Animal Eyes: How Creatures See and How Their Eyes Have Adapted to Their World

Animal Eyes is a clearly written exploration of the diversity of eyes in the animal world followed by case studies of 40 species. Vulpé is a freelance editor and writer. She begins the volume with an introductory chapter explaining the anatomy of eyes and their types: the camera eye that human’s have, light-sensitive eyespots common to some slugs and snails, simple eyes and compound eyes found in many insects and arthropods. The anatomical features of compound and camera eyes are shown in full-colour illustrations. High-quality photographs of animals are standard features on almost every page. The introduction includes a brief description of the physics of light and the electromagnetic spectrum. Again, excellent illustrations accompany the text. Many key terms are printed in italics and defined in a well-written glossary. Terms and concepts often reappear in the case studies. Perception of colours, visual fields and keeping eyes safe round out the introductory chapter.

The majority of the book is divided into two sections: Invertebrate Eyes and Vertebrate Eyes. Both sections have subsections with multiple one-page studies of an interesting animal. The praying mantis study reproduced as the excerpt above falls under the subcategory for Arthropods (Insects, Arachnids and Crustaceans). In most instances, the brief account of a species’ eyes is accompanied by interesting facts about the animal that goes beyond elaboration on features of its eyes. For example, the dragonfly, with its full-circle field of vision and amazing speed and maneuverability, has the highest success rate of any predator. There are also four additional marine invertebrates profiled, including the cuttlefish that has W-shaped pupils that may allow them to detect colour even though they only have one type of photoreceptor. Researchers have a lot to learn about the complexities of vision of many living creatures.

Half of the book is devoted to vertebrate eyes. This section is organized into subcategories for amphibians, birds, fish, mammals, and reptiles. One of the amphibians featured is the Texas blind salamander that lives underwater in caves where there is no light and no need for vision. Its eyes “have been reduced to two dots under a layer of skin.”

Through careful curation of the content, Vulpé ensures that concepts introduced in the beginning of the volume are noted when discussing specific animals. She also uses the cases to introduce new information related to eyes and vision. Writing about the bald eagle, with its sharp vision, colour perception and excellent depth perception, affords an opportunity to explain the rating system for visual acuity. While normal human vision is 20/20, an eagle’s vision is 20/5 meaning that an eagle can see an object clearly twenty feet (six m) away that a human would only see five feet (1.5 m) away.

Eyes have evolved to help animals survive in diverse environmental conditions. The caribou has UV (ultraviolet) vision that makes it easier to spot both predators and food. Cats, dogs and sharks have the tapetum lucidum, a layer of reflective tissue behind the retina that helps them to see in low light conditions. Nictitating membranes protect the eyes of hippopotamuses when they submerge beneath water. The nictitating membrane of a red-eyed tree frog is striped and helps camouflage its red eyes when it sleeps. Since the membrane is semitransparent, it also helps the frog stay alert for danger when resting.

In summation, Animal Eyes: How Creatures See and How Their Eyes Have Adapted to Their World is a marvelous, fact-filled journey into the world of eyes and vision that has developed across many forms of animal life. The content will inspire budding zoologists and naturalists while also exploring human vision and the physics of light. Unfortunately, there are no bibliographical references nor index. Detailed photo credits show that most images came from Shutterstock.