Humans as "Super-Predators" – New Study Offers Startling Information about Hunting and Fishing

Bighorn sheep

A prized specimen for hunters, but how does removing the biggest and best affect the long-term health of the herd? Photo by bmass via Flickr.

Most areas of the National Park System are closed to hunting, a long-standing policy which is the subject of ongoing debate. A recently released study offers a scientific basis for the value of that policy to the overall health of both animal and plant species—and it includes some startling information about the impacts of humans as the "Super-Predators" in today's world.

I'd like to offer one disclaimer at the onset: I'm certainly not opposed to hunting, and properly-regulated hunting can be a useful wildlife management tool, especially in areas where natural predators have been removed from the equation.

That said, areas such as NPS sites where hunting is not allowed are valuable for many reasons, including the opportunities they provide for an increasingly urban population to readily observe a variety of wildlife species.

A new study in the Proceedings of the National Academy of Sciences provides an even more important reason to continue protecting wildlife and plants in parks from human predation: those populations may prove to be critical to the overall health or even the survival of some wild species.

Dr. Chris Darimont is a biologist at the University of California, Santa Cruz, and the lead investigator for the study,"Human Predators Outpace Other Agents of Trait Change in the Wild." Co-authors are five scientists from respected universities across North America.

The study looked at data on 29 species, including fish, invertebrates, mammals and plants. Several species studied are of particular interest in a number of parks: bighorn sheep, caribou, and American ginseng.

The study found that fishing and hunting, as currently managed, are causing surprisingly rapid changes in the body size of a variety of species, along with impacts on their ability to reproduce. The average body size of harvested populations was found to be 20 percent smaller than previous generations, and the average age of first reproduction was 25 percent earlier.

"By harvesting vast numbers and targeting large, reproductively mature individuals, human predation is quickly reshaping the wild populations that remain, leaving smaller individuals to reproduce at ever-earlier ages," said Darimont.

The rate of these changes was also startling. In animal and plant populations subject to human predation, observable changes were occurring three times faster than in natural systems.

Why is this a problem? Earlier breeders often produce far fewer offspring. Taken together, the "reduction in size and decrease in breeding age of fish and other commercially harvested species are potentially jeopardizing the ability of entire populations to recover."

"The pace of changes we're seeing supercedes by a long shot what we've observed in natural systems, and even in systems that have been rapidly modified by humans in other ways," Darimont noted. "As predators, humans are a dominant evolutionary force…Harvested organisms are the fastest-changing organisms of their kind in the wild, likely because we take such high proportions of a population and target the largest. It's an ideal recipe for rapid trait change."

So, what does this have to do with restrictions on hunting in most NPS areas?

I asked Dr. Darimont to comment on the idea that protected areas such as national parks can serve as reservoirs of genetic vigor and diversity for wild animals and plants, since other than losses due to poaching, the larger and older individuals are more likely to live and reproduce longer in those areas. He responded:

"Yes, protected areas, both marine and terrestrial, can safeguard fishes and mammals from potential evolutionary influences of human predation. The trick is to have them large enough to adequately protect mobile species that cannot recognize the boundaries of smaller parks or no-catch areas."

What about areas—in parks and elsewhere—where sport and subsistence hunting is allowed? You don't see many photos of proud hunters with spike bucks in hunting magazines, and conventional wisdom has been that removal of trophy-quality individuals from a population is not a problem.

This research offers a different opinion that's bound to generate some controversy—and keep in mind that the research findings deal not only with hunting, but also fishing:

"Ironically, some wildlife and fish management policies contribute to the rapid pace of trait changes. "Fishing regulations often prescribe the taking of larger fish, and the same often applies to hunting regulations," said Darimont. "Hunters are instructed not to take smaller animals or those with smaller horns. This is counter to patterns of natural predation, and now we're seeing the consequences of this management." In Alberta, Canada, for example, hunters who are permitted to target the largest specimens of bighorn sheep have caused average horn length and body mass to drop by about 20 percent during the last 30 years.

Even more startling than the reduction in size is the unexpectedly rapid rate of change in these individuals.

"The public knows we often harvest far too many fish, but the threat goes above and beyond numbers," said Darimont. "We're changing the very essence of what remains, sometimes within the span of only two decades. We are the planet's super-predator."

