Sexual Differentiation of Aggressive Behavior in the Chicks of the Black-Headed Gull (Larus ridibundus, Laridae, Charadriiformes) in the Natural Environment

• Published in: Biology bulletin of the Russian Academy of Sciences Vol. 50; no. 9; pp. 2278 - 2285
• Main Authors: Minina, M. A., Agafonova, E. Yu, Druzyaka, A. V.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-12-2023; Springer Nature B.V
• Subjects: Aggressive behavior; Aggressiveness; Behavior; Biochemistry; Biomedical and Life Sciences; Cell Biology; Ecology; Gender differences; Intruder; Juveniles; Larus ridibundus; Life Sciences; Males; Sex differentiation; Sexual behavior; Social behavior; Social interactions; Stress response; Territorial behavior; Zoology; field research; aggression; behavioral type; personality; behavior; ontogeny
• ISSN: 1062-3590; 1608-3059
• DOI: 10.1134/S1062359023090248

Sexual differentiation of social behavior in gulls and its mechanisms remain unexplored during the pre-fledging period. We described the development of aggressive territorial behavior in males and females of black-headed gulls at the age of 1–4 weeks, modeling the intrusion of a peer into the nesting territory. We also hypothesized that the sex differentiation of aggressive behavior may appear as a consequence of the development of small early differences between siblings in the behavioral stress response. To test this assumption, we investigated the relationship between the priority among brood in aggressive contact with the intruder and the intersibling level of activity of a given chick to stress. To measure the behavioral stress response, we used the social isolation of chicks within a small water area with an island in the middle. Longer attempts to swim outside the fenced area were considered as a more proactive stress response. At the age of up to three weeks, there were no sex differences in the aggressiveness, but the stress response of males was more proactive than that of their sisters. A more proactive chick in the brood was usually the first to attack the intruder. At the fourth week of life, the aggressiveness of males increased significantly, and in broods of two sexes, brothers began to play a leading role in protecting the nesting territory in the absence of parents. They attacked an intruder more often and made aggressive calls more frequently. Thus, we were the first to reveal sexual differentiation of territorial behavior in gull chicks during the pre-fledging period. Our results suggest that, more proactive males attack the intruder earlier than their sisters do. Under natural conditions, intruder does not persist in staying in the other nest, but recedes immediately when counteracted. As a result, male chicks gain experience in aggressive interactions and develop higher abilities of aggressive responses to social challenges.