Camouflage In Wild Nature: Chameleons, Seahorses, Amphibians And Banded Peacock Butterfly

Introduction:

Camouflage increases the chance of an organism’s survival by blending it in with curtain aspects of their environment to prevent being recognized by predators. Humans have made use of camouflage from a young age as a means of strategy to win a game of hide-and-seek, to adulthood with sniper recon soldiers blending in with their surroundings to avoid being detected by the enemy. In nature however, animals use camouflage in more sophisticated, efficient manners. These manners include concealing coloration, disruptive coloration, mimicry, and disguise (Font, 2018).

The most common form of camouflage being concealing coloration is when an animal hides itself against a background of the same color. Disruptive coloration works by breaking up the outlines of an animal with a strong contrasting pattern (Font, 2018). Disguise is when an animal blends in with its surroundings by looking like another object (Font, 2018). Several animal species can copy the appearance and/or behavior of a different animal by using a method called mimicry (Font, 2018). There are three forms of mimicry used by both predator and prey: Batesian, Muellerian, aggressive and self-mimicry (Font, 2018).

Batesian mimicry is a prey protecting itself from predators by resembling a dangerous or poisonous species (Font, 2018). Muellerian mimicry is two or more unrelated dangerous organisms expressing similar warning systems such as the same pattern of bright colors (Font, 2018). Aggressive aka Peckhamian mimicry is a predator copying its prey in order to catch it, and self-mimicry is one animal’s body part mimicking a body part of a different animal giving it more time to escape from its confused predator (Font, 2018). Species of reptile, bird, insect, and aquatic organism are known to utilize these categories of camouflage. This paper will synthesize published work regarding the evolution of disruptive coloration across studies of various organisms.

Body:

Chameleons are iconic members of camouflage due to their color-changing abilities. In this study Resetarits & Raxworthy (2016), explored white ventral line markings in species across the genus Chamaeleonidae to function as a camouflage pattern against diurnal predators. Diurnal predators are predators that hunt during the day (Resetarits & Raxworthy, 2016). Resetarits & Raxworthy (2016), hypothesized chameleons expose their ventral line markings more often to predators when they do the ring-flip behavior. The ring-flip behavior referred to the chameleon’s reaction of flipping to the opposite side of the branch when the stick was near the chameleon (Resetarits & Raxworthy, 2016).

White-lined chameleons, Furcifer viridis, were captured at three different forest sites in Makay Massif, Madagascar, and were put through behavioral trails (Resetarits & Raxworthy, 2016). During the behavioral trials, the white-lined chameleons were placed on a branch for 5 minutes to adjust to the new environmental conditions with no moving objects nearby (Resetarits & Raxworthy, 2016). After the 5 minutes, the chameleons were slowly approached by a stick aka “predator” (Resetarits & Raxworthy, 2016). The Furcifer viridis chameleons did indeed expose their ventral line markings more frequently during ring-flip behavior in response to an approaching predator (Resetarits & Raxworthy, 2016). Morphology comparison analysis of 86 arboreal chameleon species showed a positive correlation between ventral line markings with arboreal habitat (Resetarits & Raxworthy, 2016). These results suggest that modern arboreal chameleons developed ventral line markings and the ring-flip behavior to act as disruptive coloration against visual diurnal predators (Resetarits & Raxworthy, 2016).

Seahorses are typically difficult to spot due to their small size, and remarkable talent of blending in with coral or seaweed. Duarte et. al. (2019), evaluated if disruptive coloration in seahorses affected their habitat selectivity. For 45 days, scuba divers recorded and photographed longsnout seahorse, Hippocampus reidi, from the crevices of holdfasts sites located north-east of Brazil (Duarte et. al., 2019). A holdfast is a root-like structure that anchors seaweed, algae, sponges, and other immobile aquatic organisms (Duarte et. al., 2019). Thus, the seahorses would camouflage to resemble either a seaweed, algae, or sponge.

Afterwards, 82 photographs of longsnout seahorse were analyzed comparing seahorse and background color while registering which holdfast the seahorse was on (Duarte et. al., 2019). Duarte et. al. (2019), later tested whether disruptive coloration or plain coloration predicted which holdfast backgrounds the seahorses would inhabit. The amount of correlation between seahorse morph/color with background color of holdfast was calculated to determine the seahorses’ preference of habitat to blend into (Duarte et. al., 2019). Possibly, the availability of seahorse mates could have influenced the seahorses’ habitat selectivity (Duarte et. al., 2019). Both seahorses with disruptive coloration and plain coloration occupied the same number of holdfasts, but seahorses with disruptive coloration settled in more habitats (Duarte et. al., 2019).

