Spider Monkey , any of four species of small American monkeys characterized by their long, slender limbs and great agility. Spider monkeys occur between southern Brazil and central Mexico. They travel in small bands in forest trees, moving swiftly by making tremendous leaps, sprawling out like spiders, and grasping tree limbs with their prehensile tails. The fur is yellowish-gray to brown, with lighter undersides; the face has white eye rings and is shaded by projecting hair that is either light or dark in color. The animals mainly eat fruits supplemented with nuts, seeds, leaves, insects, and eggs .