[♪ INTRO ].

If I asked you to picture a forest, you might envision a sunny grove with some deer gently nibbling on leaves as they mosey on through. But those deer could actually be searching for a baby bird or two to munch on.

Yes, deer can be carnivorous. In fact, many supposed plant-eaters sneak the occasional fleshy snack, usually because some nutrients are just easier to get from animal parts. So here are six so-called vegetarians that regularly eat meat and bones—including ours. [1.

Deer]. Everyone knows that Bambi and his friends are vegetarians. I mean, deer are quite literally built to eat plants.

As ruminants, they have the ability to ferment plant material in their specialized stomachs, which allows them to live off a diet that would be way too fibrous for most creatures. But lots of deer apparently missed that memo, as they’ve been caught eating everything from baby birds to human bones. Yes, I said human bones.

A 2017 paper suggested that deer might frequently gnaw on bodies left exposed in their habitats. We don’t have any evidence that deer kill people, outside of accidental encounters with vehicles. But they do most definitely kill birds.

Like, a lot. Nest cameras in North Dakota have filmed white-tailed deer snacking on chicks more often than traditional predators. And on an island in Scotland, red deer have been seen biting off the heads of seabird chicks and chewing on birds’ legs.

Scientists think these deer are specifically targeting bones, since they’re rich in phosphorus, calcium, and other minerals that are less common in plants. They need those nutrients to build strong bones for themselves, as well as those impressive antlers that deer are so known for. Sure, a rich mineral lick would suffice, but those aren’t always around … whereas baby birds are everywhere.

You’d expect that other ruminants would have similar dietary needs, and therefore might also snack on the occasional bone. And … yeah. They do.

Sheep, cows, and even giraffes have been seen sucking on bones or actively killing small animals—usually baby birds. Apparently they’re just a super convenient source of minerals, if you don’t happen to have a salt lick at hoof. [2. Squirrels].

Rodents are another group of animals that are well known for their vegetarian diets—especially ones like squirrels and chipmunks. They just scamper along branches and stuff their furry little cheeks full of yummy acorns, right? Well, it turns out when they’re not busy stashing nuts and eating the cherries off my cherry tree, squirrels and chipmunks take full advantage of their climbing ability to go after bird eggs and nestlings.

They also seem to have no qualms eating frogs, lizards, snakes, and even turtles. And they’ll kill and eat all sorts of small mammals, including other species of squirrel … or each other. Maybe that shouldn’t be so surprising, since rodents are notorious for eating their own young.

But when they do, it’s usually considered a sign something is going wrong. Squirrels will act as predators when completely healthy, so there must be some other reason. Like with deer, one important clue is that they seem to target bones.

Forensic scientists note that squirrels frequently gnaw on skeletons, for example—and their tiny teeth can cause enough damage to obscure important clues about the cause of death. So, they might be looking for those extra minerals like deer are. Or they could just be looking to grind down their teeth.

All rodents have continuously-growing incisors—you know, those rodent-y things in front—so chomping on hard bones might keep them in check. But in many cases, like with the baby birds, squirrels definitely seem target flesh, which might mean they hunt for the most obvious reason: Food. Just extra calories.

Lab experiments have shown that hungrier rodents are more likely to attack live prey. And other rodents like mice, beavers, and bunnies will also make a habit of dining on meat if the option is available. Meat consumption is so widespread in rodents that some scientists argue that they really should be thought of as omnivores, not herbivores.

And given that about 40% of all mammals on the planet are rodents, that go-with-the-flow approach to their diet might have helped them conquer the world. [3. Butterflies]. Anyone who has tried to grow their own veggies is all too familiar with the leaf-destroying abilities of most caterpillars.

But some moth and butterfly larvae have decided plants are overrated, opting instead to snack on tasty flesh. Like inchworms in Hawaii with claw-tipped arms, which will eagerly feast on flies. Or silk-weaving caterpillars that tie down snails so they can slurp them from their shells.

And all the caterpillars in the subfamily Miletinae eat aphids. But eating snails and insects pales in comparison to the moths and butterflies that dine on carrion. That’s right.

There are scavenging butterflies. A lot of them, actually — especially when they’re caterpillars. Most of these caterpillars normally eat plants, but when the tastiest leaves are taken, they’ll go for decaying flesh.

As the saying goes, this is life, and no one gets out alive, so being able to eat dead things is a pretty good way to make a living. I’m not sure that was a saying, but it is now. Caterpillars’ tough jaws—strong enough to tear through starchy leaves—have no trouble with decaying meat.

Some species are so common on corpses that they’re used in forensics. Even adult butterflies get in on the scavenging action at times, to get nutrients not found in nectar. They may flock to dead fish for the salts—the same reason they hang out on mineral licks or sip turtle tears, which yes, is a thing.

But some scientists think they suck down rotting flesh for the amino acids—the molecular building blocks of proteins. The species caught using bait made of decaying meat are known to be super mobile butterflies, and all that extra protein probably helps them build and keep their flying muscles. [4. Duikers].

Duikers are teeny little antelopes native to Africa. They are really cute. There are almost two dozen different species, each more adorable than the last.

