Which innovative packaging design for a wildlife conservation product featured an empty outline of an endangered animal that gradually 'filled in' as donations increased?

Conservation organizations use various packaging and marketing strategies to raise awareness and funds for endangered species. Some designs have become iconic in the conservation world, driving significant awareness and donation campaigns. Test your knowledge about innovative packaging designs that have made a difference in wildlife conservation efforts!

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WWF's 'Disappearing Species' labels that slowly faded when exposed to light
National Geographic's 'Last of Their Kind' chocolate bars with endangered animals that melted away when unwrapped
The 'Donation Silhouette' water bottles by IFAW that revealed animal shapes as water levels decreased
WildAid's 'Fill the Void' campaign with transparent packaging that gained color as donation goals were met