Why does your old dog lick mud?

well dogs dont ussually just do silly things! if your dog is licking mud it might be thirsty because well, mud is a mixture of dirt and water! you never know. dogs are very interesting. before you take your dog for a walk next time: give him/her lots of water! if this isnt the case; next time him/her goes in for a checkup at the vets; ask! im sure they would be glad to answer (; hope this helped!