An earmark is a cut or mark in the ear of livestock animals such as cattle, deer, pigs, goats, camels or sheep, made to show ownership, year of birth or sex.
[1] For example, in a case of defamation in King's Bench in 1541, the defamatory statement included "George Butteler hath eremarked a mare of one Robert Hawk.
Cattle earmarks are often a variety of knife cuts in the ear as an aid to identification, but it does not necessarily constitute proof of ownership.
Earmarks may be used,[5] although non-traumatic methods such as tattooing their tails and painting spots on white mice with crystal violet or permanent markers can be used as well.
Earmarking a mutant strain of mice called MRL/MpJ led to the accidental discovery that they had the ability to regenerate tissue very quickly, when scientists working with them found that the holes punched in their ears kept growing back.