TOEFLスピーキング Task 3

In biology, the term “behavioral thermoregulation” refers to the deliberate actions an animal takes to regulate its body temperature by moving to different environments. Unlike physiological mechanisms (like sweating or shivering), behavioral thermoregulation involves using external heat sources or avoiding thermal stress. This strategy is common among ectotherms, animals that cannot generate their own body heat, but it is also used by endotherms to reduce energy costs. The key is that the animal actively selects microhabitats that bring its body temperature into an optimal range for activity.

Professor: So, let’s take a classic example—the desert iguana. This lizard lives in the hot, dry Southwest. In the morning, the ground is cool, and the iguana’s body temperature is low, making it sluggish. To warm up, it basks on sun-exposed rocks, absorbing heat until its body reaches about 37 degrees Celsius—the ideal temperature for hunting and moving. But by midday, the desert floor can become scorching, over 50 degrees. If the iguana stayed on the rock, it would overheat. So, it retreats to the shade of a bush or a burrow, where it’s cooler. It might even change its posture, lifting its body off the hot sand to let air circulate underneath. By moving between these microhabitats—sunny rock in the morning, shade in the afternoon—the iguana keeps its body temperature within a safe range without spending extra energy. This is a perfect illustration of behavioral thermoregulation.