Seems this thread has diverged; @Valens Legacy implies that the equinox should detect magnesium containing bones such as teeth or walrus tusks, while @Steve Herschbach points out that non-conductive items will generally be invisible to the EM search of a detector unless they coincide with a void that alters the ground signal. At the very minimum I can report that the equinox does not in fact detect my cat in any obvious way, even at the highest sensitivity. I think a third possibility exists; perhaps snakes are not generally detectable, which is what you would expect, but these snakes were tagged somehow, perhaps for research and tracking purposes.