Apparently tigers have eyespots on their back as a form of mimicry to warn off any potential predators/attackers (not that tigers have many). A daily occurrence that leaves tigers particularly vulnerable is when they lower their heads to get a drink of water.

Why do tigers have eyespots on their ears?

Turns out, tigers have ocellus that are eye-like markings on their ears. ... The eye-like marking often works as a defense mechanism where a prey animal mimics the eyes of a larger predator animal.

Do all tigers have eyespots?

In the case of tigers, as well as many different types of cats, mimicry takes the form of false eyes on their ears. You may have noticed that tigers have prominent white markings on their ears. ... Known as eyespots, this type of self-mimicry is actually fairly common—and isn't limited to cats.