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).