Fission–fusion populations

obese. Applying an understanding of nutritional and evolutionary theory to the modern human nutritional dilemma has turned out to be very enlightening indeed. Who have been your most important mentors? Two people have had the greatest impact on my career. The fi rst was the late Reg Chapman as my PhD supervisor. Reg and his wife Liz Bernays were inspiring, selfl ess and incredibly tolerant. I couldn't have asked for a better supervisory team. The second was the late Sir Richard (Dick) Southwood, a distinguished ecologist and my Head of Department at Oxford for many years. Dick was an extraordinarily effective academic leader. Both Reg and Dick nurtured and brought out the best in their people and encouraged intellectual bravery. They both sent presents when our children were born. I have tried to emulate them, but cannot hope to have Dick's facility for remembering the names and personal details of every member of academic and general staff, graduate and undergraduate student who was ever in his charge. Is fi eld work fun or hard work? Both, but it is essential if you are to have a complete understanding of biology. Sometimes things work spectacularly well but more often they don't. My favourite example was a trip to Utah with Greg Sword, Pat Lorch and Iain Couzin to study why large fl ightless Mormon crickets form massive migrating bands extending kilometres. In a week we managed to conduct a series of experiments proving that the crickets are on a forced march to fi nd limiting protein and salt. The reason they keep moving is because of the threat of cannibalism: the most abundant sources of protein and salt in the habitat are other crickets and if you don't keep moving you get eaten. (A colleague later mentioned that this was a metaphor for academic life.) The discovery that cannibalistic encounters drive mass movement provided a new mechanism for collective movement, which we now know applies also to locusts. Greg and Pat had had a previous trip where a PhD student-to-be of mine, Gabe Miller, had joined the team as a fi eld assistant before starting his research project with me in Oxford. Gabe had secreted a gorilla suit in his fi eld gear. Pat lured Greg to a patch of sage brush under the pretext that a radio-collared cricket was there. Greg, wearing head phones and waving the radio antenna, homed …