1. Department of Ecology and Evolutionary Biology Princeton University Princeton New Jersey 08544 USA
2. University Program in Ecology Duke University Durham North Carolina 27708 USA
3. Mpala Research Centre PO Box 555 Nanyuki Kenya
4. Department of Zoology & Physiology University of Wyoming Laramie Wyoming 82071 USA
5. Department of Biology University of Florida Gainesville Florida 32611 USA