My husband and I were backpacking in the Sequoia National Park (CA) and at one off-trail campsite we were surprised by a young buck that came near to camp to eat the dirt where we had recently urinated. After the buck left, a marmot came by and did the same thing. Why?
Salt! Urine contains a lot of salt, so your pee spot acted just like a salt lick. Peeing is a great way to attract butterflies, too! Animals are always looking for good sources of salt.