What are Opportunistic Carnivores? (Meateating Herbivores?)

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Published on February 18, 2023
Last Updated on February 18, 2023


For a long time, people have believed that what animals ate was pretty cut and dry. If they ate meat, they were carnivores and if they ate plants, they were herbivores with animals eating both plants and meat being omnivores.

But while we categorized animals like that, nature is not that simple. Recent research has shown that the lines between being a herbivore and an omnivore are a lot more blurred than we thought.

Animals that we thought were strict herbivores such as cows, horses, and even rabbits are now known to occasionally eat meat.

While unusual, it is far from an isolated case and has happened more times than we realize. This has led to a term used to describe these herbivores, opportunistic carnivores.

Join us in Floofmania as we take a look deeper at this phenomenon and answer just what opportunistic carnivores are and why they behave as they do. 

What Makes An Animal an Opportunistic Carnivore?

The definition of opportunistic carnivores is typically plant-eating animals who eat meat under certain circumstances such as if it is offered to them. That being said, none of these animals actually require meat to survive.

Since they do not need meat to survive and do not go actively searching for it. You won’t see opportunistic carnivores chasing down prey or pouncing on animals from trees, but if there is meat sitting in front of them, they will probably eat it.

What Animals Tend to Be Opportunistic Carnivores?

With this description in mind, opportunistic carnivores tend to be herbivores including cows and horses. These animals get almost all their nutrients from plants so their teeth and stomachs are built specifically to break down plant matter. These adaptions show how little meat plays a part in their lives.

Despite that, more than one person has reported encountering a deer that has stolen hamburger meat from them or a horse nibbling on some meat left over around the farm. So while meat isn’t a big part of their diet, it doesn’t mean they never eat it.

Fact: The idea of meat-eating herbivores is not as new as you might think. Throughout the centuries there have been myths of normally plant-eating animals getting a taste for meat. The most famous of these was the man-eating horses of King Diomedes that the Greek hero Hercules had to retrieve.

Aren’t Opportunistic Carnivores Just Omnivores?

Hippo with mouth wide open.

This phenomenon has raised some questions about the classifications of these animals. If cows occasionally eat meat, aren’t they strictly speaking just omnivores?

Normally, people think of an omnivore as a just animal that eats both plants matter and animal protein such as meat, and that does, indeed, sound like the description of opportunistic carnivores.  This is, however, a bit of an oversimplification. 

What makes an omnivore, well, an omnivore is the fact that they don’t just eat meat, but that meat is an essential part of their diet. While they might not eat meat all the time, it makes up a large, significant part of their diet. 

That is not true with herbivores, even opportunistic carnivores. Their digestive systems are built specifically to break down plants. Omnivores meanwhile have bodies that can break down vegetation and meat. 

Take horses for example, while they do gain some nutrients from meat, they also have a hard time digesting it. Their livers cannot eliminate some of the harmful toxins in meat and unlike humans, they aren’t able to vomit it out. 

If a horse eats meat, it won’t have any way to expel it which makes consuming meat in large amounts not just dangerous, but potentially life-threatening. 

Fact: There is a type of omnivore known as an opportunistic eater. These are animals whose diet depends on whatever is available so if there are plenty of plants they’ll eat plants, but if there is fresh meat, they’ll go for that.

What Kind of Meat Do Opportunistic Carnivores Eat?

Since none of these animals actively hunt for meat, their options are limited to whatever they can find. The common options that these opportunistic carnivores have include.

  • Animal carcasses and carrion.
  • Bugs and other small animals.
  • Processed meats and fish, sometimes from trash.

Opportunistic Carnivores Will Scavenge Dead Animals.

Without the ability to hunt, they will instead go after animals that are already dead for a meal. Some animals such as deer and hares have been known to visit hunting sites after the predators have gotten their fill to snack on the remains of the animal carcass. 

