It's easy to see how these lithe, agile, dark coloured monkeys get their name.
From a distance, especially if you see them moving along in silhouette, they look like big black spiders weaving their way through the forests.
They grab onto tree branches with long gangly limbs. They don't only using their arms and legs but also hang on by their tails. The underside of the tail is hairless so can be used like a fifth limb to help them swing through treetops.
They make loud whooping calls to communicate and to warn each other of danger.
A benefit of their exceptional climbing skills is that they don't have many natural predators because, hanging out so high up in the trees, they are pretty difficult to catch.
Despite that some species of spider monkey are now listed as Endangered in their natural South American homelands where they have been targeted by hunters for meat or for sport.
Some protected areas have been set up to stop numbers going down further but they have been illegally hunted in those areas too.
Destruction of rainforests by humans has also contributed to their decline.
That's why its important to monitor their numbers, and support conservation projects and zoo based breeding programmes like ours.
Those we have at Chester Zoo are Critically Endangered Colombian Spider Monkeys which in the wild are found in the rainforests from west Colombia to east Panama.
They live for about 25 years though some have been known to live longer in zoos. They mainly eat fruits, but also leaves, seeds, insects and occasionally eggs and vegetables.
We were delighted to welcome 2 new additions to our Spider Monkey family in early 2015 with both mums Christine and Mary giving birth days apart from each other. Now taking the group up to 10, lead by the dominant male Popoyan who arrived in Chester in 2008.
If you can't immediately see them look up as they just love to spend time high up in the trees of their enclosure.