I prefer "litter pigs". The pig possesses high intelligence. Its problem is its messiness and sloth. And, fyi, a pig will eat bacon. I learned this by feeding and observing pigs at an outdoor education center as a child. The pig offers far better grounds for comparison to the person who litters. Reminds me of litterers, the cannibals of the environment.
While you'll never convince a pig not to roll in the mud, you can make it awfully difficult for the creature to do so through training or a change in the environment. The same goes for litter pigs, the four out of ten people who say they litter. Most can be taught to control their littering habit. They just have to stop acting like pigs, and I mean no disrespect to the pig.
If you see the words 'litter pigs' in a future post, you'll know who I'm talking about.