New study reveals electric camouflage in cuttlefish
Cuttlefish not only camouflage themselves, they also freeze to evade bioelectrical detection.
Dubbed a “master of deception and disguise,” the cuttlefish, a mollusk related to the squid and octopus, possesses innate abilities to protect itself from predators. In a study released Tuesday, researchers found that beyond the ability to camouflage, these squid-like creatures can also mask their electrical fields.
In their paper published in the journal Proceedings of the Royal Society B, researchers from Duke University and Florida Atlantic University show that cuttlefish deploy additional evasion tactics meant to cloak themselves against both visual and non-visual predators.
Sharks, the cuttlefish’s main predators, rely heavily on non-visual foraging techniques since their eyes are on the sides of their head. Sharks rely instead “on a snout studded with sensitive detectors of faint electrical fields,” write the researchers in a press release.
“Sharks can sense a faint current emanating from the tube-like siphons on either side of the cuttlefish's head, the vent where it excretes, and the gap around its mantle,” writes Christine Bedore, lead author of the study.
But luckily, the researchers observed that cuttlefish respond to these non-visual predators by freezing. This response reduces bioelectric fields and as such reduces detectability. By slowing ventilation, “throw[ing] its arms around to cover the siphons and clamp[ing] down on its mantle,” cuttlefish can reduce their microvoltage from 10-30 microvolts to about 6.
Placed in clear tanks, the cuttlefish were shown “looming videos” of predators approaching and their bioelectric response was recorded. Four out of five times, the cuttlefish responded by freezing, which “consisted of at least three of the following changes in behavior: flattening of the body against the tank bottom, reduction in ventilation rate, occlusion of the siphons, funnel, or mantle cavity opening, reduction in the amplitude of body movements during ventilation, and deimatic displays.”
Researchers found that this freezing technique led to a reduction of the bioelectric field of up to 89 percent, greatly increasing the creature’s chance of survival.
But the researchers also tested the freezing response against sharks and noted that two different species of sharks both “demonstrated fewer bites to freeze-simulating electric fields with a mean reduction of approximately 50 percent compared to the resting state stimulus.”
The research, though tested in a laboratory, provides valuable insight into how these animals survive in the wild.