Though, seahorses with disruptive coloration were found more often in holdfasts with background colors different from the seahorses’ color (Duarte et. al., 2019). These observations served as evidence to show seahorses with disruptive coloration were not picky when selecting their habitat (Duarte et. al., 2019). These results suggest modern longsnout seahorses utilize disruptive coloration to become capable of camouflaging with a variety of holdfast habitat backgrounds. This increases their chances of not being detected by predators, and for mating to occur.

Generally, moths are easy to spot on a lamp or vegetation but challenging to identify in a forest. This is due to natural selection shaping the wing coloration pattern of moths to match the pattern of tree bark or leaves. Specifically, wood tiger moths (Parasemia plantaginis) are capable of using warning and disruptive coloration (Honma et. al., 2015). Warning coloration is when a prey lets the predator know it has a bad taste or is poisonous (Honma et. al., 2015). When the wood tiger moth’s warning coloration fails, the moth plays dead, falls, and switches to disruptive coloration to blend into grass/litter-covered ground (Honma et. al., 2015).

Honma et. al. (2015), tested whether the wing coloration pattern wood tiger moths could function as disruptive coloration against certain backgrounds. Actual forewing coloration patterns of wood tiger moths were applied onto artificial paper moths and were placed on a background image of natural litter and grass (Honma et. al., 2015). Wing pattern disruptiveness was manipulated by categorizing the artificial paper moths’ forewing patterns either as marginal (brighter color patches extending to the wing margin) or nonmarginal (brighter color patches not reaching the wing margin) (Honma et. al., 2015). Each of the paper moths contained an editable food and were offered to great tits (Parus major) in a large bird cage where the birds managed to detect/attack the paper moths (Honma et. al., 2015).

The birds did not have a preference towards any moth wing coloration pattern, just had a harder time spotting paper moths with the marginal pattern (Honma et. al., 2015). Thus, paper moths with the disruptive marginal pattern were attacked less often than paper moths with nonmarginal pattern (Honma et. al., 2015). Though, disruptive coloration was obvious only when the prey was brighter than the background (Honma et. al., 2015). These results suggest modern wood tiger moths have evolved to use disruptive coloration as a backup plan if their warning coloration fails to repel away predators.

Amphibians such as toads are capable of displaying a variety of skins colors and dorsal patterns. Similar to the wood tiger moth, certain species of toad are able to express either disruptive coloration or warning coloration based on their skin pattern (Mcelroy, 2016). Mcelroy (2016), experimented whether specific skin colors and/or patterns reduced predation on a leaf litter toad, Rhinella alata. The reason leaf litter toads express warning coloration is due to them being able to excrete bufotoxins (neurotoxins) from their skin gland to paralyze or potentially kill their predators (Mcelroy, 2016). The leaf litter toad’s disruptive coloration is due to their population having different forms of skin color and pattern phenotypes (Mcelroy, 2016).

Mcelroy (2016), found the leaf litter toads on Barro Colorado Island (BCI), Panama, and used their different skin color/pattern phenotypes as models to create non-hardening clay replicas. The clay replicas consisted of the toad’s common phenotypes such as light, medium, and dark brown for skin color, and solid, striped, and diamond for dorsal skin pattern (Mcelroy, 2016). Reflectance spectra was estimated and compared between wild leaf litter toads and their clay replicas to make the replicas appear more convincing to the perception of the birds involved in the experiment (Mcelroy, 2016). A total of 1620 clay replicas were randomly placed on leaf litter and white paper to compare bird attack rates (Mcelroy, 2016). The clay replicas were repaired or replaced every 3 days (Mcelroy, 2016).

When the toad clay replicas were placed on leaf litter, only their dorsal skin pattern affected bird attack rates (Mcelroy, 2016). When the clay replicas were placed on white paper, clay replicas with different skin color/pattern phenotype had similar bird attack rates (Mcelroy, 2016). This means the dorsal skin patterns are the reason why leaf litter toad disruptive coloration is effective in reducing predation (Mcelroy, 2016). The results suggest modern leaf litter toads evolved to rely more on their disruptive coloration to preserve their neurotoxins for protecting themselves or their young from future predators.

