Dogs preferred to excrete with the body being aligned along the North–South axis under calm MF conditions. This directional behavior was abolished under unstable MF. The best predictor of the behavioral switch was the rate of change in declination, i.e., polar orientation of the MF.
I have included a PDF file >> Click here>> Dogs are sensitive to small variations of the Earth’s magnetic field.
PBS reported on this in early 2014. See >>> http://to.pbs.org/1TPkOET