Maybe it doesn’t apply ocean animals. Like they would want to see both above and below for their environment, but I’d also think for predators it would be slightly more front facing
A lot of non mammals other organs to help them perceive. Even aquatic mammals like whales have echolocation. That’s probably why the front facing rule doesn’t apply universally to all animals.
Birds? No. Though, even on the side they do often have a tilt toward frontal in a lot of predatory birds. It could be argued…
Birds of prey absolutely have their eyes positioned on the front of their heads. It’s most obvious in owls, since they have the largest eyes and wider faces, but all of them have front-facing eyes for binocular vision.
I invite you to meet the awesome jumping spider, whose eyes are very especially needed set up to be forward-facing for depth perception for their jumps, and who hunt other spiders, as well as the wolf spider, who are also a hunting (as opposed to web) spider.
In fact, you can use the chart of spider eye layouts to pretty much identify whether you’re looking at a spider who builds webs and waits or a spider who hunts:
Anyone with two big forward-facing eyes is probably looking around for their next meal; the rest are building a web, trapdoor, or taking some other approach.
Also crabs. I mean, their eyes are often on stalks and more mobile than mammalian eyes, and they’re compound, so they have a very wide field of view, but they’re still often basically in front, and they do apparently provide depth cues for hunting thanks to this.
It also occurred to me to look up about dragonflies, and it seems they mostly hunt dorsally (which is a pretty viable option if you’re flying). BUT I found this article about Damselflies, which notes that they rely on binocular overlap and line up their prey in front of them. Which is pretty cool.
Horseshoe crabs have nine different types of eyes. Even that tail is essentially a kind of eye, covered with photoreceptors. Not sure of the relevance of this horseshoe crab fact, it’s just fucking interesting.
Sloths are weird all the extinct sloths had side eyes. The ones today dont. I’m guessing depth perception for climbing. Because the list goes really big when arboreal prey animals are involved. Lemurs, sugar gliders monkeys great apes.
Convergent evolution has more to do with environment and trophic structure than it has to do with lineage. Any animal that can produce a complex eye can have similar evolutionary pressure given similar environments unless there’s some other stronger pressure.
Animals low to the ground or water often have slitted eyes (including goats who spend a of time with their heads down)
If a squirrel falls they’re probably not going to squish as hard as a monkey. Lots of scavengers also have forward facing eyes (ex racoons) and pandas notably have forward facing eyes and are herbivorous.
I think the climbing and jumping theory is better than the predator theory on account that it explains why large aquatic animals aren’t selected for close frontal eyes.
Plus many predators (cats notably) do climb and jump. Humans and monkeys also have werd postures that might lead to them falling over easier.
In reality its probably never just one pressure that leads to these kind of evolutions.
I think that’s specific to mammals. Just off the top of my head…
Invertebrates? No. All out
Fish? No. Also a Hammerhead would’ve really sold this comic lol.
Birds? No. Though, even on the side they do often have a tilt toward frontal in a lot of predatory birds. It could be argued…
Reptiles? No.
Amphibians? No. There’s no even trying to place rules on that optical chaos.
Mammals? Yeah, pretty much. Can’t think of an outlier but I’m sure there’s plenty of obvious ones.
Edit’ Ah, there we go. Of course marine mammals are an exception. But back in land, as too are llamas. Makes you wonder…what are the llamas plotting?
Maybe it doesn’t apply ocean animals. Like they would want to see both above and below for their environment, but I’d also think for predators it would be slightly more front facing
A lot of non mammals other organs to help them perceive. Even aquatic mammals like whales have echolocation. That’s probably why the front facing rule doesn’t apply universally to all animals.
Birds of prey absolutely have their eyes positioned on the front of their heads. It’s most obvious in owls, since they have the largest eyes and wider faces, but all of them have front-facing eyes for binocular vision.
I invite you to meet the awesome jumping spider, whose eyes are very especially needed set up to be forward-facing for depth perception for their jumps, and who hunt other spiders, as well as the wolf spider, who are also a hunting (as opposed to web) spider.
In fact, you can use the chart of spider eye layouts to pretty much identify whether you’re looking at a spider who builds webs and waits or a spider who hunts:
Anyone with two big forward-facing eyes is probably looking around for their next meal; the rest are building a web, trapdoor, or taking some other approach.
Also crabs. I mean, their eyes are often on stalks and more mobile than mammalian eyes, and they’re compound, so they have a very wide field of view, but they’re still often basically in front, and they do apparently provide depth cues for hunting thanks to this.
https://www.jneurosci.org/content/38/31/6933
It also occurred to me to look up about dragonflies, and it seems they mostly hunt dorsally (which is a pretty viable option if you’re flying). BUT I found this article about Damselflies, which notes that they rely on binocular overlap and line up their prey in front of them. Which is pretty cool.
https://www.sciencedirect.com/science/article/pii/S0960982219316641
Horseshoe crabs have nine different types of eyes. Even that tail is essentially a kind of eye, covered with photoreceptors. Not sure of the relevance of this horseshoe crab fact, it’s just fucking interesting.
Exception: Sloth
Sloths are weird all the extinct sloths had side eyes. The ones today dont. I’m guessing depth perception for climbing. Because the list goes really big when arboreal prey animals are involved. Lemurs, sugar gliders monkeys great apes.
not sloths, Sloth.
They want your sweater back…
Convergent evolution has more to do with environment and trophic structure than it has to do with lineage. Any animal that can produce a complex eye can have similar evolutionary pressure given similar environments unless there’s some other stronger pressure.
Animals low to the ground or water often have slitted eyes (including goats who spend a of time with their heads down)
Besides humans, aren’t most apes prey animals?
including humans.
Most primates eat fruit or leaves, but have forward facing eyes because they need depth perception for climbing/jumping, not for hunting.
Squirrels have eyes on the sides of their heads and they’re pretty fucking good at climbing and jumping. Next theory …
If a squirrel falls they’re probably not going to squish as hard as a monkey. Lots of scavengers also have forward facing eyes (ex racoons) and pandas notably have forward facing eyes and are herbivorous.
I think the climbing and jumping theory is better than the predator theory on account that it explains why large aquatic animals aren’t selected for close frontal eyes.
Plus many predators (cats notably) do climb and jump. Humans and monkeys also have werd postures that might lead to them falling over easier.
In reality its probably never just one pressure that leads to these kind of evolutions.
Aye-Ayes and Tarsiers have very forward facing eyes, yet eat mostly gruvs in trees.