White-Fronted Spider Monkey, Ateles belzebuth

The White-Fronted Spider Monkey (Ateles belzebuth), known also as the Long-Haired or White-Bellied Spider Monkey, is an endangered species of spider monkey, a type of New World monkey. It can be found in the north-western Amazon in Ecuador, Venezuela, Peru, Columbia, and Brazil, ranging as far south as the lower Ucayali River and as far east as the Branco River. In the past, the Peruvian, Brown and White-Cheeked Spider Monkeys have been treated as a subspecies of A. belzebuth. As currently labeled, the White-Fronted Spider Monkey is monotypic. It has a whitish colored belly and a pale patch featured on the forehead, which, in spite of the name White-Fronted Spider Monkey, frequently is orange-buff. They live in groups of 20 to 40, splitting into small parties of 1 to 9 when they are in activity.

All of the members of Ateles are semi-brachiators, and this species has an intermembral index of 105. They have a rather dorsally placed scapula to permit for increased mobility involved in brachiation. Their prehensile tail with hairless gripping pad featured at the end also permits for this locomotion, which then means they have increased caudal vertebrae, with about 31 caudal vertebrae rather than another platyrrhine like Cebus with only 23 on average. This tail permits for addition grasping of the branches, which means there is less lateral movement while brachiating which increases efficiency. The hairless gripping pad under the tip of the tail is frequently compared to a finger, since it allows gripping of the surface. Their curved hands with long metacarpal bones permits for easy brachiation. They don’t have an external thumb, which sets them apart from the majority of other primates.

Image Caption: White-bellied spider monkey (Ateles belzebuth) in Buenos Aires Zoo, Argentina. Credit: Fábio Manfredini/Wikipedia (CC BY 2.0)