[貼圖] The Color of Danger in Nature

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Gila Monster
Animals and plants have evolved visual warning to alert other animals (including people) that they are toxic or unpalatable.
A new study has found that nature works in predictable ways, with certain colors, patterns and visual characteristics communicating, "Back off or be sorry."
The dramatic color contrasts and patterns on this Gila Monster, for example, warn of the lizard’s venom, which it can inject into victims with swift bites.
Here's a look at the color strategies of various animals and plants.



King Cobra
The study, published in the latest  Proceedings of the Royal Society B, points out that warning colors are often red, yellow and black, with sharp color contrasts also warning others.
Anyone looking up at this venomous King Cobra, for example, would likely be in big trouble.
Why the similarities across species? "It's unlikely to be a coincidence, and there are a wide range of possible explanations for such similarities in coloration," lead author Martin Stevens of the University of Cambridge’s Behavioral Ecology Group told Discovery News. "For example, these colors are highly conspicuous across a range of environments and backgrounds."



Marbled Cone Snail
Not all striped animals are poisonous. However, stripes are relatively common as warning signals.
"Other high contrast distinctive patterns, such as blotches or spots, are also common," Stevens said.
This Marbled Cone Snail might be pretty enough to invite further investigation, but just a single drop of its venom is said to be powerful enough to kill up to 20 people.



Box Jellyfish
Although red, yellow and black are by far the most common colors sported by toxic species, "some insect larvae and poisonous frogs have blue colors," Stevens said.
The venom of the very blue-hued Box Jellyfish is among the most powerful in the world. It has caused at least 5,567 recorded human deaths since 1954. Victims are said to go into shock or suffer from heart failure before even reaching shore.



Scorpionfish
Bright colors, striped and bumps, such as those seen on this toxic Scorpionfish, may warn others, but they come at a price too.
"Being conspicuous is risky because you are very easy to find by predators and therefore may be attacked by a naive predator, such as a juvenile, which has not yet learned about warning coloration, or even by a predator that is simply very hungry and prepared to take the risk of ingesting some toxins," Stevens said.
The predator would have to be very hungry to go after a Scorpionfish, which has sharp spines coated with venomous mucus.



Insect Larvae
"Many signaling systems are based on the same basic set of underlying principles, namely avoid being harmed by predators, so they all have a number of features in common," according to Tom Sherratt, a professor in the Department of Biology at Carleton University, told Discovery News.
This insect larvae from the order Lepidoptera (includes moths and butterflies) has the common warning yellow coloration, as well as spiny projections and a distinct pattern.



The Color Yellow
“Warning signals are commonplace in the human world -- ranging from red traffic lights to danger signs -- so it is fascinating to consider the evolution of warning signals in the natural world,” Sherratt said.
Construction workers often wear hard hats colored bright yellow, or hold up white and black signs, all colors seen on this toxic and unpalatable butterfly larvae. Stevens and co-author Graeme Ruxton in their paper propose that this type of organism might be very visible close-up, but "such colors may allow distance-dependent camouflage if yellow/red and black blend to an average color that matches the background at a distance when predator vision is no longer sufficient to discriminate individual marking components."



Hoverfly
Some species cleverly mimic colors and patterns that many of us associate with dangerous individuals.
This hoverfly, for instance, mimics the look and behavior of bees and wasps, but is completely harmless.



Loris
Some mammals are venomous, such as this slow loris. The loris does not have very vivid warning coloration, but it stores a volatile, noxious toxin within its mouth. Loris bites can cause painful swellings, but are usually not fatal.
Lorises first appeared in the Asian fossil record 18 million years ago, suggesting that at least some early primates could produce and release poisonous substances within their bodies. It remains unclear when the first toxic insect or animal emerged on Earth, but scientists believe that some dinosaurs, such as 125-million-year-old Sinornithosaurus, could release venom into the wounds of victims.

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