Cuttlefish Pretend to be Crabs to Catch More Fish

The surprising behaviour has scientists asking new questions.

Imitation might be the sincerest form of flattery, but researchers in Japan don’t think cuttlefish are trying to flatter hermit crabs when they appear to mimic crustacean arm movements.

In videos from a University of Ryukyus study published in the Journal of Ethology last month, pharaoh cuttlefish are seen displaying an arm-flapping behaviour that resembles the movements of a crab, while also lightening areas of their skin. Kohei Okamoto and his research team hypothesised that the cuttlefish may be emulating hermit crabs in order to inconspicuously approach their prey or protect themselves against predators.

Hermit crabs are filter feeders and don’t pose a threat to cuttlefish prey, which includes small fish and molluscs. If cuttlefish pretend to be crabs, it could allow them to get closer to their prey without detection, Okamoto said. Mimicking crustaceans would also give off the impression of a hard shell, which might protect cuttlefish from other hungry sea animals.

Watch these pharaoh cuttlefish change their appearance and behaviour to mimic hermit crabs.

When placed in hunting scenarios, the cuttlefish that appeared to imitate hermit crabs captured twice as many fish as those that didn’t.

The cuttlefish in the study were hatched in the lab and were never exposed to crabs, said researcher Ryuta Nakajima, who is now studying possible environmental triggers for this behaviour.

“Are they learning from actual direct observation or is this programmed into genetics? [This] kind of brings up an interesting question about intelligence and complex behaviours,” he said.

One theory is that the cuttlefish observed crustaceans and learned this behaviour during their embryonic stage, Nakajima said.

Researchers first observed the jointed arm behaviour in 2011 while conducting other cuttlefish experiments, noting that the cephalopod displayed the behaviour while hunting and after they were introduced to a larger tank.

Camouflage is nothing new for cuttlefish and other members of the cephalopod family. Cuttlefish, as well as squids and octopuses, can change their body colour, pattern, and skin texture within milliseconds, which makes them some of the most adept camouflagers in the animal kingdom.

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