Freshwater Snails and Four Other Surprisingly Murderous Animals

5 Freshwater Snails

When we’re tallying up which animal’s the deadliest to humans, we don’t just look at who hunts and eats the most. We look at who kills the most. That means that the deadliest animal on Earth is the mosquito, since it transmits malaria, which kills more than half a million people annually.

Malaria kills fewer people with each passing year, however, and we’ve recently made some major breakthroughs on the path to a vaccine. If we can beat down malaria, we might knock mosquitos off that top spot in our deadliest animals list. At that point, the winner may be the one who transmits the next most deadly parasitic infection. That would be the freshwater snail, who sticks you with a disease called bilharzia.

When you get bilharzia, a bunch of worms reproduce in your blood vessels. The worms drain away nutrients from your body, make you pee blood, eat a bunch of organs and sap your brain function. As of 2019, the disease killed 200,000 people a year. Things have improved in the last couple years thanks to preventative drugs, but we’d still recommend against quenching your thirst with water that snails have been frolicking in.

The parasites that snails transmit are themselves animals, unlike the malarial ones that mosquitos shoot into you. That means these worms, Schistosoma, are also among the deadliest animals on Earth. 

4 Meerkats

We care about the number of humans an animal kills. But here’s another stat that matters: How common is it for the animal to kill one of its own species? The mammal most likely to kill one of its own is the meerkat. Lions and wolves rank pretty high, sea lions surprisingly outrank them both, a bunch of primates fill out the top of the list... and number one is the meerkat. 

A full 20 percent of all meerkats die by another meerkat’s hand. A large portion of this toll comes from mothers. Mothers don’t kill their own young, but they do kill other meerkat pups, ensuring more resources for their own children. The really surprising part is that meerkats otherwise don’t have single family units. They raise their young cooperatively, with perhaps 30 adults all living in a group and taking care of each other’s offspring. One female meerkat is the dominant entity in the tribe, and she’ll kill most of the pups that anyone else gives birth to. 

All this doesn’t make The Lion King inaccurate, by the way. The movie never claimed Timon was a representative meerkat for living in the wilderness peacefully, any more than it said Simba was a typical lion for dining on bugs. No, this fact just reveals Timon’s dark backstory. Clearly, he’s living with a warthog because if he stayed at home, his aunt would have murdered him. 

3 White-Tailed Deer

Speaking of Disney characters, you can’t get much more innocent than the white-tailed deer. Deer are prey. The whole point of Bambi is the deer getting shot, which is our way of saying we can’t remember exactly what the plot of that movie was. Deer are innocent creatures. They can’t even get out of the way when your car is barreling toward them. Anyway, here’s a photo of a deer crunching human bones:

It didn’t kill that human, but still. If you thought deer were exclusively herbivores, this sight should worry you. That human body was placed in the woods by the Forensic Anthropology Research Facility, a Texas group that was this close to choosing an acronym that spelled “FART.” They left the body unprotected to monitor how human cadavers decompose in the wild, not just from microbes but thanks to the work of scavengers. They didn’t expect a deer to come poking through, 182 days into the experiment. 

Deer don’t eat just plants. Sometimes, they’ll see a nest of birds and just gobble up a few chicks or bite the heads off live puffins. Even if their stomach lacks the ability to properly break down meat, they’re able to extract some supplementary calcium from the bones. While possibly terrifying, their penchant for the occasional chicken nugget, even when they can’t digest it, makes deer actually feel a lot more relatable. 

2 The Arctic Shrew

Some rodents can’t deal with loneliness. If you want a pet guinea pig, for example, you should buy two of them, since forcing one to live on its own would be too cruel. In Switzerland, this guideline is enshrined into law: You must provide your guinea pig with a guinea pig companion, or you are violating article 13 of the Animal Protection Ordinance. 

Other rodents are very different. The Arctic shrew is a solitary creature. Try keeping one in a cage, and it’ll be doing just fine. Put two in a cage together, however, and one will die. We don’t know through exactly what means the weak shrew dies. We see no sign of one shrew attacking the other. We just see one shrew soon dead, perhaps from psychic shrew beams. 

Since we don’t observe just how the shrew dies in another’s presence, you might say this vulnerability labels shrews as terminal introverts, rather than killers. But let’s be honest: Is there really such a difference between those two groups? You know what they say about the quiet ones. 

1 Australian Horses and Cows

We’re always talking about Australia as a place of deadly animals. It’s the land of spiders and snakes and sharks, and the home of the deadly bunyip. When Australia’s professional death actuaries tallied up exactly what kills whom, they found that kangaroos outkill all those creatures, killing five or six people each year. But at the very top of the list, ahead of even the boxing kangaroo, are horses and cows. Australian horses and cows kill the most, and they do so for one simple reason: They’ve had enough.

If we seriously had to explain why cows and horses kill so many people, we’d have to go into how many people work so closely with horses and cows compared to any other animal. When even a tiny percentage of cows see red, many humans become mush. 

The real takeaway from that Aussie leaderboard is that many seemingly deadly animals don’t kill much of anyone. Spiders? One guy dying by spider bite in 2016 was Australia’s first death by spider in decades — if a spider really did kill him, which was never certain. We have antivenom now. So, the really brave among you won’t go to Australia and rub your genitals directly on a spider’s nest, as has been proven safe. Instead, try punching a cow, right in the snout. Then flee. Flee, and don’t stop. 

Follow Ryan Menezes on Twitter for more stuff no one should see.