Biology Index
By Richard Bruce BA, MA, and PhC in Economics

Why Don't Predators Eat Humans More Often?

There are somewhere in the very rough neighborhood of a million mammalian predators in the United States and Canada that when full grown are large enough to kill and eat an adult human. Most of the predators are black bears, but there are also grizzly bears, also called brown bears, polar bears, mountain lions, and wolves. There are more than a third of a billion people living in the United States and Canada. They commonly walk around the wilderness, without any weapons, or other defense against these predators. In the average year three or four people are eaten. The mammalian predators pass up at least hundreds of millions and quite probably billions of opportunities to eat people for every time they eat one of us.

Surprisingly Close Proximity

These predators are frequently in quite close proximity to us, even when we are not in the wilderness. I have read that a mountain lion walks along a trail less than a mile from where I am sitting. There is a bike trail, that runs along the north edge of our city. The fenced in backyards of residential housing are just south of the bike trail. There is a low, waist high chain link fence a few inches to the north of the bike trail. It would not be the slightest bit difficult for a mountain lion to jump. Then there is a ditch that is usually dry. On the other side of that is the trail the mountain lion walks. I might also add that there are gaps that have been intentionally left in the fence so people can pass through, a mountain lion could also use these gaps.

In British Columbia, Canada there is a resort area, Whistler, with many black bears. Among the other attractions are paintball gun wars. They sound a horn to announce when the game begins. The bears take that as a dinner bell, they eat the paintballs, which were designed to appeal to wildlife as food so the humans would not have to clean them up. Kids playing paintball and bears peacefully coexist.

In the past, there were parks where people intentionally fed black bears. This did occasionally result in a mauling, but quite rarely, which was why the practice continued.

Coyotes and Little Children

Coyotes are too small to threaten adults but easily big enough to kill a small child. It has been estimated that there are two thousand coyotes in the Chicago area, where about one in thirty Americans live. So if we multiply these two numbers, two thousand and thirty, we get sixty thousand. We might take this as a very rough estimate of the population of urban coyotes, each one of which is likely to have many opportunities every year to kill a child. Yet there is only one known case of this happening in the last several decades. Once again predators can live in close proximity to people and they rarely attack us.

These same urban coyotes do commonly attack our dogs, cats, and other pets. In fact, our pets can be a significant part of their diet. Nevertheless, they know by instinct or otherwise that they should not attack human children.

Why Do We Coexist So Easily

So humans and mammalian predators can coexist, but it seems so weird, why? We can tell stories and give people statistics, but many people have a hard time getting past the obvious logic, they are hungry, we are food. It would help if we had a logical explanation.

Most predators live in environments where they can not simply eat anything that moves. If they did they would rapidly eat something poisonous or otherwise dangerous to eat and never reproduce.

In fact, the first animal a mammal predator is likely eat is an amphibian and amphibians are poisonous. When I was a child the easiest vertebrate to catch was an amphibian, for example, a toad. I have had far more opportunities to catch a frog or a toad, than a reptile, mammal, or bird. We see birds all the time, but they fly. Wild mammals, squirrels, are also seen all the time, but they run and climb trees. Lizards are pretty fast, and I have rarely seen snakes. Amphibians are reasonably common and relatively easy to catch. Amphibians are also normally poisonous to eat. We eat frog legs and not the rest of the frog in part because some of the other parts are poisonous. So the easiest vertebrate a predator can catch, and therefore the first vertebrate they would probably eat is poisonous.

This is not just coincidence. If it is slow and easy to catch how does it survive? One obvious answer is poison.

Beyond amphibians, there are other dangers: snakes, spiders, scorpions, bees, hornets, and other poisonous invertebrates. Predators also have to be careful about porcupines, whose quills can work there way into the predator's flesh until they harm a vital organ and kill the predator. Even skunks could be dangerous to the predator. The stench might make it difficult to hunt until it wore off and by that time the predator could have died of hunger.

