Why do Geckos drop their tails?

Geckos drop their tails when they are put under stress. Excessive heat can be a cause for stress for a gecko.

Sometimes geckos drop their tails because they are getting bullied by other geckos or pets in the same tank or space.

When a gecko gets its tail grabbed or pinched, it usually drops it as a defense mechanism.

Illness can cause the gecko to drop its tail because its sense react differently when it'ss ill.

Similar to its reaction to illness, a gecko tends to drop its tail when it is infected in a way or another. (See Why are Zoos important?)

Dropping the tail is an automated defense mechanism that the gecko uses when it is in danger or being attacked.

Some breeds of geckos have the ability to generate a new tail. While the tail might not be the same, it can function just as well as the original. However, some geckos do not have that ability, yet they adjust and adapt to being without one. It could take up to a few days for them to adjust.

As a defense mechanism, geckos can drop their tails which would continue to twitch as they escape the danger. (See How many Animals are there in the World?)