Social situations differ in their contribution to population-level social structure in griffon vultures

Abstract

Animal social relationships emerge from interactions in multiple ecological situations. However, we seldom ask how each situation contributes to the structure of a population or to the social position of individuals. Griffon vultures interact in multiple situations, including when roosting, flying, and feeding. These social interactions can influence population-level outcomes such as disease transmission and information sharing. We examined the contribution of each ecological situation to the social structure of the population and to individuals’ social positions using GPS-tracking. We found that the number of individuals each vulture interacted with was best predicted by diurnal interactions. However, the strength of social bonds was best predicted by interactions on the ground – both during the day and at night but not by interactions while flying. Thus, social situations differ in their impact on the relationships that individuals form. Given the conservation importance of vultures, these findings can inform wildlife management actions.

The use of social information in vulture flight decisions

“…In that line, and surprisingly, the presence of one preferred affiliate in a thermal tended to reduce the probability to join it. There is evidence that social bonds assessed ‘on the ground’ are often unrelated to association in flight [98]. It therefore questions whether collective flights might be used by vultures to strengthen initially weak social bonds.…”

Social interactions do not affect mycoplasma infection in griffon vultures

“…The GPS tags provide information on vulture location approximately every 10 minutes during the day. Vultures are active during the day and, to preserve battery, the solar-powered GPS tags operate only during daylight hours, providing one or two locations at night (for more details see Sharma et al, 2023). The high spatial and temporal resolution of the GPS information allow us to infer social interactions in different social situations based on temporal and spatial proximity (Sharma et al, 2023) (for more details see the 'Script S2a-b' in supplementary information S2).…”

“…Vultures are active during the day and, to preserve battery, the solar-powered GPS tags operate only during daylight hours, providing one or two locations at night (for more details see Sharma et al, 2023). The high spatial and temporal resolution of the GPS information allow us to infer social interactions in different social situations based on temporal and spatial proximity (Sharma et al, 2023) (for more details see the 'Script S2a-b' in supplementary information S2). When vultures were captured for tagging, they were inspected for injuries or diseases and sampled for mycoplasma (76 unique vultures).…”

“…We used a 25 meters distance threshold based on biological considerations of vulture behavior, and we show in the supplementary information that our results are not affected by using slightly different distance thresholds (Table S5-S6 and Figure S5-S8). Roosting interactions were only considered if they occurred within a known roost site, during the night, as defined in Sharma et al, (2023). For feeding interactions, we excluded daytime interactions that occurred within known roost sites.…”

“…Additionally, territorial behavior during the breeding season (Bertran, 2002) can contribute to the exchange of bodily fluids and the potential transmission of pathogens. We know that griffon vultures differ in their social position across social situations (Sharma et al, 2023); therefore, each individual may have a different impact on disease spread dynamics. Because pathogens can persist in the environment, shared spaces, such as communal roosts or feeding sites, are potential sources for indirect pathogen transmission.…”