Frozen Alive: Extreme Cold Survival in South Africa’s Emerald Dwarf Chameleons

The Incident

An unusual and dramatic wildlife event unfolded in the KwaZulu-Natal Midlands during a severe cold snap accompanied by heavy snow. As overnight temperatures plummeted to a harsh -7°C, whipped by gale-force winds exceeding 40 knots, twenty Emerald Dwarf Chameleons (Bradypodion sp.) fell victim to the elements. Dislodged from the trees surrounding local chalets, the chameleons were discovered at approximately 07:00 lying helpless in the snow.

The cold had rendered them completely lifeless. They were frozen so rigidly that tapping them against a window produced the distinct sound of a solid block of ice, with several individuals found fixed with their mouths gaping open.

Fortunately, quick-thinking observers—compiled bu Jean Marais with photographs and details courtesy of Donovan Carstens—intervened. The stiffened reptiles were placed carefully on a sunlit windowsill. Within one to two hours, as ambient warmth penetrated their bodies, the chameleons slowly thawed, regained movement, and were safely released back into the trees.

Physiological Commentary: Surviving the Sub-Zero Threshold

Incidents like this highlight a fascinating physiological puzzle. Reptiles are ectotherms (cold-blooded animals), meaning their internal body temperature matches the environment. When exposed to sub-zero conditions, they face a severe physiological threat: the formation of ice crystals within body tissues, which typically ruptures cell membranes and proves fatal.

At What Temperature Do They Freeze?

Liquid water inside an animal's cells and bodily fluids naturally contains solutes (like salts and proteins), which depress the freezing point slightly below 0°C (usually around -0.5°C to -2°C). However, many small ectotherms utilize a phenomenon known as supercooling, where body fluids remain liquid even below freezing temperatures in the absence of ice-nucleating agents.

When ambient temperatures drop as low as -7°C alongside high winds, the thermal buffer fails, and the water molecules inside the chameleon's extracellular spaces begin to transition into ice. When animals freeze to the point of sounding like solid ice, they have crossed their supercooling limit.

 The Mechanics of Recovery

Most reptiles are freezing-susceptible rather than freezing-tolerant—meaning internal ice formation is usually a death sentence. However, certain high-altitude or temperate-zone amphibians and reptiles possess remarkable adaptations. While true internal tissue freezing is generally lethal, small arboreal lizards inhabiting temperate zones, like Bradypodion species adapted to the mist-belt and highlands of South Africa, occasionally endure extreme micro-habitat exposures if the freezing is restricted or if metabolic shutdown protects critical organs.

The fact that these twenty individuals successfully revived after being thoroughly rigid underscores a high degree of metabolic resilience. By entering a profound state of suspended animation (where heart rate and cellular activity drop to near-undetectable minimums), they can withstand extreme cold stress for brief windows—provided they are granted a gentle, passive thaw rather than a rapid, tissue-damaging heat shock.

Physiological saline and reptile lymph freeze at slightly below the freezing point of pure water, and the reason is rooted in basic chemistry and reptile physiology. A standard physiological saline (0.9% NaCl) freezes at about –0.52 °C because dissolved sodium and chloride ions interfere with the formation of ice crystals. This phenomenon—freezing point depression—is universal in biological fluids. Reptile lymph behaves similarly: it contains salts, proteins, and small organic molecules, giving it a freezing point close to –0.5 °C, essentially matching reptile blood plasma.

Most reptiles cannot survive the freezing of lymph or blood. Ice forming outside cells draws water out of them, causing dehydration and structural damage. However, a few species—most famously hatchling painted turtles—have evolved remarkable freeze tolerance. Their extracellular fluids can supercool to about –3 °C, and they can endure controlled freezing at –4 °C for many hours. These reptiles rely on glucose and other cryoprotectants to stabilize cells and prevent intracellular ice formation.

In short, physiological saline and typical reptile lymph freeze just below zero, but certain reptiles push these limits through specialized biochemical strategies that let them survive temperatures that would be lethal to most vertebrates.

original Facebook post by Jean Marais with photographs and details courtesy of Donovan Carstens