I've tried to look for it but couldn't find the reference, where it's said that Dogs & other animals instinctively position themselves in South/North (and other directions but not with their behind facing East)?
Thanks in advance!
This is a recent answer from science, not religion. See https://www.pbs.org/newshour/science/dogs-poop-in-alignment-with-earths-magnetic-field-study-finds
Excerpt/summary: Researchers measured the direction of the body axis in 70 dogs of 37 breeds during defecation (1,893 observations) and urination (5,582 observations) over a two-year period. Directional preferences of dogs under different MF conditions were analyzed. Results: Dogs preferred to excrete with the body being aligned along the North–South axis under calm Magnetic Field conditions.
It's not a perfect match, but you might be thinking of Yoma 3:8, which says that the bull of the Kohen Gadol on Yom Kippur is positioned so that it won't relieve itself towards either the Temple or the Altar.