Influence of tannic acid concentration on the physicochemical characteristics of saliva of spider monkeys ().

Tannins are a chemical defense mechanism of plants consumed by herbivores. Variations in salivary physicochemical characteristics such as pH, total protein concentration (TP), and presence of proline-rich proteins (PRPs) in animals have been reported as a mechanism to protect the oral cavity when consuming food with variations in pH and tannins. Variations in salivary physiochemistry as adaptations for consuming tannin-rich foods have been found in omnivorous and folivorous primates, but have not yet been reported in frugivorous species such as spider monkeys.

Hand preferences in two unimanual and two bimanual coordinated tasks in the black-handed spider monkey (Ateles geoffroyi).

Spider monkeys are interesting to study with regard to hand preferences, as they are one of the few primate species that lack a thumb and, thus, are unable to perform a precision grip. Further, being platyrrhine primates, they also largely lack independent motor control of the digits and, thus, have only limited manual dexterity. It was therefore the aim of the present study to assess hand preferences in black-handed spider monkeys () in 4 tasks differing in task demand: simple unimanual reaching for food and 3 versions of the widely used tube task, including 2 bimanual versions that differ from each other in the degree of fine motor control needed and a unimanual version that does not require coordinated action of the hands.