Perception of pain by reptiles

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Perception of pain by reptiles

Postby Scotts1au » Thu May 30, 2013 4:32 pm

I don't necessarily want to turn this into a Euthanasia debate, however the issue has come up before because of the discussion about euthanasia comparing freezing for example to torture and that the sensation of freezing and associated pain is a concious experience for reptiles. This argument often gets a run in articles, notably published by people claiming to be Vets. On the other side of the equation is the bombardment of vets by animals suffering deep tissue burns from sitting on heat rocks and having no perception of burning whilst it was occuring. It seems those who are willing to argue one side of the equation completely ignore objective evidence on the other for the sake of their argument.

I note the most protocol information relating to euthanasia in reptiles recognises a pain management requirement.

Indeed I recently looked extensively admittedly through google etc and found a number of articles that made references to "recent studies" have shown that reptiles percieve pain when frozen etc - however none contained references and nothing from refereed sources.

Anyone who has kept blotchies in cold conditions will have seen them respond to stimulation such as touching even when cold - say <10C, normally by opening their eyes, they will also flinch and huff when touched, so they are perceiving the touch. It is easy to see that even at these temperatures and lower they are having a concious awareness even though their bodies are in a state of semi torpa. Are they in pain? - I doubt it.

The age old observation in venomous snake is that they are generally more aggressive in cooler weather because they perceive difficulty in evading a predator. Clearly the animals know they are cold. Also blueys with painful limbs respond by favouring other limbs so there are clearly perceptions of pain that us mammals would consider normal. This might suggest that their nervous systems are more in tune with this sort of pain than we might project onto them about our own experience of pain.

So what do we know - at least to temperatures within a normally survivable range for the species there is a concious experience. Also a range of senses are retained. Do they feel cold as painful - unlikely. Do they recognise that they are cold - clearly. Do they feel the sensation of hot or cold as pain - evidence would suggest - no or at least different to the way that we would recognise it and don't have the same reflex responses in response to a sensation.

I'd be interested in any refereed articles that can be made available, or observations that people could make to back up an argument on the matter. I'm keeping an open mind on the issue/s.
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Re: Perception of pain by reptiles

Postby Richard.C » Thu May 30, 2013 5:00 pm

Alot of probs with thermal burns in reptiles are the cause of to hot a basking area in a cold cage,hot rocks are one of the worst culprits,but all heat devices can cause issues in same way,when a reptile is cold it wants to seek warmth to raise body temp,when theres only a small hot zone in a cold cage it warms only a small part of the reptile,they still feel cold so they stay on hot bit to try evenly hheating them selves,but hot spot actually burns them as they sense they still need to raise body temp

Its an interesting topic scott
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Re: Perception of pain by reptiles

Postby Jeff » Thu May 30, 2013 7:24 pm

Scott, I too have a completely open mind on the subject. I would simply like to know the truth. I have nothing to offer toward that though. I am only responding because I want to agree that I am very interested in the topic.
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Re: Perception of pain by reptiles

Postby Spindown » Fri May 31, 2013 9:03 am

^ This. I have an open mind, I just always thought that the freezing thing was proven! I would love to see what people post that *has* been proven, or just opinions etc.
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Re: Perception of pain by reptiles

Postby Lea » Sat Jun 01, 2013 1:58 am

While I can't say it's been proven, I personally and very firmly believe that reptiles can feel pain.

From personal experience looking after many skinks with a variety of wounds, I have seen them react to interventions I make, such as dressings, cleansing wounds, injections. Whether it is an actual reaction to the pain experienced or just a reflex action to me touching them is yet to be proven, but I'm inclined to believe it is pain.

I've had animals calm down while I pick through and debride unhealthy wounds, but if I accidentally pull, push or nip at healthy tissue, I seem to instigate a withdrawal reaction, as if they are trying to remove themselves from the cause of the pain.

My interpretations may be more subjective than scientific, but it definitely influences decisions I make when performing invasive care.

On the subject of pain experienced when subjected to heat or cold, I'm also inclined to think they experience pain in a similar way to mammals, but their initial reaction to it may be slowed because of their physiology, therefore they may not be as perceptive to actually heating up or cooling down until damage has occurred. While a heat burn causes damage to tissues more obviously, burns caused by cooling, or frostbite as it's more commonly known, can also damage through the tissues and can be excruciating, especially as the tissue starts to warm up again, causing inflammation, wound breakdown, necrosis and infection. Because reptiles can not maintain their core body temperatures and lose or gain heat according to ambient conditions, they are more susceptible to thermal burning than mammals, who would detect changes more quickly, or regulate changes to maintain a core body temperature.

I think I'm talking around in circles, but my main point is made. We can assume they do or do not feel pain based on our observations. Seeing a skink limb because of gout might be because of pain, but it might be because of a deformity in the joint and nothing to do with how it feels to walk- but understanding what I know of pain and what a horrific experience it can be, I am happy to assume they feel pain and I'll want to prevent or treat it if I can.

