It is not unusual for some to sacrifice a body part when under attack. Spiders will lose a leg. Crabs will give up a claw, and some rodents are known to shed skin in order to survive. Why is it so easy for a lizard to lose its tail when threatened and yet it remains so strongly attached when under normal conditions? The bones and muscles in the tail are so important for movement and balance and yet can be separated so easily. The vertebrae which extend down the tail is constructed in a way that it has weak areas known as fracture planes. When threatened the muscles along these planes will pull apart and release the tail. There is no blood loss during this process. Since an average lizard will live for four years and it takes 4 months to grow a new tail, it is estimated that they can perform this feat at least 12 times. Unfortunately, we have not yet evolved to mimic this process.