ORIGINAL ARTICLE Luı´s M. Rosalino • Dulce Ferreira • Ineˆs Leita˜ o Margarida Santos-Reis Selection of nest sites by wood mice Apodemus sylvaticus in a Mediterranean agro-forest landscape Received: 5 September 2010 / Accepted: 6 December 2010 / Published online: 15 January 2011 Ó The Ecological Society of Japan 2011 Abstract One of the most important structures for an individual’s survival is a refuge, especially for species subject to significant predatory pressure or living in environments affected by severe climatic conditions. We studied how wood mice (Apodemus sylvaticus), inhabit- ing a Mediterranean environment, use nests and the factors that could be determining this use. Radio- tracking of 16 mice allowed us to detect 24 diurnal nests, which were used with a high fidelity rate (1.75 nests/ animal). Nest sites that had been identified using radio- tracking were matched with 24 randomly selected non- nest sites (located within an area defined by the sum of all individual home ranges), and all sites were charac- terized according to their macro- and micro-habitat parameters. Using a generalized linear model, we tested three hypotheses: (1) a nest’s use is influenced by its proximity to food patches; (2) the degree of sheltering provided by each site influences its use; and (3) nest use is constrained by a combination of food- and shelter- related features. Females had higher nest fidelity than males, and the degree of sheltering provided by each site had a positive significant influence on its use. Nests offering higher protection (e.g., under thick vegetation), good drainage (e.g., sleep slopes), and lower human and predatory disturbance (far from orchards) were most often used. The proximity to food patches seemed to negatively influence nest use. Results indicate the need to preserve patches of natural dense vegetation near riparian habitats, which is in agreement with the focus of mammalian protection plans in Mediterranean agricul- tural landscapes. These patches are important areas for Apodemus sylvaticus, an acorn disperser species, which is preyed on by raptors and mammalian carnivores. Keywords Apodemus sylvaticus Æ Cork oak forest Æ Forest rodents Æ Management implications Æ Shelter Introduction Species survival is dependent upon a variety of factors such as climate constraints, available resources, preda- tion pressure, pathologies, and disturbance (Caughley and Sinclair 1994). Limiting resources are species specific and include food, water, shelter, sexual partners, or a combination of any of those (e.g., Prenda et al. 2001; Real et al. 2009; Rosalino et al. 2005b). Shelter is particularly important to increase survival probability where environmental conditions are severe (such as extreme temperatures, wind, or rain) and as part of anti-predator strategies of vertebrate species located in lower trophic levels in predator-rich communities (e.g., Martı´n and Lo´pez 1999). Mediterranean environments are characterized by environmental heterogeneity and temporal unpredictability (called Mediterraneity; Virgo´ s et al. 1999), which impose extra constraints for species survival and likely enhance the importance of shelter. Further, the increased and generalized expansion of agricultural areas throughout Mediterranean Europe, with consequent habitat manipulation, has changed vegetation cover and height. This in turn causes varia- tion in shelter quality and availability, affecting above- and belowground nest building, and the thermal protection from heat and cold provided by those shelters (especially important in the Mediterranean due to the extremely hot temperatures registered in summer) (Jacob 2008). Rodents, and particularly the wood mouse (Apode- mus sylvaticus Linnaeus 1758), are often preyed upon by reptiles, raptors, and mammalian carnivores. In Medi- terranean environments, the wood mouse is a major prey item for those predators (e.g., Lataste’s viper Vipera latastei, Santos et al. 2007a; barn owl Tyto alba, Bontzorlos et al. 2005; common genet Genetta genetta, Rosalino and Santos-Reis 2002). Shelter therefore L. M. Rosalino (&) Æ D. Ferreira Æ I. Leita˜o Æ M. Santos-Reis Centro de Biologia Ambiental, Faculdade de Cieˆncias de Lisboa, Universidade de Lisboa, Ed. C2, Campo Grande, 1749-016 Lisbon, Portugal E-mail: lmrosalino@fc.ul.pt Tel.: +351-21-7500000 Fax: +351-21-7500028 Ecol Res (2011) 26: 445–452 DOI 10.1007/s11284-010-0797-9