This Central American striped basilisk (Basiliscus vittatus) stretches its head towards the sun and warms up on the heated stones. But the cold-blooded animals are evidently more adaptable to the cold than expected.
Typically, the body temperature of lizards is the same as their ambient temperature, which is why they are less active at low temperatures. If the outside temperature drops sharply, the lizards are even completely immobile. Researchers have already observed that sleeping animals in Miami lose their grip and fall from the trees at temperatures of around ten degrees Celsius.
In January, for example, James Stroud of Washington University in Saint Louis discovered iguanas in Key Biscayne – an island south of Miami – that were lying on their backs with their feet in the air. The night before, temperatures were below four degrees Celsius – the coldest night in South Florida in ten years. Over the next few days, the biologist and his colleagues collected lizards of various types and sizes in order to understand how they react to this extreme climate event.
The astonishing thing: When the researchers examined the scaled survivors of this coldest night, they discovered that all lizards – regardless of size, origin and species – tolerated temperatures of up to five degrees – significantly less than observed in previous years with these species. “Given the huge differences in body size, ecology and physiology, this was unexpected,” said Stroud.
The researchers attribute this to an adaptive reaction of the reptiles: “Before the cold event, there was a wide range of temperature tolerances – some, like the great brown basilisk, were very sensitive to cold, while others, like the Puerto Rican anole, were more robust “, Explains Stroud. “But now all species tolerated roughly the same minimum temperature.” It is still unclear whether this new resistance to cold arose through natural selection or through environmental adaptation of the animals.
Regardless of the underlying mechanism, the study could provide new insights into the effects of climate change and the resulting fluctuations in temperatures: “While there is no doubt that climate change is a major threat to species and ecosystems worldwide, this study gives us a clue of hope, ”says Stroud. “Perhaps tropical and subtropical species can withstand more extreme climatic conditions.”