Globally, butterflies are known for their great diversity of wing patterns and colorations. Butterflies use of their unique wing pattern/coloration to attract mates, match with the background, and express disruptive coloration of course. The stripes and bands on their wings are what allow butterflies to perform disruptive coloration (Seymoure & Aiello, 2015). Research has proven that false edges are effective when avoiding predation, but little research has been done to determine whether stripes and bands are effective in avoiding predation as well (Seymoure & Aiello, 2015). Seymoure & Aiello (2015), tested the possible wing disruptive coloration of the banded peacock butterfly, Anartia fatima.

Aerial nets were used to collect male banded peacock butterflies near Gamboa, Panama (Seymoure & Aiello, 2015). Similar to the leaf litter toad experiment, the collected butterflies were used as models to create three different types of replicas made of artificial paper and plasticine (Seymoure & Aiello, 2015). The replicas consisted of a nondisruptive type (band is shifted to the wing margin), a discontinuous edge type (discontinuous band on wing margin), and a false edge type (natural wing band pattern/control) (Seymoure & Aiello, 2015). The replicas were randomly placed on leaves and branches of rainforest plants for 3 days to observe which replica type would get attacked the most frequently by birds (Seymoure & Aiello, 2015). Ventral band and wing color reflectance were measured using a spectroradiometer to ensure the butterfly replicas were convincing for the birds to attack them (Seymoure & Aiello, 2015).

After the 3 days, the false edge type replica had a higher survivability rate against birds than the discontinuous edge and nondisruptive type (Seymoure & Aiello, 2015). There was no difference in survivability rate between the discontinuous edge and the nondisruptive type. These results suggest modern banded peacock butterflies evolved to develop more sophisticated disruptive coloration methods to become more effective in reducing predation.

Several species of spider do use disruptive coloration as a defensive mechanism to avoid being detected by predators such as birds, but spiders are also known to use disruptive coloration to prevent being detected by their prey. Though, hardly any scientific studies have looked into the importance of body patterns for camouflage of jumping spiders (Robledo-Ospina, 2017). This makes jumping spiders ideal organisms to study the evolution of disruptive coloration. Just like butterflies, spiders use their body patterns to attract mates (Robledo-Ospina, 2017). Robledo-Ospina (2017), evaluated the body pattern effectiveness of two different jumping spiders species, Anasaitis sp. and Ilargus sp., in blending with the natural backround to reduce detection by predator and prey.

Jumping spiders were collected in an ever-green tropical forest in Veracruz, Mexico using a beating tray and a pooter (Robledo-Ospina, 2017). All spiders were knocked out with CO2 and photos of their dorsal body patterns were taken (Robledo-Ospina, 2017). Afterwards, each spider species was placed in a foliage background and ground-leaf litter background and two sets of photos were taken (Robledo-Ospina, 2017). All images were converted to reflectance then to animal-vision cone-catch quanta images through an image calibration plugin (Robledo-Ospina, 2017). The purpose of the spider image conversion was to make the images appear more realistic to the perception of birds and flies included in the experiment (Robledo-Ospina, 2017).

According to bird and fly perception, both species of spider performed effective camouflage in the ground-leaf litter background (Robledo-Ospina, 2017). However, Ilargus sp. demonstrated poor camouflage in the foliage background compared to Anasaitis sp. (Robledo-Ospina, 2017). Anasaitis sp. had higher contrast stripes than Ilargus sp. meaning Anasaitis sp. was relying on disruptive coloration, while Ilargus sp. was relying on background-matching (Robledo-Ospina, 2017). These results suggest modern jumping spiders evolved to develop higher contrasting stripe body patterns enhancing their disruptive coloration to ensure capturing their prey.

Literature Cited

1. Duarte, Michele, et al. “Disruptive Coloration and Habitat Use by Seahorses.” Neotropical Ichthyology, vol. 17, no. 4, 2019, doi:10.1590/1982-0224-20190064.
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4. Mcelroy, M. T. (2016). Teasing apart crypsis and aposematism – evidence that disruptive coloration reduces predation on a noxious toad. Biological Journal of the Linnean Society, 117(2), 285–294. doi: 10.1111/bij.12669
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7. Seymoure, B. M., & Aiello, A. (2015). Keeping the band together: evidence for false boundary disruptive coloration in a butterfly. Journal of Evolutionary Biology, 28(9), 1618–1624. doi: 10.1111/jeb.12681