Animal species in rain forests have developed a series of adaptations to make themselves heard. A. Scientists have discovered that animals in rain forests adapt the length of their calls to overcome the barriers created by dense plant growth. B. Many species of predators in rain forests prefer dawn rather than dusk as the best time to hear and pursue their prey. C. Specialized frequencies facilitate sound transmission within species and also create regional sound environments that are highly stable. D. Some smaller animals that live in rain forests use special strategies to increase the volume of their calls and the distance that their calls travel. E. Because time of day affects how sound travels, many animals restrict their calls to either nighttime, when sound travels best, or dusk and dawn. F. Research conducted in the Peruvian rain forest indicates that well-ordered periods of sound alternate with more chaotic sound periods.