These common lesions are the result of trauma to the ear followed by hemorrhage between the skin and cartilage (or within the cartilage). The subcutaneous hemorrhage resolves over several weeks to months, leaving the pinna thickened and misshapen in most cases. Trauma often is caused by bites inflicted by pen mates or by violent head shaking. Head shaking is associated with mange, infestation with lice, or feed particles in the ears. Treatment and/or drainage of the fluctuant lesion is not usually attempted or likely to be successful. Amputation of the ear is sometimes undertaken in management of severe cases.