How Liolaemus lizards master thermal regulation in one of Earth's most challenging climates
In the harsh, windswept landscapes of Patagonia, where temperatures can plummet to near-freezing and the sun offers only fleeting warmth, a remarkable group of lizards has perfected the art of survival. Meet the Liolaemus (pronounced Lee-oh-LEE-mus) lizards, one of the most ecologically diverse reptile groups on Earth, thriving in environments from scorching deserts to the frigid southernmost tip of South America 2 8 .
For these cold-blooded creatures, maintaining the right body temperature isn't merely a comfort—it's a matter of life and death.
Their ability to chase the Patagonian sun determines their success in every essential activity: catching prey, escaping predators, and reproducing 2 . Recent scientific investigations have revealed that these lizards employ sophisticated strategies, from adjusting their thermal limits to developing unique relationships with their environment, offering fascinating insights into ecological adaptation in one of the world's most challenging climates 1 5 .
Unlike humans and other mammals that generate their own body heat, lizards are ectotherms, meaning they rely on external sources to regulate their body temperature 3 . A Liolaemus lizard's daily existence revolves around this fundamental need.
The relationship between temperature and physiological performance is best visualized through a Thermal Performance Curve (TPC). This curve typically has a sigmoidal shape: performance increases with temperature, reaches an optimal range, and then declines rapidly.
The actual temperature of a lizard measured in its natural habitat.
The ideal temperature range a lizard selects in a perfect laboratory environment.
The lower temperature limit at which a lizard loses coordination.
The breadth of this curve determines how well a lizard can function despite temperature fluctuations 5 .
To understand how Patagonian lizards adapt to different climates, researchers designed a compelling experiment comparing two populations of Liolaemus lineomaculatus from extreme ends of the species' distribution 5 .
Lizards from the northern Esquel population had a significantly lower CTMin (2.67°C) than their southern Calafate counterparts (4.18°C) 5 .
Both populations shared a similar CTMax, indicating that the upper thermal limit may be a more fixed trait 5 .
For short sprints, the performance curve of the northern population was shifted toward slightly higher temperatures 5 .
| Population | Location | Critical Thermal Min (CTMin) | Critical Thermal Max (CTMax) | Thermal Tolerance Breadth |
|---|---|---|---|---|
| Temperate-site (Esquel) | 42° S, High-altitude | 2.67° ± 0.48°C | Similar between populations | Wider |
| Cold-site (Calafate) | 50° S, Lowland | 4.18° ± 0.72°C | Similar between populations | Narrower |
This research demonstrates that while some thermal traits (like CTMax) are evolutionarily conservative, others (like CTMin) can be finely tuned by local environmental conditions 5 .
Research on the L. goetschi group reveals a complex evolutionary story. Some aspects of their thermal biology, such as preferred body temperature and critical thermal maximum, appear to be evolutionarily conservative—they have remained similar across different species despite environmental variation 1 .
In contrast, other traits, like critical thermal minimum and overall thermal range, are strongly modeled by the environment. Lizards living in colder areas have consistently evolved a lower CTMin, allowing them to remain active in chillier conditions 1 .
Scientists have discovered evidence of co-evolution between different thermal characteristics. Specifically, the critical thermal minimum and preferred body temperature have evolved together in Liolaemus lizards. This coordinated evolution ensures that a lizard's preferred temperature range remains aligned with its cold tolerance, creating an integrated thermal strategy 1 .
Change little across species
Vary with local climate
When we picture a lizard sunbathing on a rock, we are observing behavioral thermoregulation. Liolaemus lizards are masters of this art, using a combination of:
They constantly adjust their posture, orientation, and location between sun and shade to maintain their body temperature within a workable range 9 .
Heliothermy: Using the sun's rays
Thigmothermy: Using warm surfaces
Understanding thermal biology requires specialized tools and methods that allow scientists to measure both the lizards and their environment with precision.
Measures the temperature available to a lizard in a specific microenvironment.
A controlled racetrack to measure sprint speed at multiple temperatures.
A bacterial endotoxin used to simulate an immune challenge.
The specialized thermal requirements of Liolaemus lizards make them particularly vulnerable to human-induced environmental changes. Habitat fragmentation creates hotter, drier edges that can exceed the lizards' thermal tolerances 6 .
A 2025 study on the critically endangered L. cuyumhue found that habitats disturbed by oil and gas activities had significantly higher temperatures and lower vegetation cover, forcing lizards to higher body temperatures and reducing their detectability 9 .
However, there is a glimmer of hope. Some Patagonian lizards, like the endangered Phymaturus tenebrosus, may actually see a temporary improvement in their physiological performance with modest warming, as current environmental temperatures are often below their preferred range 3 .
Furthermore, their demonstrated ability to adapt their thermal limits, as seen in L. lineomaculatus, provides a potential buffer against climate change 5 .
Projected changes in thermal habitat suitability for Patagonian lizards under different climate scenarios
The story of Liolaemus lizards chasing the Patagonian sun is more than a tale of ecological niche—it is a profound lesson in resilience and adaptation. From the southernmost lizards in the world tolerating near-freezing temperatures to species fine-tuning their physiology to local conditions, these remarkable reptiles have revealed the intricate dance between environment and evolution.
Their survival strategies—a complex interplay of behavioral adjustments, physiological adaptations, and evolutionary trade-offs—highlight the incredible flexibility of life. As our planet undergoes rapid changes, understanding these thermal strategies becomes crucial not only for conserving the unique biodiversity of Patagonia but also for appreciating the delicate mechanisms that allow species to persist in an ever-changing world.