Determinants of Small Mammals' Body Condition in Eucalyptus Dominated Landscapes

The timber industry has increased considerably in recent decades to meet human needs for wood. In Portugal, Eucalyptus plantations are the most common use of forested land, presenting the largest coverage of Eucalyptus globulus in Europe. Although it is established that this landscape can affect biodiversity patterns, it is not clear what its role in shaping small mammals' body condition is. Here, we tested the effect of Eucalyptus plantations on small mammals' body condition, together with vegetation structure, weather, predators/competitors' abundance, and parasites' prevalence, using the Scaled Mass Index (SMI) as a surrogate. Capture of small mammals took place in 11 study areas in central Portugal from 2019 to 2022. The drivers' influence was tested using structural equation models (SEM). The response of body condition to Eucalyptus is species-specific, with Crocidura russula displaying better individual condition in native habitats (i.e., there was an indirect negative effect of Eucalyptus plantations). The overall model suggested that deer abundance, precipitation, and forest integrity promoted higher body condition levels, while wild boar abundance had an adverse effect. The management of these plantations must ensure the integrity of the remnants of native patches and control of highly abundant competitors (e.g., wild boar) to maintain a healthy and functional small mammal community.