Final answer:
Large-bodied primates are folivorous because their diet mainly consists of leaves, which are plentiful and nutritious for their size. They have small front teeth and large molars well-suited for a leaf-heavy diet and are intelligent enough to adapt their foraging strategies.
Step-by-step explanation:
Large-bodied primates tend to be folivorous because they consume mainly leaves and other plant parts which are abundant and provide the necessary nutrients to sustain their large body size. As these primates have evolved, so too have their physical characteristics to better suit a folivorous diet, including small front teeth and big molars for grinding foliage, as well as increased gut capacity to digest tough plant material. Their higher brain-to-body ratios and intelligence allow them to learn and adapt to different food sources and foraging techniques, helping them survive in various environments. Moreover, these primates often live in social groups, which can improve foraging efficiency and knowledge transmission about food sources.