We all know that there are some disgusting animals out there. Nobody wants to glance into the toilet and find a razor-clawed slime eel blinking back at them. And certainly, we can all agree to dislike the whooping mucus elephant, at least until it agrees to stop doing that thing with its glands. But there are also many perfectly normal animals -- the type you’d model a children’s plush toy on -- who are deeply, truly disgusting when you look closely. 

Hippos Poop So Much, They Kill All The Fish

The Mara River runs through Kenya’s famous Masai Mara national park, where wildlife teems along the banks. But ecologists soon realized that something terrible was lurking in the muddy waters. Every time the river flooded, thousands of fish would suddenly and inexplicably die. Seriously, all it took was a mildly heavy rainstorm and suddenly the place would have more rotting fish corpses than the fridge at Red Lobster. The ecologists suspected the Mara was being contaminated by agricultural runoff from upstream and were on the verge of summoning Captain Planet when a series of experiments revealed a more surprising culprit: Hippos were pooping all the fish to death

USAID

Worst part is that they’ll hold eye contact while they do it.

As real hippo-heads will know, hippos emerge from ponds and rivers at night in order to graze, before retreating to the cooling waters during the day. And then they just start shitting like a lazy guy living above an all-you-can-eat norovirus restaurant. The hippos in the Mara system alone are estimated to dump over 8,500 kilograms of waste into the water every day. To make matters worse, many of the hippos actually live in small ponds in the river’s floodplain. These rapidly become “a stagnant mess of ammonia, methane, hydrogen sulfide, and other chemical grotesqueries.” Basically, picture a hotel hot tub the day after the IBS convention accidentally double-booked with a clam-eating contest. In fact, just picture any hotel hot tub. 

When married ecologists Chris Dutton and Amanda Subalusky began investigating the fish deaths, they discovered that the river was so full of hippo poop that “you can put a net in the water for a few seconds, and the entire middle will just be coated with hippo feces.” But the real magic happens in the small hippo ponds, which are completely cut off from the river during the dry season. Naturally, these ponds are full of bacteria feasting on the wealth of organic matter. Dutton and Subalusky found that the bacteria consumes virtually all of the oxygen in the water. When the Mara floods enough to reach the ponds again, this low-oxygen water rushes into the river, literally suffocating the fish in its path. 

Safaritravelplus/Wikimedia Commons

“More like Hippo-poop-amus, right guys?”

This discovery required years of experiments by Dutton and Subalusky, many of which had to be carried out by a remote-control boat, since hippos will attempt to murder anyone who sneezes within crushing distance. Although working with hippo poop was probably a relief after their previous study, which involved studying the rotting corpses of hundreds of wildebeests who drown en masse every year during the annual migration. Wait, packed animal corpses, thousands of dead fish and a thick current of hippo dung? Is this a river or your mom’s bathtub? Boom, another devastating burn here at Cracked.com. 

Sloths Only Take One Massive Poop A Week (And Half Of Them Die Doing It)

Sloths are widely considered to be some of the most adorable creatures in the world, which is impressive when you consider that they move like haunted carnival animatronics and smile like a man about to get banned from an Internet cafe. But for all their laid-back charm, sloths boast the worst bathroom routine outside of an Amazon warehouse. For starters, most sloths poop once a week at most, by which point they’re so constipated that the process has been described as “like giving birth.” It’s quite common for sloths to lose between a fifth and a third of their body weight in a single bowel movement. To experience something similar, you’d have to eat only Play-Doh and chewing gum for a month, then hope to be reincarnated as a sloth when your colon explodes. 

Sergiodelgado/Wikimedia Commons

“Oohh, it worked.”

Now, you might expect sloths would want to be as secure as possible when the poopocalypse hits. And you would be absolutely wrong. For reasons nobody has ever been able to understand, sloths refuse to defecate up in the trees. Instead, they insist on climbing all the way to the ground (burning through almost a tenth of their daily energy needs). Once on firm land, the sloth will do a sort of shambling “poop dance,” just to really alert any neighboring predators. They then proceed to do their business while clinging to the trunk of their tree like a drunk clutching at a lamppost. 

Bear in mind that most sloths hardly ever leave the safety of the canopy, so their weekly trips to the bathroom are a huge risk. Some researchers believe that up to half of all sloths die from predator attacks while pooping. And let’s be fair, if there was a 50 percent chance of a jaguar lunging out every time you opened the bathroom door, you’d probably only go once a week too. 

