Investigating population dynamics in ungulates: are hunting statistics a good index of population abundance?

Time series analysis plays an important role in the detection of mechanisms that drive population fluctuations. However, long time series are rare, with ungulate data sets usually not exceeding 50 years. In this article, we describe a long-term data set of population density indices of five ungulate species obtained from the analysis of bag records collected in the Castelporziano Preserve, Rome, Italy. Hunting statistics are often used as proxies for population density; however, in the case of long time series for large mammals, there are no comparative studies to assess the validity of such data. We evaluated the ungulate time series, using two different approaches: we 1) compared hunting statistics with independent animal counts, and 2) assessed whether or not habitat composition of the drive areas was representative of habitat availability in the whole estate. Regressions between bag data and animal counts gave significant results only for three species, whereas bag data corrected for hunted area were significantly correlated to animal counts for all five species. The results suggest that use of bag records not corrected for hunting effort and without any previous validation could lead to misleading estimates of abundance indices. Finally, our analysis showed that density indices of the five species were not significantly affected by the selection of habitats where hunting drives were organised. Our data set may contribute to the understanding of ungulate ecology in the Mediterranean environment.