Mexican milk snake (Lampropeltis triangulum annulata, left) and highly venomous Texas coral snake (Micrurus tener, inset).Public Health Image Library and L.A. Dawson, Wikimedia Commons (inset)
Two movies at the top of the U.S. box office charts, "Snitch" and "Identity Thief," involve people taking on false identities. Faking out predators and prey by mimicking another specie has been a plot line in nature for millions of years.
A dangerous example of look-alike animals is the copy-cat coloration of the harmless Mexican milk snake (Lampropeltis triangulum annulata, left) and highly venomous Texas coral snake (Micrurus tener, inset). The two species look similar, inhabit the same areas and even share a taste for dining on their fellow serpents. However, although the docile milk snakes are common pets, the coral snake is a relative of the cobras and injects a potent nerve venom, or neurotoxin, with its bite.
How can herpetologist avoid a deadly case of mistaken identity? Both snakes have a combination of red, black and yellow bands, but in a different order. The rhyme, “Red next to yellow, kill a fellow...red next to black, poison lack,” accurately describes the difference in coloration and danger of the two species.
Predators don't have humans' skill at remembering life-saving rhymes, so they tend to avoid both reptiles. This type of mimicry, called Batesian, allows a harmless species to bluff their way to survival. The odd thing is, in this case, how could a predator ever learn to avoid red, black and yellow banded serpents if the coral snakes killed any predator that tried to make a meal of them?
Evolution may have embedded the fear of coral snakes in some predators. An experiment published in Science found that some birds will instinctively avoid red-and-yellow ring patterns, although they will readily attack red-and-yellow stripes or green-and-blue rings. Birds aren't the only animals leery of serpents. Primates, including humans, seem to have evolved an ability to rapidly develop a fear response to snakes, according to numerous studies. However, these instinctual fears can be overcome by conditioning or, in the case of humans, education.
Monarch (right) and Viceroy (inset) butterflies.Clinton & Charles Robertson, Wikimedia Commons; Piccolo Namek, Wikimedia Commons(inset)
For both monarch (right) and viceroy (inset) butterflies, it's good to be the king. Monarch butterflies (Danaus plexippus) dine on milkweeds and store up toxins from the plants, making the insects foul tasting to birds. The viceroy (Limenitis archippus) was once thought to be a non-toxic usurper of the monarch's unpalatable crown, but it turns out that the viceroy can be just as noxious, according to research published in Nature.
This kind of mimicry, called Müllerian mimicry, allows both butterflies to benefit from each other's nasty flavor.
Both kings of the insect world wear orange and black robes, although regional variations of the viceroy butterfly have adapted their garments to match the monarch relative holding court nearby. In Florida, viceroys coloration matches that of the queen butterfly (Danaus gilippus) whereas in Mexico, viceroys mimic the coloration of the soldier butterfly (Danaus eresimus).
Hawk and turkey vulture (inset)Snowmanradio, Wikimedia Commons; George D. Lepp/Corbis
The vultures wheeling overhead were of little concern to the rodents scurrying from rock to rock, until suddenly one of the birds broke from the slowly circling flock and dove from the sky.
The hapless mouse now in the talons of that bird learned too late that that was no vulture. That was a zone-tailed hawk (Buteo albonotatus).
From the ground, the silhouette of the hawk (right) resembles that of a turkey vulture (Cathartes aura, left). The hawk even hold its wings like a vulture and flies along with vulture flocks. But, the two birds differ in their feeding preferences. Vultures rarely eat live prey, so small animals have little to fear from them. The hawk, on the other hand, eats any small animal it can get its claws on.
Rye and wheat (inset).LSDSL, Wikimedia Commons; Kurt Stueber, Wikimedia Commons (inset)
Dude, that pumpernickel bread is made of weeds!
Rye may have started out as a weed which grew alongside wheat (inset) and barley in the Fertile Crescent. The weeds may have been accidentally harvested along with the domesticated grains. The weed seeds that were subsequently cultivated were subject to the same selective pressures as the grains. Over many generations, the wild rye weeds' seeds became larger and stuck to the stalk of the plant when they were mature, as opposed to naturally falling off. Sticking to the stalk made them more likely to be harvested along with the wheat crop. Eventually, the weed became a crop in its own right. This type of mimicry due to artificial selection is called Vavilovian mimicry.
Rye was scorned in the ancient Mediterranean, and Pliny the Elder considered it only suitable for avoiding starvation. Once rye made its way north into central and eastern Europe, it became popular since it can survive in poor soils and harsh winters that would kill other crops.
Yellow-throated and orange-throated side-blotched lizards. Davefoc, Wikimedia Commons; Chris Brown, USGC (inset)
Cross-dressing is a successful form of mimicry for the common side-blotched lizard (Uta stansburiana) of the western U.S. and northern Mexico. One color variation of the lizard mimics that of a female, which allows the male some surreptitious sexual success.
The males of this lizard actually have three color variations that work against each other like the rock, paper scissors game. Orange-throated lizards are the largest and most dominant. They guard a large territory with harems of females. Blue-throated lizards are smaller and only guard a territory with one female. Blue-throats don't have the size and strength to take on an orange-throat in combat.
Yellow-throated lizards use gender bending coloration to fool orange-throated males. By mimicking the lighter coloration of females, the yellow-throats manage sneak past the he-man orange-throats and mate with one of his harem. However the blue-throats are more vigilant, since they only have to guard one female. Yellow-throats casually can't sneak past the watchful boys in blue.
Hence, yellow beats orange...orange beats blue...and blue beats yellow.
Spotted hyena carrying her cub.Joe McDonald/Corbis
Lizards aren't the only animals that have mimicked the traits of the opposite gender for reproductive advantage. The spotted hyena has gone even further than the transvestite lizards.
Female spotted hyenas have genitals like those of a male. The clitoris is extended to form a pseudo-penis and the vulva are sealed. This results in keeping the female hyena safe from rape and impregnation by an undesirable male. Females rule the spotted hyena hierarchy. Females are larger than males and the pseudo-penis helps make sure the females are in charge of who gets to mate and when.
The females pseudo-penis can even become erect. A study in Behavioral Ecology and Sociobiology found that an erect female pseudo-penis is actually a sign of submission and a greeting.
Passionfruit flowerZSM, Wikimedia Commons
Unlike the lizards and hyenas, which seek reproductive gain, some flowers work to stop others' reproduction using mimicry.
The leaves of some species of passionfruit (Passiflora sp.) have small, yellowish colored spheres which mimic the eggs of certain types of butterflies in the Heliconius genus. The caterpillars of these butterflies feed on the leaves of the passionfruit vine. Butterfly moms don't want to lay their eggs where their young will have to compete with others, so by making an adult butterfly think that there are already eggs on the leaves, the passionfruit keeps the next generation of caterpillars at bay.
An article published in Scientific American pointed out that this kind of species-specific counter evolution in the passionfruit should be almost impossible. However, because the passionfruit leaves contain toxins that make them inedible to most herbivores, the plants could evolve the egg-resembling structures in order to fool only the few species of butterfly that actually feed upon them.