1. School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588
2. Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA 90560
3. Station d´Ecologie Théorique et Expérimentale du Centre National de la Recerche Scientifique (UAR2029), Moulis 09200, France
4. Research Department, National Headquarters, Canine Companions for Independence, Santa Rosa, CA 95407