What is the deadliest animal in America? And is the best predator the deadliest animal, or the most beneficial?

I am pre-publishing this sequence of essays here and in social media to elicit comments and other feedback. They will form the framework for my next book, Darwin, Dada, Dalí, Duke, & Devadevàya.

Deadliest Animal in America

In my years working in the E.R., the question has often come up from patients and other staff, “What is the deadliest animal in America?”

Sharks? They kill about 1 person a year.

Bears? About the same.

Alligators? The same.

Snakes? About 6 people a year.

Dogs? Getting warmer: about 30 people a year die in the U.S. from dogs. That’s still not enough to make dogs the deadliest animal in America.

But don’t forget, there are many ways to die. Not all deadly animals are predators, and not all kill their victims the same way; snakes kill people, but not from trauma, and not to eat them. Like the snake, the black widow spider kills by venom, but almost no one in the U.S. dies from black widow envenomations. So we need to think past trauma and poison.

Hint: allergic reactions. About 60 people die in the U.S. each year from insects: bees, wasps, hornets, and occasionally, our beloved southern fire ants. But that’s still not the answer.

The deadliest animal in America? Over 100 people die each year from deer, in over 1M collisions with motor vehicles. Beyond the deaths, deer are also costly. At more than $3,000 in damage per vehicle collision, deer cost over $3B annually. They are also responsible for another billion or so in agricultural damage.

Lonely Wolves

From the picture, you might have imagined that wolves are the deadliest animal in America. Wolves are actually quite shy, and avoid humans. They kill fewer people than snakes.

And there simply aren’t that many wolves left in the lower 48. In the 19th century, the contiguous United States might have supported a half-million wolves. Today a little over 5,000 remain, perhaps 1% of their previous numbers.

Which, oddly enough, is why deer are so deadly.

‘Fortunate’ Deer

Wolves hunt all manner of animals, but deer are among their favorite prey. Historically, wolves and other large predators (bear, wildcats, cougar, etc.) kept deer populations under control, at levels that preserved enough browsing area for the survivors.

In the 19th and early 20th centuries, however, humans began hunting wolves and other predators, partly out of personal safety concerns, but also to provide more deer for people to hunt. At that time, deer were an important part of the American diet.

Far fewer people hunt today, and almost none of them rely on deer as a significant source of food. So deer face fewer predators, human, wolf, or other. Not surprisingly, their numbers have exploded. That’s why they are now killing us. They’re everywhere. You might be tempted to think that this is fortunate for the deer, however.

It’s not.

Forest Catastrophe

If the goal of life is surviving and reproducing, biological success is always temporary, and illusory. Populations may briefly expand, but typically predators expand along with them and contain their numbers, so that the numbers stabilize. Any success is short-lived.

If, however, predators do not expand with the prey population, then the prey will outstrip their food supply. In which case, the ‘success’ is not only short-lived, it is catastrophic.

That is what happened with deer. Today, in forests where there are few natural predators and hunters, deer strip the forests not only of grasses and shrubs, but of all seedlings. The forest becomes like a city containing only adults: it would be quieter, more peaceful, and more ‘civilized’. Those niceties, however, would be temporary. Without children, the city has no future.

Deer Collapse, Forest Collapse

And neither does the forest. Stripped of brush, the forest is beautiful to stroll through, but it is equally doomed. When the old trees die, there will be nothing to replace them. The deer will continue to kill seedlings as fast as they appear.

And the deer won’t be doing all that well, either. Wolves and other carnivores target the young and the old, but particularly the sick, which includes the starving. With no predators, however, all deer starve, and they risk a catastrophic collapse. There are thresholds in biology, mathematical critical points; if a population drops below that point, the most probable outcome is local extinction.

But before that happens, the forests may die. Which can create other catastrophes, through extensive networks which are not always obvious to the casual observer. For instance in the U.S. northwest, deer strip the streambanks of cottonwoods. This leads to erosion, loss of topsoil and plants, and destruction of habitat for living things from microbes up through the entire food chain. All species in the area are impacted. The woodlands often serve as critical wetlands, as well. If enough forests and wetlands are destroyed, that begins to impact our oceans.

The Good Predator

What is the best way to manage deer? Even PETA agrees that predators are necessary. PETA oddly objects, however, to human predators, contending that hunters only harvest trophies.

All of the hunters I know butcher the deer they kill, and eat the meat. But either way, it is moot. An abandoned carcass still attracts and feeds the same large predators that would hunt and eat the deer otherwise. The difference is that most hunted deer die more quickly and less painfully from a bullet, while the predators avoid the dangers of the chase.

So I’m not sure the PETA position makes much sense here.

The Best Predator

This brings up a question, one that has implications in evolutionary biology. What would be the best predator? Since we have previously questioned the possibility of an impossible ideal, the best predator, or even the ‘perfect’ predator, would the optimal predator. So which of the following would that be?

1) The best predator is one that harms its prey, and diminishes its population.

2) The best predator is the one that has no impact on its prey, nor any impact on population numbers.

3) The best predator is the one that benefits its prey, and expands its numbers.

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Evolutionary biologists have traditionally focused on conflict. Darwin founded his theory of organic evolution on the concept of competition, the struggle for existence and ‘survival of the fittest.’ A lot of modern biological work continues in that tradition. With that, biologists have often struggled to build theoretical models of cooperation among unrelated organisms.

But when the only options are put in perspective, a different concept of the ‘best’ predator emerges.

The Need for Death

Death is everywhere, it is an inescapable part of life, the yang to the yin of prosperity. Given that unfortunate reality, we must conclude that the best predator is one, ironically, that helps its prey. The predator, of course, doesn’t do this consciously; it may defend a territory, keep out other predators, and thereby benefit its prey. Or perhaps, as humans do, predators preferentially hunt males, which allows populations to recover faster, and thereby support the prey. Doubtless, there are other mechanisms.

And so although the point here does not necessarily match the conventional wisdom, and although theoretical biologists are not always comfortable with the conclusion, the fact remains: the best predator, the most successful predator, is the one that helps its prey.

If our ecological models cannot explain this, then we need to retain some humility, and remember that life is more complicated than our models. Natural selection rewards the predator-prey system which can expand the fastest.

Life will often solve the problem, even if we cannot yet explain how.

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Wolves picture courtesy of Free HD Images.

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