 Good morning, John. On this, the sixth day of pizza-ness, I would like to introduce you to the manual, or palace's cat. It's a wild cat that is roughly the same size as cameo, my cat. But while they may look similar, they are not. Spread across Tibet, China, Pakistan, India, Mongolia, Iran, these solitary, grumpy, temperamental cats. He got a living on small rodents and birds, keeping warm with the longest hair of any cat, hunting not through speed, but through stealth, with fertility windows as short as one day per year. But the thing that makes them so cute is what I want to talk about today, their eyes. And you may be noticing that this cutie is a little less cute than the other manuals I've showed you so far. That's because I photoshopped house cat eyes onto it. Here's the real boy. There's something about those eyes. We've gotten used to the eyes of our cats, but they are a little bizarre. These vertically slitted pupils are complicated mysteries that have evolved separately, not just in cats, but in foxes, alligators, snakes, even some birds and sharks. And not all cats have these vertical pupils. Big cats don't have them, but most small cats do. And the European lynx, which is of moderate size, actually has intermediate pupils. And animals that have vertical pupils tend to have a few things in common. They're all hunters, they all deal with low-light conditions, and they're all ambush predators. But Palace's cat fulfills all those conditions. They're low-light ambush predators. So how do they end up with these adorable, relatable eyes? I don't know, and neither does anyone, but I found this whole thing fascinating, so let's walk through it. There are three theories as to how vertical pupils help ambush predators. First, vertical pupils rely on a curtain of stranded muscles to contract, while circular pupils rely on a sphincter. Yes, you have sphincters in your eyes, and that more complex musculature allows them to contract and expand more. But, as the Loris has shown us, this is not a hard and fast rule. Second, we have distance judgment, which is, as you might expect, pretty important for an ambush predator. There are three ways animals use sight to tell how far away something is. The first is parallax, where objects farther away appear to move more slowly than objects close up. The second is binocular stereopsis, which is the fancy way of saying normal depth perception when two eyes feed the brain slightly different images that are interpreted into a three-dimensional image. But last, and least noticed, is blur. When you look at something, especially something fairly close up, things closer to you and farther away from you from that point appear blurry. And when you're close to the ground, like a small cat or a snake, this matters more because you're closer to your prey, and thus the depth of field is shallower. Vertical pupils seem to conserve horizontal blur, which animals use as a distance judging technique, without sacrificing the vertical contrast necessary for stereopsis. Now, the third theory is a little harder to wrap your head around because it involves optics. But basically, if you want to focus on something close up with a really wide aperture, like if your pupils are super dilated because it's dark, the ability of a lens to focus kind of breaks down. Different wavelengths of light, so different colors, pass through the lens medium at different angles, so the image will never be sharp. To get that sharp image, some animals, including cats, have actually evolved to have lenses with focal gradients. The middle optimized for green wavelengths, and then red, and then blue. This works, but if you have a circular pupil, then when you contract, the area of the lens optimized for blue gets completely blocked. A vertical pupil, on the other hand, preserves all of the color optimization. Now, as is often the case when it comes to how animals perceive the world, we're not 100% on any of these things, but we do know that with its lifestyle, a vertical pupil would be advantageous to Palace's cat. So their adorable pupils, it turns out, are a mystery. An adorable mystery. They shouldn't be there, but they are. So love it. The manual, or Palace's cat, is the Bizarre Beast of this month, and I have great news. The Bizarre Beast Pin Club is opening back up just until the end of Pizzamas. So if you want this Palace's cat pin, which is very good, you can join right now! You'll also get another pin every month with a different Bizarre Beast and information about it on the card. And there are more Bizarre Beasts on their way. Pizzamas also continues. John, I will see you on Tuesday.