But don’t let their size or their cute features fool you—Duikers can be ruthless. Though they’re generally considered frugivores, or fruit eaters, animal matter is frequently found in their stomachs… by people who cut open their stomachs, apparently. Things like insects and carrion usually make up about a tenth of a percent of their diet, which doesn’t seem like very much.

But studies have found some stomachs with 10% or more of their contents animal-sourced. And … they don’t necessarily wait for their meals to die. In Angola, the yellow-backed Duiker’s taste for flesh is infamous.

According to locals, they’ve actually learned how to eat tortoises, leaving behind empty shells wherever they go. And there are tons of scientific reports of Duikers and their relatives eating all sorts of small birds, mammals, reptiles, and amphibians. More surprisingly, they seem to enjoy killing.

Captive Duikers appear to play with living food, like a cat toying with a mouse. One bay Duiker in the Zurich zoo earned a reputation for stalking, killing, and eating pigeons that landed in its enclosure. But those behaviors might not be natural in the wild.

In fact, why Duikers eat meat isn’t entirely clear. It may be that, like their distant ruminant relatives, they use meaty snacks as nutritional supplements. Studies of their wild diets suggest that the plants and fruits they eat are relatively low in minerals and protein, even though the animals fare better on a high protein diet.

But some zookeepers have found they actually do better when raw meat is excluded from their meals. We just don’t know enough about these shy, adorable, savage little antelopes to say for sure. [5. Hippos].

Hippos might look like gentle giants. But even though they’re considered herbivores, they’re one of the most dangerous beasts in Africa. Their aggressive nature is legendary — it’s said they kill more people every year than lions and leopards combined.

And that’s probably not just because they’re territorial. Recently, biologists have come to the conclusion that they actually have a taste for meat. Hippos will scavenge carcasses they come across, and they’ve been known to walk right up to a feeding crocodile and take a bite of its kill.

But much more direct and savage stories have emerged over the years, including instances where hippos have definitely killed and eaten antelopes. And that’s weird, because it’s been thought for a long time that hippos simply don’t have the stomachs—or, more accurately, the stomach bacteria—to digest meat. But a 2015 review argues that the only thing limiting meat-eating in hippos — or most herbivores, really — is their ability to catch and eat it.

And that makes sense, considering all the other supposed herbivores that eat meat when they have the opportunity. But hippos have a few meat-eating advantages over other herbivores, like their big giant mouths and teeth that can more easily tear apart hunks of flesh. And with their bulk—and surprising speed and agility—they are more than capable of taking down large prey.

Just how often hippos eat meat is uncertain, though—most diet studies get their info from plant material found in feces, which does not tell you whether or not the animal has consumed meat. And it’s hard to observe everything that goes into the hippos’ mouths because they tend to eat at night. Also ... it’s kind of tough to stay close enough to a giant aggressive hippo to see what it’s nibbling on.

You can’t really do a diet study if you become a part of the diet study. If you know what I mean... [6. Primates].

Obviously, we humans aren’t always vegetarians. And it’s no secret that chimpanzees wage wars against one another, and will hunt, kill, and consume other animals, especially monkeys. But most primates have a more peaceful reputation.

Take bonobos, for example. These chimp cousins were supposed to basically embody the 1960s hippie movement—you know, making love, not war. Even though they’re basically the same size and strength as chimpanzees, people thought they opted for a much more vegetarian diet.

That is, until about a decade ago, when anthropologists watched them hunt down monkeys and other, smaller mammals. And those observations are backed by DNA—fecal DNA, to be precise. A 2010 study of 128 bonobo poop samples found evidence for recent meat consumption in 16% of them.

One reason that these and other primates might eat the occasional steak is that it’s hard to get enough Vitamin B12 with a purely vegetarian diet. B12 is essential for healthy blood and nerve cells, and we mammals can’t make it ourselves. Some animals, like ruminants and other animals with multiple stomachs, like hippos, have bacteria in their guts that produce this key nutrient.

So they get what they need because their weird anatomy. We have some of these bacteria, too, but there’s a catch—they live so far along in our digestive tract that we just poop out all the B12 that they make. That’s probably why bunnies and some rodents eat their own feces, and if they don’t, they get B12 by having a non-vegan diet — usually, by supplementing with insects.

So it makes sense that even the most vegetarian-leaning primates might actually be somewhat omnivorous to ensure they get enough B12. Many primates probably eat insects for this exact reason, but some—like bonobos and chimpanzees—clearly have no problem subbing in a little red meat instead. And I do feel like mentioning you can get B12 without meat, it’s just us humans have a lot more dietary opportunities than wild chimpanzees.

But in the end, even animals we thought were super strict vegans might cheat a little more often—or a lot more often—than we ever imagined. But if they do eat a little flesh now and then, they probably have a good reason for it. Learning what animals eat and why can help us take better care of them in captivity and understand our own dietary needs.

If we want to go full vegan, we can just get a B12 from pills or shots, or fortified food, not from eating our own poop. Thanks for watching this episode of SciShow, which could not exist without the support of our Patreon patrons like Matthew Brant, our President of Space. Thank you Matthew for your continued support of SciShow. [ ♪OUTRO ].