Why bats need excellent hearing?

Bats need excellent hearing because they are always hunt at night, and as you know, it is very dark so they actually can't see their extractions. That is why they need their ears.

Their ears are so arranged that at the time when they make sounds of different frequencies, their muscles closes the opening of the ear

Why bats excellent hearing?

Почему Летучие мыши Отлично (хорошо) слышат?