What's up with the pigs?

This past weekend, my friend "C" was here to interview for a position with a high tech company in or around Portland. We hung out on Saturday and I showed her around town so she could start to get a feel for whether or not she wants to move here (she does!). As we wandered around, we stumbled upon The Pigs.

Now, I've seen the pigs before. They reside directly in front of our favorite gelato shop on NW 23rd. There are 4 of them, and someone has taken the liberty of giving collars and ID tags to the big ones. The 4th is a tiny baby, and as you can see from the picture, he or she is about to be squashed by the pig who is name, appropriately, "Porklandia." The other two are Petunia and Porky. I suppose Baby doesn't have a name since he/she isn't long for this world anyway.

But what's with the pigs? There is no plaque or explanation that I can find near the pigs. Googling turned up nothing. Does anyone know the story behind these statues?

For your entertainment...