The Exceptions, The Most Dangerous Predators

Among the Canadian and American mammalian predators, the most dangerous are usually thought to be the polar bear and the barren ground grizzly. The barren ground grizzly lives north of the tree line, hence the name barren ground grizzly. These bears live in environments where most or all of these poisonous, or otherwise dangerous animals do not exist. So for them, a policy of indiscriminately attacking anything that moves would be safer. This maybe part of the reason they are more prone to attack us.

However, for those of you who do not live in the very far north, remember the predatory mammals near you live in a world where they must restrain themselves from hunting and eating everything that moves. They simply would not be able to survive and reproduce if they attacked things they did not know were safe to eat. So some restraint is naturally part of the survival kit that evolution has given them.

Following Mother's Wisdom

Many mammals may simply eat what their mothers feed them when they were young. If their mother had killed a human and brought it back to them, the humans would have killed their mother, and the young would have died too. So you can safely assume that the bear you are facing was not taught to hunt, kill, and eat humans by their mother.

This allows us to make sense of statements like we are not their prey. This kind of statement is commonly made about predators, and the humans frequently think, what nonsense. Does the bear have a list, does he keep it in his pocket. Suppose the bear I am facing missed that day in school, or is illiterate and can not read. Many people feel that there is no reasonable reason why we should not be on their list of prey and that the idea that they will not hunt us is just fuzzy headed, wishful thinking.

When we realize that predatory mammals need to have a list in their heads or they could not survive then it is easier to take comfort in the fact that there are about a million predatory mammals of species that grow large enough to eat us but they only kill and eat about one out every 100 million humans living in the United States and Canada each year.

Practical Advantages, Fear Does Not Always Make You Safe

This change in perception can have major practical advantages. A friend of mine jumped off of a cliff to escape a bear. He knew there was water at the bottom of the cliff, but he did not know how deep it was. He got lucky, it was deep enough. But it seems very likely that he would have been safer if he had simply faced the bear. His excessive fear could easily have killed him. How many people die falling out of trees they climb to escape bears?

I have another friend that is afraid to come out of her cabin at night for fear of bears. She had a close encounter with a black bear fleeing a hunter. She was not harmed, but it frightened her. How many Americans are partially imprisoned in their homes avoiding bears and other big predators?

Furthermore, how many Americans avoid enjoyable, relaxing, and healthy hikes because of a misplaced fear of these predators?

Beyond this, there is the ecological issue. If we recognize that predators have to exercise restraint, that restraint is normal for them, then it will be easier to accept large predators in our environment. This may greatly enlarge the range that the predators can survive in, and reduce calls for their extermination.

Man Eaters Must Die

It should be noted that if one of the predators becomes a man-eater, we must act quickly to kill it, or confine it to a zoo. Our defense lies in their ignorance, they do not know that we are not poisonous. Once they learn they must be killed or constrained or they will continue to prey on us and teach their young to do the same. There have been dramatic examples of this here in America where a predator kills more than one person in rapid succession, but truly horrific examples come from Africa and Asia. Throughout all the land areas the big mammal predators normally avoid humans, but when they don't they are a huge problem.

When a predator kills a person, we often hear that they are just acting naturally. Natural or not, it is not normal for mammalian predators to hunt, kill, and eat humans. Mammal predators are probably forgoing a billion or more opportunities to eat a human in the United States and Canada for every time that they actually kill and eat a human. The claim that the animal is normal is a dangerous slander of the species.

If we quickly kill the very rare exception, we can live peacefully with the vast majority. Even if we kill ten every time they kill one of us, just to be sure we get the one that ate a human, this would only mean killing thirty or forty predators every year out of about a million. This will not significantly impact of these species.

Why Not Running and Making Noise Works

The realization that predators can not just eat any strange new thing that moves can also give us new ways to protect ourselves and a new appreciation of why the old ideas work so well.

It has been suggested that we wear bells when we are in bear country, so the bears will hear us and avoid us. This has lead to jokes about the bells being dinner bells. Another joke asks, how to tell good bears from bad bears. Answer: bad bears have bells in their poop. This is a good joke, and what's more an effective argument for not wearing bells.

