Monitoring populations of a guild of ungulates: implications for the conservation of a relict Mediterranean forest

Abstract

We reviewed information on the population dynamics of ungulate populations in the Preserve of Castelporziano, Italy. Based upon hunting bags, long-term series of indices of abundance are available for fallow deer (Dama dama), wild boar (Sus scrofa majori), roe deer (Capreolus capreolus italicus), red deer (Cervus elaphus), and nilgai (Boselaphus tragocamelus) for the period from 1878 to 1986. In the absence of large predators, but in presence of hunting, population regulation is basically determined by density dependence. However, our data also show that roe deer are competitively affected by fallow deer, while the dynamics of wild boar is relatively disconnected from those of cervids. The impacts of climate and habitat variations on the growth rates of ungulates appeared to have limited relevance in this ecosystem. Standardised counts on green flush areas in spring, performed annually since 1988, show the presence of important interactions among the different species and the negative impact of fallow deer on roe deer. Further, spring counts suggest that wild boar populations exhibit stable fluctuations within a 3–5-year period. Nocturnal distance sampling estimates of fallow deer and wild boar populations, available since 2002, confirmed the broad picture obtained by spring counts, but also allowed us to estimate the actual population size and compute appropriate confidence intervals. The evaluation of the pros and cons of different monitoring methods is relevant to wildlife agencies to select the ones most suitable for offering a particular type of information and to underpin informed decisions on the best management practices to implement.