The findings aren't limited to animals. Dr. Paul Paquet is a biologist at the University of Calgary, and another scientist participating in the study. He notes that as ginseng is harvested in the wild, "the robustness and size of the plant is declining." Ginseng poaching has been a long-standing problem in some parks, and this study supports the need to continue efforts to control poaching in protected areas.

While subsistence poachers of wildlife are less selective when looking for meat for the freezer, those mature elk and bighorn sheep with the prized racks are prime targets for other illegal hunters. Based on this research, the impact of such trophy selection may be greater than previously believed.

There are other implications for NPS managers.

A number of parks are wrestling with how to deal with an overpopulation of deer or elk. Where that's the case, there's plenty of debate about how to reduce those numbers—and who should do the work. Should the area be opened to public hunting, or should reductions be accomplished in a more controlled manner using pre-screened and presumably better qualified hunters? Would the best results be achieved using park or other government personnel?

That debate about the "who" goes on, but if it's deemed necessary to reduce wildlife populations in some parks, this study confirms the need for careful controls on not only how many, but perhaps even more important, which animals are taken. "This should be a wake-up call for resource managers," Darimont said. "We should be mimicking natural predators, which take far less and target smaller individuals."

I asked Dr. Darimont for his opinion about managed wildlife reduction programs. He replied,

"As a general rule, we'd expect less evolutionary impact if hunting and fishing mimics natural predation. This means forgoing our typical preference for the largest and taking far fewer individuals from a population each year. But in the context of parks, instead of control efforts, I would strongly favor restoration of natural predators like wolves over lethal control by park managers."

Not all areas are good candidates for reintroduction of predators, but the findings of this research deserve careful consideration as part of the planning for any reduction programs. It will be very interesting to watch the reaction of the wildlife management and hunting and fishing communities to this study, because it clearly calls for a reexamination of some well-entrenched practices.

There's also a significant political dimension to potential changes in hunting and fishing guidelines. In parks where hunting or fishing is allowed, regulations are usually under the control of state agencies, not the NPS. There's a lot at stake in financial as well as biological terms, and if this research receives the attention it deserves, expect some monumental political battles in the years ahead.

As a minimum, this information confirms the value of continuing to protect some animal and plant populations that are as free of human interference as possible. Those populations may prove to be invaluable—and irreplaceable—reservoirs of genetic diversity and vigor.

National parks have long been valued by many as places of "wildness" (as distinguished from "wilderness.") Henry D. Thoreau's quote, "In Wildness is the preservation of the world” is a popular one with advocates of preserving natural areas for their intrinsic values. This new study of human impacts on both plant and animal populations suggests that in recognizing the values of "wildness," Thoreau seems to have been on to something.

Comments

This new study of human impacts on both plant and animal populations suggests that Thoreau was simply ahead of his time.

Thoreau was also ahead of his time politically, which statist preservationists selectively overlook. Forgive me for a partial reposting of an 18 month-old comment, but with the continued selective quoting of Thoreau, it bears repeating.

Thoreau wrote in Civil Disobedience (and I highly urge those who have recently commented about following rules to read or re-read it):

I HEARTILY ACCEPT the motto, — "That government is best which governs least"; and I should like to see it acted up to more rapidly and systematically. Carried out, it finally amounts to this, which also I believe, — "That government is best which governs not at all"; and when men are prepared for it, that will be the kind of government which they will have. Government is at best but an expedient; but most governments are usually, and all governments are sometimes, inexpedient. The objections which have been brought against a standing army, and they are many and weighty, and deserve to prevail, may also at last be brought against a standing government.

Thoreau would not approve of government land management because it's "inexpedient" (not tending to promote a purpose; not tending to the end desired; inadvisable; unfit; improper; unsuitable to time and place).

Using Thoreau, an anarchist, to support statist premises is highly absurd and anachronistic.

Frank_C:

You accurately point out the perils of taking a brief quote from any writer and applying it to another topic, so I'll happily modify my use of it slightly:

This new study of human impacts on both plant and animal populations suggests that in recognizing the values of "wildness," Thoreau seems to have been on to something.

I'll respectively decline to infer what Thoreau would or would not "approve of..." :-)

Well, if you cite Thoreau, I'll reply with Stephen Colbert: What a heck of governments have we established in Iraq and Afghanistan then.

Our society has become too complex and fractional to leave it to the "invisible hand". No one but a national government can build and maintain national infrastructure. And the small-government- (or better "starve-the-beast"-) ideology already damaged the ability to maintain this infrastructure and the infrastructure itself, from bridges to restrooms in National Parks (to finally get back to our topic here on the traveler).

