The 10-pointer stepped out of the brush, took a quick look around, lowered his head and strolled toward the corner of the bean field. I smiled and put tension on the bowstring. The wind was perfect for where I was sitting, and in less than a minute the buck’s route would take him down a shallow funnel less than 25 yards below my treestand.
The buck kept coming, nose to the ground, but at a distance of 40 yards he stopped, flinched, peeked up and wheeled back into the cover. What the…? Had sunlight shone off the stand? Had I moved a muscle? I didn’t think so. All I knew was that the buck was gone, and I was left to wonder what went wrong and marvel at the big brute’s vision.
Early Research On Deer Vision
The first studies on deer vision, performed decades ago, found that deer have a higher density of rods in their eyes than cones. Rods are highly sensitive to light but not as sensitive to color. In layman’s terms: Deer have better nighttime vision than we do but poorer daytime and color vision.
Subsequent research in the 1990s performed at the University of Georgia found the high number of rods in a deer’s eye also serves as the ultimate motion sensor, allowing deer to detect even the slightest hint of movement. The researchers observed that, in an effort to identify a strange object that might present danger (like you or me), a deer shifts its head from side to side, moves it up and down, and stares from several different angles.
The Latest Science
Just how far to the left or right can a deer see? According to a new study of animal vision performed at UC Berkeley and first reported to the deer-hunting world by the Quality Deer Management Association (QDMA), a deer’s eye positioning and pupils allow for an amazing 300-degree panoramic view of the surroundings. (For comparison, your field of view is less than 180 degrees.) To cover the 60-degree blind spot in the back, a deer simply turns its head slightly left or right to eyeball things directly behind its rump. The old “That buck must have eyes in the back of his head” saying is just about spot on.
If you think that’s interesting, this next snippet of deer vision info will blow your mind. According to Marty Banks, professor of optometry and vision science at UC Berkeley and lead researcher on the aforementioned study, a deer’s eyes can rotate independently in different directions to maintain alignment with the horizon.
“If you imagine a line coming out of the center of the animal’s eye, the eye is spinning around that line,” Banks told the QDMA. “So when an animal pitches its head down, the left eye has to rotate clockwise and the right eye has to rotate counterclockwise. We think we can see each eye rotating about 50 degrees. One is going 50 degrees and the other is going minus 50 degrees, so the difference is about 100 degrees. It’s a pretty remarkable ability.”
The technical term for this eye-rotation ability is cyclovergence. For deer, cyclovergence keeps the horizontal bands of vision in each eye aligned and level with each other, maintaining the deer’s panoramic view of its surroundings even when its head is tilted downward at ground level to feed or when walking nose to the ground on a hot doe trail.
Bottom line: Cyclovergence allows deer to maintain the wide view and motion-detecting benefits of side eyes and horizontal pupils, whether scanning the woods, walking, or standing still with head down, feeding or smelling.
Beat A Buck’s Eyesight
The research, old and new, all points to one thing you already know: movement. If you shift your body or try to draw your bow at the wrong time, a deer will bust you and break your heart. It happens all the time.
When a buck or doe comes in from left or right, looks your way and picks you out as potential trouble, freeze. Do not move a muscle. When the animal appears to have calmed down, don’t let your guard down. It’s likely the deer is still peering in your direction and is simply trying to fake you out by head bobbing and stopping, head bobbing and stopping.
Often, a wise old doe or buck will do some head bobbing and then turn and look off to the side. Though it may appear that the deer is looking away from you, it’s actually spying you out of the corner of its eye, trying to get you to make the first move.
Only when the bobbing and weaving stop for good and the deer relaxes and seems satisfied that you are not a threat should you shift in your stand or get ready to draw your bow. This might take 20 seconds or several minutes, so don’t move too soon and get busted.
The “Way Out” Bust
What about those times when a cruising buck is 100 or more yards out from your stand and coming on a string but stops dead in his tracks, lifts his head and burns holes through you? Yep, it can and does happen. Just because a buck is some distance out doesn’t mean you can let your guard down. Mirror those movements you would employ if he were only a stone’s throw away. Deer not only have a super-wide field of view, but, as we have noted, their eyes are built for picking up the tiniest flicker of movement.
When a deer is boring in, remember to freeze. It’s best to move only when its eyes go behind a tree or cover. Sometimes if the woods are open, I’ll let a buck walk right below my stand, then move. Nerve-racking for sure, but a deer typically won’t crane its head back and look straight up unless you bang the stand with your boot or do some other foolish thing.
Finally, remember that strange word “cyclovergence.” Just because a buck drops its head to feed or sniff the ground doesn’t give you the “all clear” to stand up in your stand or draw your bow. His eyes are still spinning and looking, remember? Be super careful, watch the deer and move when you can, preferably when his head is hidden by a tree or cover.