So why don’t sloths just let loose from above, like every other tree-dweller? Well, one theory is that the sloths have a symbiotic relationship with a species of moth. The carefully deposited sloth dung is a perfect hatching place for moth eggs. In return, the moths fertilize the algae that grows on sloth fur. This is where the theory breaks down a little, because it’s not clear why sloths would want their algae fertilized, unless they’re secretly eating it when nobody’s watching. Other researchers reject the sloth moth theory and suggest it’s actually all about mating, with the stinkiest droppings marking the sexiest trees in the whole jungle. But essentially, nobody knows. Although our personal theory is that it’s a survival tactic, since there’s no quicker way to enrage a hunter than dropping a week’s worth of sloth shit on him from above. 

Prairie Dogs Are Murderers

Prairie dogs are possibly the animal with the laziest name in history, rivalled only by the guinea pig and the pygmy mountain whatever. They’re also adorable. Adorably good at murder that is. Back in 2007, prairie-based scientists discovered a prairie dog playing with a mutilated ground squirrel corpse. Led by the University of Maryland’s John Hoogland, the scientists quickly launched a murder investigation. Over years of careful surveillance, they built up files on over 100 squirrel deaths, plus profiles of 47 prairie dog murderers. Sadly, this didn’t end with a researcher slamming their fist on a tiny desk and screaming “you’re gonna talk dammit” at a startled rodent, but the results were almost as surprising.

Wikimedia Commons

Aww, look at their little murder-noses. 

The study found that prairie dogs were regularly (and brutally) murdering ground squirrels, before leaving the rotting bodies as a stark warning of prairie dog might. Now, you’re probably thinking, “So what? Animals kill each other all the time. A panda shot my grandmother once. No big deal.” But it actually is a big deal. The prairie dog murders are the first time we’ve ever observed herbivorous mammals killing other herbivores without feeling threatened or having any interest in eating them. It would be like if horses were just constantly mutilating cattle, or if you occasionally passed a chipmunk waving a severed mouse head on a toothpick. What the hell’s going on between prairie dogs and these squirrels?! 

Well, it’s clear that killing ground squirrels has major benefits for prairie dogs and their prairie pups. The study found that the offspring of prairie dogs who killed squirrels had a way higher survival rate than the offspring of prairie dogs who embraced the way of peace. What’s even weirder is that killing squirrels was literally the only thing that seemed to change the pups’ survival rates. Other factors like the health of the mother made no difference at all. The only thing that mattered was whether their parents got out there and murdered some squirrels. Although note that this only applies to prairie dogs, you should not try to massacre squirrels until your child achieves immortality.

Cburnett/Wikimedia Commons

“Swear to god mom, if there isn’t a dead squirrel outside this burrow tomorrow I’m going to walk straight into a hedge trimmer.”

Prairie dogs and ground squirrels eat the same plants, so presumably murdering the competition allows prairie dog pups to enjoy a more plentiful diet. Which makes sense, although scientists were still surprised to find the behavior among herbivores. They even risked their lives to study a particularly angry prairie dog, dubbed “Killer Supreme” who massacred at least nine squirrels, even nibbling on their brains to make sure they were fully dead. The good news is that prairie dogs only live up to five years, so Killer Supreme is long gone...but his long-lived grandchildren might still be lurking out there. Quick, everyone try not to look like a squirrel. 

Crows Are Necrophiliacs

Crows have long been considered one of the smartest animal species, right up there with dolphins, elephants, and the mighty brain-vole. Some chimpanzees may have mastered tools, but crows are so smart that they’ve remastered Tool’s entire back catalog and are currently being sued by RCA Records. That’s why researchers studying crows were recently surprised to observe some surprisingly primitive behavior. Crows have long been known to hold “funerals,” in which they gather around the bodies of their dead. University of Washington ecologist Kaeli Swift was trying to trigger this behavior by placing a dead crow underneath a nest. Instead she was surprised to see a living crow fly down and start copulating with the body. 

Polyoutis/Wikimedia Commons

In fairness, this one was pretty far gone.

Now, most of us would just have hammered a sign to the tree reading “Warning: Bird Pervert” and moved on with our day. But Swift was a scientist, so she decided to investigate further. She had only two tools, a boundless sense of curiosity and a car trunk full of dead crows, which she began leaving all over town to see how the birds would react. Sure enough, in roughly 4 percent of the cases at least one crow would try to breed with the corpse. And these weren’t candles-and-chocolate sort of encounters. The crows would often turn violent, scratching and ripping at the corpse even as they tried to copulate with it. Sometimes the crow’s mate would even join in to help tear the corpse apart. 

