Autotomy — The defensive shedding of a body part under threat, such as when a predator grabs an animal. Tail autotomy in lizards is the best-known example, but reptiles differ in whether and how they shed or regenerate the tail.
Understanding by example
A leopard gecko can regrow its tail after losing it, but the regenerated tail differs from the original in shape, scale arrangement and internal support. Distinguishing an original tail from a regenerated one makes comparisons among body-condition photographs more useful.
Common misconceptions
Autotomy is not a cost-free tail replacement. It removes tissue and stored energy, and some species do not regrow the tail. Never pull a tail or try to trigger autotomy. The fact that a tail detached also does not reveal the cause of the incident by itself.
Related reading and sources
For species-specific context, see Leopard Gecko Tail and Defensive Behavior. Browse the full glossary.
Basic reference: Merck Veterinary Manual: Overview of Reptiles.