Friday, January 13, 2012

Lizards sacrifice their tails to save their lives

Lizards rely on speed and agility to flee from danger. But if running does not suffice, then the lizard brings its tail into use. Most lizard species shed their tails when they are threatened, an action that not only tends to confuse the attacker but focuses its attention on the distracting tail while the lizard makes a dash for safety. So the lizard offers its tail as a snack, albeit a fairly paltry and fleshless one, for the safety of the rest of its body. Predatory monitor lizards take full advantage of this and feed almost entirely on such discarded tails.

A lizard's detachable tail has sections that can be snapped off at will by the simple contraction of some of the lizard's muscles. In spite of the fact that the fracture occurs across the spine, the loss causes the creature little discomfort. This is because the joints at the 'crisis point' where the tail breaks off are made of cartilage rather than bone, and blood vessels and nerves are constricted to reduce the pain and blood loss.

Although a lizard's tail is not essential, it does play an important role in balance and in breeding success. The lost tail grows again with time, although it may differ in length or pattern from the original, and the lizard may even end up with more than one tail. Victorian records, for example, tell of a lizard which had seven. But regrowing a tail takes considerable energy. If a predator refuses to eat the snack, some skinks have been known to return to eat their own discarded tails.

The glass snake is really a lizard with no legs. It takes its name from its extraordinary ability to shatter its own body. If under stress, this 5 ft (1.5 m) long creature fractures its tail at all or most of its joints. Each piece then wriggles around on its own, while the snake itself slips away - sometimes reduced to two-thirds of its original length.

A species of gecko found in Puerto Rico also dismantles itself spectacularly when in danger. It sheds bits of skin from all over its body, or even its whole outer covering, and moves off to safety.

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