It doesn’t matter what the animal the predators were eating was, if opportunistic carnivores are hungry enough, they will eat it. That means they can eat things including the remains of predators or even members of their own species! Animals like elk have even been known to eat the bones of animal carcasses, including other elk.

The most common source of meat for opportunistic carnivores are animals that have expired from natural causes or even meat left out by humans. The former is true during winter were many animals can succumb to the cold while the latter method is how scientists were able to learn about opportunistic carnivores in the first place.

Opportunistic Carnivores Sometimes Eat Smaller Animals That Wander Too Close.

Aside from carcasses, opportunistic carnivores have also been known to eat living animals as well. The animals they snack on are usually small and don’t tend to put up much of a fight, eliminating the need to actually hunt them. Think of things like insects, mice, and birds (though the latter is rare due to how difficult they are to capture.)

But if they don’t hunt these animals, how do opportunistic predators manage to eat them? There can be different ways this happens such as the smaller animal being injured or cornered so they can’t escape or perhaps they made the mistake of thinking that they would be safe around opportunistic carnivores.

This is why farmers need to be especially careful as cows and horses have been known to eat other farm animals like baby chicks if left unsupervised.

Some Herbivores Have Been Trained to Eat Fish.

Herbivores like cattle and horses have been trained to eat fish and processed meat despite it not being part of their usual diets. 

Fishing and hunting can be incredibly different tasks for animals, especially herbivores who are not built for that activity, but when meat and fish are provided, they can be trained or habituated to eat it and make it a part of their diet. 

Many farmers in places such as India and Iceland are known to supplement their animal diets with fish, especially when other sources of food are difficult to come by. 

How Long Have There Been Opportunistic Carnivores?

Elephant standing in water, seen from below.

Research into this has only begun recently so it is difficult to tell how long our animal friends have been occasional meat eaters. There are different viewpoints on how long this has been going on. 

For the former scientists think that this phenomenon has actually been happening for millions of years and that we simply have not noticed it. 

While this might sound strange, since opportunistic carnivores do not eat meat very often, it is easy for people to miss it. Although cases have been recorded cases since ancient times of herbivores eating meat, these were usually treated as unusual situations.

Giving some credence to this theory is the fact that some opportunistic carnivores’ ancestors may have been omnivorous. Some of the ice age ancestors of deer for example have been known to also eat insects and small mammals as part of their diet. These carnivorous tendencies might be a leftover trait.

Even today, some people believe that this is a way for plant eaters to adapt to climate change and habitat loss. Being able to eat meat gives them more options to survive as they can scavenge from more successful predators or rummage through our thrash.

Why Would Animals Become Opportunistic Carnivores?

Since many of these animals do not require meat to survive, it raises the question, why would they bother eating meat at all? That’s not where they get their nutrients and some of these animals are specifically built to eat plants. It seems like a contradiction.

While true, this is not always possible for animals as their circumstances might affect their diet.

Some Animals Turn to Meat Depending on the Season.

For animals like snowshoe hares, winter has been when they most commonly indulge in meat eating. There are several reasons for this, first is that finding meat is much easier during winter since there is more likely to be carrion for them to find. 

The second is that plant life is a bit harder to find due to the blanket of snow that covers the ground. While they will still eat plant matter like tree bark and twigs, it makes eating meat more desirable since it is easier to find and make up for any lost nutrients. 

Opportunistic Carnivores Might Be A Way Animals Evolve

Raw steak and rosemary on wooden cutting board.

While only a theory, the idea that this might be an evolutionary development is still worth noting. In a world where climate change and habitat loss are becoming serious issues, animals need to adapt to survive, and one of those adaptations is changing their diet. 

Being able to eat a variety of foods gives animals the best chance of surviving as it means they have more access to more food. Generalist eaters, or omnivores, are animals that eat whatever is available whether it be plants or meat, and because of that ability, they are more flexible when it comes to finding something to eat. 

Meanwhile, specialized eaters are animals who only get their nutrients from certain places which limits their diet and leaves them more vulnerable because if that one source of food disappears, so do they. 

