So, just because you're not a predator doesn't mean you don't have binocular vision. Compare the brown bear where vegetable matter comprises the majority of its diet (in most locations) with the almost entirely carnivorous polar bear, and you don't see much difference in binocular overlap. Note that all these carnivorans also have front-facing eyes, regardless of dietary preference. Polar bear, a very predatory bear closely related to the brown bear. Image source (Procyon_lotor)_2.jpgīrown bear, an omnivorous carnivoran with a highly varied diet. Raccoon, an omnivorous carnivoran that hunts by touch rather than eyesight and common prey of larger predators. Maybe the forward facing eyes of the carnivorans are just a relic of their ancestry, a quirk of fate that left the major mammalian predators with binocular vision? How can we test this? By looking at carnivorans that are not dietary carnivores, of course! Like primates, all these animals belong to the same taxonomic order, the carnivorans. Surely all the other animals conform to our initial expectations?Įxcept what are those animals that are predators and have forward facing eyes? Lions. See the picture of the patas monkey above? With eyes as forward facing as all the other primates? There doesn't seem to be much selective pressure to push this prey animal to evolve wide angle vision.Īll right, so we have one group of animals that are plant eaters and often prey. Patas monkeys, on the other hand, live in open savanna and are not very predatory. So what about the primates that don't live in the trees? Humans, of course, laze about in living rooms, not jungles - but they get a pass for also being predators. They also need to make accurate pounces, just they are grabbing boughs rather than squirming victims. They live in trees and need binocular vision to jump from branch to branch. Although the eyes of the tarsier are really freaky looking.īut wait, you say. Greater bushbaby (Galago), eats fruit and small animals. Indri, eats leaves, seads, fruit, and flowers. Image source ĭwarf lemur, nectar eater with the occasional insect opportunistically added to the diet. Squirrel monkey, a fruit and insect eater. A ground-dwelling, mostly-herbivorous but somewhat-omnivorous primate. Human, a deadly predator of large game, small game, and pretty much everything else. Tarsier, a skilled primate pouncing predator of bugs, lizards, birds, and small mammals. are predators more binocular-capable than non-predators? A serious study would go and take actual measurements on preserved specimens in a natural history museum, but that's a bit beyond the level of detail I want to go in to. The ideal photo for this purpose would be from overhead, but such photos are hard to find (and may not be public domain or creative commons). I will try to use photos with a perspective that gives a reasonable idea of the degree of binocular overlap, but judging this is tricky. Do the predatory primates, at least, have eyes that are more forward facing than the herbivores?įor this discussion, I will rely on photographs. Many are entirely herbivorous, others will opportunistically take small animals for food but these are usually encountered at close range while foraging, or otherwise under conditions that don't require accurate pounces, and the meat thus gained is but a small contribution to their diet. With two exceptions, none of these are primarily predators. All primates, for example, including lemurs, bushbabies, tarsiers, old-world monkeys, new-world monkeys, and the great apes, have forward facing eyes. It seems that there are a lot of animals out there that are herbivores and have their eyes set squarely in the front of their face. Like this Diana monkey:ĭiana monkey, a herbivorous prey animal with forward-facing eyes. Therefore, we can confidently predict that if you find an animal with forward facing eyes, it will be a predator, and all herbivores will have sideways-facing eyes. Horse, a prey animal with sideways-facing eyes. Image source ĭog, a predator with forward-facing eyes. It makes sense, and all we have to do is look at our favorite furry friends to confirm our belief.Ĭat, a predator with forward-facing eyes. Prey animals, meanwhile, have sideways-facing eyes so they can see in all directions to make it hard for predators to sneak up on them. Predators have eyes facing the front of their face to gauge the distance to their prey, for accurate pouncing.
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