It also is unlikely that humans would be an exception here. However, my money still is on "Extraordinary claims require extraordinary evidence". Animals may be capable of magnetoception, but I don't think that has been proven yet.

For example, those foxes could try and minimize their shadows or changes in their shadows. They might do that using an internal clock. Alternatively, they might be able to perceive the polarization of the sky, and use that to guess where the sun is (note the high variation in successful angles)