Impact of ungulates on Mediterranean small mammal communities: a case study in the Côa Valley

• Autor(a) principal: Sabino, Ana Sofia Fialho
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/34467
• topic: Rodents; Insectivorous; Ungulates; Rewilding; Portugal

The Côa Valley is a biodiversity hotspot, however, in recent decades, the rural abandonment, the restoration of some areas and the agroforestry policies adopted have made the landscape of this region particularly vulnerable to rural fires. The introduction or reintroduction of ungulate species in a semi-wild regime has been tested as a way to control phytovolume and plant biomass, and thus decrease the probability of fire occurrence. As keystone species of the Mediterranean ecosystem, ungulates exert a range of impacts not only on vegetation, but also on other vertebrate communities. In this study, small mammals were defined as a model group in order to evaluate the impacts of ungulate grazing at different levels of pressure on wildlife communities. Small mammals play a fundamental role in food chains, with top-down effects on plant and invertebrate communities and bottom-up effects on the mammals and birds that feed on them, being important bioindicators with a relatively fast response time to disturbances. In this study, small mammals were captured in four areas with different levels of ungulate pressure (two replicates per plot) in the Faia Brava reserve, Quinta do Sol and Quinta de São Paulo. At each sampling point, the captured species, body metrics and parasite load were recorded. Camera trapping was used to determine the effective use that ungulates and mesocarnivores make of the sampled areas. During the two sampling periods (autumn 2020, spring 2021), individuals from four species were captured: the rodents Apodemus sylvaticus, Mus spretus and Eliomys quercinus and the insectivore Crocidura russula. Here, I used Generalized Linear Mixed Models (GLMM) to determine which variables determine the abundance and body condition of small mammals. The abundance of small mammals was higher in the exclusion area and reduced in the area with high density of ungulates. The intermediate-pressure area revealed high values in the abundance of small mammals and the highest richness of rodents, ungulates and mesocarnivores. The area of intermediate-pressure was characterised by the highest percentage of vegetation, shelter and food for small mammals. The results showed a negative influence of high grazing intensity on the abundance of small mammals, with the exception of A. sylvaticus. Body condition of A. sylvaticus was positively influenced by the presence of ungulates. The body condition of C. russula presented very similar values in all areas with a slight increase in the intermediate-pressure area, while M. spretus were negatively impacted. These results revealed that the reintroduction of ungulates at intermediate densities does not cause a marked disturbance in the small mammal community, as it contributes to maintain landscape heterogeneity and favours different densities of shrubs and tree cover. These results represent an important step towards the restoration of the functionality of Mediterranean ecosystems.