bs_bs_banner Animal Conservation. Print ISSN 1367-9430 Connecting endangered brown bear subpopulations in the Cantabrian Range (north-western Spain) M. C. Mateo-Sánchez1, S. A. Cushman2 & S. Saura3 1 EUIT Forestal, Technical University of Madrid, Madrid, Spain 2 Rocky Mountain Research Station, US Forest Service, Flagstaff, AZ, USA 3 ETSI Montes, Technical University of Madrid, Madrid, Spain Keywords Abstract brown bear; connectivity; animal movement; corridors; road defragmentation; landscape The viability of many species depends on functional connectivity of their popula- matrix permeability; UNICOR. tions through dispersal across broad landscapes. This is particularly the case for the endangered brown bear in north-western Spain, with a total population of Correspondence about 200 individuals in two subpopulations that are separated by a wide gap with María C. Mateo-Sánchez, EUIT Forestal, low permeability. Our goal in this paper is to use state-of-the-art connectivity Technical University of Madrid, Ciudad modeling approaches to provide detailed and quantitative guidance for conserva- Universitaria s/n, Madrid 28040, Spain. tion planning efforts aimed at improving landscape permeability for brown bears Tel: +34 91 336 76 64; in Spain, with a particular focus on alleviating the barrier effect of transportation Fax: +34 91 336 76 70 infrastructure. We predicted a regional connectivity network for brown bear by Email: [email protected] combining a multiscale habitat suitability model with factorial least-cost path density analysis. We found that the current composition and configuration of the Editor: Matthew Gompper landscape considerably constrain brown bear movements, creating a narrow bot- Associate Editor: Sadie Ryan tleneck that limits flow of individuals between the two subpopulations. We iden- tified key locations along the predicted corridors where efforts to increase road Received 23 July 2013; accepted 15 and railway permeability should be prioritized. The results provide a foundation January 2014 for the development of spatially optimal management strategies to enhance con- nectivity within and between the subpopulations and to mitigate the impact of doi:10.1111/acv.12109 potential barriers to movement. Introduction may lead to inappropriate characterization of connections and ecological flows between habitat patches (Cushman Habitat connectivity plays a crucial role in enabling disper- et al., 2009). Instead of experiencing landscapes as categori- sal and gene flow within and among populations (e.g. cal mosaics (habitat/not habitat), it is more likely that Hanski, 1998; Flather & Bevers, 2002; Crooks & Sanjayan, organisms experience their surroundings as gradients of dif- 2006; Cushman, 2006; Cushman et al., 2013; Saura, Bodin ferential habitat quality (McGarigal & Cushman, 2005; & Fortin, 2014) and thus is considered a key consideration Cushman, 2006; Cushman et al., 2010a), and adopting this in evaluating regional viability of animal populations. perspective can profoundly change the conservation plan- Despite the clear importance of habitat connectivity for ning guidelines at the landscape scale. population persistence, the best ways to mitigate population Several approaches are available to evaluate connectivity isolation remains an object of intense debate (Crooks & across complex landscapes, including least-cost path Sanjayan, 2006; Awade, Boscolo & Metzger, 2012), and modeling (Adriaensen et al., 2003; Cushman et al., 2009, specific factors mediating connectivity are largely unknown 2010a; Cushman, Chase & Griffin, 2010b), circuit theory for most species (With, Gardner & Turner, 1997; Bowne & (McRae & Beier, 2007; McRae et al., 2008), other forms of Bowers, 2004; Cushman, 2006). One commonly proposed network analysis (Urban et al., 2009; Saura et al., 2014), approach to conserve population connectivity involves the resistant kernel modeling (Compton et al., 2007; Cushman creation and protection of movement corridors (Haas, 1995; et al., 2010b), agent-based movement (Palmer, Coulon & Beier & Noss, 1998; Crooks & Sanjayan, 2006; Cushman, Travis, 2011), gene flow simulations (Landguth & McKelvey & Schwartz, 2009). However, the ‘classic’ Cushman, 2010), statistical modeling (Cushman et al., 2006; concept of a corridor as a narrow strip of habitat that facili- Compton et al., 2007; Spear et al., 2010) or empirically tates movements of organisms between habitat patches derived understandings from detailed movement data (Simberloff et al., 1992; Rosenberg, Noon & Meslow, 1997) (Sawyer et al., 2009; Cushman et al., 2011). Most past appli- is a point of controversy, given limited evidence of their cations of these methods have focused on delineating move- effectiveness and issues related to scale and