toxins Tactile sensation in the mouth Physiochemical effects on the gastrointestinal tract Relief from infestation of internal parasites Masked titis are tree monkeys. It is not customary to find them on the forest floor. It is speculated that they prefer to remain in the rainforest trees to avoid snake predation. They remain at least 5 meters above the ground for 99% of their daily activities. Due to their frugivorous nature, they have rarely been observed on the ground foraging for insects or small vertebrates. Instead they prefer to remain high in the tree limbs of the dense eastern Brazilian rainforest. Because they prefer not to be on the ground, researchers have observed them eating soil found atop ant mounds. This is an added advantage to the masked titis for the following reasons: It is a safer location to choose soil because it allows the monkeys to scan for surrounding predators and gives them close access to the protection of the trees Aggregate soil is easier for them to grasp with their opposable fingers than forest floor topsoil (which is not as held together as soil that has been cemented together by leaf-cutting ants) There is less leaf litter and forest debris on ant mounds, thus decreasing the amount of time they are exposed to predators For many years, researchers believed that geophagy might be used by the masked titi's as a sodium supplement as their high foliage diets were quite low in sodium. However, results of geochemical analysis of the soils eaten by C. personatus demonstrated that these soils did not contain high quantities of sodium. Although the soil consumed by masked titis was found to contain many different minerals in comparison to random soil samples, these minerals where not necessarily a valuable component of the titi diet. Therefore, it was concluded that soil was not a nutritionally significant portion of their diet. Another hypothesis suggested that the soil served as an antacid. However, results of the most recent studies demonstrated that the soil consumed by the monkeys contained a very low pH compared to random soil samples. Therefore, it seems geophagy is not principally used to buffer the stomach pH levels. In addition, because the clay molecule has a large flat structure that is ideal for toxin absorption, researchers also suggested that soil could serve to absorb the toxins acquired by the consumption of such a high quantity and