Caudal autotomy is a defensive adaptation observed in many lizards and some salamanders (there are some scattered reports of this behaviour being observed in certain snake species). The vertebrae at the joint between the tail and the pelvis are weakened and easily broken, so when the animal is threatened by the predator or seized by the tail, the tail breaks off. The actual loss of the tail occurs as the animal tightly contracts the muscles at the posterior of the pelvis, breaking the vertebrae and causing the tail to fall off. The fact that the tail is lost through muscular contraction rather than an external force (ie., being torn off by the predator) has the added benefit of reducing blood loss, as the muscle contraction closes the major arteries and veins running from the trunk of the body to the tail.

Caudal autotomy is a particularly effective antipredator behaviour since the predator is often left with the wriggling tail as a meal while the animal makes its escape. The dropped tail may continue to move and writhe for up to ten minutes after separation, making it a particularly interesting prey item to the predator.

Losing one's tail is not an insignificant experience for the animal in question. While the adaptation may allow the animal to escape, the risk of infection is significant since the wound left can be of substantial size. Most species will regenerate the tail in relatively short order, but these regenerated tails often have a deformed appearance. This regeneration is costly, however. While growing back its tail, the animal ceases growth and, during the reproductive season, gamete production.

As a final note, some species of herpetile do not drop just their tails, but also their digits or limbs.

God help me, but I can't stop giggling over the idea of a three-legged, twelve-toed tailless lizard telling his buddy: "You know, this voluntary leprosy really is something, isn't it!"

Loss of the tail (while saving the animals life) makes the animal vulnerable in the short and long term. It is less able to find a mate, capture food and the loss usually makes them run more slowly and unable to swim. The tail is a status signal for mates, serves as a 5th leg (no dirty jokes here) and sometimes even allows a lizard to hang suspended. The tail also serves as a balance beam while running. The tail holds stored fat and protein; which is lost to future growth and/or reproduction.

Lizards without a tail may not even be capable of physically (or physiologically) reproducing. The may not be able to attract a mate, they may not be able to do the actual act of mating due to loss of balance and they may have reduced gamete production due to low energy reserves.

A small aside from the /msg box ..."when I hear 'mating' I normally think the act, not the process, ya know?" Thanks to Cletus the Foetus for help in clarifying physical vs. physiological as it relates to lizard sex life. :D

Tail loss also makes the lizard more likely to fall prey to predators, (especially visually oriented snakes and birds) in the future. Skinks without tails are the first to bolt and therefore first seen by the predator. They are also about 15% slower than intact skinks. A skink takes about 60 days to regrow its tail. It has no safety net in case of attack during that time so it hides more and therefore captures less food and is less able to heal, bad cycle.

Faster types of lizards seem to lose their tails more often than slower lizards. Probably the slower lizard would just get eaten anyway so evolution didn't risk autotomy. The quicker (and generally smaller) the lizard the less of the tail that will be shed; it may be just the tip. A slower, tail shedding lizard (often also a larger lizard) will lose almost the entire tail. (The better to feed you with and keep you occupied longer - my dear predator!). Many lizards have brighter colored tails when young (and smaller) to attract predators to this *relatively* more expendable piece of the body and away from the head and torso.


Log in or register to write something here or to contact authors.