But suppose we think of a bell as similar to a rattle snake's rattle. Animals that are poisonous call attention to themselves to warn the predators to stay away. Humans are functionally poisonous from the predator's point of view. If the predator kills us, the other humans will hunt the predator down and kill it.

Similarly, it has been suggested that we carry an umbrella and open it when we see a predator so we look bigger. As a teen or young adult, I was at a camp and talked to a farmers wife from a neighboring farm. A mountain lion had just attacked their horse. Even with an umbrella, I wouldn't have looked as big as the horse. Perhaps, however, the opening the umbrella would simply make you look weird. The predator might be thinking, mother never taught us to eat those things with umbrellas, maybe they are poisonous.

Note that the puffer fish, by blowing itself up is following something like the umbrella strategy, and puffers are highly toxic. I believe it is commonly thought that puffers are trying to become big so they will not be eaten. Perhaps puffers are trying to be weird to warn predators of their poison, just as poison arrow frogs warn predators with their bright colors, and rattlesnakes warn predators with their rattles.

Much more common than any of the above, is the classic advice, don't run. We are told that if we run they will think we are prey. Maybe the real answer is, poisonous animals stand their ground. The lizard runs for cover, the poisonous snake assumes a strike posture. When you do not run you are telling the predator there is something about me that is dangerous, trying to eat me would be a fatal mistake. In some sense you are bluffing, except you aren't, you are part of a human community that will usually kill the predator if it kills you.

Part of the reason that this works is that a total bluff would not work. If an animal that was not poisonous or otherwise dangerous, and was easily distinguished from animals that were poisonous or otherwise dangerous tried to bluff, eventually the predators would call their bluff. They would be quickly slaughtered and probably be driven into extinction.

Note that animals that look similar to animals that are poisonous are not completely bluffing either. The predator that calls their bluff better be able to distinguish between them and the poisonous look alike or the predator is likely to eat the wrong one and die before they reproduce.

So we can see that there are practical applications to the idea. Perhaps there are practical applications for you, or people you know. For example, my friend who is living in a cabin in the woods said that this message reassured her. It might help your friends if you would refer them to this page, and of course, I welcome the referral or link.

Beyond Anglo North America

In all the above I have been focusing on mammalian predators of the United States and Canada. This may reflect my bias that I live in the United States, and I do not live on a seacoast. But it also reflects the ease of finding statistics on the number of predators, and people killed by predators in the United States and Canada.

But much of what I have written about North American land-dwelling mammals applies more generally. Most animals large and strong enough to eat people through the land areas and even in the sea refrain from eating us. The Nile and saltwater crocodiles are perhaps the biggest exceptions. The point I have made about poison is generally applicable to most environments, the arctic land environment being the big exception and applies to mammals, reptiles, and fish.

Of course, many of the reptiles and fish are not raised by mothers and thus have to get their list some other way. In many cases, the fish and other animals at sea may think we are so weird that it is best to be wary. Weird, somewhat awkward, slow-moving animals tend to be poisonous. If you haven't eaten it before, it is best not to take a chance, at least until after you have seen another predator eat it. Could this be a source of the famous shark feeding frenzy phenomena? The sharks are wary until one starts to feed, then they take that as a signal that the prey is not poisonous. I have a more extensive treatment of the sharks, feeding frenzies, and blood in the water here.

The Nile and the saltwater crocodile may see us as just another mammal coming to the waters edge. From their point of view we are not big enough, like an elephant, a hypothalamus, or a rhinoceros, to be dangerous. Almost everything that walks on long legs under its body is reasonably safe to eat. So our difficulty with the crocodiles may be that we seem similar to them to what they have learned is safe prey. The two crocodilians that are the most dangerous are the largest. Smaller crocodilians tend to leave humans alone. They are perhaps more focused on fish as prey.

But my speculation at this point is getting a bit sketchy, perhaps I should leave a few mysteries to be solved by the trained biologists.


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