Sticklebacks are small fish that often fight over territory and mates. When two male stickleback fish encounter each other, the fish will either display an aggressive signal or fight. The dominant stickleback often forces the less dominant stickleback to swim away. A behavioralist interested in stickleback interaction conducted two experiments in order to study the dominance hierarchies (rankings) and their role in stickleback behavior. In the experiments described below, 5 male sticklebacks were placed in an aquarium, and their interactions were observed and noted.
Experiment 1
To investigate the possible role of various traits in the establishment of a dominance hierarchy, the behavioralist recorded each fishʼs mass (in ounces), age (in weeks), and number of fin movements. He also noted the order in which each fish was placed into the tank, and each fish’s overall aggressiveness, ranked from 5 (most aggressive) to 1 (least aggressive).
Experiment 2
The sticklebacks were placed back in the tank in the same order as noted in Table 1. The results of all aggressive interactions between pairs of stickleback were tallied in the table below. The males that swam away were determined to be the “losers” of each aggressive encounter; the males that stayed, “winners”.
Table 3 presents the results of all of the encounters for each stickleback.