A tusk is a long, pointed tooth that grows outside an animal's mouth and keeps growing throughout its life. Elephants have the most famous tusks: those massive ivory curves extending from their upper jaw, which they use for digging, stripping bark from trees, and defending themselves. Male elephants often have larger tusks than females and use them when competing with other males.

Walruses also have impressive tusks, which they use to haul themselves out of icy water onto ice floes and to create breathing holes. Both male and female walruses have tusks, though males typically grow larger ones. Wild boars have smaller tusks that curve upward from their lower jaw, useful for rooting in soil and protection.

Tusks are made of dentine, the same material as regular teeth, but they're specialized for purposes beyond eating. Unlike antlers, which deer shed and regrow each year, tusks are permanent and continue growing. Sadly, the value of ivory has made elephants targets for poachers, putting these magnificent animals at risk.