Catlow has been getting out daily the last several days. She was walking through the electric fence. I fixed it repeatedly, but I was too chicken to test it myself. It turns out that we had wired the new larger pasture incorrectly and so it wasn't hot all the way around! It took this long for a horse to figure it out and brave the fence. And of course, it's because their pasture is becoming eaten down, but it is by no means barren of grass. She just discovered how easy it was to graze through the fence, and then just step through, bagging out the wire as she went. Cody and Chico still respected the fence and so they never went through.
So, we fixed the connections, and then increased their pasture to include the lower part of the field too. They've got some NICE long grass to graze now.
Here are some pictures of them exploring the new pasture, with the dogs tagging along and getting in trouble for chasing them when they ran at one point!