Scientists confirm– Hurt crabs feel pain

From ANIMAL PEOPLE, May 2009:


BELFAST–Hermit crabs feel pain when
injured and change their behavior to avoid the
source of pain, reported Robert Elwood of the
School of Biological Sciences at Queen’s
University in Belfast, Northern Ireland, on
March 27, 2009.
“With vertebrates we are asked to err on
the side of caution and I believe this is the
approach to take with crustaceans,” concluded
“Ripping the legs off live crabs and
crowding lobsters into seafood market tanks are
just two of the many practices that may warrant
reassessment,” warned Jennifer Viegas of the
Discovery Channel.

More than 4,130 news web sites amplified
Elwood’s findings, soon to be published in the
journals Animal Behavior and Applied Animal
Behavior Science.
The hermit crab study was Elwood’s second
well-publicized attempt to establish to the
satisfaction of most remaining scientific
skeptics that crustaceans feel pain. New
Scientist in November 2007 published Elwood’s
findings about the behavior of 144 prawns after
he daubed one of their antennae with a solution
of diluted acetic acid. The prawns immediately
groomed and rubbed the daubed antennae, but not
their other antennae. This, Elwood wrote, was
“consistent with an interpretation of pain
The Guardian headlined a report about the
prawn study “Blow for fans of boiled lobster.”
But other researchers alleged fault with Elwood’s
“Even a single-cell organism can detect a
threatening chemical gradient and retreat from
it,” University of Utah pain researcher Richard
Chapman told Guardian reporter Ian Sample.
Elwood designed the hermit crab study to
respond to the criticisms of the prawn study. He
and colleague Mirjam Appel collected hermit crabs
from rock pools in County Down, Northern Ireland.
“All of the crabs survived the
experiments and were later released back into
their native habitat,” reported Viegas.
Hermit crabs, rather than forming their
own shells, occupy shells discarded by other
animals. Once they find a satisfactory shell,
they are reluctant to abandon it. Their usual
response to a threat is to retreat farther into
the shell.
Elwood and Appel offered the hermit crabs
alternative shells to move into, but shells less
attractive to them than the shells they already
Elwood and Appel then gave some of the
crabs small electric shocks while they were
inside their old shells.
hells. They also groomed themselves in a manner
that Elwood and Appel described as “a protective
motor reaction, viewed as a sign of pain in
vertebrates.” Crabs who were not shocked did not
take the opportunity to change shells.
“There has been a long debate about
whether crustaceans including crabs, prawns and
lobsters feel pain,” Elwood summarized in a
media release. “We know from previous research
that they can detect harmful stimuli and withdraw
from the source of the stimuli but that could be
a simple reflex without the inner ‘feeling’ of
unpleasantness that we associate with pain. This
research demonstrates that it is not a simple
reflex but that crabs trade their need for a
quality shell with the need to avoid the harmful


“Such trade-offs are seen in
vertebrates,” Elwood wrote, “in which the
response to pain is controlled with respect to
other requirements. Humans, for example, may
hold a hot plate that contains food, whereas
they may drop an empty plate, showing that we
take into account differing motivational
requirements when responding to pain.
“Trade-offs of this type have not been
previously demonstrated in crustaceans,” Elwood
continued. “The results are consistent with the
idea of pain being experienced by these animals.”
Elwood spoke specifically to the
treatment of crustaceans by the seafood industry.
“More research is needed in this area where a
potentially very large problem is being ignored,”
he said. “Legislation to protect crustaceans has
been proposed [in Britain] but is likely to cover
only scientific research. Millions of
crustaceans are caught or reared in aquaculture
for the food industry. There is no protection
for these animals, with the possible exception
of certain states in Australia.”
In Elwood’s Applied Animal Behavior
Science paper, he and co-authors Stuart Barr and
Lynsey Patterson cite seven reasons for believing
that crustaceans suffer. In addition to the
findings of the hermit crab and prawn
experiments, they explain, crustaceans placed
under stress demonstrate physiological changes
consistent with feeling pain, including release
of adrenal-like hormones. If crabs are given
anesthetics or analgesics, they appear to feel
relieved, showing fewer responses to negative
Contrary to the supposition that having a
brain is necessary to feel pain, Elwood et al
argue, crustaceans have “high cognitive ability
and sentience.”
Feelings of pain and stress in mammals
are associated with the neocortex. Because
crustaceans lack a neocortex, prevailing belief
until recently was that they lack the
physiological structure necessary to suffer.
Responds Elwood, “Using the same
analogy, one could argue crabs do not have vision
because they lack the visual centres of humans.”
In fact, fish, lobsters and octopi all have
vision, and some species have relatively
advanced vision, despite lacking a visual
cortex. The explanation is that their
neurological systems are organized in a different
manner, with different control structures.
“It was also thought,” said Viegas of
the Discovery Channel, “that since many
invertebrates cast off damaged appendages, it
was not harmful for humans to remove legs, tails
and other body parts from live crustaceans.
Another study led by Lynsey Patterson, however,
found that when humans twisted off legs from
crabs, their stress response was so profound
that some later died.”

