Colobine primates are well adapted for eating leaves. what leaf-eating traits have evolved in these monkeys?

They are very arboreal, have high and pointed molars which are good for shearing leaves and a three or four chambered stomach similar to that of a cow. Colobine are leaf-eating specialists with high-cusped molars and multi-chambered stomachs housing mutualistic microbes that digest cellulose and detoxify plant defensive compounds. Leaves are a major component of many species diets up to 90% in a population of Ugandan red colobus.

In some developing nations the percentage of the animal protein from fish in the diet can be as high as 25 percent.  about 85% of fish caught is used for human consumption.  the remainder is converted into fishmeal and fish oil.