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

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) 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.

Achieving landscape‐scale deer management for biodiversity conservation: The need to consider sources and sinks

“…Although deer fertility and survival rates found in this study (Table B.1, available online at www.onlinelibrary.wiley.com) were within the range found elsewhere in the United Kingdom and Europe, for roe, these rates vary among regions (adult fertility: 0.35-1.80 fetus/doe; juvenile fertility: 0.30-1.60; neonatal survival: 0.17-0.75; (Ratcliffe andMayle 1992, Focardi et al 2002). Thus, managers must establish regionally relevant demographic measures, particularly as effective control may result in density-dependent increases in fertility (Focardi et al 2002, Pettorelli et al 2003. Although this requires consistent measurement of reproductive parameters for culled individual, fetus counts in the uterus of culled females are straightforward and are routinely collected by many stalkers; further training for novice hunters is available from deer management groups.…”

Reproductive potential of Roe Deer (Capreolus capreolus L.)

“…The number of fawns per doe was higher in the area with lower density. Effects of density also reflected in fawn sex ratio, as the proportion of male fawns was higher in the area of higher density (Focardi et al, 2002). However, there was no observed link between density and fawn sex ratio in studies done in Belgium (Wauters et al, 1995).…”

“…Roe deer fecundity, similar to that of some other ungulate species, depends on body mass (Gaillard et.al., 1992;Gerhart et al, 1997;Hewison and Gaillard, 2001;Focardi et al, 2002;Macdonald and Johnson, 2008; also see Table 2). Hewison and Gaillard (2001) investigated the number of fertilized ovulations per reproductive roe deer doe (by counting the number of corpora lutea in ovaries) from nine different populations in Great Britain.…”

“…In this context, density is considered to affect fertility through different indirect parameters, such as stress, food availability, body masses, etc. Roe deer body mass can be density-dependent; as population density increases, there is a reduction in body mass of roe deer Petorelli et al, 2001;Focardi, 2002) and roe deer fawns (Petorelli et al, 2001;Toïgo et al, 2006). Population density effects are also reflected in home-range size and in intraspecific interactions, e.g.…”

“…Impacts of population density on reproductive parameters have been detected in various large herbivore species (red deer: Bonenfant et al, 2002;McLoughlin et al, 2008;other species: Bonenfant et al, 2009;Hamel et al, 2009a). In the case of roe deer, it is reflected in the number of fertilized ovulations and fertility of does (Focardi et al 2002), litter size and number of fawns per doe (Vincent et al 1995;Focardi et al, 2002), fawn sex ratio (Focardi et al, 2002) and age of primiparity (Vincent et al, 1995).…”