Conservation of the Black-Tailed Prairie Dog

Saving North America's Western Grasslands

John Hoogland

• Publisher: Island Press
• Year: 2013
• Print ISBN: 9781559634984, 9781559634977
• eBook ISBN: 9781597268523
• Subtopic: Zoology

The prairie dog is a colonial, keystone species of the grassland ecosystem of western North America. Myriad animals regularly visit colony-sites to feed on the grass there, to use the burrows for shelter or nesting, or to prey on the prairie dogs. Unfortunately, prairie dogs are disappearing, and the current number is only about 2% of the number encountered by Lewis and Clark in the early 1800s.

Part I of Conservation of the Black-Tailed Prairie Dog summarizes ecology and social behavior for pivotal issues such as when prairie dogs breed, how far they disperse, how they affect other organisms, and how much they compete with livestock. Part II documents how loss of habitat, poisoning, plague, and recreational shooting have caused the precipitous decline of prairie dog populations over the last 200 years. Part III proposes practical solutions that can ensure the long-term survival of the prairie dog and its grassland ecosystem, and also are fair to private landowners. We cannot expect farmers and ranchers to bear all the costs of conservation while the rest of us enjoy all the benefits.

With 700 references, 37 tables, 75 figures and photographs, and a glossary, Conservation of the Black-Tailed Prairie Dog is a unique and vital contribution for wildlife managers, politicians, environmentalists, and curious naturalists.

CHAPTER 1

Introduction: Why Care About Prairie Dogs?

John L. Hoogland

 

 

 

 

 

Black-tailed prairie dogs—hereafter, simply “prairie dogs”—are burrowing rodents that inhabit the grasslands of western North America. Coloniality is perhaps the most striking feature of these plump, brown, non-hibernating, herbivorous squirrels that stand about 30 centimeters (12 inches) tall, weigh about 700 grams (1.5 pounds), and forage aboveground from dawn until dusk.

Whether or not one likes prairie dogs, they are hard to ignore. Their colony-sites sometimes contain thousands of residents and extend for kilometers in all directions. The vegetation at colony-sites is unusually short, because prairie dogs systematically consume or clip grasses and other herbs that grow taller than about 30 centimeters (12 inches). Colony-sites contain hundreds of large mounds—as high as 0.75 meter (2.5 feet) and with a diameter as great as 2 meters (7 feet)—that surround most burrow-entrances.

After emerging from their burrows at dawn, prairie dogs forage, fight, chase, “kiss,” vocalize, and play aboveground until they submerge for the night at dusk. Prairie dogs thus differ markedly from other burrowing mammals, such as pocket gophers and moles, which people rarely see. Further, colony-sites foster the growth of plants such as black nightshade, fetid marigold (also called prairie dog weed), pigweed, and scarlet globemallow—all of which are uncommon away from colony-sites. Finally, colony-sites attract fun-to-see animals such as American badgers, American bison, black-footed ferrets, bobcats, burrowing owls, coyotes, ferruginous hawks, golden eagles, mountain plovers, prairie falcons, pronghorn, and swift foxes.

About 200 years ago, prairie dogs inhabited eleven states, Canada, and Mexico, and their numbers probably exceeded five billion. As pioneers moved west, however, they often viewed prairie dogs as pests. Ranchers observed the reduced amount of grass at colony-sites and logically deduced that prairie dogs must compete with their livestock for food. Ranchers also concluded, again logically, that their livestock would incur leg fractures after stepping into prairie dog burrows. Farmers learned that the large mounds at burrow-entrances impede plowing and the growth of crops, and that prairie dogs sometimes eat crops.

Often with assistance from local, state, and federal agencies, ranchers and farmers have shot and poisoned billions of prairie dogs, or have converted prairie dog habitat to farmland. More recently, plague (a disease introduced into North America from Asia) has killed millions of prairie dogs, and urban development has eliminated some of the best prairie dog habitat. The current number of prairie dogs is less than 2% of the number that Meriwether Lewis described as “infinite” 200 years ago (Burroughs 1961).

Because of the drastic decline in numbers of prairie dogs over the last two centuries, the United States Fish and Wildlife Service (USFWS) concluded in 2000 that the prairie dog was a candidate species (i.e., was under consideration for the Federal List of Endangered and Threatened Wildlife and Plants (FLETWP) (Chapter 12). In 2004, USFWS reversed this decision by concluding that the prairie dog is no longer a candidate species (Chapter 12). Regardless of technical designation, the inescapable conclusion is that prairie dog populations have declined sharply over the last 200 years and are still victimized today by recreational shooting, poisoning, plague, and elimination of habitat.

