Coyotes are adaptable predators that thrive in diverse environments across North America. Their ability to thrive in nocturnal and crepuscular settings often leads to questions about their sensory capabilities. The impressive night vision of these canids prompts curiosity about whether they can perceive light outside the human visible spectrum. Examining the structure of the coyote’s eye and the physics of light perception reveals how their vision works and whether it extends into the invisible world of infrared.
Defining the Limits of Biological Vision
Infrared (IR) light is electromagnetic radiation that exists just beyond the red end of the visible light spectrum, typically starting at wavelengths longer than 700 nanometers. This radiation is associated with heat, as all objects above absolute zero emit thermal infrared energy. A typical mammalian eye, including the human eye, is designed to perceive light wavelengths roughly between 400 and 700 nanometers, known as the visible spectrum.
Mammals lack the specialized biological structures necessary to convert the longer wavelengths of infrared light into a visual signal. While a few non-mammalian species, like pit vipers, possess specialized organs that detect thermal radiation, mammals do not have this adaptation. This physiological boundary means that most mammals, including all canids, are restricted to the same basic visual spectrum as humans. The eye’s optics and the chemistry of its light-sensitive pigments are not configured to absorb and process radiation from the infrared range.
The Reality of Coyote Sight
Coyotes definitively cannot see infrared light, as their eyes operate entirely within the visible light spectrum. Their visual acuity is tailored to maximize function in low-light conditions, achieved through a specific structure of photoreceptor cells in their retina.
Coyotes possess a retina dominated by rod cells, the photoreceptors responsible for superior scotopic, or night, vision compared to humans. In contrast, they have fewer cone cells, which are responsible for detailed color vision in bright light. This difference results in dichromatic color vision, meaning they primarily perceive the world in shades of blue and yellow.
Another adaptation that enhances their low-light vision is the tapetum lucidum, a layer of reflective tissue situated behind the retina. This layer acts like a mirror, reflecting light that passes through the retina back across the photoreceptor cells, effectively amplifying the available visible light. This mechanism is the source of the familiar “eyeshine” seen when a light beam hits a coyote’s eyes at night. Critically, the tapetum lucidum can only reflect light within the visible range; it does not enable the detection of infrared radiation.
Using Infrared Technology Around Coyotes
The inability of coyotes to see infrared light is precisely what makes certain human technologies effective for wildlife observation. Standard trail cameras, for instance, often use near-infrared (NIR) light, typically in the 850-nanometer range, to illuminate a scene for night recording. Coyotes cannot see this emitted NIR light, allowing for their natural behavior to be captured without disturbance.
However, many NIR illuminators, especially those operating at lower wavelengths, produce a faint, visible red glow from the light-emitting diodes (LEDs) when viewed directly. While the coyote cannot see the projected infrared beam, it may notice this slight red glow if it looks straight toward the camera lens. Additionally, the mechanical click or whirring sound of a camera activating or pivoting can alert an animal, causing it to spook, even if it cannot see the light.
Thermal imaging is a different technology altogether, detecting heat signatures rather than light. True thermal scopes operate in the far-infrared spectrum (long-wave infrared), which is not about illuminating a scene but about measuring the subtle temperature differences of objects. Since coyotes are warm-blooded mammals, their body heat is readily visible to a thermal device as a bright signature against a cooler background. The coyote remains completely unaware of this detection, as the technology is sensing biological heat emissions that their eyes are not designed to perceive.