The Survival Game: How Environmental Factors Determine Animal Coloration Strategies

Research reveals how environmental factors collectively determine which protective coloration strategy is most effective for animals.

The animal kingdom displays a remarkable array of colors, each serving a crucial role in the ongoing battle for survival.

Most animals utilize camouflage, adopting inconspicuous patterns to conceal themselves from predators. In contrast, others showcase vibrant, bold colors to signal to potential predators that they are unpalatable. This second strategy is known as aposematism or warning coloration. Though less prevalent than camouflage, warning coloration has independently evolved hundreds of times across diverse species including butterflies, beetles, bugs, sea slugs, poison frogs, and certain bird species.

Photo Credit: Reuters

Scientists have long questioned why species adopt one strategy over the other. Is one approach generally more successful? Under what specific conditions does one strategy provide greater advantages? Our new research, published today in Science, provides insights into these questions.

Evaluating multiple theories

Camouflage and aposematism frequently coexist within the same geographical region. Australia offers numerous examples of camouflaged insects such as spotted predatory katydids and lichen spiders.

Conversely, species like the cotton harlequin bug – a common stink bug found in urban environments – and the handmaiden moth display bright orange and red coloration to advertise their unpalatability to predators. Some animals, though fewer in number, such as mountain katydids, employ both strategies by changing color or revealing and concealing colorful body parts.

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Various localized studies have independently examined the effects of different factors in isolation. For instance, research has shown that light levels significantly impact the effectiveness of camouflage strategies. Similarly, the success of warning coloration often depends on predators having previously encountered the prey and learned to avoid specific warning signals.

But which is more influential: lighting conditions or a predator's learning capacity?

Findings from a single location inform us about that specific environment, but these strategies appear worldwide. Do these strategies perform consistently across different environments?

To investigate this question, our extensive team of collaborators conducted identical experiments in 16 different countries globally, across forests with varying light levels and diverse prey and predator communities.

15,000 paper moths

Our team deployed more than 15,000 artificial prey – paper moths – featuring three different color patterns: a classic orange-and-black warning pattern, a cryptic brown that blends with surroundings, and an uncommon bright blue-and-black coloration. Each paper target was baited with a mealworm, allowing us to measure the survival rate for each color type. If the bait was consumed, we assumed a predator had chosen to eat that target.

The typical warning coloration represented the widely distributed orange-and-black combination observed in many toxic animals, such as monarch butterflies and poison frogs. The uncommon warning coloration corresponded to a less frequently used warning pattern that remains highly visible, similar to the Ulysses butterfly.

Including these two warning colorations enabled us to determine whether predators avoid the orange-and-black signal due to familiarity or simply because of its high visibility.

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We discovered there is no single "optimal" strategy. Instead, local predators, local prey populations, and forest light conditions collectively determined whether camouflage or warning colors provided better protection.

The predator community present – and the intensity of their attacks – had the most significant impact on which prey coloration most successfully avoided predation. In environments with numerous predator attacks – where food competition is likely intense – predators were more inclined to attack prey that appeared dangerous or distasteful. This meant camouflage offered the best protection in areas with high predation pressure.

However, camouflaged prey couldn't conceal themselves effectively in every environment. In well-illuminated settings, for example, camouflage benefits diminished, while lighting conditions did not affect the performance of orange-and-black prey.

Familiarity with prey also proved important. In locations where camouflaged prey was abundant, hiding proved less effective, as predators likely learned how to locate camouflaged prey.

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Conversely, in areas where warning colors were common, predators became better at avoiding the typical warning signal but not the atypical one. This suggests predators learn to avoid familiar warning signals, helping explain why many animals share similar color combinations.

Anticipating future changes

Our study demonstrates how multiple environmental features collectively determine which strategy provides better protection. It also reveals that the success of camouflage strategies may depend more on ecological context than warning signals do.

As climate change transforms habitats, conditions vital to the success of different antipredator strategies may also change.

For instance, camouflage strategies might become less effective in transformed habitats with reduced vegetation cover and increased light exposure.

Our findings can help better predict how these environmental changes might affect animals using different color strategies against predators and develop appropriate mitigation measures.

Iliana Medina, Lecturer in Ecology, The University of Melbourne; Alice Exnerova, Associate Professor in Zoology, Charles University; Amanda M Franklin, DECRA Fellow, Department of Ecological, Plant and Animal Sciences, La Trobe University; Kate Umbers, Associate Professor in Zoology, Western Sydney University, and William Allen, Associate Professor in Evolutionary and Sensory Ecology, Swansea University

This article is republished from The Conversation under a Creative Commons license. Read the original article.