Nebraskaland

50 Nebraskaland • November 2023 MIXED BAG Eyes on the side hide, eyes on the front hunt. The size, ability and position of the eyes of animals can vary widely depending on the species, environment and whether the animal is predator or prey. Some animals can move their eyes independently; some can see in ultraviolet light; and others can't really see much at all. Throughout this article, we will take a closer look into four types of animal eyes and their uses and functions. Dragonflies Dragonflies are often considered the apex predators of the insect world, despite their small size. They have the ability to catch food right out of the air during flight, thanks to their humongous, globular compound eyes. Compared to African lions, which have a capture success rate of 25 percent when pursuing prey, dragonflies are successful about 95 percent of the time. A dragonfly's compound eyes cover most of its head, and they can see nearly 360 degrees around them. Two separate eyes come together at the top, and within each eye are smaller lenses. Depending on the species, a dragonfly's eyes can be composed of up to 30,000 facets or little lenses. Owls Not many avian predators can outrank owls in vision. They are considered perfect nocturnal hunters, possessing many of the adaptations needed to excel in stalking prey at night. One characteristic in particular is their eyes. An owl's eyes are located facing forward on its head, very similar to humans. This eye arrangement is effective in tracking the movements of potential prey. Owls actually have the most forward-facing eyes out of any group of birds. Owls have what is known as 3-D or binocular vision, a trait they share with many other predatory animals. This helps with acute depth perception and allows them to gauge distance when planning an attack. Behind the retina is a layer called the tapetum lucidum, which catches any light that may have passed through the retina and bounces it back to the sensitive rods. All these adaptations add up, and some owl eyes can be as much as 100 times more sensitive to light than human eyes. Snakes In Nebraska, there are 29 species of snakes. Some of these are nocturnal, meaning they are awake at night, while others are diurnal, meaning they are awake during the day. Snakes, overall, have a diverse set of rods and cones in their eyes — the specialized cells in the retina that an animal uses to detect light. One adaptation is that snakes have multiple types of visual pigments inside the cones, which allows them to see in color because the pigments are sensitive to different wavelengths of light. So, snakes that hunt during the daytime have lenses in their eyes that block ultraviolet light, which allow them to see clearly in bright conditions — similar to people wearing sunglasses. Conversely, nocturnal snakes that hunt at night have lenses that allow more UV light in, which help them see in the dark. An old myth that is still in circulation claims that a snake's pupil shape can help people determine whether it's venomous or non- venomous. The myth is that all venomous snakes have elliptical- shaped pupils. Unfortunately, this is inaccurate, as venomous snakes can have elliptical, round or even keyhole- shaped pupils. Therefore, the presence or absence of venom has nothing to do with pupil shape. Bats Contrary to the phrase "blind as a bat," these flying mammals have extremely sensitive vision, which helps with their nocturnal lifestyle. In Nebraska, the 13 species of bats are known as insectivores, and to find their food, they have to do it in the dark and often while flying, which requires extraordinary eyesight. In Nebraska, bats also utilize an adaptation known as echolocation, when bats produce sounds which bounce off objects to help them navigate to their food. However, research shows that many bats prefer to use eyesight as opposed to sound when they hunt. These species have particularly sharp vision, and some can see ultraviolet lights. A few species of bats can even see in color, thanks to two light-sensitive proteins at the backs of their eyes. ANIMAL VISION By Monica Macoubrie, Wildlife Education Specialist JUSTIN HAAG JEFF KURRUS JENNY NGUYEN-WHEATLEY ERIC FOWLER

• Cover