|Many lizards are able to shed their tails when
caught by a predator. By deliberately sacrificing its own tail, a lizard can
free itself and distract its attacker. Tail shedding is an effective and
very complex defense mechanism. Many factors – including the danger of its
circumstances and the normal escape strategies of its species – dictate whether
or not a reptile will shed its valuable tail.
Why Tails Are Shed: Lizards are popular prey for many kinds of predators – from eagles to snakes. The lizards’ main defenses are their camouflaged skin and the ability to stay motionless or to rush away. As a last resort, many lizards have the ability to lose their tail. In some species the tail is brighter than the rest of the body. This provides a more visible target for a predator than the head or body. Many lizards have green or blue tails that are bright enough to distract a predator, yet not so conspicuous that they make the lizard easy to spot from far off.
As a lizard runs away from a predator, it can easily shed its tail. But it is more difficult to shed the tail when the lizard is being held in place. Thus, shedding is probably not an automatic or purely physical response, but a choice made by the lizard according to the circumstance.
Ability to Shed: Some lizards lose all or part of their tails, depending upon the escape strategies of their species. A larger, slow moving lizard will usually give up more of its tail than a smaller, faster one, but there are exceptions. A desert lizard, for example, loses its whole tail because hiding places in its habitat are scarce, so the lizard needs time to escape. Some iguanas are able to shed their tails when they are young. But they lose this ability as they mature. Instead they develop the ability to defend themselves. The tail does not always break at the same place each time, nor does it always snap off when pulled with the same amount of force.
Hoe Tails are Shed: Tail shedding is not common to all lizard species. But for those lizards that do shed, two different methods of tail loss have evolved. Most lizards have areas of weakness in the vertebrae, or backbone, of their tails that run through the surrounding connective tissue and muscle. If a lizard is caught by its tail, it will contract the muscles in front of the weak area to split a vertebrae and shed the part of its tail held by the attacker. Splitting a vertebrae is called intravertebral autonomy. A more primitive method of tail loss involves the tails breaking between vertebrae (intervertebral autonomy). Tails lost in this way are less likely to regrow.
Tail Renewal: A regrown tail looks like the original tail, but there is often a joint or a change in color where the old tail broke off. Also, a new tail has tough cartilage instead of bone. A lizard can shed a regrown tail only above the place where the old one broke off.
Tail Loss and Renewal:
Cost of Tail Loss: A lizard sheds its tail as an escape tactic. Where predators are rare, this drastic method of defense is less likely to be used. It is also less common among lizards that have other means of defense, such as thick armor or powerful teeth and claws. Because the lizard gives up its tail to escape, tail shedding is more common among fast-moving lizards than among larger, less agile species. These slower moving lizards are more likely to fall victim to a predators second attack. The cost of tail loss may be higher than it appears. Losing a tail may save the lizard from a predator, but it may prevent the lizard from catching food or reproducing successfully.
Lizards use their tails for balance when running and for climbing and swimming. A few species run faster without their tails. But most tailless lizards are actually slower without the proper body balance that a tail provides. Climbing species use their tails as a fifth limb. Iguanas and some geckos, for example, have adhesive pads on their tails and use them in gravity defying maneuvers – even feeding while suspended by their tails. Skinks and other aquatic lizards cannot swim after losing their tails. Some lizard species use their tails to signal status. Tailless lizards lose rank and find it difficult to hold territories or to mate. Lizards also use their tails for energy storage. A tailless lizard may starve if food becomes scarce.
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