Lizards are cold-blooded animals, meaning they rely on external sources of heat to regulate their body temperature. If a lizard gets too cold, it can have serious negative effects on its health and survival. In this article, we’ll explore what exactly happens when a lizard gets too cold and the consequences it faces. We’ll also look at how lizards try to prevent getting too cold and behavior changes when their body temperature drops. Let’s dive in!
What is the normal body temperature range for lizards?
Lizards are ectothermic, meaning they depend on external heat sources to control their body temperature. They do this through a process called thermoregulation. The optimal body temperature range for most lizards is between 85-95°F during the day when they are active. This can vary slightly between different lizard species. For example, large lizards like monitor lizards have higher average body temps of 89-100°F. Smaller lizards may have lower temps down to 75°F. At night, a lizard’s body temperature will drop significantly since their main heat source – the sun – is gone. Their nighttime body temperature range is typically 65-75°F. If the temperature falls out of their acceptable range, either too high or too low, it begins causing problems for the lizard.
What happens if a lizard gets too cold?
If a lizard’s body temperature drops too much below its optimal range, a number of negative effects start to occur:
– Slowed metabolism – The chemical reactions that drive metabolism happen more slowly. Digestion and use of energy sources are impaired.
– Muscle function declines – Contractile properties of muscle tissues are affected. Movements become slower and weaker.
– Nerve transmission slows – Low temperatures reduce neural conduction velocity. Reflexes and response time suffer.
– Immune function impaired – Lower temperatures negatively impact immune system function and activity levels. Risk of disease increases.
– Organ damage – Sustained suboptimal temperatures can damage organs like the heart, lungs, and brain. Cellular processes are disrupted.
– Behavior changes – Lethargy, loss of appetite, and reduced activity levels as the lizard tries to conserve energy.
– Cannot digest food – Due to slowed metabolism, the lizard cannot adequately digest food at very low body temperatures. Eating becomes impossible.
– Loss of brain/motor function – When the body temperature drops dangerously low, the lizard begins to lose brain and motor functions. This leads to a comatose, non-responsive state.
– Death – If the lizard’s temperature keeps falling substantially below their minimum tolerated range, it will eventually result in death.
So in essence, a lizard whose body temperature drops too much will experience impaired biological function on multiple levels. The lizard becomes sluggish, inactive, and struggling to survive.
At what temperature do these effects start occurring?
The onset of these cold-induced effects depends on how far the lizard’s body temperature has declined below its optimal range. Here are some general guidelines:
– At 5-10°F below optimal temp – Movement and appetite begin slowing. Minor coordination issues appear.
– 10-15°F below optimal – Significantly slowed. Struggles to digest food. Increased susceptibility to illness.
– 15-20°F below optimal – Severe loss of function. Muscles stiffen and nerve reactions are stunted. Near comatose state.
– 20-30°F below optimal – Critical loss of brain/motor function. Organ damage likely. Death risk high.
– 30+°F below optimal – Organ failure, coma, and death imminent.
The exact degree of temperature drop that causes problems will vary between lizard species. Smaller lizards tend to tolerate bigger drops than larger ones. And some species are more cold tolerant overall based on their native climate. But in general, once a lizard’s temperature falls 15-20°F below where it should normally be, severe impairment sets in.
Do lizards become cold-blooded or chilled?
Lizards are already cold-blooded (ectothermic) animals, meaning they rely on external heat sources like the sun to provide their body heat. They do not generate enough internal body heat from their metabolism to maintain their optimal temperature range alone.
So when a lizard gets too cold, it is not actually becoming cold-blooded since that defines their entire physiology already. However, a lizard whose body temperature has dropped substantially can be described as ‘chilled’ since it is feeling the effects of coldness more severely than normal.
A chilled lizard will act very sluggish and still as its slowed metabolism and muscle function prevent normal activity. You can tell a lizard is too cold if it is moving very little and feels cool or cold to the touch, signaling a significant temperature drop.
Can lizards freeze to death?
In very extreme cases, yes, some lizards can literally freeze to death when exposed to subfreezing temperatures for too long. This happens when their body fluids and blood freeze due to the cold, damaging tissues and organs.
Most lizards are not adapted to survive below freezing conditions. However, a few species like the wood frog have evolved antifreeze proteins and glucose levels in their blood that allow them to tolerate some freezing. But they can still only survive partial freezing of their bodies for a limited time.
If temperatures drop low enough for long enough to completely freeze a lizard solid, it will almost certainly die. The freezing causes irreparable cellular damage. Even species with adaptations that let them handle partial freezing are unlikely to recover from being fully frozen.
So while ‘freezing to death’ does not happen to lizards under typical winter conditions, it can occur in extreme cold. This demonstrates just how devastating low temperatures can be for these cold-blooded creatures.
How do lizards prevent getting too cold?
Lizards have evolved a variety of behavioral and physiological adaptations to help them maintain proper body temperature and prevent getting too cold:
– Basking – Lizards bask in sunny spots to absorb heat from the sun’s radiation. Their dark scales capture solar energy efficiently.
– Orienting – Turning their bodies perpendicular to incoming sunlight to maximize heat absorption.
– Posture changes – Pressing down against warm surfaces, flattening out to heat faster.
– Location changes – Moving to warmer microclimates, underground burrows, CREVICEs, etc.
