TOEFL Speaking Task 3

In biology, the concept of 'behavioral thermoregulation' refers to the deliberate actions an animal takes to regulate its body temperature by exploiting its environment. Unlike physiological mechanisms, such as sweating or shivering, behavioral thermoregulation involves choices—like moving to a warmer or cooler spot, changing posture, or altering activity patterns. This strategy is crucial for ectotherms (cold-blooded animals), which rely on external heat sources. By adjusting behavior, they can maintain optimal body temperatures for essential functions like digestion, movement, and reproduction, without expending metabolic energy.

Professor: Let’s take a lizard, the desert iguana, as an example. In the early morning, when the desert is cool, the iguana emerges from its burrow and flattens its body against a sun-warmed rock. This maximizes surface area exposed to the sun, absorbing heat quickly. As the day heats up, the lizard becomes too warm. So, it moves into the shade of a cactus or climbs onto a branch, lifting its body off the hot ground to catch cooler air. During the hottest part of the day, it may even retreat underground into its burrow to avoid overheating. But when the sun starts to set and temperatures drop again, the iguana comes out one last time to bask on the still-warm rocks, raising its temperature before the cool night. By choosing these spots and postures throughout the day, the iguana keeps its body within a narrow range that allows it to hunt and digest efficiently.