My rabbits have a very large hutch and run with 24h access. The run has turned into a quagmire right now and they are spending most of their time in the hutch. I let them in the garden too at least for a few hours a day, so they do have plenty of exercise. I did think of straw, but that will just get soggy, then I thought of wood chippings, but I'm not sure if that will get really hot in the summer? Another thought was a couple of wooden decking tiles. Any ideas? They do have a tarp.