“So what?” you might say. Should we care that the prairie dog, once so common, now occurs at less than 2% of its former numbers? The answer, I think, should be yes, as briefly outlined below and as further explored in the next 17 chapters.

Many people think about problems in terms of dollars and cents, so let’s talk first about the finances regarding prairie dogs. Since poisoning began in the late 1800s, thousands of people per year have worked together to eliminate prairie dogs, with a cumulative cost of billions of dollars (Chapter 8). But the financial costs of eradication often exceed the benefits (Chapters 5, 8 and 9), because: poisons and the efforts necessary to dispense them are expensive; colonies often repopulate quickly after poisoning; competition between domestic livestock and prairie dogs is sometimes insignificant; and livestock only rarely step into prairie dog burrows. Perhaps money used for widespread poisoning could be reallocated for financial compensation to those ranchers and farmers who lose money because of prairie dogs (Chapters 14 and 17). This solution would cost less than trying to eradicate prairie dogs, would satisfy most ranchers and farmers, and would allow prairie dog populations to recover.

Most people think that all organisms have the right to exist, and that deliberate eradication of any native species is unacceptable. Indeed, this reasoning was a major factor in the passage of the Endangered Species Act (ESA) and applies specifically to prairie dogs (Chapters 7, 17, and 18).

Every species affects other species, and this axiom is especially relevant for prairie dogs (Johnsgard 2005; Chapters 4 and 5). Via foraging and clipping of vegetation and the mixing of topsoil and subsoil during excavations, prairie dogs alter floral species composition at colony-sites. Their burrows and colony-sites provide shelter and nesting habitat for myriad other animals such as tiger salamanders, mountain plovers, burrowing owls, black-footed ferrets, and hundreds of insect and arachnid species.

In addition, prairie dogs serve as prey for numerous mammalian and avian predators, such as American badgers, black-footed ferrets, bobcats, coyotes, ferruginous hawks, golden eagles, and prairie falcons. Consequently, conservation is important not only for the prairie dogs themselves, but also for the many plants and animals that associate with prairie dogs and depend on them for survival. Many conservation biologists—probably most—are more concerned about the grassland ecosystem than about prairie dogs (Chapters 4, 12, 17, and 18).

Prairie dogs provide several direct benefits to humans. Many people, for example, enjoy watching them and the many other animals attracted to their colony-sites (Chapter 15). Further, laboratory research with prairie dogs has led to a better understanding of the mammalian kidney and of diseases of the human gallbladder (Chapter 18). By removing woody plants such as honey mesquite, and by improving the nutritive value and digestibility of certain grasses, prairie dogs sometimes improve the habitat for livestock (Chapter 5). Finally, because they are uniquely social, prairie dogs have helped researchers to understand perplexing issues such as inbreeding and infanticide that affect humans and other social animals (Chapters 2 and 3).

So, yes, I think that we should care that prairie dog populations have plummeted over the last 200 years. I also think that we must try to reverse this trend. For the conservation of prairie dogs, at least four aspects are noteworthy:

• Regarding natural history, we know more about prairie dogs than we do about most other species that are on, or candidate species for, FLETWP. At Wind Cave National Park, South Dakota, for example, I studied eartagged, marked prairie dogs of known ages and genealogies for 15 consecutive years (Hoogland 1995). The prospects thus are higher than usual for using information about ecology, demography, and population dynamics to formulate realistic, promising plans for conservation.
• Many endangered animals affect only a small geographic area; consequently, their impact is often localized, and sometimes almost undetectable. The prairie dog, by contrast, originally inhabited eleven states and parts of Canada and Mexico and is highly conspicuous. Its perceived impact on ranching and farming is gargantuan.
• The rarity of most endangered species has resulted, incidentally rather than deliberately, from human activities such as conversion of habitat for agriculture, suppression of fire, and construction of factories and houses. These activities also have contributed to the decline of prairie dogs, but in addition there has been a calculated war with poison that has killed billions of prairie dogs over the last 100 years (Chapters 8 and 9).
• The outlook for many endangered species is dim—indeed, almost hopeless. For prairie dogs, however, the potential for conservation is enormous. Chapter 16, for example, lists 84 potential sites for large sanctuaries. Chapters 5 and 9 suggest ways to minimize competition between prairie dogs and livestock. Chapter 11 tells us which areas are least prone to outbreaks of plague, and Chapter 3 emphasizes how prairie dogs have a knack for overcoming seemingly impossible odds.