That means, in the future, it might be possible to see some of these animals eating meat more frequently, but this is far from certain and we do not even know how certain this theory is.

Some Animals Might Not Know What They’re Eating

We also cannot discount the possibility that some animals might not fully understand what they are eating. It’s important to remember that as humans, we have the benefit of all this information gathered through scientific research, something animals don’t have. 

Many animals are curious creatures and if they find something that seems edible they will decide to eat it without a second thought. If herbivores have been known to eat toys and other discarded items, it’s not impossible to think they might do the same with meat.

During one of the experiments to test whether deer ate meat or not, scientists left out the intestines of animals for the deer to find. Since it was just the intestines, there is a chance that deer did not recognize what they were and just knew it was edible.

While it might indeed be harmful to them, animals cannot comprehend this idea unless they are already feeling the pain.

Take horses for example, our equestrian friends love salt and use it as a source of nutrients. If they were to find some salted meat left over from people. They might find the salt on it and eat it, not knowing it is from the carcass of an animal.

Animals Can Be Trained To Becoming Opportunistic Carnivores

Whitetail deer standing in  a clearing, looking toward the viewer.

Not all opportunistic carnivores are acting only by their instincts, they sometimes receive coaxing from humans. For domesticated animals like livestock and horses, humans play a big role in shaping their behavior, including their diet. 

It should not be surprising to hear then, that some humans have taken to training their farm animals to eat things like meat. 

This practice usually happens in places where domesticated animals do not have the resources to sustain themselves naturally. Think of remote mountains, tiny islands, or harsh tundras.

In these places, things like plants, hay, and fodder are much harder to come by so humans will sometimes look for alternatives like meat and fish. Depending on their location, these might be easier to come by and meat helps warm the body due to the higher calorie count which can be a useful ability depending on where they are.

While many opportunistic carnivores cannot naturally eat meat in large quantities, humans can train these animals to eat it and develop a strong tolerance for meat over time. In places like Nepal and Iceland where there is limited plant life, they have trained their horses to also eat things like meat and dried fish to supplement their diet.

Can Opportunistic Herbivores Survive Without Meat?

While opportunistic carnivores might snack on the occasional animal carcass, they do not need meat to survive. If anything they are better off without ever touching meat. For many of these animals such as cows and horses, since they are primarily plant eaters, their bodies and digestive systems are designed to break down plants. 

That means they can’t remove harmful toxins and bacteria from meat when they digest it. While consuming small amounts of meat shouldn’t be a problem, eating large amounts of it can be dangerous or even fatal in some circumstances. 

Fact: Some horses, especially those ridden by endurance riders are given some form of meat for extra protein. However, this meat is enriched with plant- or animal-derived oils which can reduce the negative effects. These diets are introduced gradually to get the horse used to them.

What Are Some Examples of Opportunistic Carnivores?

Hundreds of animals can be counted as opportunistic carnivores, far more than people realize. It is hard to blame them either, most humans will agree that the taste of beef and chicken is hard to resist.

But aside from being more numerous than we realize, the animals that are counted as opportunistic carnivores can also be shocking. Some of our favorite “vegetarian” critters are actually meat eaters without us realizing it.

The Snowshoe Hare Will Resort to Meat-Eating During Winter.

Snowshoe hare sitting under naked tree branches on snow.

It is hard to picture something as timid as the snowshoe hare being a meat eater, but there have been many instances of this occurring. Snowshoe hares make their homes in the boreal forests of Canada and parts of the United States and though they are well-adapted to survive in the cold, finding enough food during the winter is a challenge.

During harsh winters, food is harder to come by. Plant matter on the ground is buried deep in the snow, while the freezing temperatures make biting tree bark more difficult.

Without enough plants to eat, snowshoe hares turn to other sources of nutrients. Research has shown that some snowshoe hares are willing to eat carrion leftover by predators to supplement their diet.

