Evidence for plasticity in magnetic nest-building orientation in laboratory mice

Previous studies have shown that mammals exhibit two distinct forms of magnetic behaviour: spontaneous magnetic alignment and learned magnetic compass orientation. However, it remains to be determined whether the type of magnetic response is species specific (i.e. species exhibit either learned magnetic compass responses or spontaneous magnetic orientation). Alternatively, learned and spontaneous magnetic orientation may be context dependent and expressed in the same species under different conditions, e.g. motivational, physiological and/or environmental. Using C57BL/6J laboratory mice, we provide evidence for multiple spatial responses to magnetic cues in the same species. In a series of three similar nest-building experiments in which mice were trained to construct nests in one of four magnetic directions, mice either positioned nests along a fixed northeast-southwest magnetic axis (Series 1), independent of the trained direction, and similar to spontaneous magnetic alignment responses in other vertebrates, or exhibited learned magnetic compass orientation in the direction away from (Series 2) or towards (Series 3) the sheltered end of the magnetic axis they had been exposed to during the training period. Importantly, the responses elicited in each series paralleled changes in the experimental protocols and may help to explain the variation in magnetic behaviours. Furthermore, the plasticity in the magnetic orientation exhibited by laboratory mice suggests that magnetic cues play important role in the spatial ecology of epigean rodents. Characterizing the factors that elicit these responses will shed light on the adaptive significance of spontaneous magnetic alignment, a widespread but poorly understood spatial behaviour. In addition, future studies with similar nest-building assays will likely play a role in helping to determine whether magnetic compass orientation and spontaneous magnetic alignment are mediated by the same underlying mechanisms of magnetoreception.