How do animals navigate using Earth's magnetic field?

The answer

Magnetoreception - sensing Earth's magnetic field - guides migration in birds, sea turtles, salmon, and even lobsters. European robins use a quantum mechanical process in cryptochrome proteins in their retinas, which may allow them to literally 'see' magnetic field lines as light patterns. Sea turtles imprint on the magnetic signature of their birth beach and return decades later to nest within kilometers of it. In 2021, a study in Nature revealed that dogs preferentially align along the north-south axis when defecating, suggesting they too sense magnetic fields. Magnetotactic bacteria contain chains of magnetite crystals that function as nano-compasses, orienting them along field lines since the Archean eon.