In most species, sport hunting of male trophy animals can only reduce overall population size when the rate of removal of males is so high that females can no longer be impregnated. However, where males provide extensive paternal care, the removal of even a few individuals could harm the population as a whole. In species such as lions, excessive trophy hunting could theoretically cause male replacements (and associated infanticide) to become sufficiently common to prevent cubs reaching adulthood. Here we simulate the population consequences of lion trophy hunting using a spatially explicit, individual-based, stochastic model parameterized with 40 years of demographic data from northern Tanzania. Although our simulations confirm that infanticide increases the risk of population extinction, trophy hunting could be sustained simply by hunting males above a minimum age threshold, and this strategy maximizes both the quantity and the quality of the long-term kill. We present a simple non-invasive technique for estimating lion age in populations lacking long-term records, and suggest that quotas would be unnecessary in any male-only trophy species where age determination could be reliably implemented.
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Acknowledgements We thank the government of Tanzania for permission to conduct research; K.W. was supported by the Wildlife Conservation Society, Big Game Special Projects Foundation, John D. & Catherine T. MacArthur Foundation, Graduate School of the University of Minnesota, Dayton-Wilkie Foundation, and Global Wildlife Trust; C.P. was supported by the McKnight Foundation and NSF LTREB and Animal Behavior programmes. We thank T. Gelatt, P. West, G. Hopcraft, M. Craft, B. Kissui, L. Frank, S. Mduma, T. Ramme, W. Testa, T. Coulson and N. Leader-Williams for advice, assistance and discussion.
Acknowledgements We thank the many taxonomic specialists and field technicians who collected and identified plant material during the study, and the A. W. Mellon Foundation, the NASA-LBA Program, the Conservation, Food and Health Foundation, the US National Science Foundation, the MacArthur Foundation, the National Institute for Amazonian Research (INPA), and the Smithsonian Institution for support. Comments from O. L. Phillips, J. A. Pounds, S. L. Lewis, S. J. Wright, K. Winter, T. R. Baker, R. K. Didham, R. Harrison, T. A. Kursar and P. D. Coley improved the manuscript.