A tusk is a kind of tooth that extends past the confines of an animal’s mouth. Tusks often keep growing throughout a creature's life, and they may be constantly worn down by use. Many different kinds of animals have tusks, including elephants, certain kinds of wild pigs, and walruses. They serve different purposes in different species, and often have several uses, including self-defense or as a tool. People use tusks to make ivory, which can have a lot of utility for people, but the use of ivory has put a lot of strain on the population of the elephant.
One of the main uses for a tusk in animals is fighting. Sometimes they use them to fight off predators that might be attacking, or they might simply be used to fight off other animals in their social group, especially in relation to mating. For example, two male elephants will occasionally lock tusks in much the same way deer will fight with their antlers, and sometimes elephants can be severely wounded in these fights. When it comes to using tusks for self defense against predators, one of the more commonly-used examples are various species of wild hog, which have been known to wound other animals badly with their tusks. Two other fairly common uses for tusks are as a tool for digging and as a physical display for sexual purposes.
A tusk is actually a tooth that is drastically oversized. The teeth that eventually grow into tusks can vary a lot in different species. Canines and incisors are the most common teeth to eventually become tusks, and between the two, the canines are generally more common. Walruses, for example, have tusks that are actually canines, while elephants have tusks that are actually incisors. The tusks themselves never stop growing in most cases, so that even if the animal uses them until they start to wear down, it will generally grow it all back.
The tusk of an animal is used to make the substance known as ivory. Over the years, ivory has been used for many different things, including ornaments, piano keys, and jewelry. Primarily, people have taken ivory from elephants, although ivory can also come from many other tusked animals. The buying and selling of ivory has generally put the elephant population under threat of extinction and reduced their numbers massively in many different areas. Laws have been passed in many areas to protect the elephant with mixed levels of success.