Pinecone Trivial Pursuit

We have a giant pine tree in our yard, and periodically I collect the pinecones that have fallen to the ground:

Last week I gathered some up and laid them on our picnic table outside. At the time they looked just like the ones pictured above.

It rained that night and the following day. Later that day I went outside, and saw this:

They had all closed up! I didn't know they could do that!
And this sunny, windy morning they have returned to their "openness" once again.