The tusk of the narwhal (Monodon monoceros L.): interpretation of its function (Mammalia: Cetacea)

Abstract

For over a century, scientists have speculated on the biological function of the tusk of the male narwhal. Proposed functions have included use of the tusk as a weapon, use for opening breathing holes in sea ice, use in feeding, use as an acoustic organ, and function as a secondary sex character. The weight of evidence in this literature review supports a theory that the narwhal tusk serves as a secondary sex character of males, for nonviolent assessment of hierarchical status on the basis of relative tusk size. Relative tusk size is evidently determined in frontal encounters by rival males.