The wounds of dolphins and whales are known to heal rapidly and thoroughly in both natural and controlled situations. Healing rates vary with the severity of the injury but, in general, even the most severe wounds, exposing deep muscle tissue, heal almost completely within 5 to 8 months. However, the scars resulting from deep wounds and mutilations along the edges of dorsal fins are known to last for years, and potentially throughout an individual's life, and thus provide a useful set of marks which can be used to distinguish individuals in the field.