Tusks are elongated, continuously growing frontteeth that protrude well beyond themouth of certainmammal species. They are most commonlycanine teeth, as withnarwhals,chevrotains,musk deer,water deer,muntjac,pigs,peccaries,hippopotamuses andwalruses, or, in the case ofelephants, elongatedincisors. Tusks share common features such as extra-oral position, growth pattern, composition and structure, and lack of contribution to ingestion. Tusks are thought to have adapted to the extra-oral environments, like dry or aquatic or arctic.[1] In most tusked species both the males and the females have tusks although the males' are larger. Most mammals with tusks have a pair of them growing out from either side of the mouth. Tusks are generally curved and have a smooth, continuous surface. The malenarwhal's straight singlehelical tusk, which usually grows out from the left of the mouth, is an exception to the typical features of tusks described above. Continuous growth of tusks is enabled by formative tissues in the apical openings of the roots of the teeth.[2][3]
Other than mammals,dicynodonts are the only known vertebrates to have true tusks.[4]
Tusks have a variety of uses depending on the animal. Social displays of dominance, particularly among males, are common, as is their use in defense against attackers. Elephants use their tusks as digging and boring tools. Walruses use their tusks to grip and haul out on ice.[5] It has been suggested that tusks' structure has evolved to be compatible with extra-oral environments.[1]
Tusks of"Mammut" borsoni from Greece, which are the longest tusks ever recorded.
Elephant tusks aresexually dimorphic, being on average larger in males than in females, and entirely absent in femaleAsian elephants. Elephants with large tusks each at least 45 kilograms (99 lb) in weight are known as "tuskers", sometimes also called "big tuskers" or "great tuskers". While tuskers are rare today, it is thought that they were more common in the past, prior to human impact on elephant populations. The two record holders for longest and heaviest recordedAfrican bush elephant tusks are around 3.49 metres (11.5 ft) long measured along the outside curve, and 107 kilograms (236 lb) in weight respectively, while the longest and heaviest Asian elephant tusks are 3.26 metres (10.7 ft) long and 73 kilograms (161 lb) respectively. Even larger tusks are known from some extinctproboscideans, such as species ofStegodon,Palaeoloxodon, andmammoths, with the longest tusk ever recorded being that of a specimen of"Mammut" borsoni from Greece, which measures 5.02 metres (16.5 ft) in length, with an estimated weight of 137 kilograms (302 lb) with some mammoth tusks exceeding 4 metres (13 ft) in length and probably 200 kilograms (440 lb) in weight.[6] The largest walrus tusks can reach lengths of over 95 centimetres (3.12 ft).[7] The longest narwhal tusks reach 3 metres (9.8 ft).[8] The upward curving maxillary tusks ofbabirusa can reach lengths of over 20 centimetres (7.9 in).[9]
Tusked animals in human care may undergo tusk trimming or removal for health and safety concerns.[10] Furthermore, surgical veterinary procedures to remove tusks have been explored to mitigate human-wildlife conflicts.[11]
