Social Pressure Triggers Dieting In Fish

By Lizzie Buchen | May 13, 2008 1:24 pm
Do these polka dots make me look fat

It’s the hackneyed backbone of many movies and television shows about high school: the popular kids get all the dates and constantly threaten the freaks and geeks, who humbly remain on their lower rung of the social ladder to avoid provoking any physical or social abuse. These stereotypes and simplifications don’t tend to play out in real life—unless you’re a tiny coral-dwelling fish called a goby.

Researchers at the ARC Centre of Excellence for Coral Reef Studies and James Cook University recently discovered that the cool kids of goby social circles use the threat of expulsion from the group to deter subordinates from trying to climb the mating ladder. In a goby group, only the two largest two fish (a male and a female) mate—the rest are non-breeding females, who are consistently smaller than their next largest rivals.

The researchers’ latest findings revealed that the reason subordinates are smaller isn’t because the dominant ones are stealing their lunch money—it’s because the latter deliberately control their weight to avoid posing a challenge to the dominant fish. Dieting helps the subordinate fish show that they know their place— once a fish creeps into the dominant fish’s weight class, the bigger fish begins to feel threatened. In a compensatory move, the bigger fish then beats up the social climber and exiles it from goby society (and its protective coral turf). Alone in the open water and ignored by its so-called “friends,” the fish is likely to be eaten by a predator.

The researchers tried to slip the subordinate gobies some extra food to fatten them up, but, presumably not wanting to disturb the social status quo, the gobies refused.

MORE ABOUT: fish, social hierarchy

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