Melissa
Kaplan's
Herp Care Collection
Last updated
January 1, 2014
Tail, Limb and Skin Autotomy
©2000 Melissa Kaplan
Autotomy (auto = self, tomos = cut) is the self-induced releasing of a specific body part. In certain lizards, it is the tail that autotomizes; in plethodontid salamanders (terrestrial salamanders lacking gills and lungs in the adult form), it is their tails, digits, and portions of their limbs. Lizards do not autotomize their digits or limbs. If your lizard's toes have are falling off, this is a serious medical problem that requires veterinary attention now. In a few lizards, it is pieces of skin that autotomize, a defense strategy known as "fragile skin."
Tail
Autotomy
In lizards
who have evolved tail autotomy as an escape strategy, the tail color,
pattern and movements are often such that the predator's attention is
directed to the tail: bright tail color, sharply contrasting colors and
patterns, and stereotypic "twitching" back and forth as the
lizard remains still or slowly repositions itself so as to launch itself
away from the predator, are various ways in which such lizards may be
identified. One notable exception is the species of legless lizards: despite
looking like they are all tail, they can autotomize their actual tail
(caudal to the vent).
Lizard tails separate at "fracture planes" that are regularly spaced along the length of the tail, either in between vertebrae or in the middle of each vertebrae. Just as tissue and skin grow to fill in a scratch, gouge or excised (surgically removed) tissue, so, too, does it regrow in those lizards who evolved autotomy.
Tail loss is costly: it represents a loss of fat and protein (energy), both that stored in the tail and that which is dedicated towards the regrowth of a new tail. During this time, young lizards especially are at higher risk for being preyed upon (there may be little or nothing else to drop). During the recovery period, they stop growing. If it happens to an adult, their reproductive life goes on hold, with gamete production stopped during this period.
Since color and pattern is so important both in predator evasion and in social communication with conspecifics (other members of the same species), the absence of a tail can affect the lizard's ability to survive and to find mates and reproduce. While autotomy is costly in terms of the overall loss to the lizard, it is apparently quite effective as a survival strategy as this defense strategy is fairly widespread through the lizard families.
Fragile
Skin
Some lizards
(some skinks and geckos) release skin rather than a digit, limb or tail.
That part of the skin that has been grabbed by a predator is release.
Such releases apparently happen only when the skin is seized, as opposed
to tail drops in which the tail may be dropped before it is actually seized.
This "fragile skin" trait is so well developed in one gecko
that its scientific name reflects this trait: Gehyra mutilata (mutilated
gecko).
A Note About Mice:
As I found
out the hard way one day when "swing-bonking" a mouse to kill
it before feeding it out, they can slough off the sheath of skin and fur
covering their tails, leaving you standing there with the sheath as the
mouse scurries off. Be sure to grasp the mouse close to the base of the
tai or, better yet, use carbon dioxide gas, a faster
and more humane method.
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