Good manners may not be something you expect to find beneath the ocean, but one species of fish appears to enforce them surprisingly well. A 2010 study found that male cleaner fish punish females when they break the rules during feeding, revealing behavior that closely resembles a form of human social punishment, as per a report by Live Science.
Human-like sense of social punishment
A study published in the January 8 issue of the journal Science found that male Labroides dimidiatus, commonly known as cleaner fish, punish females that misbehave while feeding. The findings surprised researchers because the males were not directly harmed by the females' actions, making the behavior resemble what humans call third-party punishment.
Why do cleaner fish punish each other?
Cleaner fish survive by removing tiny parasites from larger marine animals. Those parasites become food for the smaller fish, while the larger "client" fish benefit from being cleaned.
However, the relationship works only if the cleaners stick to eating parasites. The fish actually prefer feeding on the clients' mucus tissue, but doing so annoys the larger fish, which may simply swim away.
When that happens, the meal ends for everyone. Researchers found that male cleaner fish respond by chasing away females that choose the preferred mucus instead of the parasites. After being punished, the females became less likely to repeat the behavior, as per a report by Live Science.
How did scientists test the behavior?
To study this unusual interaction, researchers from the Zoological Society of London recreated the feeding situation in a laboratory.
Instead of using live client fish, they placed an underwater feeding plate containing both fish flakes and prawns. The prawns represented the preferred but forbidden choice.
Whenever either cleaner fish ate a prawn, researchers immediately removed the plate, mimicking a client swimming away after being bitten by a predator.
Even in this controlled setting, the male cleaner fish consistently chased the female after she selected the prawn. The researchers observed that this punishment reduced the females' tendency to choose the preferred food during later feeding attempts, as per a report by Live Science.
What did the study reveal?
At first glance, the males appeared to be defending the larger client fish. But the researchers concluded there was another explanation.
As study author Nichola Raihani said in a statement, "By punishing cheating females, the males are not really sticking up for the clients but are making sure that they get a decent meal."
The researchers suggested that the same behavior would likely benefit the males in the wild because discouraging females from cheating would keep the larger client fish from leaving too soon, allowing both cleaner fish to continue feeding.
The findings indicate that while the behavior resembles a human-like form of social punishment, it ultimately serves the males' own interests by protecting their food source.
FAQs
Why do male cleaner fish punish females?
They punish females that eat the clients' mucus, which can cause the clients to swim away.
Where was the study published?
The findings were published in the January 8 issue of the journal Science.
