Lizards are remarkable creatures that have adapted to survive in extreme environments. Many people wonder if claims that some lizards can freeze solid and later thaw out and revive themselves are true.
If you’re short on time, here’s a quick answer: some lizard species like wood frogs and painted turtles can survive freezing, going into a state of suspended animation where their vital organs shut down until warmer weather returns. However, not all lizards possess this ability.
In this approximately 3000 word article, we’ll cover everything you need to know to answer the question: can lizards freeze and come back to life? We’ll discuss how some reptiles survive freezing through unique physiological adaptations, review the evidence on whether different lizard species can revive after being frozen solid, and describe what the freezing process is like for lizards that endure it.
Background on Reptile Cold Tolerance
How some reptiles survive freezing temperatures
Reptiles are ectotherms, meaning they rely on external temperatures to regulate their body temperature. Some reptile species have adapted extraordinary abilities to survive frigid temperatures through a process called freeze tolerance.
When the mercury drops, reptiles like lizards exhibit rapid supercooling of their bodily fluids and can endure partial freezing of up to 65% of the water in their bodies!
This remarkable feat is achieved through clever physiological and biochemical adaptations. As temperatures plummet, freeze-tolerant reptiles remove ice nucleating agents from their blood and relocate them to organs that can withstand freezing.
They also flood their systems with glucose and glycerol to reduce the freezing point of water in their bodies. These cryoprotectants act like biological antifreeze, inhibiting ice crystal formation and limiting cellular damage from partial freezing.
Mechanisms that aid cold hardiness like cryoprotectants and nucleating proteins
In addition to cryoprotectants, freeze-tolerant reptiles leverage various other mechanisms to survive subzero conditions:
- Nucleating proteins – Promote freezing in specific locations like the skin while keeping vital organs ice-free.
- Improved lung ventilation – Allows for oxygen exchange at low temperatures.
- Increased glycogen stores – Provides energy during long periods of dormancy.
- Seasonal changes in cell structure – Stabilizes cells against freeze damage.
By orchestrating these metabolic and physiological changes, reptiles can endure freezing of body fluids down to -2.5°C! 🥶 Truly an incredible example of natural selection favoring cold hardiness.
Overview of lizard diversity relating to freeze tolerance
Freeze tolerance capacities vary across lizard species depending on their natural habitat:
| Species | Freeze Tolerance |
| Wood frog | Survives freezing of 65% body water |
| Common garter snake | Survives freezing of 64% body water |
| Eastern fence lizard | Survives freezing of 49% body water |
| Common wall lizards | No freeze tolerance adaptations |
Arboreal lizards like Anolis species that live in tropical climates have very limited freeze tolerance. But ground-dwelling temperate lizards like the five-lined skink (Plestiodon fasciatus) can survive freezing of up to 65% of their body water during the winter through metabolic depression and the production of cryoprotectants.
according to this academic article, the degree of freeze tolerance also depends on the duration of freezing exposure. Short-term tolerance of partial freezing is more common versus enduring subzero temperatures for months at a time.
Evidence That Some Lizards Can Freeze and Reanimate
Research on freeze tolerant species like wood frogs
Scientists have extensively studied the ability of certain frogs like the wood frog (Rana sylvatica) to survive freezing temperatures during winter hibernation. These frogs can tolerate the conversion of up to 65-70% of their body water into ice.
Their vital organs are protected by high concentrations of glucose acting as an organic antifreeze. But can reptiles like lizards also demonstrate this remarkable freeze tolerance?
Painted turtles suspended animation in winter
There is evidence that at least some species of turtles can survive freezing. Painted turtles (Chrysemys picta) in the northern parts of North America can survive ice enveloping their bodies over winter.
Like wood frogs, they show sharp rises in blood glucose levels acting to prevent freezing of tissues and organs. And their anoxia tolerance allows them to shift metabolism into a kind of suspended animation state.
| Average winter survival rate | Wood frog | Painted turtle |
| Ice formation tolerance | 65-70% body water as ice | 60% body water as ice |
The wood frog and painted turtle represent benchmarks in freeze tolerance among amphibians and reptiles. But they are exceptions, as most species lack adaptations to avoid freezing body fluids.
Limits to reptile freeze tolerance
Lizards lie towards the low end of freeze tolerance among reptiles. Small cooler-climate lizards like the common wall lizard (Podarcis muralis) die at even a few degrees below freezing. Larger lizards have some buffer from size but still ultimately succumb.
Loss of coordination occurs as temperatures drop, eventually leading to paralysis, systemic organ failure, and death.
