Let the punishment fish the crime

Bluestreak cleaner wrasses (Labroides dimidiatus) punish their partners if they act in a way that puts off high value clients, reports a new study in Proceedings of the Royal Society B.

Pairs of male and female cleaner fish feed by removing parasites from larger ‘client’ fish. However, sometimes cleaners get greedy and bite their clients rather than sticking to parasites. This usually results in the meal coming to an abrupt end as the disgruntled client fish swims off.

Now, scientists from the Zoological Society of London (ZSL) and a number of other leading scientific institutions have shown that the male cleaner fish distinguish between high and low value meals and will punish their female partner more severely if she drives off a high-value client by biting them. This is the first example of non-humans adjusting the level of punishment to fit the value of the ‘crime’.

Lead author Dr Nichola Raihani says: “Cleaner fish and humans may not share many physical traits, but cleaner fish punish cheating individuals, just as we punish people who step outside of the law. In both situations, harsher punishment may serve as a stronger deterrent against future crimes.”