Antibiotics affect migratory restlessness orientation

The role of microbiome in shaping animal’s behavior is well established. Accordingly, the use of antibiotics may have profound effects on behavior, which are seldom examined. Recently, the symbiotic magnetic-sensing hypothesis has been forwarded as a mechanistic explanation for the phenomenon of animal magnetoreception. It suggests a symbiotic relationship between magnetotactic bacteria (MTB) and the navigating host. To establish a research protocol for future behavioral studies, we examined the effect of a widely used antibiotic substance on migratory restlessness orientation and on magnetotactic bacteria. Using migrating Eurasian reed warblers, we show that in contrast to the control group, antibiotic treatment caused a lack of clear directionality in an Emlen funnel experiment. Accordingly, the antibiotic treatment group showed a significant increase in directional variance. This effect of antibiotics on behaviors associated with animal magnetic sensing might be considered as preliminary experimental support of the symbiotic magnetic-sensing hypothesis. Further, we lay a preliminary experimental protocol that could be implemented in experiments aiming to prove or refute the symbiotic magnetic sensing hypothesis.