A lot of people I know pride themselves on being a "non-conformer." That is, they don't give into the social obligations that many of us tend to follow. Although that's fine and dandy for the human population, that's not always the best method for other animals. For many animals, particularly aquatic ones, conformity is used as a defense. The thinking is, if you stand out in a crowd, a predator has a better chance of picking you out, where if you are more inconspicuous, you blend in with your conspecifics, and your chance of being someone's meal is decreased.
Recently, there has been research on color change and its effects on predator avoidance and social interaction. Specifically, one study, Colour change and assortment in the western rainbow fish, written by Rodgers et. al., looked at this dynamic interaction. The authors used controlled experiments to assess the influence that body pigmentation has on shoaling.
This area of research is not very recent, many studies on color change, mimicry, and coloration anomalies have been done. So what makes this one special? Well, many papers that have been published regarding color change in respect to predator defenses and other interactions have used artificial coloration of the fish (or other study organism) and not natural color change. The authors of this paper argued that the artificial coloration gives less conclusive results because predators in the wild use natural coloration to choose their prey. The major goal of this study was to investigate the relationship between color pattern change and grouping decisions. They tested the relationship by exposing the individuals to different colored environments for two weeks and observing their subsequent grouping behavior.
The results of the experiment supported the hypothesis.
One example from their results is that the fish exposed to the dark aquaria showed a darkened body color patterns and preferred to associate with other dark colored fish. The figure above was taken from the paper, showing the coloration differences between the fish that were kept in the dark aquaria (left) and the fish that were kept in the pale aquaria (right). The take home message from reading the paper was that there is more to the coloration than what it seems. This paper in particular focused on the impact of color on shoaling preferences and anti-predator defenses, but it also provided information on other related concepts. The paper is a great resource for information about color change in the wild, the benefits of color change, and the mechanisms behind schooling and shoaling preferences.
Colour change and assortment in the western rainbowfish
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