Squirrel Power?

Ever since we moved in last fall, we've stored bird seed under our back porch (which is underpinned in lattice) in hard plastic recycled kitty litter tubs with tight snap-on lids. When I went out to feed the birds yesterday, this is what I discovered. We had seen squirrels on our lattice and porches, so we can only assume that these critters were the culprits... nothing else could squeeze through the lattice, we're thinking! But who would believe they could chew right through this hard plastic!

At any rate, the bird seed is now in the garage, and the critters are on probation - no more seed for a few days!