A dirty bush pig could also be described as an unclean human being that looks like they just came out of an extended camping trip where no water was available.
“Don’t be act like dirty bushpigs! Clean up after yourself! You look terrible! Have you been into the pills again?!
"Hey man, last night was so crazy! I was getting it on with Melissa and I went to stick it in but I got lost in the bushes and ended up down a dirt road."
"What did she say to that?"
"All she said was, 'Wrong hole but keeping going'!"