The human imagination is pretty limited when it comes to animal senses. We call people with good vision "eagle eye," and believe that toucan's can smell cereal because they have big noses. It turns out the animal kingdom has plenty of creatures whose senses go beyond what we can conceive without our head exploding. For instance ...

Humans use smell to get us excited about pie before we actually put it in our mouths, and not much else. Our superheroes have X-ray vision and super hearing, but the ability to sniff out clues is usually left to cartoon dogs. But that's just because we can't imagine what the world smells like to a bloodhound. When we walk down the street, our senses tell us who's doing what at that moment, and which one of them smells like urine. A bloodhound's nose allows it to perceive that same street across time.

His nose is a time-traveler.

It knows who walked down the street last night at 11PM, what the soles of their shoes were made of, the brand of cigarette they were smoking. Your eyes see this...

... and tell you Ingrid had a secret admirer last spring when they fixed the sidewalk. Your dog knows Ingrid is buried under there and that you shouldn't turn your back on the doorman who smokes Pall-Malls.

Fortunately for the sake of this article, and unfortunately for the sake of everyone who's afraid of bears, the silvertip grizzly's sense of smell is seven times stronger than that of the bloodhound.

Known to the Japanese as a blood-murdering cuddle-monster.

You see, silvertips can smell your fear, just like any other scary-ass predator. But unlike most predators, they can smell your fear over distances measured in double digits. In miles. These bears can smell a carcass from 18 miles away. When a silvertip enters a clearing, you're screwed even if you left 48 hours before. And if you're still there, all that sweating, pissing yourself and crapping your pants while you ran away will be laying down a neon-colored trail for the bear to follow until you get tired.

Part of the reason for this is because, despite what some scientists would have you believe, predators are scavengers as well, and the ability to smell a dead body close to 20 miles away goes a long way toward helping get a free meal. Since bears scare the shit out of every other living thing (except maybe wolverines), being able to smell someone else's kill is like being a 250-pound bully in eighth grade; no one is going to fuck with you when you walk up to him and take his food. Not even entire packs of wolves.

Being a gigantic bear is nature's way of saying, "Fuck off!"

We've shown you before just how scary-advanced jumping spiders can be -- they're like nature's tiny modern velociraptors. But they aren't just better at hunting flies than you are; they also have vision that would put the most sharp-eyed fighter pilot to shame.

They have what is called tetrachromatic vision. That means that where we see three primary colors, they see four. In a matter of speaking, their eyesight goes to 11.

This is actually a much bigger deal than simply thinking the Pink Floyd laser light show is 25 percent more fabulous than the rest of us. In much the same way your computer monitor uses red, blue and green to create images covering the spectrum from white to black to yellow (and colors that require a shot of Jaeger just to maintain manliness after mentioning, like chartreuse and fuchsia), adding a fourth color opens an entire new realm of perception.

That's because the fourth color they see is ultraviolet, which actually appears like an entire extra spectrum to creatures that can see it. Law & Order: SVU fans might recognize ultraviolet light as the stuff that reveals how many times the corpse was ejaculated upon. There are many things besides body fluids that would be perfectly visible if you had the eyes of a jumping spider.

For instance, it would open your eyes to the history behind objects. UV light is what revealed that ancient Greek statues were painted, not white, and made it clear that dino bones were hollow a lot earlier than we figured it out with our stupid three-color eyes. We suppose it's a small price to pay for being able to sleep in a hotel room.

"These are a curse ... A CURSE!"

For the jumping spider, it's even better. While some animals are perfectly invisible under normal light, they become night-and-day obvious in ultraviolet. This means it's hunting insects that are blissfully unaware that their evolutionarily awesome camouflage is completely useless against the death machine running or leaping towards them on eight giant legs. Even the normally black emperor scorpion, which is not coincidentally what the Hells Angels named their biker gang before they knew it was taken, glows a bright blue-green in UV vision.

On the bright side (if you're a bug), a jumping spider's primary eyes have a field of vision that only ranges from two to five percent. Unfortunately, they have eyes placed around their heads, so they can actually see in 360 degrees.

And they can see your ass hiding against that flower.

The only thing scarier than spiders with super-vision would be something like a Navy SEAL with 360-degree vision outside the normal spectrum, but that's impossib- Oh shit ...

IMAX would rule so hard.

There's a particular species of starfish that has calcite crystals embedded in its skin, surrounded by chromatophores (color-changing cells found in the octopus and cuttlefish as well) that allow it to not only change color in ways a chameleon would envy but also to control the amount of light passing into the calcite crystals. Oh yeah, those crystals? They are tied to nerve bundles designed to detect light and are formed into lenses. This makes the entire creature, in a manner of speaking, a single eye the size of a man's open hand.

The whole array of lenses acts like an interferometer, with each of the separate crystals acting together like the facets of a compound eye, their individual images combining to form a single clear picture.

Like this, only with less NASA.

To add strange to weird, the light-collecting lenses focus light on the skeleton of the creature, which then redirects it to "windows" of clear material in the skeleton that focus the light onto the optic nerve bundles, which then relay the information to a ring of nerves around the central disc of the body. With their entire body essentially acting as a complex fiber-optic network, it's not totally surprising that they have to eat with their assholes.

So, in the end, probably not worth it.

Internal GPS tops the wish list of anyone who's ever found himself stranded in a deserted wasteland, right after "I wish I could teleport everywhere" and "I wish this deserted wasteland were made of pizza." Pigeons can leave the wishing to the humans and focus on important things like defecating on windshields, thanks to deposits of magnetite just above their beaks that make their heads work like living, thinking compasses. Science spent years experimenting with little magnetic pigeon helmets to figure this out. We bring that up to drive home just how eerily impressive it is that there's one creature whose navigational abilities science still can't explain.

The monarch butterfly's northward migration every spring looks like the sort of poorly planned bullshit you expect from mass animal migrations, with hundreds of millions spreading out across North America, presumably wherever they damn well please.

In August, they fly back south, and things get spooky. First of all, there's the fact that all hundred million fly directly to the same tiny patch of trees in Mexico 1/100th the size of Manhattan's Central Park. So what? It's not like you can have too many butterflies, right?

Wrong.

But the truly baffling part is that monarch butterflies live only for a few months. That means the migration spans generations. Every August, hundreds of millions of butterflies wake up from caterpillardom and know how to find the exact patch of trees that their great-great-grandfathers left six months earlier. This would be like being born knowing exactly how to get to the home your great-great-grandfather was born in, and your mother never told you and you don't even know that he exists or what a great-great grandfather even is because you're a fucking butterfly.