TOEFLスピーキング Task 3

In biology, the term “behavioral thermoregulation” refers to the active behaviors animals use to control their body temperature within a preferred range. Instead of relying solely on physiological mechanisms like sweating or shivering, many species alter their position, posture, or activity patterns to exploit or avoid environmental heat sources. This selective use of microhabitats helps them maintain optimal temperatures for essential functions such as digestion, movement, and reproduction. Behavioral thermoregulation is particularly common among ectotherms, which cannot generate their own body heat and must depend on external conditions.

Professor: Let me give you a concrete example. Consider the desert lizard, the chuckwalla. On a cool morning, the chuckwalla emerges from its rocky crevice and basks on a sunlit rock. It flattens its body to maximize surface area exposed to the sun, absorbing heat quickly. As the day becomes too hot, the lizard climbs onto a vertical rock face, orienting its body perpendicular to the sun’s rays, minimizing exposure. When midday temperatures soar, it retreats into the shade under a boulder or into a crevice, where it stays until the afternoon cools. Finally, in the late afternoon, it may re-emerge to bask briefly before returning to its shelter for the night. This daily pattern of moving between sun and shade, and changing posture, allows the chuckwalla to keep its body temperature within a narrow, safe range without relying on internal heat production.