u/Solid-Still-7590

The Pygmy Marmoset (Cebuella pygmaea) is the smallest monkey in the world and primarily a gummivore. It's diet consists mostly of tree sap, gum, resin, and latex obtained by gnawing holes in tree bark with specialized lower incisors. Studies show that 60-80% of their feeding time is spent consuming exudates. They supplement this diet with fruit, insects and other small animal prey.

With such an abundance of trees, why isn't gummivory more common in mammals?