The spider monkey's brain

The spider monkey brain is twice the size of a howler monkey's of equivalent body size; this is thought to be a result of the spider monkeys' complex social system and their frugivorous diet, which consists primarily of ripe fruit from a wide variety (over 150 species) of plants and this requires the monkeys to remember when and where fruit can be found. The slow development may also play a role: the monkeys may live 20 years or more, and females give birth once every 3-4 yearsThe diet of spider monkeys consists of about 90% fruits and nuts. They can live for long periods on only one or two kinds of fruits and nuts. They eat the fruits of many big forest trees, and because they swallow fruits whole, the seeds are eventually excreted and fertilized by the feces.