Expansion of native wild boar populations is a new threat for semi-arid wetland areas

Joaquín Vicente,Christian Gortazar,Javier Viñuela,Antonio Carpio,Xurxo Piñeiro,Mariana Boadella,Carlos Zumalacárregui,Jose A. Barasona

doi:10.1016/j.ecolind.2021.107563

Abstract

Wildlife management and conservation requires monitoring of species distribution and population indicators, especially when the unbalanced demographic changes of some species can affect the whole ecosystem functioning. The populations of wild boar (Sus scrofa) have, over the past few decades, undergone an expansion around the world, reaching situations of overabundance that can cause serious economic, ecological and health problems. This numerical increase of wild boar and its new spatial invasion can affect certain vulnerable species in sensitive ecological zones, such as the main inland wetland complex in SW Europe.In this context, we aim to (i) examine the association of wild boar abundance and that of lagomorphs, and waterbird productivity, controlling the possible effects of wild carnivores and other environmental predictors, and (ii) applying a survey method useful for managers to evaluate expected effect of wild boar abundance.Overall, the presence of wild boar has been detected in 80.8% of the monitored wetlands (n = 26), but a high variation of abundance rates was found. Wild boar abundance negatively associated with the productivity of the entire community of waterbirds, a priori highly vulnerable, breeding on shores or islands, both colonially (genus Gelochelidon, Himantopus, Recurvirostra, Sternula, Glareola, Tringa and Phoenicopterus) or solitary (genus Anas, Spatula, Mareca, Charadrius, Vanellus, Anser, Ardea, Aythya, Fulica, Netta, Oxyura and Tadorna).In addition, we evidenced a clear negative association of wild boar and wild rabbit (Oryctolagus cuniculus) population abundance in the monitored wetlands. Rabbits are a keystone species in the study area and represent stable prey for many endangered predators.Our results suggest that potential impacts caused by high wild boar abundance may be already reaching unsustainable levels for some wetlands. Inter-species integrated monitoring is key to address the population management plans of wild boar populations in wetlands and to preserve the most vulnerable species.

Highlights

The Eurasian wild boar (Sus scrofa) is adapted to a broad range of environmental conditions and nowadays is considered one of the most widely distributed mammals in the world (Baskin & Danell, 2003)
Our results suggest that potential impacts caused by high wild boar abundance may be already reaching unsustainable levels for some wetlands
A variety of factors have been related to ongoing wild boar expansion, such as high reproductive rates and adaptability of a species suffering low predation rate, large-scale favourable changes in habitat, legal restrictions on hunting, as well as hunting strategies aiming sustainable harvesting (Barrios-Garcia & Ballari, 2012)

Summary

Introduction

The Eurasian wild boar (Sus scrofa) is adapted to a broad range of environmental conditions and nowadays is considered one of the most widely distributed mammals in the world (Baskin & Danell, 2003). The impact of over-abundant wild boar on biodi versity conservation and socio-economic interests include sanitary risks to wildlife, livestock and people, vehicle collisions, crop damage, and reduction in plant and animal abundance and richness (Massei & Genov, 2004; Barrios-Garcia & Ballari, 2012; Vicente et al, 2013) Besides their direct effects on plant and animal communities (e.g. predation), wild boar can indirectly affect the whole ecosystem functioning through cascading effects caused by modification of vegetal community and habitat structure induced by extended rooting, so it can be considered a relevant ecosystem engineer (Massei & Genov, 2004; Teichman et al, 2013; Carpio et al, 2014). Wildlife manager interested in developing management policies to mitigate the emerging problem of wild boar expansion requires precise information about the potential ecological effects of wild boar on other species

Objectives

Methods

Results

Conclusion