"I've picked up hundreds since I started and I've been doing it on my holidays too. I'll keep picking them up until people start caring more and stop dropping them on the ground," he said.
" I just realised that maybe the animals would start choking on them if they were all over the ground. It's just not right."
He and Sadie have a family cat at home named Binck and the pair will remain committed to their campaign for their pet's sake and other similar small animals.
Although his campaign was not widely known at his school, Charlie said "that's all right, I'm just really doing it for the animals".
Charlie's mother, Janelle Preston Searle, said she and her family were proud Charlie and his little sister had on their own developed such care for animals and their world, and she was "so pleased that at a young age they are aware of environmental issues".
Grandmother Lois Preston called the campaign their "little mission to save the universe" and likewise applauded Charlie and Sadie.