"Super predator" is an unfortunate term, often applied by White Conservative ideologues to sectors of the human population (whose skin is not white) they'd prefer to see behind bars, and thus out of their consciousness. It's unfortunate when an innocuous term is hijacked like that, but still I personally wish scientists would now stop using it.
I think a better term to use is apex predator.

Apex predators are a vital part of the overall health of an ecosystem. Reintroducing gray wolves back into Yellowstone NP was arguably a very good thing for that system, if for the only reason being we took the "management" out of the process. The removal of this keystone species certainly gave us humans the opportunity to see just how drastic an effect our management decisions could have.
When wildlife managers remove apex predators from an ecosystem, within which those actors also function as keystone species, we severely alter the natural balance. Following this line of logic I would say that the human presence within an ecosystem is often too harshly examined, and altering our predatory behavior may not always be necessary.

Humans are certainly apex predators, indeed the apex predator of the planet. But are we a keystone species? I guess that depends on the particular environment/geographic area we find ourselves in at any given time, or the ideological system we live our lives by.
When utilized in solely recreational ways our predatory instinct tends to cause "imbalance". At least that's the knee jerk reaction we conservationists and preservationists have been programmed into believing, but is this always the correct conclusion? Why must we humans, with our self-assigned dominant role within the gaia, remove ourselves from the evolutionary process?
Commenting on the study, Dr. Darimont states: "We're changing the very essence of what remains, sometimes within the span of only two decades. We are the planet's super-predator." I say, so what? We are not the only apex predator at work on this planet.

Dr Darimont again: "This should be a wake-up call for resource managers," he said. "We should be mimicking natural predators, which take far less and target smaller individuals." Why??
We humans are part of nature, not above it. We are part of evolution, and sounding alarms about our effect on accelerated evolution isn't always necessary.

NPS managers have a hard enough time managing the human personnel process. Maybe they should take a step back from managing predators and see how the ecosystems correct themselves.

I'm glad to see this. As an Environmental Educator for the NPS, I often see my colleagues in state agencies pressured to present hunting as "necessary for healthy wildlife populations." I've often thought that was BS, simply a way to justify hunting - "oh the predators are gone so we must take their place." The fallacy of that argument is shown up by wildlife management practices in Alaska which include destroying wolves and other predators to establish just that "unhealthy" condition artificially. In the end, the limits of habitat, such as food, shelter, weather and disease will limit wildlife populations far better, and probably in a far healthier way, than hunting. Hunt if you must, but don't portray it as for the wildlife's benefit.

When asking whether human evolutionary impacts on other species should just be treated as another natural selective force, the question we should fundamentally be asking is whether that force is tending to undermine the broader health of the system. And I'm defining health here not in some aesthetic sense, but whether biomass and complexity are decreasing. Such a trend over time will also undermine our own health.

Biologists have shown that the extinction rate resulting mostly from our growing land use has increased 1000-fold over what they sometimes call "natural" rates, what we might here call pre-industrial rates. The effects of this apex species do not appear to be benign and something that will be just a part of the evolutionary mix over time. Was that asteroid that hit earth 65 million years ago and caused the extinction of most species "natural"? Of course. If another was heading this way and we had a chance to deflect it, should we?

Also, as to "the government that governs least, governs best" may have been commented on by Thoreau, but it was spoken by Jefferson. Bu Jefferson's belief in that motto applied to when things were going well. He supported much stronger government action if things weren't going so well. He called for high property taxes in France to deal with unused land owned by the wealthy when tenant farmers had no land. Land redistribution in such a situation would not have been so foreign to him. In the runup to the Louisiana Purchase, he knew that he did not have the authority to do it. Initially he wanted a constitutional amendment. But when told that Napoleon would not wait, and might sell it to the Spanish in the interim, he set his principles aside and bought it. He was quite pragmatic.

Jim, your article's link to the study takes you to a press release about the study, but not the actual study. Do you have a link to the actual study?

Scot -

Good question. At the time I wrote the article, I had to rely on the abstract for the study, which you'll find at http://www.pnas.org/content/early/2009/01/12/0809235106, and on e-mails with the author of the study and the press release.

There were some links on that page for some additional information in .pdf format, but they weren't loading correctly at that time, so I was reluctant to include them and have readers be frustrated.

Hope the above link will help.