Bystanders affect allogrooming duration and interventions in feral cattle

Dyadic interactions are key to sociality, with economic decision-making affecting partner choice and investment in affiliation. The presence of nearby individuals (bystanders) can affect an animal’s defection temptation and motivation, with bystanders themselves intervening to increase access to social partners; however, the role of bystanders in affiliative ungulate interactions is unknown. We investigated the presence of bystanders on the likelihood of intervention and the duration of allogrooming in a mixed-sex feral cattle herd in Hong Kong. We recorded duration, bystanders and intervention attempts for 239 allogrooming bouts, from 56 animals. Approximately 20% of bouts were successfully terminated by a third party. Allogrooming duration increased with number of bystanders, with more bystanders resulting in longer allogrooming bouts. Dominance status affected the likelihood of intervention; allogrooming was more likely to be successfully interrupted when there was a large negative rank difference between the allogrooming performer and the highest-ranking bystander. Our results are key to how cattle can perceive social rank, and highlight the importance of social context and partner choice in cattle grooming decisions.