1.INTRODUCTION
Animal movements are a consequence of an organism’s internal state (e.g., sex, age, breeding stage) and environmental factors (e.g., food availability or weather), and can affect individual fitness and ecological processes at local and global scales (Hansson & Akesson, 2014). Individual movements are also influenced by inter and intraspecific relationships (e.g., competition), which may lead to spatial compartmentalization and the maintenance of population-specific movement patterns over time (Nathan et al., 2008). Deciphering how these factors modulate individual movements and how the latter are compartmentalized in space and time is essential to understanding population dynamics (Costa-Pereira et al.,2022) and identifying priority areas for conservation and management (Katzner & Arlettaz, 2020).
Home-range size and cumulative distance travelled are key elements in the study of animal movement ecology (Kie et al., 2010; Tucker et al., 2018; Thaker et al., 2019; Shaw et al., 2020), defining foraging patterns at the individual and population-level, and assessing their stability over time (e.g., Shaffer et al.,2017). For example, investigating variation in home-range size and cumulative distance travelled may reveal that certain individuals behave as central-place foragers during only a specific period of their life cycle (e.g., the breeding season; Carrete & Donázar, 2005; Delgado-González et al., 2022). Similarly, the study of home-range overlap allows the analysis of attraction or repulsion relationships that may affect space use, for example, to avoid competition for resources (Cecere et al., 2018; Winner et al., 2018; Bolnick et al., 2003). This information could be used to explicitly map intra and interspecific meeting sites and prioritise high-quality habitats for communal roost or feeding hotspots (Kane et al., 2015; Cortés-Avizanda et al., 2014).
Vultures from the Gyps genus (which include seven species) are among the largest flying birds, showing high sociality and covering large areas in search of ephemeral and unpredictable resources such as carrion (e.g., 162,824 km2 on average in case of Cape Vultures, Gyps coprotheres ; Jobson et al., 2021). The Eurasian Griffon Vulture Gyps fulvus is a monomorphic social species that breeds colonially (Donázar, 1993; Harel et al., 2017; Zuberogoitia et al., 2018; Almaraz et al., 2022). Individuals forage over vast areas to satisfy their energetic requirements (e.g., ranging from 140 to 4,233 km2, Nathan et al., 2012; Montsarrat et al., 2013; Fluhr et al., 2021; Xirouchakis et al., 2021,), frequently congregating around both wild and domestic ungulate carcasses (Cortés-Avizanda et al., 2010; 2012 but see also Delgado-González et al., 2022). Although information exists on Griffon vulture movement ranges (Xirouchakis & Mylonas, 2007; García-Ripollés et al., 2011; Zuberogoitia et al., 2013; Spiegel et al., 2013;2015; Harel et al. 2017; Arrondo et al. 2018, 2020; Arkumarev et al., 2021; Xirouchakis et al.,2021; Fhlur et al., 2021), virtually nothing is known about the spatio-temporal variation in the movement patterns of adult individuals, as well as, on the factors (e.g., sex, breeding region) governing the spatial ecology and home range fidelity of this species from a mechanistic perspective.
In this paper, we gather movement data from 127 GPS-tagged adult Griffon Vultures captured in five breeding regions of peninsular Spain, the largest vulture population in Western Palearctic encompassing up to 37,000 breeding pairs (90% of all European populations) (Del Moral & Molina, 2018). Our main aim is to assess the effect of individual and environmental factors on movements and spatial use indicators. Specifically, our objectives are: 1) to estimate annual and monthly home-range sizes, monthly cumulative distances travelled, and monthly home-range site fidelity; and 2) to investigate the effect of season, sex and breeding regions on individual monthly home-range size, site fidelity, and cumulative distance. We hypothesize that adult Griffon Vultures, being a large monomorphic colonial species, will exhibit large home-ranges and will travel long distances to fulfil their requirements (mainly food), especially during the autumn and winter, when food availability is the lowest (Spiegel et al., 2013). We also predict that the fidelity of monthly home-ranges should be similar between sexes due to the lack of dimorphism, but would differ between seasons, as foraging constraints are more likely during the breeding period (see Carrete & Donázar, 2005). Finally, we expect differences between breeding regions due to difference in resources availability (Morant et al., 2022).