delineation that ment corridors among small collections of habitat patches at 430 Animal Conservation 17 (2014) 430–440 © 2014 The Zoological Society of London M. C. Mateo-Sánchez, S. A. Cushman and S. Saura Enhancing connectivity to allow brown bear persistence relatively fine spatial and have not accurately accounted for the brown bear to provide an evaluation of the population- the distribution and density of dispersing organisms across wide connectivity network in the study area. The brown the landscape. To provide meaningful guidance to regional bear is a long-lived omnivorous mammal with a solitary conservation efforts, it is often essential to expand the scope social structure and promiscuous mating system (Nores & of analysis to shift from local, patch-level definition of Naves, 1993; Schwartz, Miller & Haroldson, 2003). Males habitat connectivity to a broader gradient perspective on have larger home ranges than females, and both males and landscape structure to assess performance of populations females have intra- and intersexually overlapping home across complex landscapes (Berger, Cain & Berger, 2006). ranges (Dahle & Swenson, 2003). Dispersal in brown bear One framework that is useful to accomplish this expan- populations has been reported to be sex biased, with highly sion in scope is to evaluate landscape connectivity among all philopatric females establishing their breeding home ranges the individuals of a population across the entire occupied in or adjacent to their natal areas and males dispersing long range and across multiple landscape resistance scenarios distances from their mothers’ home range (Blanchard & (e.g. Cushman et al., 2006). Synoptic least-cost movement Knight, 1991; McLellan & Hovey, 2001; Palomero et al., analysis on species-specific landscape resistance map is a 2007). Recent multiscale habitat modeling has revealed that helpful approach to comprehensively analyze the effects of the preferred habitat of brown bear in Spain consists of landscape structure on animal movement. Resistance repre- large landscapes with low human footprint and large extents sents an integration of several behavioral and physiological of forest cover (Mateo-Sánchez, Cushman & Saura, 2013). factors such as aversion, energy expenditure or mortality The brown bear population in the Cantabrian Range risk when moving through a particular environment (Zeller, (north-west Spain) has suffered a dramatic decline in the last McGarigal & Whiteley, 2012), and cost is the cumulative several centuries as a result of human persecution and pro- resistance incurred in moving from the source to the desti- gressive loss and fragmentation of its habitat (Naves et al., nation locations (Adriaensen et al., 2003). Therefore, by 2003). Currently, the Cantabrian brown bear occurs in two integrating least-cost movement assessment in a spatially small and endangered subpopulations (Palomero et al., extensive scope of analysis (i.e. across all occupied locations 2007) with limited gene flow between them, with potentially within a population), the strength of corridors and locations deleterious effects on viability (Pérez et al., 2009). The iso- of movement barriers can be rigorously evaluated lation of these two subpopulations is considered to be a (Cushman et al., 2009, 2013). result of the distribution of suitable habitat being separated Many published studies analyzing least-cost corridor by intensively modified intermediate landscapes and trans- models have made several simplifying assumptions that may portation infrastructure, which has created potential barri- lead to unrealistic characterization of organism behavior. ers to dispersal between the two subpopulations (Nores & First, very often movement parameters, such as the resist- Naves, 1993; Wiegand et al., 1998). Brown bears have been ance to movement presented by different landscape features, protected in Spain for over three decades. Much of the have been estimated through expert opinion due to lack of known range of the species is included within protected detailed information on animal movement (Zeller et al., areas such as European Nature 2000 Network, natural 2012), which is not desirable (Seoane, Bustamante & parks and recovery plans of each of the regional institutions Díaz-Delgado, 2005). To overcome this limitation, some involved in its management. Although recent studies authors proposed that resistance to movement could be esti- revealed that both subpopulations are growing, loss of mated as an inverse function of a habitat suitability model genetic diversity due to small population size and demo- (e.g. Ferreras, 2001; Chetkiewicz, St. Clair & Boyce, 2006; graphic stochasticity has hampered the recovery of O’Brien et al., 2006; Beier, Majka & Spencer, 2008). Second, the