Chimps choosing materials

Chimpanzees demonstrate expertise in selecting materials for various tasks. They use soft leaves for comfort, flexible stems to fish ants, and rigid stalks to mash palm cores. For cracking nuts, they choose rocks, showcasing their understanding of material properties. This knowledge significantly eases their daily activities.

Why do chimpanzees need to find a harder material for cracking nuts?

What challenges do chimpanzees face when selecting rocks for cracking nuts?