– Activity changes – Being active during the warmest parts of day then resting at night.
– Social huddling – Grouping together with other lizards to share body heat.
– Color change – Darkening skin color to capture more solar energy.
– Vasodilation – Widening blood vessels to increase blood flow and heat distribution.
– Metabolic heat – Burning calories from food generates some internal body heat.
– Insulation – Scales and fat layers minimize heat loss.
Through these mechanisms, lizards maintain temperatures within their proper range to ensure optimal function. This allows them to avoid the issues caused by getting too cold.
What behavior changes occur when a lizard gets too cold?
When their body temperature drops too low, lizards exhibit a number of behavioral changes in an attempt to conserve energy and raise their temperature:
– Reduced activity – Lizards minimize movements and remain still to preserve calories.
– Basking and sun-seeking – They urgently move into sunny areas to warm up.
– Pressing on surfaces – Flattening themselves against warm rocks, asphalt, etc.
– Huddling – Crowding together with other lizards is done for shared body heat.
– Lethargy – Remaining inactive and slow-moving even in sunlight until warming up.
– Loss of appetite – Eating requires heat and energy so chilled lizards do not eat.
– Hiding – Seeking out insulated shelters to trap any heat.
– Sunning positions – Perching in a headstand or lateral spread to maximize sun exposure.
– Shivering – Vibrating muscles to generate a small amount of metabolic heat.
These behavioral shifts temporarily allow a cold lizard to gain back a few vital degrees until it can fully warm up again. The changes persist until their body temperature rises back into normal range.
How long can a lizard survive when too cold?
How long a lizard can survive with a dangerously low body temperature depends on these factors:
– How far below optimal range the temperature has dropped – The colder it is, the less time they have.
– The lizard’s natural cold tolerance – Some species handle cold better than others.
– Exposure time – Longer duration is more harmful than brief cold snaps.
– Access to heat – Can they reach sunlight or a warm shelter to reheat?
– Fat reserves – Good energy stores prolong survival time.
– Health status – Age, injury, or illness make them more vulnerable.
– Environmental conditions – Wind, precipitation accelerate heat loss.
Under mildly cool conditions just below their optimal range, most lizards can survive for several hours up to a full day. But at very cold temperatures 15+ degrees below normal, survival time may be reduced to less than an hour. Small lizards succumb even faster than larger ones.
So while a healthy lizard may endure mildly cool temps for a while, once their temperature drops into very cold territory their time is severely limited before impairment or death. Quickly rewarming is critical at that point.
What temperatures are lethal to lizards?
There is no single lethal temperature that applies to all lizards. The specific temperature that becomes deadly depends on the species and its natural climate. But here are some approximate lethal temperature thresholds:
– Desert lizards – 50-60°F. Their native habitat is very hot and dry.
– Tropical lizards – 60-65°F. Adapted to warm, stable tropical environs.
– Subtropical lizards – 50-65°F. Intermediate cold tolerance.
– Temperate lizards – 40-55°F. Used to varying seasonal temperatures.
– Higher latitude/altitude lizards – 35-50°F. The most cold-resistant species.
– Freezing temperatures – Usually lethal to all but a few species.
These lethal temperature ranges are when organ damage, coma, and death become imminent if the lizard cannot quickly rewarm. Smaller bodied lizards tend to have 10 degrees F higher mortality thresholds than their larger cousins.
Again, the key is that sustained exposure to these cold temperatures is what actually kills the lizard. Brief exposure while they seek heat may only result in impairment, not death. But several hours or more below these ranges when the lizard cannot adequately rewarm crosses into lethal territory.
Can lizards recover from being too cold?
If a lizard’s temperature drops substantially below normal but not long/cold enough to be truly life-threatening, they can recover and bounce back to normal function. Here is how they recuperate:
– Absorb heat from sunlight or a warm external source.
– Vasodilation and increased blood flow distribute warming blood.
– Muscles, organs, and nerve function improve as temperature rises.
– Metabolism speeds up and returns to normal activity levels.
– Movement increases and digestion resumes as they heat up.
– Appetite returns, allowing them to replenish energy.
– Immune function strengthens again once warm.
– Given time to fully warm and recover, they exhibit normal behavior again.
So when given the chance to rewarm before cold exposure becomes severely damaging, lizards can make a full recovery. Their survival instincts drive them to urgently seek heat sources. This allows them to raise their body temperature back into their normal functional range and overcome the negative effects of being too cold.
Conclusion
Lizards rely entirely on external heat sources to maintain appropriate body temperatures for optimal biological functioning. When their temperature drops substantially below normal levels, impaired muscle and nerve activity, slowed metabolism, reduced immune function, and trouble digesting food can occur. Behavior changes radically as they become still and lethargic in an attempt to conserve energy.
Prolonged exposure to very cold temperatures becomes life-threatening as organ damage happens and the risk of coma and death increases. How long they can survive depends on the degree of cold and the lizard species’ natural climate. But many types of lizards face grave peril after even an hour with a body temperature 15-20°F below normal. Quickly seeking heat is critical for their survival at that point.
Lizards have evolved adaptations like basking and huddling together to minimize their chances of getting too cold. But if they do experience significant chilling, warming back up can allow them to make a full recovery before the cold causes irreversible harm. Understanding lizard cold tolerance gives reptile owners and ecologists insight into properly supporting their health and survival.