Humane response

Much of the humane community has believed
for decades that the treatment of crustaceans
should become a topic of urgent concern–if only
to avoid practices that might encourage callous
treatment of other species.
In 1952, for example, delegates from 25
nations agreed at a convention hosted by the
World Federation for the Protection of
Animals–one of the three ancestors of the World
Society for the Protection of Animals– that
boiling live crustaceans sets a bad example of
how animals should be treated, and should be
PETA has staged heavily publicized live
lobster releases almost annually for more than 25
years. In 2006 two members of Animal Rights
Croatia locked themselves into a fish tank to
dramatize the fate of lobsters.
Serious efforts have also been made by
the humane community to assemble scientific
evidence that crustaceans suffer. The Scottish
organization Advocates for Animals in 2005
published a volume entitled Cephalopods & Decapod
Crustaceans: Their Capacity To Experience Pain &
Suffering, assessing all that was known at that
Such efforts have brought some results.
Notably, the grocery chain Whole Foods in 2006
quit selling live soft-shelled crabs and lobsters
for humane reasons.
But the humane community has also been
embarrassed by incidents such as a crab cook held
in 2005 to benefit the Prince Rupert SPCA. A
sequel was cancelled in 2006 by the British
Columbia SPCA, parent organization to the Prince
Rupert SPCA, after Sea Shepherd Conservation
Society founder Paul Watson led a campaign
against it.

Concern for fish

Concern about crustacean suffering is
rising parallel to campaigns on behalf of fish.
Hong Kong SPCA executive director Sandy
Macalister, for instance, editorialized
recently in the membership magazine Paw Prints
against the practice of restauranteurs keeping
giant groupers and other species on display in
cramped tanks, until bought and killed for
someone’s dinner.
“These wonderful animals, which since
the 1940s have lived and bred in the coral
depths, now lie behind thick distorting glass in
a narrow tank on the footpath,” wrote
Macalister. “How many times have we walked past
such horrific living conditions for these animals
without a second thought? Is it because we
consider them to be `just fish’? If a passer-by
or a restaurant patron knew that these
magnificent creatures were more than 65 years
old, would that make a difference?”
Macalister’s editorial attracted
extensive sympathetic coverage from Simon Parry
of the South China Morning Post.
“Fish are vertebrates like us,”
University of Hong Kong biologist Yvonne Sadovy
told Parry. “They have a backbone, and a lot of
the biology and physiology have some similarities
to us. Our nervous systems and hormonal systems
in some ways are very similar. I think most
biologists would say there is absolutely no
reason to believe they would not feel pain. How
they perceive it is obviously incredibly
difficult to know, but you pick up a fish and
take it out of water and put a hook in its mouth
and it struggles. There is something clearly
uncomfortable and not right and that fish
perceives stress.”
“When you consider what a fish does in
its daily life–it can tell where it is,
identify things and make decisions–it is clear
there’s far more going on than anyone suspects,”
Macalister said. “They learn, and they have
memories, and they can identify people. They
feel stress and they feel pain. People used to
believe fish couldn’t remember anything for
longer than three seconds, but we know now that
isn’t true.”
Fish in Hong Kong, as in most of the
world, have only scant protection under existing
anti-cruelty laws, but Macalister pointed out
that laws follow public opinion.
“Attitudes, as well as the law, have to
change,” Macalister told Parry. “It’s an issue
of education.”
Industry notice
Some people in the seafood industry are
also beginning to notice animal welfare issues.
Adam Anson, who writes for The Fish Site, The
Pig Site, The Beef Site, and other online
animal industry periodicals, noted in March 2009
that “Fish welfare needs have been left behind”
in developing the aquaculture industry, even
though “In 1997, the Treaty of Amsterdam agreed
that throughout the European Union the concept of
welfare is the same in fish as it is in mammals
and birds and necessary protection should be
This concept was reinforced in an April
8, 2009 communication to the European Commission
by the EC Fisheries Directorate.
” This communication recognises the
importance of the welfare of farmed fish for the
development of sustainable aquaculture,”
summarized Eurogroup for Animal Welfare.
“Eurogroup is pleased to see that the Commission
plans to launch a project to evaluate fish
welfare in aquaculture with a view to possibly
introducing legislation on this topic,”
Eurogroup added.
Assessed Anson, “Research into this area
has not just been hampered by a lack of
investment, but also by the complexity of the
issue and the difficulty in achieving scientific,
relevant measurementsÅ A further complexity is
added by the numerous different species of fish
that are now used in farming. Research must
identify all the varying degrees of behavioral
patterns and social activities. Welfare standards
must, in turn, take these natural drives into
account, applying unique welfare standards for
each different species.”
Noted Anson, “Some natural conditions
will be impossible to recreate in a fish pen.
For instance, Atlantic salmon will never be able
to make their monumental migrations, risking
life to reproduce, whilst trapped inside the
confines of a net.
“It is easy to see how fish welfare is a
complex and potentially very expensive issue for
the industry,” Anson concluded, “but the more
that is understood, the more necessary the
research seems.”

Print Friendly

Leave a Reply

Your email address will not be published.