Those plastic annihilating little critters might be red squirrels . They have destroyed a few plastic gas containers and also completrly devoured a gas cap and the spout on my snowblower one summer. One fall my insulated gloves would mysteriously disappear if I happened to leave them on the wood pile low and behold there they were expertly tore apart and turned into cozy little nests in various nooks and crannies in the wood stcks. Tried trapping them but after catching a couple birds I folded. Hell give em some credit for ingenuity.