Some Fish Can't Tolerate 'Bad Manners'

According to a new scientific study, it would appear that even certain fish species are very fond of etiquette and polite behavior, especially during feeding. The paper shows that the males of a select few fish species will punish females if they “misbehave” while eating. What really amazed researchers was the fact that this correlation held true even when the females' behavior did not affect the males directly, LiveScience reports.

This means that these fish exhibit a form of human behavior and social interaction that is called third-party punishment. The new work was conducted on Labroides dimidiatus, a type of cleaner fish. These animals get their daily meal by scraping parasites and other “bugs” off larger fish. However, while the receivers of this royal treatment do enjoy having their bodies tidied up, they will swim away if any of the cleaner fish takes a bite out of its mucous tissue.

While this may seem awkward at first, cleaner fish do prefer mucus to other parasites. But they must refrain from eating it, because otherwise their meal provider would simply swim away. It stands to reason that, when many cleaner fish start tidying up a larger marine creature, the race is on for food. Some of the cleaners may get the idea to start biting away at the mucous tissue, but in doing so they ruin the chance for everybody else to feed too.

In a lab setting, Zoological Society of London investigators recreated this scenario. They placed fish flakes and prawns on a submerged plate, in a tank filled with Labroides dimidiatus. As long as the cleaners ate the fish flakes, there was no problem. But as soon as the prawns were touched, the researchers would take the dish away, mimicking what would happen in the wild. In the instances when they did so, the males of the species exhibited a behavior that puzzled everyone.

They started chasing the females away from the food source, and did not stop until they were removed. Upon returning, the “banished” fish were less likely to attempt to eat the prawns again. What also amazed researchers was that the males exhibited this behavior even in the relatively unfamiliar setting of the lab tank. “By punishing cheating females, the males are not really sticking up for the clients but are making sure that they get a decent meal,” expert Nichola Raihani explains. He is one of the authors of a new paper detailing the findings, which appears in the January 8 issue of the top journal Science.