In the spring of 2011, I came upon a lizard while parked at Red Pass on the Titus Canyon Road in Death Valley National Park. It was early spring and still a little chilly so the lizard was easy to catch. However, as I caught it, it took off to run away and I got ahold of its tail. Immediately, the tail came off and fell to the ground as the lizard escaped. The tail started to squirm and wiggle. This is a natural defense mechanism in the lizard called Autotomy.
Below is a youtube video of the experience with the lizard at Red Pass.
From Answers.com - the spontaneous casting off of a limb or other body parts such as the tail of certain lizards or the claw of a lobster, especially when the organism is injured or under attack.
From Wikipedia, the free encyclopedia
Autotomy (from the greek auto = self, and tomy = severing)
or self amputation is the act whereby an animal severs one or more of its own appendages, usually as a self defense mechanism designed to elude a predators grasp. The lost body part may be regenerated later.
This is a Mediterranean Gecko that Bryan caught in our yard. I was photographing it and accidently grabbed its tail and it came off. The tail quivered for about 4 or 5 minutes until it stopped. In the wild the quivering tail would draw the attention of the predator so that the lizard or gecko could escape.