Have you ever thought about what a dog smells as it stops to sniff at a tree? Or what a cat is watching as it stares intensely off into space? What about animals in the wild? What do they see, hear, smell, and feel? How do they perceive their surroundings? This is the illusive world. A world filled with fascinating stimuli that we are not equipped to detect. This is particularly true because we tend to rely so heavily on our eyes or ears. We are figuratively, and literally, blind to this part of the natural world. This part, which is full of stimuli we cannot perceive, encompasses the daily lives of so many animals. Beneath our feet are ants, moles, and spiders using vibrations to coordinate colonies and communicate danger. In the oceans, turtles, fish, and octopi are sensitive to magnetic and electric fields, as well as tasty morsels at the tips of their tentacles. In the skies, owls and raptors can see deep into a lake or pierce the night with highly sensitive eyes. This book brings together all these animals and their amazing sensory abilities in an exploration of how animals perceive their world. Within these pages are wonderful and exciting stories of organisms using their senses to perform sophisticated communication with nestmates, find hidden prey in the dark of night or murky of depths, and call to lovers both near and far. This book will open the door to this illusive world and will take you on a journey into the illusive world and see how different the world is when perceived through another animal's senses.