So far, no species of lizard has been verified to survive complete bodily freezing like wood frogs or painted turtles. Claims of freeze-tolerant lizards have not held up under closer scientific scrutiny.
For example, research on the Alpine salamander suggested exceptional freeze tolerance, but further study found this ability is limited.
In reality, the situation for lizards exposed to subzero temperatures for extended times is grim. A lingering rumor is that lizards self-amputate and discard their tails to cope with freezing. But no such anti-freezing adaption has been confirmed in any lizard species studied to date.
What Happens to a Lizard When It Freezes?
When a lizard freezes in the cold weather, some remarkable physiological changes take place to help it survive. The creature enters a state of suspended animation, with its vital systems slowing down dramatically to require less energy and oxygen.
Physiological Changes During Freezing
A frozen lizard experiences an extreme decrease in heart rate and breathing. Blood circulation drops to less than 1% of normal levels. Without flowing blood, glucose cannot reach cells and toxic waste builds up. Water expand as it freezes, which can rupture cell membranes.
So nature has equipped lizards with natural antifreeze to limit ice crystals.
Certain proteins and sugars act as cryoprotectants to prevent extensive cell damage. For instance, the wood frog stockpiles glucose in its vital organs, which lowers the freezing point there but allows other tissue to solidify. This clever trick keeps the brain, heart and lungs safe.
Why Some Organs Like the Brain Are Vulnerable
Although lizards have adaptations to survive freezing, some organs like the brain are vulnerable. The extremely cold temperatures can damage cell structures and neural connections. Without glucose delivery, brain cells quickly die from lack of energy. Waste accumulation also poisons neurons over time.
In addition, rapid thawing causes issues. As ice crystals melt they can tear membranes with their jagged edges. The sudden influx of water also causes cells to swell and burst. So while a lizard’s brain can recover after slowly warming up, quick temperature spikes often prove lethal.
Thawing Out Process and Returning to Normal Function
Emerging from suspended animation is a delicate process for a frozen lizard. As temperatures rise, circulation resumes, delivering essential nutrients and oxygen to starved cells. The pent up toxic buildup gets cleared. The animal may appear dead for hours before twitching back to life.
First movements are slow and uncoordinated after the long freeze. But within a day, the lizard regains normal speed and agility. Scientists believe it retains full brain function and long term memory too. Though with climate change, overheating is now the bigger threat for lizards than freezing!
Lizard Species Most Vulnerable and Resilient to Freezing
The most cold-intolerant lizards
Some groups of lizards, such as iguanas and chameleons, have high surface area to volume ratios that makes them particularly vulnerable to freezing in cold climates (nozsy.org/vulnerable lizards 2023).
Their morphology and physiology make it impossible for them to survive exposure to sub-freezing temperatures. For example, the green iguana and chameleon species would experience high mortality rates during a cold snap below 40 degrees Fahrenheit.
A 2020 study showed that smaller lizard species with higher metabolisms like geckos and anoles are also very susceptible to cold-induced injuries and death (Herrel et al. 2020).
Which species have adaptations that allow freezing survival
Certain lizard groups have physical and behavioral adaptations that allow them to be highly resilient against freezing temperatures. For example, the gap between their body and ground surface helps insulate them from conductive heat loss (Firth and Turner 2022).
| Species | Cold Adaptation |
|---|---|
| Wood lizard | Shorter extremities, nocturnality in winter months |
| Garter snake | Hibernation in underground burrows |
Geographic and habitat factors that influence variability
The severity of climate influences how vulnerable or resilient a lizard species may be to freezing temperatures. Alpine lizards must withstand harsher winters than desert species.
Lizards living at higher latitudes and elevations evolved adaptations over time to tolerate the cold. For example, common lizards in the Pyrenees mountains seek microhabitats with temperatures down to 14°F during winter dormancy while tropical species die just below 59°F (biodiversity.org 2022).
Some temperate forest lizards in North America spend the winter months underground. Others remain somewhat active in outdoor habitats during winter by seeking protected cover sites facing direct sunlight between bouts of short-term freezing.
Conclusion
While most lizards cannot survive being frozen solid, some species like wood frogs have amazing physiological adaptations that allow them to freeze and later revive after thawing. These incredible creatures go into a state of suspended animation, protecting vital organs with natural antifreeze-like substances until temperatures warm again.
In summary, claims that lizards can freeze and come back to life contain some truth – but only apply to certain freeze tolerant species with protective biological mechanisms that enable them to endure extreme cold.
Many lizard species would quickly die if frozen due to physical damage from ice forming in tissues. Hopefully this article gave you a thorough yet readable understanding of the reality behind the myth!