The purpose of Conservation of the Black-Tailed Prairie Dog is threefold. In Part I, other authors and I summarize the biology and natural history of prairie dogs. To formulate rigorous plans for conservation, we need good information on issues such as when they breed, how far they disperse, how they affect other organisms, and how much they compete with livestock. In Part II, we summarize how poisoning, plague, recreational shooting, and loss of habitat have caused a precipitous decline of prairie dog populations over the last 200 years—so that we can correct these problems and avoid similar mistakes in the future. In Part III, we propose practical solutions that we hope will ensure the long-term survival of the prairie dog and its grassland ecosystem, and that also will be fair to landowners. We cannot expect farmers and ranchers to incur all the costs for the conservation of prairie dogs while the rest of us enjoy all the benefits.

PART I

Natural History of Prairie Dogs

John L. Hoogland

We cannot save an animal without knowing its biology—where it lives, what it eats, its predators and parasites, and so forth. The next four chapters summarize the natural history of prairie dogs. With this information, politicians, environmentalists, and wildlife managers will be better able to make prudent decisions about conservation.

In Chapter 2, I explain that prairie dogs are colonial, burrowing rodents. Within colonies, they live in territorial family groups called coteries, which usually contain one adult male and several genetically related adult females (mothers, daughters, granddaughters, sisters, nieces, and so forth). Because young males disperse from the natal coterie and thereby preclude matings with mothers and sisters, and because older males do not remain in the same coterie for more than two consecutive years and thereby preclude matings with daughters, incest among prairie dogs is rare. But prairie dogs regularly mate with more distant kin such as first and second cousins. Information about the prairie dog’s social organization and mating patterns leads to better conservation. When trying to establish new colonies via translocation, for example, knowledgeable wildlife managers can assemble new coteries whose ages and sex ratios resemble those of coteries under natural conditions.

Wildlife managers also benefit from knowing about the prairie dog’s demography and population dynamics, which I summarize in Chapter 3. Such information helps managers to know when livetrapping is least likely to cause unwanted mortalities or, conversely, when recreational shooting is most likely to severely reduce colony size. Because both male and female prairie dogs are able to reproduce as long as they live, managers do not need to worry that translocated prairie dogs will be too old. And because prairie dogs commonly disperse 2–3 kilometers (1–2 miles), and sometimes as far as 6 kilometers (4 miles), managers can estimate how to optimize spacing of colonies when establishing a new sanctuary—an important consideration, because new, small colonies are unlikely to persist if they are too isolated. The more we can learn about prairie dogs, the better we can conserve them.

Following the identification of the prairie dog as a keystone species about ten years ago, efforts to conserve them have skyrocketed. Amateur naturalists, conservationists, environmentalists, and wildlife managers suddenly have begun to appreciate more fully that prairie dogs affect ecological phenomena such as cycling of nutrients and minerals, and that colony-sites provide prey, shelter, and suitable habitat for hundreds of diverse organisms. The prairie dog is thus a linchpin of the grassland ecosystem of western North America. But what exactly is a keystone species? When examined closely, does the prairie dog warrant designation as a keystone species? In Chapter 4, Natasha Kotliar, Brian Miller, Richard Reading, and Tim Clark try to answer these controversial questions.

As a keystone species, the prairie dog substantially affects myriad other organisms. Kotliar et al. list numerous species that depend on prairie dogs for survival and reproduction, and they examine three species that are especially dependent: black-footed ferrets, mountain plovers, and burrowing owls. More important, these authors argue that scores of other vertebrate and invertebrate species probably also depend on prairie dogs, but that documentation of such dependence is arduous. They also emphasize that dependence varies over space and time. Finally, Kotliar et al. point out that recognition of keystone status enhances efforts to conserve not only the prairie dog, but also its grassland ecosystem.

Most ranchers think that prairie dogs compete with their livestock for forage. Do they? This is perhaps the most important and provocative question addressed in all of Conservation of the Black-Tailed Prairie Dog. In Chapter 5, Jim Detling concludes that the simple answer is yes: prairie dogs eat many of the same plants that livestock otherwise would consume. Chapter 5 thus substantiates the ranchers’ age-old disdain for prairie dogs. Especially within young colony-sites, however, vegetation often is more nutritious than vegetation on the outside. Consequently, livestock commonly prefer to feed at colony-sites, so that the net effect of competition is less than might be expe...

Table of contents

• About Island Press
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• Preface
• CHAPTER 1 - Introduction: Why Care About Prairie Dogs?
• PART I - Natural History of Prairie Dogs
• PART II - Why Have So Many Prairie Dogs Disappeared?
• PART III - Conservation of Prairie Dogs
• Appendix A. Common and Scientific Names
• Appendix B. Acronyms
• Appendix C. Calculations for Chapter 10
• Glossary
• References
• List of Contributors
• Index
• Island Press Board of Directors