Commentary on: dominance and subordination in the smooth dogfish, Mustelus canis (Allee & Dickenson, 1954)

In, 1954, Warder C. Allee and Joshua C. Dickinson decided to establish that “dominance-subordination” hierarchies are present in the Chondrichthyan phylogenetic line. To do so, they confined sixteen fished smooth dogfish (Mustelus canis) in tanks and observed their behaviour. They found neither competition over food, in spite of starving the animals for up to six days at times, nor any clear example of aggression, though it is through aggressive actions that such hierarchies are, by definition, established. They therefore used collision avoidance to support their hypothesis that the sharks had established a rigid size-dependent dominance-subordinate hierarchy, and claimed to have established that such hierarchies are present in Chondrichthyans. However, ethological studies since then have not identified the hierarchies in elasmobranchs that this study claims to be present, but they have found that smaller sharks tend to avoid colliding with larger individuals, which is the simplest explanation for their observations.