If there is one thing I will "personify" about my animals, it would probably be the pain experience. To assume they don't feel pain just doesn't seem an option.
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Re: Perception of pain by reptiles

Postby Scotts1au » Sat Jun 01, 2013 7:53 pm

I have no doubt that they experience pain, I suppose what I'm trying to get at is how. If I push hard enough on my finger eventually I will feel pain, yet if I touch my finger with a needle the prick sensation is instantaneous and met by a withdrawal response. This is innate, not a learned response. I believe they do have a withdrawal response to the pinprick analogous pain but evidence suggests that other forms of pain, they don't have the same sort of reaction to heat. Do they know a part of the enclosure is warmer?, yes. I suggest that part of the reason for this is simply that if they did then they would feel pain response every time their environmental temperature fluctuated, related stress responses etc, from an evolutionary perspective this wouldn't make sense.
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Re: Perception of pain by reptiles

Postby Jeff » Sun Jun 02, 2013 8:36 am

When considering the freezing-to-death issue, I'm curious about the pain of it even in terms of mammals. What is the level of pain experienced by humans who have come close to death in this manner? My understanding is that while it can be extremely uncomfortable to experience the kind of extreme cold that we have all felt at one time or another, that there is a point where victims of hypothermia simply "fall asleep". If they are not rescued at this point, they die before ever regaining consciousness.

I have also heard that frost bite doesn't hurt while the affected area is still frozen. It's only when the dead tissue is thawed out that there is pain, and I would imagine that is in the surrounding tissue that is still living. Of course reptiles are likely to experience vastly different levels of discomfort/pain than mammals, but my assumption (unsupported) is that a reptile would likely experience less pain than a mammal, rather than more.
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Re: Perception of pain by reptiles

Postby El Lobo » Sun Jun 02, 2013 4:49 pm

A paper "How I Treat Pain in Reptiles" presented by Douglas R. Mader, DVM

viewtopic.php?f=19&t=17731
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Re: Perception of pain by reptiles

Postby Scotts1au » Sun Jun 02, 2013 5:05 pm

Here is a link to the Actual AVMA document.
https://www.avma.org/KB/Policies/Pages/ ... anasia-pdf

Note that the reference is "may cause ice crystal - may cause pain". The cited reference are both guidance documents not studies, of course these references would need to be read to see what studies they may or may not reference to be sure.
See refs 52 and 401 in the document.
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Re: Perception of pain by reptiles

Postby trex » Tue Jul 30, 2013 5:12 pm

This may be a tad off topic, but judging from a very unfortunate experience I had with my old leopard gecko, I'd say 99.99% sure reptiles can feel pain.

I once dropped my leopard gecko from chest height onto my kitchen tiles. It was not on purpose, obviously. And i felt really bad about it. The animal hit the floor belly first as if it was "belly flopping" onto the ground. The leo instantly closed its eyes and opened it's mouth really wide. Simultaneously, it's legs and tail started doing very quick twitching moments.

This convulsion lasted for about 5 seconds. When i picked it back up (gently), its eyes were still closed and stayed that way until i put him back into his cage. He just kinda sat there for a while. After watchign for about 5 mins to see if anything else happened, I saw him finally walk slowly into his hide and stay there. I think he went to sleep.

I never dropped him ever again, and (from what i remember) didn't cause anymore pain for the rest of his life. I never saw him do that reaction again.

BTS, from what I read, seem to be more intelligent animals than leos, so if my leo reacted like that, I can only imagine what BTS and more intelligent reptiles can feel/think.

Do i think reptiles can feel pain? Definately. I would go so far as to say most, if not all, vertebrates can.
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Re: Perception of pain by reptiles

Postby Scotts1au » Thu Aug 01, 2013 9:07 pm

The question isn't so much whether they do, but rather, how? and/or what they don't feel.
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Re: Perception of pain by reptiles

Postby saisaac » Mon Sep 09, 2013 2:23 pm

I have had some experieneces that would lead me to believe that reptiles do feel pain associated with extreme temperatures. I used to keep crested geckos for a while. I typically used vinegar/water to clean the glass of their enclosures. One day I was cleaning one of the tanks with one of the geckos hanging out on my chest. For some reason he decided to leap from my chest and landed in some scalding hot water. Not so hot it would seriously burn someone, but hot enough that it would case burns on your hands. The gecko immediately panicked and frantically tried to get out of the bowl. This made it harder for me to actually get him out. Once he was out of the water he reacted in a manner similar to Trex's experience above. His mouth appeared almost stuck open and his feet clenched closed. Surprisingly, he did not drop his tail. We isolated him in a tuperware with high humidity for 12 hours. He shed his skin two times over the next few days, but made a full recovery. I never let any of my animals near hot water again, but the experience taught me that he definitely felt pain.

We also rescued a box turtle when I was young who had recently lost one of its legs. When we cleaned and treated the wounds the animal tensed from the burning sensation.
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Re: Perception of pain by reptiles

Postby Dood » Wed Sep 25, 2013 7:47 am

Interesting topic.

I think we can all agree that reptiles feel pain but the question is how do they perceive thermal pain and if Hypothermia is a humane form of euthanasia.

