Migratory songbirds can perceive the Earth’s magnetic field for the purpose of navigating their exceptional voyages or orienting in their local habitats. One particular modality of this sense, a magnetic inclination compass, is thought to rely on magnetically sensitive radical pairs formed photochemically in cryptochrome proteins in the animal’s retinae. This process is a striking example of a truly quantum mechanical process in sensory biology. It necessitates long-lived electron spin coherences in the radical pair.
An important requirement of this hypothesis is that the electron spin relaxation is slow enough for the Earth’s magnetic field to have a significant effect on the coherent spin dynamics of the transient radical pair. This proposal aims to elucidate spin relaxation pathways based on a comprehensive analysis of the thermally induced motions in the radicals and their surroundings.