Magnetoreception possibly. Lots of animals including toads and frogs can sense Earth's magnetic field and they're probably just pointing to one of the poles.
Nah, they're all facing towards Frogga (Frog Mecca) for salah (Islamic frog prayer)
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Seriously though, @grimreaper is most likely right. Not all frogs have magnetoreception but some do.
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Seriously though, @grimreaper is most likely right. Not all frogs have magnetoreception but some do.