Predation risk drives aposematic signal conformity

Area of Science:

• Evolutionary biology
• Animal coloration
• Behavioral ecology

Background:

• Aposematic signals, used by prey to warn predators, often display significant variation within species.
• This variability contradicts the expectation that clear signals enhance predator learning and prey recognition.
• Striped skunks (Mephitis mephitis) exhibit diverse coat patterns, ranging from mostly white to mostly black.

Purpose of the Study:

• To investigate the ecological factors influencing the variation in aposematic signal patterns in striped skunks.
• To determine the relationship between predator diversity and skunk stripe pattern conformity.
• To explore the influence of environmental factors, such as humidity, on skunk coloration.

Main Methods:

• Analysis of 749 museum skins of striped skunks collected across North America.
• Quantitative assessment of stripe patterns, including border length, symmetry, and extent of white pelage.
• Correlation of pattern variations with geographical data on predator species diversity and environmental conditions like humidity.

Main Results:

• Skunks in areas with higher predator diversity exhibited longer white-black borders and more symmetrical stripes.
• Increased predator diversity correlated with reduced variability in white pelage extent and border length, indicating stronger selection for conformity.
• Skunks in humid regions showed larger black pelage areas, consistent with Gloger's rule.

Conclusions:

• Relaxed predation pressure is a primary driver of warning signal variation in striped skunks.
• Stronger predation pressure leads to greater conformity in stripe patterns, suggesting selection for more effective warning signals.
• Environmental factors like humidity also influence skunk coloration, independent of predation pressure.