This behavior was extremely strange because crows usually treat other dead crows as a sign of danger. Crows will often start avoiding areas where dead birds have been found and the crow “funerals” are believed to be a way for crows to learn about potential threats. And the crows certainly weren’t turning to necrophilia out of pure horniness, since many of them had mates already. In one very weird case, a breeding pair inspected one of Swift’s dead birds and then became so overwhelmed they started mating right in front of it. Additionally, the violent mating behavior was unusual for crows, so just what the hell is going on? 

Vikram2784/Wikimedia Commons

Our theory? Crows have a fetish for freaking out scientists. 

Swift’s theory is that during breeding season, crows can become so overwhelmed with hormones that they lose the ability to distinguish between an intruder or a mate. The panicked birds then launch both responses at once, simultaneously attacking and mating with the corpse. In any case, crows certainly aren’t the only animal necrophiliacs, since the behavior has also been observed among dolphins, lizards and ground squirrels. Which ... might actually explain a lot of the prairie dog anger from the last entry. 

Mice Lure In Lady Mice By Crying

Sensitive men have long been considered extremely attractive. Why, you can’t even shed a single tear during a particularly moving poetry slam without being found three days later in the bathroom, hovering near death from sexual exhaustion. Don’t believe us? Well just ask mice, who find nothing hotter than a male sobbing uncontrollably. According to a study published in 2010, female mice who came into contact with male mouse tears were three times more likely to thrust their rumps and tails upwards in preparation for mating. 

Disney

Mickey knows what he’s doing. 

That’s because mouse tears contain a pheromone called ESP1, which we believe stands for Extra-Sexy Pheromone 1 Million. When male mice do that weird face-rubbing thing that passes for grooming among rodents, ESP1 gets spread from their eyes to the rest of their body. From there it spreads around the whole nest. Which is helpful, because ESP1 doesn’t spread by smell, the female actually has to brush up against it. But as soon as they do get a taste of that spicy tear juice, they get hornier than an ibex at an orgy. 

This could actually have very helpful implications for lab work. Researchers have long known that lab mice don’t breed at the same rate as their wild counterparts. This has made it tricky to breed enough mice to give every undergrad a chance at earning a “Scientists Cure Cancer!” headline in the Daily Mail, with the accompanying “in mice” disclaimer in paragraph 35. But the discovery of ESP1 pointed towards a big part of the problem: lab mice just aren’t crying enough. Which goes against everything The Rats of NIMH taught us (joke disclaimer: mice actually cry to moisten their eyes, not due to sadness). The researchers have no patented ESP1 for use as a mouse aphrodisiac. Look, it’s not quite developing a COVID vaccine, but how many rodents have you made horny today? 

A Lizard Shoots Blood Out Of Its Eyes Into Things’ Mouths When Threatened

Animals have many different ways of defending themselves. The South African punk tortoise claims to have an uncle in the mafia, while the North African rock crab owns a gun. But all those tactics pale in comparison to the horned lizard, which has an impressive array of horns. Also, it shoots its own blood out of its eyes at you. Maybe we should have led with that second one.

Walter Siegmund/Wikimedia Commons

Damn, it even knows how cool it is. 

When a horned lizard feels threatened, it will first resort to the traditional lizard tactic of standing completely still and hoping everything kind of sorts itself out. If that doesn’t work, it will carefully assess the situation and deploy the perfect response for each predator. If it's a rattlesnake, the lizard will simply run away, since rattlesnakes usually try to ambush prey instead of chasing it. On the other hand, whip snakes are faster than horned lizards, so the lizard will simply puff its body up as much as possible, making it harder for the snake to swallow it whole. But if the threat is from a coyote or bobcat, then somebody call Blade, because it’s bloodbath time. 

Using blood pouches beneath its eyes, the lizard can spray a stream of concentrated blood up to six feet. The blood apparently tastes repellant to canines, although humans can taste it without any problems. Yes, scientists have tested that. Even weirder is that none of them gained lizard-powers and had to be defeated by a blood-drenched Spider-Man. We’d like to note that the tests involved a dog named Dusty, who was specially trained to provoke lizards into spraying her with blood, because there is literally nothing dogs won’t do to help out. They had to use Dusty, because horned lizards are very good at identifying threats and refuse to waste good blood spraying it at humans, no matter how much you get on all fours and impersonate a coyote. 

This hemophil-attack doesn’t always work, but don’t worry, horned lizards do have one last line of defense. The spiny lizards frequently get lodged in coyote’s throats, choking them to death in one last act of defiance. So here’s to you, horned lizards, the first animal created during God’s brief heavy metal phase. And don’t worry: Of course we’re going to show you a video of the blood thing. 

Top image: Enrico Pescantini/Shutterstock

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