Spatial patterns and density dependence in the dynamics of a roe deer (Capreolus capreolus) population in central Italy

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Abstract
The demography of roe deer living in a mountain area of central Italy was studied from 1995 to 1999 with 104 radio-tagged animals, including fawns and adults of both sexes. From spring surveys we estimated population density by mark-resighting (average: 53.8±4.8 individuals km–2) and found an average fawn/doe ratio of 0.75±0.4. The fawn/doe ratio was negatively correlated to density suggesting density-dependent regulation in this population. Using culled and net-trapped individuals we evaluated the dressed body weights of adult males (23.1±1.0 kg) and females (22.0±1.0 kg), which indicated a low level of sexual dimorphism. The potential litter size (1.44±0.1 embryos) depended on female body weight and a threshold of 20.9±1.4 kg separated adult females carrying one or two embryos. Both fawn (0.38±0.07) and adult survival (0.90±0.07) were evaluated from radiotagged individuals and no gender effect was observed in either age class. During the study period we recorded a population decline in one part of the study area and an increasing fawn mortality, which was attributed to the spreading of an enteropathogenic desease. The study revealed an unexpected spatial structure in population dynamics at a scale of few square kilometres. In the two studied subareas, which are very close and ecologically similar, we documented significant differences in several demographic parameters: females in the subarea with the highest deer density produced smaller litters and allocated their reproductive effort preferentially to males, which is consistent with the hypothesis that local resource competition determines sex allocation in roe deer. The importance of spatial variability with respect to roe deer demography was overlooked in previous studies and our results raise new interesting research questions relative to the study of population equilibria which are also relevant for the management of this important game species.