From the "Little Mermaid" character Sebastian to pet hermit crabs, people think crabs are wonderful — but some experts believe the way we treat crabs is downright barbaric.
"If crustaceans screamed when they were dropped into boiling water, I doubt we'd still be having these kinds of discussions."
Like many other decapods (the class that also includes lobsters, shrimp, crayfish and prawns), crabs are a popular food item. It is common to prepare them by dropping them while still alive into a boiling pot, then cracking open their shells to suck or scoop out their tasty inner flesh.
Of course, even if humans weren't regularly sending crabs to a boiling death, we have so polluted the oceans that crabs are losing their sense of smell and failing to develop healthy shells. In other cases, literally billions of crabs have disappeared due to climate change. Overall, it seems that humans are much kinder in practice to fictional crabs than to real ones. But scientists supposedly tell us that crabs are nothing more than stupid sea bugs. Is that truly the case?
"I think we should separate the question of whether an animal is intelligent from whether they are sentient (i.e., can experience positive and negative feelings)," Dr. Andrew Crump, a lecturer in animal cognition and welfare at Royal Veterinary College, told Salon by email. "Intelligence isn't, on its own, relevant to the question of whether we should care about animal welfare. But sentience is. The human case illustrates this point — we don't think that people with lower IQs are less capable of suffering."
From there, Crump informed Salon that experiments on crabs and hermit crabs have revealed "remarkable cognitive abilities." Even if crabs can't master Cartesian metaphysics, "the evidence for pain, anxiety, and other feelings in decapods is much more compelling."
"Electrical stunning devices have also been developed, at least for larger decapods. More research is needed, but there's some compelling evidence that these render crabs and lobsters insensible, so they can then be humanely slaughtered using other methods."
Crump is referring to the fact that crabs repeatedly demonstrate an aversion to experiences that they have learned can result in adverse consequences to their bodies. One could argue that this aversion is mere instinct or reflex, like a command that was pre-programmed into a machine. Since that is true, how does one then differentiate a superficial impulse from a deeper emotion?
"In the past, the reactions to trauma (that would result in pain in humans) were dismissed in non-human animals as 'reflex' reactions, like when the doctor taps on your knee," Gregory Jensen from the University of Washington's School of Aquatic and Fishery Sciences wrote to Salon. "But what I've always argued is that there is no incentive to avoid that trauma if there is no negative association with it (i.e., pain). If we look at all the pain-inducing defenses that different animals (and plants) have, it is ridiculous to conclude that they all developed to protect them from humans."
Even if we cannot definitively state whether crabs are capable of more complex emotions, "it makes perfect sense that pain is a universally unpleasant experience," Jensen said.
Dr. Edward Pope, an associate professor in marine biology at Swansea University, explained to Salon by email that "pretty much anything with a nervous system will be able to detect damage to itself. Whether that signal is then processed as 'pain' is a little more nuanced. The term 'sentience' is used a lot in this kind of research, which broadly means the capacity to have feelings, both negative and positive. The evidence for sentience in decapod crustaceans (crabs, lobster and shrimp) is pretty good."
"Pretty much anything with a nervous system will be able to detect damage to itself. Whether that signal is then processed as 'pain' is a little more nuanced."
Pope added that, when the British government commissioned the London School of Economics and Political Science to perform a meta-analysis on the evidence of sentience in both cephalopods (octopuses, squids, etc.) and decapods by reviewing more than 300 studies, it "concluded the evidence for sentience was strong for both groups of animals." Indeed, even on occasions when a test failed to prove sentience, "it was overwhelmingly because the work had not been done (lack of evidence, not evidence of absence)."
There is not enough scientific information about the most humane ways to slaughter decapods. Certainly boiling them alive or dismembering them alive is extremely painful, but it is not easy to kill them humanely in one stroke, as Crump observed to Salon. For instance, a crab's central nervous system is better described as a decentralized nervous system.
"You can't simply destroy one central brain to kill the animal (like you could for a fish, say)," Crump explained. "To abolish nervous system activity, I'd tentatively recommend stabbing crabs through two ganglia (one at the front and the other at the back of the body) and slicing lobsters down the midline (through all thirteen ganglia). These methods require skill and training, so should probably be left to trained cooks."
Crump added, "Electrical stunning devices have also been developed, at least for larger decapods. More research is needed, but there's some compelling evidence that these render crabs and lobsters insensible, so they can then be humanely slaughtered using other methods."
Jensen said that for himself, "when I cook crab, I first chill them down to the point where they are unresponsive. When dropped into the water they seem to be killed by the temperature shock before they 'wake up.'" Like Crump, he also suggested stabbing or breaking down the middle to simultaneously destroy their brain and thoracic ganglion. Another advantage of this method is that it makes it easier to fit multiple crabs into one pot, since you can throw away the guts and carapace. "I think this is a very humane method. (I usually don't do this because I don't need the space and think the body meat tastes better when they're cooked whole)."
Jensen later added, darkly, "If crustaceans screamed when they were dropped into boiling water, I doubt we'd still be having these kinds of discussions."
