 30 metres up. The name comes from the way they dangle by the tail with long limbs hanging, like a spider on a thread. Their hands are hooks with little or no thumb, which is where the genus name, from a Greek word for incomplete, comes from. The black-headed species, the largest, averages about 11 kilograms for males. Only gibbons are said to be more agile.
Fruit makes up 71 to 83 percent of what they eat, and because they swallow it whole, they scatter seeds through the forest. Bands of 15 to 25 split into small foraging parties during the day, often guided by a lead female who plans an efficient route. Unusually for primates, females leave their birth group at puberty while males stay together for life. Meta-analyses in the 2000s ranked spider monkeys the most intelligent New World monkeys, and their calls include barks, horse-like whinnies and long screams. Threatened by a human, they shake branches and may drop limbs weighing up to 4 kilograms.
Their lives run slowly. Gestation lasts about 226 to 232 days, a female raises one infant every three to four years, and the young depend fully on their mothers for six to ten months, riding first on the belly and then on the back with tails entwined. Gummy, thought to be the oldest in captivity, died at 61 at a zoo in Rome, New York.
All seven species are under threat, one critically endangered, from hunting and logging. Spider monkeys also run through Mesoamerican culture: Ozomatli, Spider Monkey, names the eleventh day of the Aztec 260-day calendar, and Classic Maya artists often painted them carrying cacao pods.
Source: Spider monkey
