Introduction
The social relationships among animals emerge from interactions in
multiple ecological and social situations. Relationships can result from
both affiliative interactions, such as grooming and food sharing, and
agonistic encounters, such as direct aggression and indirect supplanting
(Whitehead 2008). Social structures have important population-level
outcomes such as disease dynamics and the spread of information.
Traditionally, different types of interactions have been studied either
separately or in aggregate, without distinguishing among them (Croftet al. 2008; Wey et al. 2008; Krause et al. 2010;
Pinter-Wollman et al. 2014). However, observed social
relationships are a product of interactions that take place in different
social and ecological situations (Finn et al. 2019; Dragićet al. 2021) (Fig. 1). Social animals can benefit from certain
types of associations by gaining knowledge about the location,
availability, and quality of resources (Dall et al. 2005;
Giraldeau & Caraco. 2018). However, the potential costs of sociality,
such as fast depletion of resources, competition over mates, and
increased exposure to pathogens all impact social dynamics (Silk 2007).
The balance between the costs and benefits of sociality can determine
how each social situation contributes to the global social structure
(Evans et al. 2020). Thus, a closer examination of interactions
that occur in different social situations and their relative
contribution to the social structure of a population may provide more
accurate information about the mechanisms that underlie social
structures and the function of sociality in population-level processes
(Silk et al 2018).
Each social and ecological situation may contribute differently to the
position of an individual in a society because individuals may differ in
how much they engage with others in each social situation. For example,
certain individuals may be important for stabilizing a social group
(Flack et al . 2006), or are important in foraging situations,
leading groups to scarce resources (Mccomb et al. 2001; Foleyet al. 2008; Brent et al. 2015). However, those
individuals may play a more peripheral social role in other situations,
such as caring for offspring, or group defense. The common approach of
aggregating all interaction types makes it impossible to distinguish
between an individual that has many interactions in one particular
situation and an individual that has few interactions with unique
individuals in a diverse set of situations. Thus, treating social
interactions in different situations as components of a unified social
structure can produce unexpected inferences about the role of
individuals in their society (Finn et al. 2019). For example, in
a recent study of paper wasps, the potential of an individual to become
a queen was revealed only when social interactions in multiple
situations were considered simultaneously, but not when interactions in
each situation were considered separately or when all interactions were
aggregated without distinguishing among situations (Sharma et al.2022). Similarly, in primate societies, certain individuals were
identified as important in the social structure only when multiple
social situations were considered together, but not when each social
situation was examined separately (Barrett et al. 2012;
Smith-Aguilar et al. 2019). By considering multiple situations,
certain situations emerge as more important in shaping the sub-structure
of the society than others (Smith-Aguilar et al. 2019). Thus,
uncovering which social and ecological situations influence individuals’
social roles in each situation has important implications for
determining survival and exposure to pathogens (VanderWaal et al.2016) as well as social foraging (Boogert et al 2014), which are
important for wildlife conservation and management.
Griffon vultures (Gyps fulvus ) interact in different social
situations to share social information about the location of roosts and
feeding sites. Like most other vulture species, griffons are large
obligate scavengers that search for and consume large carcasses (Houston
1974). Because carcasses are an unpredictable resource, griffons rely
heavily on social information and recruitment to locate food (Jacksonet al. 2008; Spiegel et al. 2013a; Cortés-Avizandaet al. 2014). Recruitment to food results in local enhancements
and feeding aggregations of tens of individuals, which may share food
and/or engage in aggressive interactions (Mundy 1992; Carrete et
al. 2010). Griffons roost and nest in communal roosts, which can serve
as information centers for locating resources (Harel et al.2017). Thus, interactions in different situations may provide different
information and contribute in different ways to the relationships that
vultures form. Furthermore, individuals may differ in their need for
food as well as in their knowledge about the location and quality of
current resources, which depend on their recent movements and their
interactions with conspecifics in different situations (Spiegel et
al. 2013b). For example, if information about food location is obtained
through co-flying (e.g. Cortés-Avizanda et al. (2014), vultures
that spend much time flying with others might have greater access to
food than those who tend to fly in smaller groups or alone. In contrast,
if information sharing at the roost is more important for locating food,
then individuals that roost with more individuals and/or with better
informed ones will have greater access to food (Harel et al.2017). In addition, interactions on the ground (e.g., when roosting or
feeding) may expose vultures to information about social status and
potential mates, but also to pathogens. Thus, individuals that spend
more time in ground-based interactions might have more exposure to
certain information and to disease compared to those that interact
predominantly during flight. Because the population of griffons that we
study is of extreme conservation concern (Hatzofe 2020), uncovering what
types of social interactions are important for structuring the social
relationships in the population and identifying which individuals are
exposed to different types of information and risks (pathogens and
poisoning) can inform wildlife management actions. The prevalence of
poisoning as the main mortality reason for griffons and many other
vulture species (Ogada et al . 2012) highlights the importance of
social foraging and of identifying the social situations that affect
social aggregations and individuals’ unique roles in these social
structures.
The goal of our study is to examine how different behavioral situations
contribute to the social structure of a vulture population and to
determine how individuals differ in their social position based on the
social situations in which they interact. Specifically, we consider
three social situations: diurnal interactions on the ground (e.g., while
co-feeding), diurnal interactions in the air (co-flying), and nocturnal
interactions on the ground (e.g., while co-roosting). We ask if
individuals that have a central role in one social situation, carry over
their social role to other situations. We further ask if social
situations contribute in different ways to the population-level social
structure. We predict that social situations with brief interactions,
such as co-flying, will have a lower impact on the strength of social
bonds compared to situations in which interactions are long, such as
those that occur on the ground. We further predict that social
situations in which movements are shorter (i.e., on the ground) will
result in fewer unique interactions relative to situations in which
vultures move larger distances (i.e., when flying). Disentangling the
role of social interactions in different situations, both at the
individual and the population levels, will shed light on the
complexities of animal societies and may guide wildlife management
actions.