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Lobster.Sándor Fizli

That lobster might actually feel something when you're cooking it.

Adding new arguments to an old debate, a biologist says he has documented the best indication yet that crustaceans could experience pain.

The study conducted by Professor Bob Elwood, an expert in animal behaviour at the School of Biological Sciences of Queen's University, in Belfast, is described in a paper published in this month's issue of the Journal of Experimental Biology.

It shows that crabs quickly learn to avoid a shelter area after they receive mild electrical shocks when they go there.

Pain has an evolutionary function, being not just an unpleasant feeling but also one that makes animals change their behaviour to avoid harm, Prof. Elwood said in a phone interview Thursday.

The experiment was designed to differentiate between nociception, a reflex response to a stimulus, and the awareness of pain, which leads to behavioural change.

"The advantage of pain is that it trains your attention to what caused it so you can learn and change your behaviour in the future," Prof. Elwood said.

For his study, he used 90 common littoral crabs, caught in baited pots in Strangford Lough, on the east coast of Northern Ireland.

The crabs were individually placed into a lab tank full of seawater.

A copper wire had been looped around their rear legs and could administer a 10-volt electrical pulse. At each end of the tank, plastic sheets created dark shelter areas.

Crabs usually prefer dark places and were more likely to crawl towards the shelter ends. Some of the crabs that entered the dark shelters then received an electrical shock.

After a short rest time of a few minutes, the crabs were reintroduced to the tank and again most crawled to the dark shelters. Once there, those that had been previously jolted got a second electrical shock.

By the third occasion, the crabs that had received shocks twice before had learned to avoid the dark shelter.

"It shows clearly that the animals are learning, they're discriminating between a safe area and an area that isn't," Prof. Elwood said. "It's a criterion that has been tested and been found to be consistent with pain."

Past experiments Prof. Elwood and other researches had conducted on crabs, prawns and hermit crabs.

He said those previous studies had not clearly shown whether the change of behaviour in a crustacean was truly a result of pain, either because the change was not swift enough or because it might have stemmed from a natural inhibition.

While the latest research shows a change in behaviour, a key criterion for pain, the paper cautions that this alone is not conclusive proof invertebrates feel pain.

Nevertheless, Prof. Elwood said it should give humans cause for reflection.

Whatever pain he inflicted on his test subjects, which were released afterward, pale next to the way billions of shrimps, crabs and lobsters are handled by the food industry, he said.

While mammals are given some measure of consideration when they are slaughtered, it is common for crustaceans to have their bodies ripped while alive, Prof. Elwood noted.

"An unmentionably large number are abused in extreme ways and perhaps through this experiment there might be some changes in attitudes and practices."