The+use+of+cryptic+coloration+as+a+defense+by+tropical+animal+species

by Samantha Ginzel Northeastern State University
 * The use of crypsis as a defense by tropical animal species **

Introduction:
Crypsis includes various types of mechanisms that enable organisms, including predators and prey to remain undetected (Nilsson and Ripa 2010). Studying cryptic coloration can help scientists see into how organisms evolve over time to adjust to their environments. With the increased changes across various habitats worldwide, including tropical habitats, this is an important topic to understand. Under the category of cryptic coloring there is a large variety of different techniques used by many different species. Some of the many species that exhibit cryptic coloration include peppered moths, Heliconius butterflies, caterpillars, lizards, long-tailed manakins and sloths.

Cryptic coloration is a phrase that envelops several different forms of predator avoidance techniques. Some organisms have sensory organs and tools to help them match themselves to backgrounds that hide their bodies. While organisms use disruptive coloration which employs random markings or colored shapes on the animals body to help distract predators from their real shapes. And yet other organisms use flicker-fusion camouflage or startle displays to “scare” or distract their predators to give them enough time to escape. There are countless adaptations that organisms have acquired that help increase their survivability, of all of them mimicry and camouflage are the two most common groupings of adaptations used (Nilsson and Ripa 2010).

Peppered moths are a species that often comes up in regards to cryptic coloration. They were one of the primary organisms studied in regards to how organisms change to better blend into their environments and how these changes lead to better survival. The cryptic coloration of peppered moths was first noticed during the industrial revolution when environmental changes were occurring that caused moths with darker coloring to survive better because they were better concealed from predators. As this was noticed by scientists, an interest in the concept of cryptic coloration began to grow and was further carried out by scientists including Bates and Muller. Credits

Mimicry, one form of cryptic coloration occurs when a species mimics the defense mechanism of another species. For example, Heliconius butterflies mimic a poisonous species of butterflies to warn off predators (Jiggins et al 2004). Heliconius butterflies mimic the wing pattern of other members of their genus. These groups of similarly patterned butterflies create Müllerian mimicry rings that often include both poisonous and non-poisonous species. Fritz Müller first proposed the idea of species mimicking other species thus gaining similar physical characteristics. As predators attempt to eat one member of the Müllerian mimicry ring, it links the pattern of the butterfly to the foul taste. When the predator has made this connection, the entire ring of similarly patterned butterflies now has an increased protection from that predator. Mimicry benefits the organism in a variety of ways. Most commonly known is the aid it gives the organism in avoiding predation as in the example of the Heliconius butterflies.

Batesian mimicry is another common form of mimicry and is commonly found in butterfly species. Batesian mimicry is when one species that lacks a poison or other form of distaste mimics a model species, where the model species is often poisonous or inedible. One of the most commonly studied example of Batesian mimicry are species that mimic the poisonous monarch butterfly. One study specifically looked at how wing patterns effected bird predation on a moth species (Jeffords et al 1979). In this study, moths were painted yellow and black to mimic edible swallowtail butterflies and orange and black to mimic poisonous monarch butterflies. The moths with the yellow and black wing pattern exhibited a much higher amount of wing damage then the moths painted orange and black. This showed that the bird species that were preying on these moths were less likely to eat an organism that they had previously experienced as harmful or distasteful.

The numbers of Batesian mimics are regulated in nature. Research has shown that if the ratio of models to mimics is low, meaning there are more mimics than models, that the effects of mimicry do not benefit the mimic as greatly as a 1:1 or higher ratio in favor of the models (Nilsson and Ripa, 2010). This occurs because when there are more mimics than models, predators are more likely to taste and consequently eat a mimic and have no adverse experience. In future preying opportunities they are more likely to eat a mimic again. When this happens, the mimicry is not aiding the organism in avoiding predation. While eventually a predator will eventually eat a model organism, it may take a few negative experiences with the organism before the predator will avoid eating both models and mimics. Research has shown that in cases such as this, mimics begin to change to match the mimic with greater accuracy. This checks and balance system found in nature shows how organisms are able to regulate their numbers to bring the most benefit to them from an adaptation.