They will eat whatever meat is readily available, including their own kind! That’s right, snowshoe hares technically practice cannibalism. Desperate times call for desperate measures it seems.

Horses Are Known to Eat Meat Both on Farms and in the Wild.

Three horses running together in a field of grass next to trees.

Although it is hard to think of our loyal equine companions as voracious carnivores, that image is not entirely without merit. There have been many documented cases of horses deciding to chow down on meat and even some video evidence.

There have been several viral videos of horses eating live chicks and other small birds on farms.

The same is true in the wild as horses in the forests have been observed eating meat. Anecdotal evidence claims that feral horses will occasionally eat small mammals or birds. In most of these claims, the viewer says that this was due to a strong winter limiting the horse’s access to grass. While there is no official research confirming this, the idea can’t be fully dismissed either.

Fact: In 18th Century India, there was supposedly a horse notorious for having a taste for human flesh that had claimed the lives of two people. The horse was eventually captured and spent its days in a cage where it bared its teeth and lashed out at anyone who got too close. This horse became known as the “Man-Eating Horse of Lucknow.”

Deer Are Known To Eat Meat Left Out

Whitetail deer walking through undergrowth.

If you are lucky, you might get a chance to see a deer when you’re out on a camping trip, and one of these fellas might even approach you, especially if you have food. While deer will usually approach if you have things like carrots or crackers, some have also been known to also accept meat like burgers!

But just accepting the meat offered isn’t all deer do. There have been cases of deer approaching animal carcasses or campsites after the predator and humans have left. Deer do this to search for food, and they will also sometimes munch on any meat left over.

When they discovered this, some scientists conducted an experiment where they intentionally left bits of meat for deer to discover. To their surprise, they saw that the deer, acting on their own, would also approach the meat and eat it as well as any plants they found.

Scientists believe that deer might get some nutrients from meat that they otherwise might not get from plants.

An Elephant in India Was Discovered to Have Been Eating Humans.

Elephant walking through field of bown grass.

In 2011, an elephant was hunted down after being responsible for attacking at least 17 people. While that was bad enough, an autopsy on the elephant revealed another gruesome detail, there were human remains in the elephant’s stomach, meaning it had eaten at least some of its victims.

Rumors immediately abound about how this was possible, but while horrific, many believed it was part of a growing issue. In India, there has been an increasing number of tiger and elephant attacks in rural areas which have been attributed to habitat loss and increasing environmental pressures.

With a shrinking habitat, some of these animals are becoming more aggressive toward the local people. With less room to roam around, conflicts between humans and elephants are more likely and some elephants might even view humans as a source of food.

Cattle Sometimes Eat Other Farm Animals.

Dairy cow standing on green grass.

When we think of animals eating farm animals, we usually picture things like coyotes or wolves breaking into the farm, but sometimes the animals responsible are other farm animals such as cattle.

Not only have there been instances of cattle eating mice and chicks but there are even viral videos of it (nasty as it is.) As disturbing as it is, incidents like that are more common than people realize. 

Experts believe that cows do this as a result of mineral deficiencies. When cows and other herbivores don’t get enough nutrients from plants, they might turn to other sources such as meat. The chicken was just the unfortunate victim of that.

Thankfully, this behavior is incredibly rare, especially with cattle since there are alternatives to treating mineral deficiencies. At the very least this means there (probably) won’t be a bunch of flesh-eating cows in the future.

Author: Quade Ong

Hello there, my name is Quade. I have been a writer for three years but an animal lover for over two decades. I grew up in one of the most biodiverse areas in the world, which has given me the blessing of seeing all sorts of beautiful animals. Now I strive to learn not just about the animals I am from, but those all over the world!


  • Quade Ong

    Hello there, my name is Quade. I have been a writer for three years but an animal lover for over two decades. I grew up in one of the most biodiverse areas in the world which has given me the blessing of seeing all sorts of beautiful animals. Now I strive to learn not just about the animals I am from, but those all over the world.

    View all posts

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