Bats can know about their prey at a distance even in the night by emitting

Bats detect their prey in complete darkness by emitting ultrasonic sounds, a biological process known as echolocation or biosonar [4]. These animals emit high-frequency vocalizations, typically ranging from 20 kHz to over 200 kHz, which are beyond the human hearing threshold [2]. When these ultrasonic waves hit an object or prey, they bounce back as echoes [4]. By listening to and processing these returning echoes, bats can determine the precise location, distance, size, and even the velocity of their prey through the Doppler effect [4]. While some bats rely on vision in dim light, most specialized insectivores use frequency-modulated (FM) or constant-frequency (CF) ultrasonic signals to navigate and hunt effectively at night [4]. This sophisticated auditory feedback system allows them to adapt their call patterns as they approach a target, ensuring successful capture [3].

Sources

1. [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC3667242/
2. [4] https://en.wikipedia.org/wiki/Animal_echolocation
3. [2] https://pmc.ncbi.nlm.nih.gov/articles/PMC3178000/
4. [3] https://www.science.gov/topicpages/b/bat+echolocation+signals