Other Batesian Mimics

Other Batesian Mimics
Batesian mimicry is common among insects. It is also common in many other invertebrates.

Some of the most remarkable mimics in this group are nudibranchs. A nudibranch is a kind of sea slug. Nudibranchs eat algae, anemones, coral polyps, and sponges. Some species also eat other nudibranchs. Their colorful meals provide much of their own color. This helps some species blend in with their surroundings.

Many nudibranchs store the venomous stings or bad-tasting poisons of their prey and use them in their own defense. Predators learn that the colors of these nudibranchs are warning colors. They learn to leave them alone. Other nudibranchs mimic the colors of the dangerous nudibranchs, and so do ocean-dwelling flatworms.

Batesian mimicry also appears in vertebrates. It is particularly widespread in fish. The common sole, for example, is a European fish with a fin on its back that is edged in black. It mimics the weeverfish, which has venomous black spines in its back fin. Both fish are well camouflaged by color and shape as they hide in mud and sand underwater but raise their black-edged fins as a warning when disturbed. Poisonous flatworms and venomous sea urchins and sea snakes are also mimicked by fish.

One of the most remarkable fish mimics is a harmless species called the comet, which lives on coral reefs of the Indian Ocean and western Pacific Ocean. The comet is black with white spots. When threatened by a predator, it dives into a crack in the reef, leaving its hind end sticking out. Then the fish raises the fins on its tail, back, and underside. This reveals a large black spot surrounded by a white ring. Now the comet’s hind end looks almost exactly like the head of a whitemouth moray eel, a ferocious predator that lurks in crevices on the reef.

Some reptiles also use mimicry. In southern Africa, a bushveld lizard is camouflaged when fully grown, but it has black with white spots and a dull red tail when it is young. This makes the young lizard’s small body look like that of an oogpister beetle, which sprays a smelly, burning fluid at predators. The little lizard even walks like a beetle, with its tail held down so that it blends in with the sand.

Scientists have found lizards in South America that mimic invertebrates, too. One species of lizard curls its tail over its back to show its orange underside when it is bothered. This makes it look like a venomous scorpion. Another kind of South American lizard has young that look like a poisonous millipede.

Some caterpillars mimic snakes, as do other snakes. The false cobra of Asia, for example, is mildly venomous—its bite is not deadly like a cobra’s. But when it is bothered, the false cobra rises up, spreads its neck like a hood, and hisses loudly, just as the real cobra does.

In North America, non-venomous bull snakes mimic rattlesnakes. A bull snake does not have a rattle, but if threatened, it will shake its tail rapidly. This rustles the leaves and grass around it, and can startle a predator into thinking that it is dealing with a rattlesnake.

The most famous example of snake mimicry centers on coral snakes. There are about 65 species of coral snakes found in parts of North, Central, and South America. They are highly venomous and clad in warning colors of black and red with yellow or white bands. Snakes that share these colors are known as false coral snakes. Some false coral snakes are mildly venomous. Others, such as the scarlet king snake, are non-venomous.

For many years, scientists assumed that the coral snake was the model and the other snakes were mimics. However, it may be that the mildly venomous false coral snakes are the models. A bite from such a snake would hurt a predator, but not kill it. The predator would learn to avoid such snakes in the future. These would create a population of “educated” predators that have learned to avoid red, yellow, and black snakes.

A bite from a deadly coral snake, however, would kill the predator. This would mean that the coral snake could never “educate” predators to leave it alone. Thus, the deadly snake may mimic the less deadly one—it benefits from having the less deadly snake educate the predators. The non-venomous mimics benefit, too.