Hi Sabrina,
A few years ago I put mine in a field a guy had had a few bonfires in to get rid of some old wood/garden waste before I put them in and after a few weeks he said he kept seeing them at the spots where he’d had the fires. They’d eaten all the bits of old charcoal and all the ash got eaten too. Licked it down to the earth underneath. Maybe it’s minerals or maybe it’s that they like the taste of it?
Who knows as I’ve found they are all a bit mental. Another one I’ve watched pee on the ground then before it soaked in she’ll turn round and slurp it up.
Before anyone asks, plenty of water, feed blocks and salt licks etc in the fields with them.
Maybe they just like the taste of that particular earth they are eating?