Hunted red deer management: a new tool for population survey
Résumé
Many wild deer populations in the world are considered as threatened and deserving protection measures for population increase; in contrast, some managed deer populations are presently increasing to the point of becoming a nuisance or a permanent pest. In France, free ranging Cervus elaphus populations recently showed a strong increase, the global annual hunting plan rising from 10,000 to 71,000 individuals over the last 30 years. Frequently the local picture was an alternation of population peaks followed by crashes, with an approximate 10-years cycle. Such an evolution results largely from the ineffectiveness of the exhaustive counting methods previously used for deermanagement. Considering both the importance of estimating vital rates for managing deer populations and the extreme difficulty of obtaining reliable data in the field, we devised a new method to survey populations, in order to provide managers with a simple and effective tool. Our method takes advantage of the rich data sample provided by the annual cull, and the fact that hinds are shot randomly in driven hunts; hence the hind cull is a reliable representation of the hind population age structure. The mandibles of all animals killed by hunters are collected and analyzed, which allows the calculation of the ratio of yearling hinds in the total hind cull. Measuring mandible lengths is also an indicator of the populations physical condition. We conducted a survey of the deer population of Paimpont forest (Brittany, France) over ten years, which showed that the standard management methods underestimated population increases, while our yearling hind ratio allowed to more efficiently diagnose population increase and predict population crash. Our method has also been continuously applied since 2007 for deer management in the Indre District (annual cull of some 2000 deer) with promising results. The yearling hind ratio in culls is a simple management tool, dispensing with difficult field counts and allowing for gradual annual correction of management plans. Our study also demonstrated that this approach is applicable in this country on the scale of a whole district, given ad hoc imposed legislation and active contribution of hunting associations and management authorities.