Why does the US military invest in cuttlefish research every year? Because cuttlefish are plump, soft-bodied critters that somehow survive in an ocean filled with finely-tuned killing machines. Through evolution, these cephalopods have developed a variety of nigh-unbelievable predator avoidance tactics, such as remarkable color-changing abilities that may inspire military camouflage technology (see unbelievable video here). And now, researchers have discovered a new way cuttlefish avoid predators: they cloak their bioelectric emissions, like undersea Jedis.
Why does this matter? Sharks and some other oceanic predators find prey by sensing faint bioelectric emissions using specialized sensors on their snout. In other words, it doesn't matter how good your color-changing abilities are if you're still emitting bioelectric potentials-- and if you're alive, you are.
When the cuttlefish were exposed to fish predators (such as sharks-- and don't worry, the researchers only showed them silhouettes), they froze, slowed down their breathing, and carefully covered all of their body openings with their arms. They behaviours occurred "almost exclusively in the presence of fish stimuli," and each behaviour reduced electric emissions. Most interestingly, their results indicate that not only did cuttlefish reduce their electric fields passively-- by freezing and breathing more slowly-- but they covered up their body orifices, which are sites of ion "leakage." In other words, "in addition to the passive reduction in the electric field that occurred with reductions in ventilation, S. officinalis further reduced propagation of electric cues by actively insulating their ion-leaking structures in the presence of certain predators."
In light of this new evidence, the outcomes described in this XKCD comic seem ever more likely.
Thank you to Elliott Bannan for sending along yet another epic article!
Cuttlefish have a unique stealth ability that allows them to shield their electric fields from sharks. The creatures were already known to be masters of camouflage. Now scientists have discovered they also employ undersea electronic countermeasures to escape being detected and eaten. Sharks, one of the cuttlefish's main enemies, home in on faint bioelectric fields generated by the bodies of their prey which they pick up using sensitive detectors on their snouts. A common cuttlefish at rest produces a bioelectric potential of 10-30 microvolts, which is about 75,000 times weaker than an AAA battery. But the scientists found that when the animal feels threatened it freezes and drops the current down to about six microvolts.