Reptiles, the last major group of ectotherms (cold-blooded animals) to appear on Earth, evolved in the Carboniferous Period, about 300 million years ago (MYA). Equipped with protective scales and shell-covered eggs that could be deposited away from water, reptiles were able to colonize the drier landscapes of our planet. Turtles and crocodilians appeared in the Triassic Period, some 200 MYA, in concert with the first dinosaurs and earliest mammals; current evidence indicates that dinosaurs, like birds and mammals, were endotherms (warm-blooded creatures able to inhabit colder regions of the globe). Among the last reptiles to evolve were snakes and true lizards, both of which arose during the Cretaceous Period, about 100 MYA; some of these more modern lizards bear live young rather than laying eggs.
Early to mid autumn is often the best time of year to observe reptiles in the American Heartland. Chilly nights make them sluggish, diminishing their hunting ability and forcing them to bask on logs, fenceposts, rock piles, trails or roadways to warm up in the morning sun. In addition, they will soon be entering hibernation and meeting their nutritional needs becomes especially important.
For both of these reasons, reptiles of the Temperate Zone are more conspicuous during the first half of autumn than they tend to be in late spring or summer. Box turtles appear on roadways, snakes slither across trails during our morning hikes, lizards scramble up fence posts or scurry across rock piles and aquatic turtles crowd stream banks or gather on dead limbs that jut from ponds. It is, indeed, reptile season in the Heartland.
