Abstract
Simple SummaryWe examined the relationship between the number of tail lifts of lizards (Pogona vitticeps) and environmental factors, such as the calendar month, daily mean temperature, daily mean humidity, daily mean atmospheric pressure, lunar phase (full moon/new moon), and K index as a geomagnetic disturbance index using 16 months of data. We set up an extremely low-frequency electromagnetic field (ELF-EMF) group and a control group. In a multiple linear regression analysis, the independent determinants associated with the number of tail lifts were the full moon, the temperature, February, March, April, and May in the ELF-EMF group and March, April, May, and June in the control group. The P. vitticeps in the ELF-EMF group responded to the full moon whereas those in the control group did not.We previously showed that the agamid lizard Pogona vitticeps responded to an extremely low-frequency electromagnetic field (ELF-EMF; frequency: 6 and 8 Hz; peak magnetic field: 2.6 µT; peak electric field: 10 V/m) with tail-lifting behavior. In addition, the tail-lifting response to ELF-EMF disappeared when the parietal eyes of the lizards were covered by small round aluminum caps. This result suggests that the parietal eye contributes to light-dependent magnetoreception. In the present study, we set up an ELF-EMF group to evaluate the long-term effect of the ELF-EMF on lizards’ behavior and examine our hypothesis that exposure to ELF-EMFs increases the magnetic field sensitivity in lizards. We therefore include the lunar phase (full moon/new moon) and K index as environmental factors related to the geomagnetic field in the analysis. The number of tail lifts per individual per day was the response variable while calendar month, daily mean temperature, daily mean humidity, daily mean atmospheric pressure, full moon, new moon, and K index were the explanatory variables. We analyzed an ELF-EMF group and a control group separately. In a multiple linear regression analysis, the independent determinants associated with the number of tail lifts were the full moon, the temperature, February, March, April, and May in the ELF-EMF group and March, April, May, and June in the control group. The P. vitticeps in the ELF-EMF group responded to the full moon whereas those in the control group did not. In addition, in the ELF-EMF group, the number of tail lifts was higher on days when the K index was higher (P = 0.07) in the first period whereas there was no such tendency in either period in the control group. There is the possibility that the exposure to ELF-EMFs may increase magnetic-field sensitivity in lizards.
Highlights
A wide range of taxa, such as mollusks, crustaceans, insects, fishes, birds, mammals, and amphibians, have a magnetic sense and use magnetic compasses to orient themselves in what is referred to as magnetoreception in animals [1]
P. vitticeps occurs in spring [13] and that the lizard Leiocephalus carinatus curls its tail as a component of display during courtship [12]
In the extremely low-frequency electromagnetic field (ELF-EMF) group, the number of tail lifts was higher on days when the K index was higher (P = 0.07) in the first period whereas there was no such tendency in either period in the control group
Summary
A wide range of taxa, such as mollusks, crustaceans, insects, fishes, birds, mammals, and amphibians, have a magnetic sense and use magnetic compasses to orient themselves in what is referred to as magnetoreception in animals [1]. One is that magnetoreception employs a chemical compass based on a radical pair mechanism and the other is that magnetoreception has a magnetite-based mechanism [9,10]. The tail-lifting response to ELF-EMF disappeared when the lizards’ parietal eyes were covered by small round aluminum caps. This result suggests that the parietal eye is involved in light-dependent magnetoreception
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