Spontaneous magnetic alignment behaviour in free-living lizards
Several species of vertebrates exhibit spontaneous longitudinal body axis alignment relative to the Earth’s magnetic field (i.e., magnetic alignment) while they are performing different behavioural tasks. Since magnetoreception is still not fully understood, studying magnetic alignment provides evidence for magnetoreception and broadens current knowledge of magnetic sense in animals. Furthermore, magnetic alignment widens the roles of magnetic sensitivity in animals and may contribute to shed new light on magnetoreception. In this context, spontaneous alignment in two species of lacertid lizards (Podarcis muralis and Podarcis lilfordi) during basking periods was monitored. Alignments in 255 P. muralis and 456 P. lilfordi were measured over a 5-year period. The possible influence of the sun’s position (i.e., altitude and azimuth) and geomagnetic field values corresponding to the moment in which a particular lizard was observed on lizards’ body axis orientation was evaluated. Both species exhibited a highly significant bimodal orientation along the north-northeast and south-southwest magnetic axis. The evidence from this study suggests that free-living lacertid lizards exhibit magnetic alignment behaviour, since their body alignments cannot be explained by an effect of the sun’s position. On the contrary, lizard orientations were significantly correlated with geomagnetic field values at the time of each observation. We suggest that this behaviour might provide lizards with a constant directional reference while they are sun basking. This directional reference might improve their mental map of space to accomplish efficient escape behaviour. This study is the first to provide spontaneous magnetic alignment behaviour in free-living reptiles.
KeywordsBasking behaviour Lacertidae Lizards Magnetic alignment Magnetoreception
The results presented in this paper rely on the data collected at Observatori de l’Ebre. We thank the Instituto Geográfico Nacional (Spain) for supporting its operation and the INTERMAGNET for promoting high standards of magnetic observatory practice (www.intermagnet.org). Field work in Balearic Islands was supported by the grants CGL2012-39850-CO2-02 and CGL2015-68139-C2-2-P from the Spanish Ministry of Economy and Competitivity.
FJDR conceived the study and wrote the manuscript; FJDR, VPM and APC conducted all the experimental work and FJDR carried out the statistical analysis. All authors gave final approval for publication.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Ethical standard statement
All applicable institutional and/or national guidelines for the care and use of animals were followed.
Field work in Balearic Islands carried out by VPM and APC was supported by the grants CGL2012-39850-CO2-02 and CGL2015-68139-C2-2-P from the Spanish Ministry of Economy and Competitivity. FJDR received no funding.
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