Final answer:
Diurnal primates may not worry too much about being noticed by predators due to adaptations for predation and for visual acuity, which assist not only in hunting but also in predator avoidance during their active daylight hours.
Step-by-step explanation:
The question pertains to why diurnal primates are not highly concerned about being easily noticed by predators. According to Matt Cartmill, a professor of anthropology, certain traits such as forward-facing eyes, grasping hands and feet, and the presence of nails instead of claws may have been adaptations that aided early primates not just in arboreal habitats but as predators themselves. This Visual Predation Hypothesis suggests that these characteristics evolved to assist in hunting insects and other small prey, thereby implying that diurnal primates had developed certain predatory advantages that might reduce their concerns about being noticed by predators.
Diurnal animals, as implied, are very active during the day and thus rely heavily on visual cues for survival, both in hunting and in avoiding becoming prey themselves. Their acute vision and other adaptations like camouflage and mimicry, as seen in animals like the dead leaf mantis and the chameleon, can also serve to protect them from predators. In the daytime, they might be more alert and have better chances to see and therefore evade predators, compared to if they were to be active at night.