Monarch butterflies are tracked by people, who use the unique identifiers on the passive tags to identify butterflies and record where they were spotted/capture

Monarch butterflies are tracked by people, who use the unique identifiers on the passive tags to identify butterflies and record where they were spotted/captured. The tags themselves are no more than a sticker designed to stick to butterflies without impeding or harming them - they started making them in 1992, afterall. GP is talking about active tags that get their coordinates by using GPS satellites and (I assume) phone home in some way.