Ivory from the tusk of an elephant is thought by many to be the only true ivory. To most collectors, the term ivory also includes such natural materials as walrus, hippopotamus, or whale teeth or tusks, and some of the vegetable materials that are of similar texture and density. Other ivory items may be found in the Scrimshaw and Netsuke categories. Collectors should be aware of the recent laws limiting the buying and selling of elephant ivory and scrimshaw. Elephants are an endangered species, and their tusks can no longer be used to make new jewelry or carvings.