Unfortunately there isn't a lot if supporting evidence that hypothermia is not humane but it is still considered inappropriate for euthanizing reptiles and other ectotherms.

http://m.ilarjournal.oxfordjournals.org ... 4/186.full
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Re: Perception of pain by reptiles

Postby Scotts1au » Mon Oct 21, 2013 3:32 pm

Thanks for this. This will be a good place to keep adding relevant articles etc as we find them.
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Re: Perception of pain by reptiles

Postby jdheff1982 » Wed Oct 23, 2013 12:06 pm

trex wrote:This may be a tad off topic, but judging from a very unfortunate experience I had with my old leopard gecko, I'd say 99.99% sure reptiles can feel pain.

I once dropped my leopard gecko from chest height onto my kitchen tiles. It was not on purpose, obviously. And i felt really bad about it. The animal hit the floor belly first as if it was "belly flopping" onto the ground. The leo instantly closed its eyes and opened it's mouth really wide. Simultaneously, it's legs and tail started doing very quick twitching moments.

This convulsion lasted for about 5 seconds. When i picked it back up (gently), its eyes were still closed and stayed that way until i put him back into his cage. He just kinda sat there for a while. After watchign for about 5 mins to see if anything else happened, I saw him finally walk slowly into his hide and stay there. I think he went to sleep.

I never dropped him ever again, and (from what i remember) didn't cause anymore pain for the rest of his life. I never saw him do that reaction again.

BTS, from what I read, seem to be more intelligent animals than leos, so if my leo reacted like that, I can only imagine what BTS and more intelligent reptiles can feel/think.

Do i think reptiles can feel pain? Definately. I would go so far as to say most, if not all, vertebrates can.


I would take this a step further and say any living creature with a nervous system has the potential to feel a certain a threshold of pain.
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Re: Perception of pain by reptiles

Postby Scotts1au » Wed Oct 23, 2013 4:03 pm

Just to clarify the issue here is not whether reptiles feel pain but, how they perceive it, or rather what aspects of pain. There are clear examples where snakes happily wrap themselves around light bulbs and suffer burns and don't remove themselves from the source of the heat. People also make claims that reptiles feel pain when they are cold, however with many temperate species for example they routinely endure significant cooling, would those people be suggesting that the reptiles feel pain associated with this?

The question I see raised in relation to freezing as a means of euthanasia relates to whether pain is experienced in animals as a result fo cellular lysing due to the the formation of ice crystals. This process happens upon freezing of cells, however it should also be pointed out that freezing of water containing salts and other substances occurs below 0 celcius at sea level as opposed to freezing of pure water. Most of the information available suggests the posibility that reptiles may feel pain through their nervous system down to temperatures approaching freezing i.e. 4C.

So if they are not feeling general cold (thermal cold) as pain and their nervous systems would not operate at temperatures below 0C and freezing of water in their cells would not occur until some point below that depending on osmolarity where would the line in the sand be?
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Re: Perception of pain by reptiles

Postby trex » Wed Oct 23, 2013 10:17 pm

Perhaps this has been brought up before, but maybe the reason why snakes wrap around heat sources and injure themselves without removing can be due to the fact that they might have slower nervous systems?

If their sensory receptors aren't able to transmit external stimuli quickly, then a cascade effect can follow. The central nervous system cannot decode it in time, and as a result, bodily injury is ALREADY done to the animal before it can even sense the pain. I'd aliken this to the sensation of a papercut. When it happens, you KNOW you have just been slashed, but oftentimes you don't instantly feel the pain. It is a split second afterwards that the sharp pain is felt. Then the throbbing pain follows.

Maybe the snakes feel the burns very late in the cycle and it is so brief that permanent nerve damage is already on the way, which leads to them losing all sense of pain later.

This would be my hypothesis on the perception of pain by reptiles. I am only deducing this from my studies of human anatomy and pharmacology. I'm not a vet :)
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Re: Perception of pain by reptiles

Postby Scotts1au » Wed Oct 23, 2013 10:19 pm

Not sure about that because if you touch a snake on the side they will recoil away from it/flinch fairly quickly. Just a thought.
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Re: Perception of pain by reptiles

Postby Jeff » Wed Oct 23, 2013 10:35 pm

I wouldn't want to do it, but I wonder if anything could be learned from freezing an animal in a freezer with a glass door. I know that many people euthanize reptiles by freezing them (usually under the assumption that the animal feels no pain from this), but I have never heard anyone claim that they watched the animal during the process. It seems like watching how the animal reacts might give some insight into whether or not they are experiencing "pain"?

I am not suggesting an experiment, just moreless asking if anyone has ever monitored an animal while it is being euthanized by freezing.
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Re: Perception of pain by reptiles

Postby trex » Thu Oct 24, 2013 3:22 pm

Scott that is true that most reptiles i encounter instantly flinch when touched, but i have a strong feeling that their sensory receptors for pain (nociceptors) may not be wired to transduce information as quickly as pressure receptors.

I have a hard time coming up with any other reason why a snake would burn it self.

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