Another benefit mimicry lends an organism is a decreased energy loss through the actual production of a poison or larger size. For example, caterpillars and lizards that employ the protection of counterfeit predator eyes convince their predators that are much larger than their actual size, deterring predation (Janzen et al 2010). Many caterpillars and pupae have defense mechanisms in the form of these counterfeit eyes. Along with these fake eyes, these organisms also often create small tunnels out of leaves, which helps to conceal the actual size of the caterpillar or pupae from predators, which are often insectivorous birds. When a predator approaches one of these caterpillars or pupae, the first thing they see is the large eyes “peering” out of the tunnel. In most cases, the size of the “eyes” tricks the insectivorous bird into thinking that the caterpillar is a much larger prey than they can handle and as a result the bird will fly away. Credits

Camouflage is another form of cryptic coloration that organisms can employ to help them avoid predation. Manakins are a bird species that are sexually dichromatic, meaning the males and females have different coloration patterns (Doucet et al 2007). Within this species, it is the females that exhibit camouflage with their dull green-brown plumage. This is beneficial to the organism for a variety of reasons. One reasoning being that it protects the females from predators. The other, less obvious reason is that it protects the nest. Brightly colored females could draw predator’s eyes to the location of the nest whereas a cryptically colored female allows her to stay close to the nest and the nest stays hidden from predators. Manakins are not the only birds that use cryptic coloration to protect their nests. Ptarmigans, a bird species commonly found in areas of Canada and northern areas of North America show some of the most varying color schemes throughout the year (Montgomerie et al 2001). In the deep of winter when their habitat is blanketed in snow, both males and females exhibit snow white plumage. As the snow begins to melt in the spring and eggs are laid, females molt their white feathers and begin to grow brown mottled plumage to hide them during the summer months. Juveniles of this species, born during the summer months are also equipped with mottled brown feathers to help them hide from predators. Some species, like the manakins and ptarmigans are genetically programmed with cryptic coloration while others, like the sloth obtain their cryptic coloration through symbiotic relationships in their environment. Credits

All six of the known living species of sloth have been known to have algal communities growing in their hair shafts (Suutari et al 2010). Sloth’s hair shafts are long and course with multiple grooves. As the alga grows in the grooves of the sloths hair, the sloth begins to have a greenish tint that helps it blend into the canopy where it lives the majority of its life. Three-toed sloths exhibit the most drastic green tint because of their symbiotic relationship with green algae. Other species have symbiotic relationships with other species of algae resulting in less drastic green-brown colorations. However, no matter the algal species, any help in evading predator eyes in needed. Blending in is essential for these animals as they are slow moving and cannot quickly escape predators that are able to reach them high in the canopy.

Sloths do not appear to present any behaviors that suggest they are trying to stop the algal communities from growing on their fur, but they do not control the algae. Cuttlefish, however, are able to control their camouflage techniques (Shohet et al 2006). Cuttlefish are cephalopods that have the unique ability to see and process their environment and adjust their body positions accordingly to give them the highest level of camouflage protection. Research has been done to examine how these organisms lay their bodies on the sand patterns to best hide themselves. It was found that majority of the time, cuttlefish will align their bodies orthogonally with the lines in their environment and parallel to the flow of water. This was shown to provide them with optimal concealment from predation. This research shows that some animals are able to control their cryptic coloration to benefit themselves to the highest degrees.

Conclusion:
Cryptic coloration is a mechanism used by many organisms both plants and animals to evade or aid in predation. Cryptic coloration is important and should be studied because it allows scientists to see how organisms are able to adapt to their environment (Forbes 2011). As habitats continue to change due to deforestation and human impacts, how organisms are able to adapt is important to understand to help scientists look into the future and predict what changes may occur.


 * Sources**

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Forbes, P. 2011. Masters of Disguise. Scientific American 304.

Holmes, B. 2005. In the blink of an eye. New Scientist 187:2507.

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Jeffords, M.R., J.G. Sternburg, and G.P. Waldbauer. 1979. Batesian Mimicry: Field Demonstration of the Survival Value of Pipevine Swallowtail and Monarch Color Patterns. Evolution 33:275-286.

Jiggins, C.D., C. Estrada and A. Rodrigues. 2004. Mimicry and the evolution of premating isolation in Heliconius melpomene Linnaeus. Journal of Environmental Biology 17:680-691.

Montgomerie, R., B. Lyon, and K. Holer. 2001. Dirty ptarmigan: behavioral modification of conspicuous male plumage. Behavioral Ecology 12: 429-438.

Nilsson, J and J. Ripa. 2010. The origin of polymorphic crypsis in a heterogeneous environment. Evolution 64-5: 1386–1394.

Shohet, A. J., R. J. Baddeley, J. C. Anderson, E.J. Kelman and D. Osorio. 2006. Cuttlefish responses to visual orientation of substrates, water flow and a model of motion camouflage. The Journal of Experimental Biology 209: 4717-4723.

Suutari, M., M. Majaneya, D. P. Fewer, B. Voirin, A. Aiello, T. Friedl, A. G. Chiarello, J. Blomster. 2010. Molecular evidence for a diverse green algal community growing in the hair of sloths and aspecific association with Trichophilus welckeri (Chlorophyta, Ulvophyceae). BMC Evolutionary Biology 10:86-97.