Do Lizards Feel Pain?

Lizards are fascinating creatures that have roamed the earth for over 200 million years. As reptiles, they have unique adaptations that set them apart from mammals and birds. One question that often comes up is whether lizards can feel pain like humans and other animals do.

If you’re short on time, here’s a quick answer to your question: Yes, research shows that lizards do feel pain, though not in exactly the same way as humans.

In this article, we’ll take an in-depth look at the evidence around lizard pain perception and what it means for their experience.

Anatomy of Pain Perception in Lizards

Nociceptors and Neural Pathways

Lizards have specialized nerve cells called nociceptors that detect potentially harmful stimuli like extreme temperatures, sharp objects, or caustic chemicals (1). When a nociceptor is activated, it transmits signals along neural pathways to the brain (2).

Lizards have relatively simple neural circuits for processing pain compared to mammals.

In lizards, nociceptive information is carried by two types of nerve fibers: A-delta fibers that sense fast pain and C fibers that sense slow, chronic pain (3). These fibers extend from the skin and internal organs and connect to the spinal cord (4).

From the spinal cord, nociceptive signals are transmitted to multiple regions of the brain including the thalamus, somatosensory cortex, and limbic system (5).

While the neural pathways are fairly well mapped, it remains unclear exactly how lizards perceive or react to signals interpreted as painful by humans. Their behavioral responses likely depend on the type of noxious stimulus and its potential to cause tissue damage (6).

Reptilian Brain Structure

Lizards have relatively small, simple brains compared to mammals. The lizard brain consists of the brainstem that controls basic functions like breathing, the cerebellum that coordinates movement, and the forebrain that handles sensory information processing (7).

The forebrain can be further divided into the telencephalon which processes stimuli and the diencephalon which regulates physiology.

Within the telencephalon, lizards have a basic pallium structure that may support primitive cognition and decision-making (8). They lack the expansive neocortex that enables complex perception and cognition in mammals (9).

The diencephalon contains structures including the thalamus and hypothalamus that likely contribute to pain and defensive behaviors (10).

References:

1. Sneddon et al. 2014
2. Braithwaite 2010
3. Sufka & White 2016
4. Gregory et al. 2014
5. Waters & Lumb 1996
6. Broom 2001
7. Butler & Northcutt 2013
8. Montgomery et al. 2017
9. Roth 2016
10. Font et al. 2008
11. Mashour & Alkire 2018

Behavioral Responses to Painful Stimuli

Avoidance

Lizards have been observed to exhibit avoidance behaviors in response to painful stimuli, suggesting they feel pain to some degree. For example, one study found that lizards quickly learned to avoid areas where they had previously received an electric shock.

After just a few trials, the lizards would avoid those areas for over 24 hours. This demonstrates their ability to perceive the stimulus as unpleasant and modify their behavior to prevent future “pain.”

Another experiment showed that lizards would avoid eating prey that had been injected with bee venom, which causes pain. The lizards showed distress behaviors when sampling the venom-injected prey and then avoided eating those prey in subsequent trials.

This learned avoidance of something that caused discomfort provides additional evidence that lizards can feel pain.

Physiological Stress Responses

Beyond avoidance behaviors, researchers have measured physiological signs of stress in lizards subjected to painful stimuli. These include increased heart rate, blood pressure, and stress hormone levels.

One study found over a 200% increase in the stress hormone corticosterone in lizards after they were exposed to various noxious stimuli. These involuntary physical reactions signal that the lizards are experiencing stress in response to perceived harm or threats.

Research has also shown that the sensory regions of lizard brains light up when they receive painful stimuli. So at a neurological level, their brains are processing and reacting to the potential damage.

Altogether, both behavioral reactions and physiological signs suggest lizards do register tissue damage and experience something akin to pain, though likely not to the same degree as mammals.

