Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: thedoc on 19/06/2012 18:42:16
Title: Do slugs and snails feel pain?
Post by: thedoc on 19/06/2012 18:42:16
Chris
I'd like to know if slugs and snails feel pain?
They are the bane of my horticultural life and I would like to know which is the most humane way of dispatching them, apart from natural predators?
K x
Asked by Karen Wells
Visit the webpage for the podcast in which this question is answered. (http://www.thenakedscientists.com/HTML/podcasts/show/2454/)
Title: Do slugs and snails feel pain?
Post by: thedoc on 19/06/2012 18:42:16
We answered this question on the show...
I wasn’t actually sure about the answer to this to start with, whether things like slugs and snails do actually feel pain. The way that the medicines and the drugs work that you put into slug pellets is they basically just cause them to expire through various toxic ways which are not going to affect humans and other animals and mammals. You're exploiting a chemical problem that the snail has when it eats this stuff compared with us. Then I looked back at a story I wrote about 5 years ago - "Can prawns feel pain?" Bob Elwood, at Queens University Belfast, published a paper showing that prawns, when he dabbed a vinegar onto their pincers and on their antennae, seem to flinch, and he suggested this was because they felt pain. Then I found that he’s actually published a follow up paper and I've looked that up for you. I'm actually quoting from Science Daily, but it says here:
“New research published by Queens University Belfast Academic has shown that crabs don't just suffer pain, but they also remember it too. The study looked at the reactions of hermit crabs to small electric shocks and it was carried out by Professor Bob Elwood at the School of Biological Sciences at Queens University Belfast, and published in Animal Behaviour. Professor Elwood, who has previously carried out a study showing that prawns endure pain, said that his research highlighted the need to investigate how crustaceans used in food industries are treated."
Obviously, this is about crabs and you're asking about slugs and snails, but they are closely related in the grand scheme of things, and therefore, it’s reasonable that if we read what happens to a crab, we can sort of extrapolate to a snail. Now he goes on to say, wires were attached to the shells of the hermit crabs to deliver small shocks to the abdomens of some of the crabs in their shells. The crabs that got out of their shells were those that had received shocks, indicating the experiment was unpleasant for them and it shows that central neuronal processing, in other words, they realise it was unpleasant the they decided to vacate their shell. It wasn’t just a reflex response. He also says that crabs that have been shocked that had remained in their shell were appeared to remember the experiment of the shock because they quickly move towards a new shell when they were offered one, compared with the shell they were already in. In other words, they prefer certain shells over others and if they're in one that they're already been uncomfortable with and you then shock them, they're much more likely to vacate the premises and go for a new shell. So, this would suggest that simple creatures like prawns and also crabs, and hermit crabs can experience pain. Therefore, I think it’s probably not unlikely that if you bring a snail to an untimely end by pouring salt over it or poison it with some slug pellets, it’s probably not very pleasant for the slug or the snail.
Title: Re: Do slugs and snails feel pain?
Post by: evan_au on 20/06/2012 10:52:40
I think that snails must feel pain. As a child, I poked snails in the eye, and they withdraw their eye-stalks to protect their eyes. It's like the human reflex when we get a poke in the eye. [I know its an anthropomorphic argument.]
Title: Re: Do slugs and snails feel pain?
Post by: Don_1 on 20/06/2012 14:40:40
Quote from: thedoc
........cause them to expire through various toxic ways which are not going to affect humans and other animals and mammals.
Sorry Doc, but I must take issue with you on this point.
Metaldehyde & methiocarb are the active ingredients in slug pellets. The former causes the slug to swell and the later cause’s damage to the mucus cells resulting in the over-production of mucus. Death is the result of dehydration.
Both these poisons are dangerous to other animals.....
...... can and do result in direct poisoning of non target animals and indirect poisoning of non target animals is only too common. Dogs, cats and even horses have been known to ingest these pellets, causing anything from slight to severe illness and even death.
The pellets may be ingested accidentally by grazing or intentionally for the cereal based carrier.....
..... Run off can lead to poisoning of streams and ponds.
