Dominance in a socially dynamic setting: hierarchical structure and conflict dynamics in ravens' foraging groups

Abstract

Dominance hierarchies typically emerge in systems where group members regularly encounter and compete for resources. In birds, the ‘open’ and dynamic structure of foraging groups may prevent the emergence of structured hierarchies, although this assumption have hardly been tested. We report on agonistic data for ravens Corvus corax , collected over two 18-month periods for 183 marked individuals of a wild (fluid) population and 51 birds from six captive (stable) groups. We show that the dominance structure (steep and transitive) in wild foraging groups is strikingly similar to that found in captivity. In the wild, we found that higher ranks are mainly occupied by males, older and more aggressive individuals that also tend to receive fewer aggressions. Exploring the mechanisms sustaining the wild dominance structure, we confirmed that males are more aggressive than females and, with age, tend to receive fewer aggressions than females. Males that are about to leave the foraging groups for some months are less aggressive than newcomers or locals, while newcomers are specifically targeted by aggressions in their first year (as juveniles). Taken together, our results indicate that the socially dynamic conditions ravens face during foraging do not hinder, but provide opportunities for, using (advanced) social cognition. This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’.

The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies

“…[ 33 ] and Boucherie et al . [ 74 ]), long-term individual-based observational studies (Anderson et al . [ 67 ] and Dehnen et al .…”

“…Boucherie et al . [ 74 ] examine hierarchical structures in wild and captive raven groups and find that, while wild groups have much more fluid group membership than the captive groups, linear dominance hierarchies emerged in both. These results suggest that ravens are capable of maintaining many differentiated relationships in the face of considerable demographic change.…”

The spatial and temporal exploitation of anthropogenic food sources by common ravens (Corvus corax) in the Alps

“…At this game park, ravens scrounge food from captive animals all year long, reaching numbers of approximately 30 individuals in summer and up to 120 in winter [14,23]. The frequent use of the game park by ravens has made it a reliable trapping location and facilitated the long-term monitoring of the local population, with over 500 individuals marked with patagial wing tags and / or coloured leg-rings since 2007 [48]. At the Konrad Lorenz Research Station (KLF), situated 700 m away from the game park, some raven individuals that were parent-raised in captivity were released into free-flight (80 m 2 ) [33].…”

“…Based on previous studies, we predicted that movement and AFSuse would vary widely among individuals and cohorts. For the latter, we expected differences between age (i.e., juvenile versus adult) and origin (i.e., wild-reared versus captive-released) cohorts, but not sex [23,42,46,47], as both categories reflect potential differences in experience and social ranking [33,48]. We also expected seasonal differences, with wider-ranging movement patterns and increased AFS-use in winter as natural resources in the environment deplete, thermoregulatory expenses increase, and some predictable anthropogenic seasonal food sources such as ski huts become available [23,32,49].…”

Perturbations of key individuals trigger shifts in group-level dominance patterns

“…While removal of individuals from the group has been extensively studied, the introduction of new individuals through birth and immigration or the return of absent group members has received less attention as these processes in wild populations are harder to follow (but see Firth et al 2017;Boucherie et al 2022). For example, in ravens, returning birds after an absence receive more aggression but primarily when they are juveniles, suggesting that in the fission-fusion society of ravens, both social history (tenure) but also individual characteristics (age) influences reintegration into a group (Boucherie et al 2022). In great tits, reintroduced birds reassociate with their same flock mates as before their removal (Firth et al 2017).…”