Drivers of wood mouse body condition in Mediterranean agroforestry landscapes

Abstract

Agriculture and pastureland for cattle grazing are common land uses in Mediterranean landscapes. These activities significantly alter the habitat conditions, affecting the body conditions of wild communities, especially those with low vagility, such as small mammals. We aimed to evaluate how cattle grazing and the habitat composition affected the body condition of the wood mouse Apodemus sylvaticus in a southern Mediterranean agroforestry system using the Scale Mass Index (SMI) as an indicator of individuals condition. To assess variation in body condition, wood mice were live-trapped in a gradient of grazed sites with different stocking intensities, as well in sites excluded to grazing at different time periods (1998, 2004, and 2008). Wood mice body conditions were influenced by both microhabitat and macrohabitat drivers, with sex-biased patterns, while for the females, only the shrub species had an influence (a microhabitat variable); for the males, both the shrub species and the undercover density (and specifically their interaction) were the important drivers (microhabitat and macrohabitat variables). Unexpectedly, the physical condition variation detected between periods was not directly proportional to the exclusion period, but rather, a certain degree of similarity was found between the different sites (sites excluded since 2004 paired with grazed sites). These results suggest that the presence of food and shelter are determinants to the wood mouse’s physical condition: for females, securing food sources enhance the body condition, while for males, the degree of cover, and consequently refuge against predators, seems to be determinant. These results reinforce the need for sustainable landscape management to assure the maintenance of habitat heterogeneity.