Nature's Blockbuster Identity Thieves

The Serpent and the Rainbow Coloration

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.

All the King's Butterflies

 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).

Where Hawks Dare

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.

Read more at Discovery News