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Scientists from the University of Otago—Ōtākou Whakaihu Waka found that sex-changing fish can exhibit dominating behavior within minutes following a pecking order transition.
The Department of Anatomy’s study in Proceedings of the Royal Society B investigates the New Zealand spotty, or paketi, a type of fish that can transition from female to male during adulthood in reaction to social hierarchy.
After removing a dominating spotty from a group, sex transition happens almost rapidly.
The whole sex transformation takes weeks, however a second-ranked fish can take advantage of the power vacancy and impose dominant behaviors in a few minutes.
During these aggressive behaviors, known as “rushes,” the dominant fish would swim quickly in the direction of the subordinates.
The dominant fish may bite the subordinates, generally on their tail and fins. The subordinate frequently swims away from the dominant fish during these aggressive activities.
The researchers predicted behavior changes within sixty minutes of eliminating the dominant fish, but were shocked by how fast they may occur.
In several fish tanks, the second-ranked fish were aggressive within minutes of the dominating fish’s removal.
According to the researchers, spotties’ dominating behavior during a female-to-male sex change does not signify a change from “female” to “male” behavior, as clownfish change from male to more dominant female fish.
The researchers found that larger spotties dominate smaller ones in linear dominance hierarchies.
They wanted to know which fish in the hierarchy would change sex when given the chance.
Results suggest dominant, larger fish are more inclined to change sex, while less dominant fish can swiftly adapt to new opportunities when social hierarchies are disturbed.
The study also found that the fish brain’s social decision-making network is crucial to spotties’ dominance.
The network of dominating fish differed significantly from all other rankings.
The findings highlight the complicated relationship between social behavior and brain processes in these fish.
They also show how social context shapes individual behavior, offering insight into social behavior evolution and brain processes’ adaptability to changing social settings.
The findings may help us understand social dynamics in other species, including humans.
Sources:
Haylee M. Quertermous et al. (2025). Behavioural and neural correlates of social hierarchy formation in a sex-changing fish, Proceedings of the Royal Society B: Biological Sciences. DOI: 10.1098/rspb.2024.2097
Sex-changing fish quick to assert dominance. https://phys.org/news/2025-06-sex-fish-quick-assert-dominance.html
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