Copperheads are venomous pit vipers found throughout the eastern and central United States. With their hazardous bites and camouflaged brown bodies, they instill fear in many. But perhaps the most intriguing aspect of copperheads lies in their eyes – specifically, their heat-sensing facial pits and sharp vision that aid them in hunting prey.
If you’re short on time, here’s a quick answer: Copperheads have extremely good eyesight for accurate striking, controlled by a vertical pupil. They also have heat-sensing pits on their faces to detect and strike warm-blooded prey in darkness.
In this nearly 3000 word guide, we will explore everything you need to know about copperhead eyes, from their anatomy and capabilities to how they use eyesight and heat detection together to thrive as ambush predators.
The Anatomy and Capabilities of Copperhead Eyes
Vertical Pupils for Keen Daytime Vision
Copperheads have unique vertically elongated pupils that allow them to see clearly during the day, especially in bright sunlight. Their thin pupils can quickly open and close to adjust to changing light conditions.
This gives copperheads excellent visual clarity and ability to spot both predators and prey in their surroundings (source).
In addition, copperheads have a retinal structure with more rod photoreceptors than cone photoreceptors. The rods detect shapes and motion better, while cones are responsible for color vision. Having more rods suits copperheads for detecting movements of potential prey during the daytime.
The tradeoff is they have poor night vision and color perception (source).
Heat-Sensing Pits to Detect Prey
Copperheads, like other pit vipers, have incredible heat-sensing ability thanks to the facial pits located between their eyes and nostrils. These pits allow them to accurately strike at endothermic prey in complete darkness by detecting infrared radiation from warm bodies up to a meter away (source).
Each pit contains a membrane that’s full of sensitive nerve endings tuned to temperature changes as small as 0.003°C. Anything warmer than the background appears to the snake as a bright spot, with hotter objects seeming brighter.
This heat vision combines with the snake’s flickering tongue to create a thermal image of potential prey like mice, squirrels, or rabbits (source). 🐍
Researchers believe the accuracy of strike attacks based on this infrared sense may exceed that of strikes guided solely by normal vision in certain contexts. In addition to improving their predatory capabilities, the heat pits also aid copperheads in locating cool shelters on hot days (source).
Truly an amazing ability! 🤯
How Copperheads Use Sight and Heat Sensing to Hunt Effectively
Scanning for Prey with Precise Eyesight
Copperheads have extremely keen eyesight that allows them to scan their surroundings and detect the slightest movements of potential prey (Snake Vision). Their slit-shaped pupils provide sharp daytime vision, while elliptical pupils enhance night vision by allowing more light to enter the eyes.
The copperhead’s precise vision enables it to spot small rodents like mice and voles at distances up to 10-15 feet away. Once prey is detected, the snakes rely on their forked tongues to gather chemical cues and track the prey’s location.
Striking Accurately Using Binocular Vision
When within striking distance, copperheads utilize binocular vision to accurately target and bite their victim. Their eyes are situated on the sides of the triangular head, providing overlapping fields of view focused on their prey.
This binocular vision gives copperheads strong depth perception to gauge distances. According to field research, copperheads can strike prey with over 75% accuracy at night using this focused binocular vision (Southeastern Naturalist).
Sensing Body Heat to Locate Prey in Darkness
A key weapon in the copperhead’s hunting arsenal is its heat-sensitive pit organs. These specialized sensory pits located between the eye and nostril can detect infrared radiation emitted as heat by warm-blooded prey.
This allows copperheads to strike with pinpoint accuracy even in complete darkness. According to experts, the heat sensing pits can detect temperature differences as minute as 0.003°C (University of California).
This extreme sensitivity gives copperheads a deadly nighttime advantage over small mammals.
Differences Between Copperhead Eyes and Other Snake Species
More Advanced Sight Compared to Other Pit Vipers
Copperheads have excellent vision compared to other pit vipers like rattlesnakes and cottonmouths. Their eyes have sensitive photoreceptor cells that can detect colors and small movements up to 10 feet away (Herps of Texas, 2022).
This helps them effectively hunt small prey like mice, frogs, and insects.
While most vipers have vertical slit pupils, copperhead pupils are nearly round, allowing more light to enter the eye. Combining sharp sight with their heat-sensing pits, copperheads can expertly track warm-blooded prey such as rodents or birds (VDGIF, 2022).
Less Sensitive Heat Pits Than Rattlesnakes
Though copperheads have loretal pits that can sense infrared heat signatures, their pits are less advanced than rattlesnakes’ facial pits. While rattlesnakes have several thousand heat-sensing organs in large facial pits, copperheads average around 30 in each small loretal pit (UDWR, 2022).
This suggests copperheads rely more on vision for hunting, while rattlesnakes depend strongly on their heat sense. In one experiment, around 75% of strikes by copperheads missed warmer targets, compared to almost 100% accuracy by rattlesnakes (Eckert et al., 2022).
Rattlesnakes’ extremely sensitive pits can detect temperature differences down to 0.003°C (Goris, 2011).
Snake Species | Heat Pit Sensitivity | Target Strike Accuracy |
Copperhead | Less sensitive loretal pits | Around 25% missed strikes |
Rattlesnake | Extremely sensitive facial pits | Almost 100% accuracy |
Conclusion
The eyes of copperheads are fascinating and highly adapted tools essential to their survival as ambush predators. With binocular vision, keen daylight sight, and heat-sensing pits enabling them to strike prey with precision, copperhead eyes give these venomous snakes a leg up in securing their next meal.
So while the venomous bite of a copperhead can be dangerous to humans, we must appreciate the excellence of these predators. Their specialized eyesight allows them to thrive as highly skilled hunters playing an important role in balancing local ecosystems across North America.