Living on the Edge: Roe Deer (Capreolus capreolus) Density in the Margins of Its Geographical Range

Abstract

Over the last decades roe deer (Capreolus capreolus) populations have increased in number and distribution throughout Europe. Such increases have profound impacts on ecosystems, both positive and negative. Therefore monitoring roe deer populations is essential for the appropriate management of this species, in order to achieve a balance between conservation and mitigation of the negative impacts. Despite being required for an effective management plan, the study of roe deer ecology in Portugal is at an early stage, and hence there is still a complete lack of knowledge of roe deer density within its known range. Distance sampling of pellet groups coupled with production and decay rates for pellet groups provided density estimates for roe deer in northeastern Portugal (Lombada National Hunting Area - LNHA, Serra de Montesinho – SM and Serra da Nogueira – SN; LNHA and SM located in Montesinho Natural Park). The estimated roe deer density using a stratified detection function was 1.23/100 ha for LNHA, 4.87/100 ha for SM and 4.25/100 ha in SN, with 95% confidence intervals (CI) of 0.68 to 2.21, 3.08 to 7.71 and 2.25 to 8.03, respectively. For the entire area, the estimated density was about 3.51/100 ha (95% CI - 2.26–5.45). This method can provide estimates of roe deer density, which will ultimately support management decisions. However, effective monitoring should be based on long-term studies that are able to detect population fluctuations. This study represents the initial phase of roe deer monitoring at the edge of its European range and intends to fill the gap in this species ecology, as the gathering of similar data over a number of years will provide the basis for stronger inferences. Monitoring should be continued, although the study area should be increased to evaluate the accuracy of estimates and assess the impact of management actions.

Propagule pressure and land cover changes as main drivers of red and roe deer expansion in mainland Portugal

“…In turn, roe deer populations have always persisted in a few patches on the north of the Douro River, where its presence was restricted to forested mountain areas (Vingada et al, 2010). Despite this population increase, roe deer densities have remained low, particularly when compared to central and northern European populations (Valente, Marques, Fonseca, & Torres, 2016;Valente et al, 2014). Despite this population increase, roe deer densities have remained low, particularly when compared to central and northern European populations (Valente, Marques, Fonseca, & Torres, 2016;Valente et al, 2014).…”

Estimating red deer abundance using the pellet-based distance sampling method

“…A wide variety of techniques have been used to estimate ungulate density . Among indirect methods, pellet group counting has been widely used to estimate deer densities throughout the world (Marques et al 2001;Jathanna et al 2003;Smart et al 2004;Herrero et al 2013;Valente et al 2014) and while some authors have argued against it (e.g. Morellet et al 2007), others have recommended it, claiming that it can be used to efficiently assess the population size and trends (e.g.…”

“…Acevedo et al 2008). For many species direct methods are not often feasible and are potentially biased in woodland habitats due to elusive animal behaviour leading to extremely reduced detectability (Torres et al 2014b;Valente et al 2014). Advantages of pellet group counts include being easy to implement over large areas, requiring low financial and logistical resources and being especially useful in areas with low visibility (Marques et al 2001;Smart et al 2004).…”

The success of species reintroductions: a case study of red deer in Portugal two decades after reintroduction

“…A histogram is then built, which constitutes the main basis to density and abundance estimates. This methodology requires two conversion factors -the pellet group disappearance rate and the production rate -to convert the density of pellet groups into the density of animals (see Valente et al 2014 for details). The pellet group disappearance rate used was of 581 ± 55 days, obtained for red deer in the same region (Alves et al 2013), while the production rate used, of 25 pellets a day, was based on literature (Mayle 1996).…”

“…The project aimed to increase and restore the herbivore biodiversity of the region but it also had hunting purposes (Vingada et al 2010). In order to evaluate the success of the abovementioned releases, as well as to provide valuable data for management plans, we used an indirect method (pellet group counting) coupled with distance sampling (Valente et al 2014;Torres et al 2015), to estimate the current density and distribution of red deer populations in Lousã mountains, two decades after their reintroduction.…”