Each year thousands of them are boiled or torn apart whilst they are still alive, and now there is strong evidence to suggest that crustaceans experience discomfort.
That was the stark message delivered by Robert Elwood, an animal behaviour researcher at Queen’s University Belfast, to the Behaviour 2013 meeting in Newcastle, UK.
Crustaceans — crabs, prawns, lobsters and other creatures — are usually not protected by animal-welfare laws, despite massive numbers of them becoming caught or farmed for human consumption. The exclusion has been primarily based on the belief that these animals cannot experience pain — usually regarded as an ‘unpleasant feeling’ — and alternatively only have nociception, a reflex response to move away from a noxious stimulus.
This is a useful belief, as crustaceans are subjected to what Elwood calls “extreme procedures” — lobsters in factories having their legs removed although they are still alive, crabs being kept alive but tightly bound for days in fish markets, and reside prawns being impaled on sticks for eating. Such procedures, he notes, “would never be permitted with vertebrates”.
One way Elwood attempted to figure out whether crustaceans can experience discomfort was to look at avoidance studying: can the animals truly discover from discomfort, or do they just continue to respond to a stimulus? To answer this, Elwood and his colleague Barry Magee presented shore crabs with a option of two distinct shelters. Getting into one shelter resulted in an electric shock for the animal, which was repeated if the animal remained there. The other shelter was a safe haven.
Crabs shocked the second time the experiment was run have been far much more likely to choose the other shelter in the subsequent trial, whilst crabs by no means left a non-shocking shelter. This, says Elwood, shows that the shock is aversive.
In another experiment Elwood investigated whether hermit crabs could make motivational trade-offs as a outcome of discomfort. They presented Pagurus bernhardus crabs with two kinds of shell, one of which the animals are recognized to favor, and gave some of the animals small electric shocks when they have been inside these new residences.
When these crabs had been later presented with a new shell they could move into, the shocked crabs had been far more likely to take up this supply, and they did so more speedily.
“Assessing pain is tough, even within humans”, Elwood told the Newcastle meeting. But there is a “clear, extended-term motivational adjust [in these experiments] that is completely consistent with the notion of pain”.
Such evidence would be sufficient to prevent mice being subjected to the deaths that crustaceans experience, he says.
Robert Hubrecht, deputy director of the Universities Federation for Animal Welfare (UFAW) and the organizer of the session at which Elwood gave his talk, says that the data for crustaceans appear equivalent to the kind of information that are used to give mice the advantage of the doubt, and hence award them protection from attainable pain below the law.
“We’re behaving in an illogical way at the moment” by defending mice but not crustaceans, he notes.
No matter whether wider society is ready to consider crabs as issues that can feel pain and should be protected is not clear. “This is somewhere science has to lead”, says Hubrecht.