The Brown-headed spider monkeys are large and elegant primates that are one of the most vulnerable animals in the country of Ecuador and in general South America. Just like all types of spider monkeys, the Brown-headed spider monkey has hands in the shape of a hook with no thumbs, they have long, slim arms, a round abdomen and a prehensile tail, or in other words a strong firm tail that they use like a fifth limb. When the Brown-headed spider monkey is just a child it has a light pink face and pink ears, however as it grows hair the hair on its head turns brown, and that’s where the name originated from. The monkey uses a high frequency sound, kind of like a whine to communicate with fellow spider monkeys, for example they use it to warn others about a possible prey attack. As well as adult males and females are very difficult to determine and impossible to tell apart just by looking at it due to the very dark brown shade they both have.