Skunks are famous for their distinctive black and white stripes which serve as a visual warning to predators that they possess a potent defense mechanism. A recent study has found that the intensity of these warning stripes can change depending on the presence of predators in their environment.
Coloration as Skunk Defense
Skunks are animals from the Mephitidae family which are famous for their ability to spray a liquid with an unpleasant odor from their anal glands. Aside from this strong scent, skunks are also known for having iconic black and white stripes signal its toxic anal spray.
Striped skunks are easily identified with their fur color: two thick white stripes along the back and tail which sharply contract a black coat. Their head, body and tail are also striped with specific patterns which can vary among individuals.
There are skunks, however, which show very varied fur color which ranges from all black to thin or thick black and white bands to all white individuals. This variation can be seen mainly across the North American continent.
According to Professor Tim Caro from Bristol's School of Biological Sciences, warning coloration is a type of defense from predators where a conspicuous signal advertises the ability of an animal to escape predation. In most cases, predators have to learn the importance of this signal, so it is assumed that warning coloration looks very similar across prey individuals of the same species in order for it to be effective. However, there are colored prey which show different advertisements even with the same species.
Unveiling the Secrets of Skunk Color
Scientists from the University of Bristol, Montana and Long Beach, California have tested the ecological correlates of this variation in skunks. In the study "Predation risk drives aposematic signal conformity", they suggest that this is a result of relaxed selection in black and white pelage.
Using museum specimens, researcher Hannah Walker from the University of Montana documented the distribution of these different pelage colors of skunks across North America. The data were plotted against a set of variables which are thought to drive this color variation.
It was found that fur color was varied even within the same litter in locations where skunks overlapped with few mammalian predators that are capable of killing them. In places where there were many species of more dangerous predators, the skunks showed little variation.
Aside from skunks, owls and raptorial predators were also examined by the research team, but they were not as evident even if the effects were the same. The experts believe that this might be due to the fact that birds have a poorer sense of smell and are less affected by smelly anal defenses.
The results of the study indicate that relaxed predation pressure is a crucial warning signal variation in skunks, where stronger pressure results in signal conformity and stronger signals. As explained by Professor Caro, if relaxed selection works within species, then it should also do so across prey species.
The research findings reveal the reason why not all skunks look alike, and why the members of other colored species look different from each other. More broadly, it provides another insight in explaining the evolution of coloration in nature.
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