What can't be seen without its tail?

Simple puzzle but makes 99% of players "give up".

Brain teaser for language enthusiasts and observant people. The question is "What animal can't be seen if it loses its tail?"

If you find the answer in the fastest time, leave the answer in the comments below and see how many people think the same as you.

Giang Pham

Source: https://vtcnews.vn/con-gi-bo-duoi-thi-khong-nhin-duoc-ar970930.html