Depends on the animal, as many simply "observe" (perhaps literally) the magnetic field: https://en.wikipedia.org/wiki/Magnetoreception https://en.wikipedia.org/

Depends on the animal, as many simply "observe" (perhaps literally) the magnetic field: https://en.wikipedia.org/wiki/Magnetoreception https://en.wikipedia.org/wiki/Magnetoreception VLF transmissions probably don't twig the senses all that much, but it's an interesting hypothesis.