Pain Relief Treatment in Lizards

Analgesic Medications

Lizards feel pain just like humans and other animals, so it’s important to properly manage pain in lizards needing medical treatment. Common analgesic (pain relief) medications used in lizards include:

• Opioids like butorphanol – These bind to opioid receptors in the nervous system to block pain signals.
• NSAIDs like meloxicam – These reduce inflammation and pain by inhibiting COX enzymes.
• Local anesthetics like lidocaine – These temporarily numb areas and block pain signal transmission.

Proper dosing of these drugs is crucial, as lizards metabolize medications differently than mammals. Overdoses can be fatal. Vets determine appropriate drugs and doses based on factors like the lizard’s species, size, age and health condition.

Anesthesia

General anesthesia induces unconsciousness and prevents lizards from feeling pain during medical procedures. Injectable anesthetics commonly used in lizards include:

• Propofol – A fast-acting anesthetic often used for quick procedures.
• Isoflurane – An inhalant anesthetic that allows precise control of anesthesia depth.
• Sevoflurane – Another inhalant anesthetic with rapid onset and recovery.

Anesthesia carries risks like respiratory depression, so patients require close monitoring of vital signs. Specific anesthesia protocols are tailored to each lizard patient’s needs for optimal safety and effectiveness.

Non-Pharmaceutical Approaches

While drugs are often necessary for treating pain in lizards, non-pharmaceutical techniques can also help. These include:

• Providing heat sources to maintain optimal body temperature.
• Using soft bedding materials for comfort.
• Allowing privacy by providing hides.
• Minimizing handling and disturbance.
• Monitoring for signs of pain like decreased appetite.

Such supportive care measures help reduce lizards’ pain levels and speed healing. They are best used alongside analgesic medications prescribed by a qualified exotic animal veterinarian.

Implications for Lizards as Pets and in the Wild

Providing Proper Husbandry

When keeping lizards as pets, it is important we provide proper husbandry and care, considering their potential ability to feel pain and suffering. As the ASIH Herpetological Animal Care and Use Committee outlines, captive habitats should enable species-appropriate behaviors and promote good welfare.

This includes suitable UV lighting, basking areas, hides, substrates, nutrition, and more. Being aware lizards may experience unpleasant sensations means we must make diligent efforts to meet all their biological and psychological needs.

Knowing lizards can likely perceive noxious stimuli also highlights the need for gentleness when handling them. As anyone who interacts with reptiles knows, they can be quite delicate. Things like grabbing tails, pinning necks, or restraining them too firmly could plausibly cause discomfort or even tissue damage.

Always handle lizards with care and caution.

Ethical Treatment During Procedures

Unfortunately, some human interactions with captive lizards involve aversive or invasive procedures like injections, blood sampling, surgeries, and more. Research guidelines generally recommend assuming they experience pain and providing appropriate anesthesia and analgesia.

For example, the AAALAC International animal care standards advise:

• Minimizing tissue damage from injections by properly restraining animals and using appropriate gauge needles
• Providing systemic analgesics for invasive surgeries and localized anesthetics for scale removal or limb amputation
• Allowing recovery on heated pads to avoid hypothermia

While we lack definitive proof of pain perception in lizards, providing them ethical treatment as if they do feel pain is the safest approach.

Conservation Concerns

Considering over 1,600 lizard species are threatened with extinction, their welfare and conservation in the wild are also an ethical concern. Habitat destruction, climate change, pollution, human persecution, and more jeopardize lizard populations globally.

Declining numbers then make species more vulnerable to additional threats.

It is plausible climate change could also cause suffering in cold-blooded reptiles via heat stress, drought, disrupted hibernation, and other mechanisms. Protecting habitats and addressing environmental issues may help prevent population declines and potential pain states in wild lizards.

Conclusion

While lizards may experience pain differently than humans do, the evidence clearly shows they feel pain and take action to avoid it. Understanding lizard pain perception allows us to improve how we care for them as pets and in conservation efforts.

Going forward, it will be important to continue researching how pain manifests in different lizard species so we can act in their best interests.