1. Department of Animal and Range Sciences; New Mexico State University; PO Box 30003, MSC 3-I Las Cruces NM 88003 U.S.A.
2. Mpala Research Centre; PO Box 555 Nanyuki Kenya
3. Department of Ecology and Evolutionary Biology; Princeton University; Princeton NJ 08544 U.S.A.
4. U.S. Geological Survey; 2290 S West Resource Blvd Moab UT 84532 U.S.A.