Monarchs

When monarch butterflies leave Wisconsin, they fly to a valley they have never seen before in Mexico. They were born in the USA. There seems to be some kind of hereditary memory involved. I've no idea how this works.

I wonder how long it takes for such a hereditary memory to develop.

I suspect that in the past four years the butterflies have learned that wherever you see this sign, someone with white fluff on a long stick is going to snare you, grab you, and poke a sticker on your wing, and then all the other butterflies will laugh at you.

They have been extremely skittish this year.

UPDATE: But seriously: "When applied as directed, the tags do not interfere with flight or otherwise harm the butterflies." But if mates are looking for symmetrical wings, the tagged ones (the not-so skittish ones) may not mate as often.