Caption: "A depiction of a bat, its ultrasound call, and the echo from an object."
As is well known, bats use echolocation help navigate: the time delay of the echo allows them to determine distances.
Slightly less well known is that they use of the Doppler effect for sound with echolocation. They emit high-frequency sound and judge relative speeds based on the frequency of the echo---and they don't need any formulae---just megayears of evolution (see Wikipedia: Echolocation: Doppler effect).
See Bat videos below (local link / general link: doppler_effect_bat.html):
Credit/Permission: Petteri Aimonen,
2009 /
Public domain.
Image link: Wikipedia:
File:Animal echolocation.svg.
Local file: local link: doppler_effect_bat.html.
File: Waves file:
doppler_effect_bat.html.