1. Cuevas, Ma. Fernanda (1,2) ; Ricardo Ojeda (1) and Fabián M. Jaksic (2) (1) Grupo de Investigaciones de la Biodiversidad (GIB), IADIZA, CCT-Mendoza CONICET, Av. Ruiz Leal CC 507 (5500) Mendoza, Argentina. (2) Center for Advanced Studies in Ecology and Biodiversity (CASEB), Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile. fcuevas@mendoza-conicet.gov.ar Multi-scale patterns of habitat use by wild boar, Sus scrofa, in the Monte Desert of Argentina Introduction Results Material and Methods Study Area Protected areas are widely recognized for their value in the conservation of the biodiversity. A large number of protected areas have been impacted by biological invasions, threatening their diversity. Understanding habitat requirements of invasive species can be crucial for management and conservation decisions. Wild boar is one of the largest invasive species in Argentina. It was introduced in the early 20th century for hunting purposes. The quality of its habitat is determined by the availability of free water and food; and by vegetation cover. Objective : To asses the habitat use patterns of wild boar in the MaB Reserve of Ñacuñán, Argentina, at two scales (large and small scale). The Man and Biosphere Reserve of Ñacuñán (34° 02' S - 67° 58' W; 13,200 ha, 540 m elevation), Mendoza, Argentina, belongs to the Monte Desert (Fig 1a). The landscape is heterogeneous and characterized by a mosaic of vegetation patches known as “algarrobal” or Prosopis woodland (Prosopis flexuosa), “jarillal” or Larrea shrubland (Larrea cuneifolia) and “medanal” or sand dunes. The climate is semiarid and strongly seasonal, characterized by hot, humid summers and dry, cold winters. Eighty transects of 1 km were set up, covering the study area (Fig. 1b). Transect surveys were conducted two times in the year 2008 (wet and dry season). Wild boar signs (tracks, nests, faeces and rooting) were recorded within 5 m of either side of each transect. At each sign we established a plot (50 m2) where we recorded information on habitat (cover of herbs, grasses, litter, shrubs < 1m, shrubs, trees and bare soil) and anthropogenic variables (distance to nearest water source, road and human habitation). We measured the same variables in plots were the wild boar was absent. To detect patterns of habitat use at the large scale we used Chi-squared contingency test. To analyze patterns of habitat use at a small scale we used multiple logistic regression analysis. To construct the model we used the variables where the correlation among them was greater than 0.6. We found 70 wild boar signs in the wet season and 99 in the dry season. To analyze the habitat selection at large scale we used signs of rooting activity and tracks. During both seasons we found significant differences between the frequency of available habitat and the rooting sites used by wild boar (X²= 16.83, df = 2, p= 0.0002 wet season; X²= 6.51, df=2, p= 0.038 dry season), with more rooting than expected located within the Larrea shrubland. We found no significant differences with respect to tracks (Fig. 3). A dependence on free water and behavioral responses to high environmental temperatures are commonly reported for wild boars in arid climates (Baber & Coblentz, 1986). In this study the wild boar showed a preference on Larrea shrubland for feeding (based on rooting signs) avoiding Prosopis woodland and sand dunes during both seasons. They traverse the 3 habitats recognized in relation to availability. The Larrea shrubland is the habitat which is associated with the herbaceous cover (Fig.2), which is the main food item in the wild boar’s diet (Cuevas et al., 2006). At the small scale we found a positive association with herbaceous cover during the wet season. This suggests that wild boars select their habitat for foraging depending on the availability of food during this season. The association with the free water source could be explained by the high ambient temperatures during the summer and their need to maintain a positive water balance. During the dry season the wild boar was not associated to distance to nearest water source, and their presence was associated with shrubs < 1m and litter cover. Acknowledgements: Solana Tabeni. Project financing by ALARM- 6to marco Unión Europea; Agencia PICT 25778, CONICET PIP 5944; FONDECYT-FONDAP 1501-0001. Figure 2: PCA used to characterize the different macrohabitat. We found that the presence of wild boar during the wet season was mainly associated to herbaceous cover and distance to nearest water source. Instead, during the dry season we found a positive association of wild boar signs with shrub < 1 m and litter cover, and a negative association with herbaceous cover (Table 1; GLMs, α =0.05; R²= 1.61 wet season, R²=11.65 dry season). Habitat selection at large scale (macrohabitat) Habitat selection at small scale (microhabitat) GiB Discussion SeasonLogistic ModelAssociationpDeviance explained WetHerbaceous cover(+)<0.00110.3 % Distance to nearest water source(+)0.0025.75 % Plant cover(-)0.1251.4 % Shrub < 1m(-)0.1851.03% Litter cover(-)0.2960.6% Distance to nearest road(+)0.2890.6% DryShrub < 1m(+)0.0035.5% Herbaceous cover(-)0.0273.05% Litter cover(+)0.0273.1% Distance to the nearest human habitation(-)0.1681.2% Grasses(+)0.2590.8% We characterized the different macrohabitats to determine which variables are associated to the 3 available habitats. The Principal Components Analysis (PCA) showed that CP1 explains 73% of the variability and PC2 the remaining 27%. The Prosopis woodland is associated with bare soil and tree cover. The Larrea shrubland is associated with shrubs, herbaceous and litter cover; while the sand dunes are associated with shrubs < 1m and grasses (Fig. 2). Table 1: Logistic models of habitat selection at small scale. (+): positive association and (-) negative association. Habitat characterization * * * *** Figure 3: Habitat selection at large scale during the wet and dry seasons. Figure 1: a) Monte desert biome and location of the Reserve MaB of Ñacuñán. b) Sites of study. Sand dunes Prosopis woodland Larrea shrubland a) b) Figure 2: Habitats available on the Reserve.