Magnetoreception in mammals and birds: a comparison (Mammalia, Aves)

Abstract

The magnetic compass systems of birds and mammals differ in their functional modes and are based on different physical principles: The inclination compass of birds is not sensitive to polarity; it is light-dependent; with the direction indicated by spin-chemical processes in the photo-pigment cryptochrome. The polarity compass of mammals works also in total darkness and is based on magnetite, a biogenic iron-containing substance. Aside from the compass, birds include magnetic components in their navigational ‘map’; these components are based on magnetic intensity and are perceived by magnetite-containing receptors. Mammals probably also have a ‘map’, but its components are unclear. Reception based on magnetite particles appears to be the primary form of sensing the magnetic field, which, in the course of evolution, developed in different ways in the various animal groups: in mammals into a compass system to determine directions and in birds into parts of the ‘map’ to determine position.