Magnetic map navigation in a migratory songbird requires trigeminal input

Alexander Pakhomov,Henrik Mouritsen,Dominik Heyers,Nikita Chernetsov,Anna Anashina,Dmitry Kobylkov

doi:10.1038/s41598-018-30477-8

Abstract

Recently, virtual magnetic displacement experiments have shown that magnetic cues are indeed important for determining position in migratory birds; but which sensory system(s) do they use to detect the magnetic map cues? Here, we show that Eurasian reed warblers need trigeminal input to detect that they have been virtually magnetically displaced. Birds with bilaterally ablated ophthalmic branches of the trigeminal nerves were not able to re-orient towards their conspecific breeding grounds after a virtual magnetic displacement, exactly like they were not able to compensate for a real physical displacement. In contrast, sham-operated reed warblers re-oriented after the virtual displacement, like intact controls did in the past. Our results show that trigeminally mediated sensory information is necessary for the correct function of the reed warblers’ magnetic positioning system.

Highlights

To perform true navigation, migrating animals need both a compass and a map[1,2,3,4,5]
When we tested Eurasian reed warblers in the natural magnetic field of Rybachy, they oriented in their seasonally appropriate NE direction (α = 42° [all directions in this paper are indicated relative to geographic north], r = 0.54, n = 49, P < 0.001, 95% confidence interval of the group mean direction [CI_mean] = 22°–61°)
After the orientation tests at the capture site, and prior to the virtual magnetic displacement, we split the birds into two groups with very similar circular distributions

Summary

Introduction

To perform true navigation, migrating animals need both a compass and a map[1,2,3,4,5]. Since we did not manipulate magnetic cues in the real displacement experiments, we could not demonstrate that magnetic information was used/blocked To critically test this hypothesis, it was necessary to perform a virtual magnetic displacement study[9], in which the magnetic information was the only parameter changed while all other potential cues remained unaltered. The results of this crucial study are reported here. The birds never left the highly homogeneous magnetic field area in the centre of the coil system Both the housing cages and the Emlen funnels provided the birds with free access to all non-magnetic cues including unaltered photoperiodic, celestial, olfactory, and landmark cues[10]

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Conclusion