See this report in the Farmers Guardian (http://www.farmersguardian.com/metaldehyde-at-risk-if-leaching-into-watercourses-not-contained/23785.article).
In higher animals (including humans), these molluscicides can cause skin, eye and mucus membrane irritation by exposure to the vapour and dermatitis and conjunctivitis with long term or repeated exposure. Ingestion can cause kidney and liver damage severe abdominal pain, nausea, vomiting, diarrhoea, fever, convulsions, and coma. Other problems related to these poisons are increased heart rate, panting, asthma attack, depression, drowsiness, high blood pressure, inability to control the release of urine and faeces, incoordination, muscle tremors, sweating, excessive salivation, tearing, cyanosis, acidosis, stupor, and unconsciousness.
The biggest problem with slug pellets is their effect on wildlife. The dead or dying slug may become the prey of Hedgehogs, frogs, toads, birds etc. By taking a poisoned slug or snail, the predator inadvertently ingests the poison and may well suffer the consequences. The decline in the Hedgehog population in the UK has already been partly attributed to the ingestion of poisoned slugs and it is certain that other wild animals, frogs and toads in particular, are also suffering the same fate.......
See the whole post here:- http://www.thenakedscientists.com/forum/index.php?topic=44496.msg390642#quickreply (http://www.thenakedscientists.com/forum/index.php?topic=44496.msg390642#quickreply)
Used properly, slug pellets should not be a problem, but the trouble is they are all too often used incorrectly, with far too much being put down at a time.
The doses required to kill slugs falls well short of the doses required to have any effect on other animals. However, Angela Squires, who runs a Hedgehog hospital, claims to be finding poisoned hedgehogs. See this. (http://www.bournemouthecho.co.uk/news/9706385.Wildlife_warning_as_hedgehogs_are_killed_by_slug_pellets_in_Dorset/) And in 2009, the Daily Mail reported this case (http://www.dailymail.co.uk/news/article-1189773/Homebase-slug-pellets-killed-lovely-labrador--clear-warning.html) of dog poisoning. Amazing, maybe, but horses have also died from low doses of metaldehyde. NCBI (http://www.ncbi.nlm.nih.gov/pubmed/1134493)
You might also read this entry (http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/212000.htm) in the Merck Veterinary Manual and this (http://pmep.cce.cornell.edu/profiles/extoxnet/haloxyfop-methylparathion/metaldehyde-ext.html) from the Cornell University.
Our tortoises have free range in our garden, so we do not use slug pellets. Having tried other remedies with only limited success, we turned to nematoads and so far with 100% success.
I think slug pellets need more investigation into their affect on other animals and what concentrations might prove dangerous. Although the active ingredients of slug pellets are said to neutralise on ingestion by slugs and snails, I wonder if this might not be the case where large quantities have been ingested, or if the dead slug can be described as 'safe' when ingested by another animal.
Title: Re: Do slugs and snails feel pain?
Post by: chris on 21/06/2012 10:39:31
I've checked my "child-friendly" slug pellets, which tell me that they don't contain the stuff listed above but are instead based on aluminium sulphate - so they won't kill me, but they could give me Alzheimer's if I eat the whole tub. Now I'm wondering if slugs can get Alzheimer's too...
Title: None
Post by: Anonymous on 07/10/2013 20:31:21
I'm sorry, but you CANNOT compare snails and crustaceans like that. That is like comparing apples and carrots. It is not right to extrapolate the results of what happens to crabs to what happens to snails, as they are in almost no way related. Crustaceans are arthropods, while snails are molluscs. Besides, insects and crabs are both arthropods, but it has been proven that most insects (with the exception of the fruit fly) do not experience pain. The same for oysters. Snails, oysters and slugs are all molluscs, yet oysters have no central nervous system.
However, I have read some reports that nociceptors have been found in the gastropods Aplysia (a sea slug) and Helix (garden snails) have nociceptors and are capable of operant conditioning, so pain is not out of the question for these two gastropod groups. So if you have to kill them, do it quickly to avoid any potential pain.