The tragedy of the commons: unsustainable population structure of Iberian red deer in hunting estates
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Hunting can influence population structure with consequences in ecological and evolutionary processes. Populations of Iberian red deer (Cervus elaphus hispanicus) in Spain occur under two different management regimes: fenced and unfenced (open) estates. We compared census data, hunting bags and data from hunted individuals between both types of estates. Harvest on stags was moderate in fenced estates but strong in open ones, probably due to the competition between neighbouring landowners over the same deer populations. On the contrary, female culling was low in open estates compared to fenced ones. As a result, populations in open estates have mostly young males and strongly female-biased sex ratios. Female-biased population structure in open estates did not result in higher number of males being harvested per year compared with fenced estates, probably due to negative effects on development, survival and reproduction, and harvested males were younger, and hence, with smaller antlers. There is published evidence for undesirable effects of biased population sex ratio and age structure in these red deer populations. Our results indicate that this type of management may be unsustainable and recommend that harvest on males in open estates should be reduced and that on females increased, in order to maintain a more balanced population structure that may allow sustainable population dynamics and the operation of natural evolutionary processes.
KeywordsGame management Ungulates Iberian red deer Cervus elaphus hispanicus Fenced estates Open estates
Our study was initiated under a collaborative agreement between the University of Extremadura and Consejería de Medio Ambiente of Junta de Andalucía. We thank R. Arenas and the staff at Consejería de Medio Ambiente in Córdoba for their support at different stages of our study. We are also grateful to the owners and wardens of the estates studied and to the hunters. C. Sánchez-Prieto, L. Castillo, J.M. Seoane, A. Casado, O. Linares and P. Montero helped in laboratory and fieldwork. This work complies with current Spanish laws. Additional financial support came from Spanish Ministry of Science, project CGL2010-17163.
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