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J. Range Manage.
50:459-466
Viewpoint:
The black-tailed prairie dog-headed for extinction?
GEORGE WUERTHNJ3R
The author may be reached at POB 3975, Eugene, Ore. 97403.
Abstract
The black-tailed prairie dog (Cynomys
ludovicianus) is
1 of 5
western prairie dog species, and the only species found on the
Great Plains. Some authorities believe the black-tailed prairie
dog may have been the most numerous of mammalian herbivores
found on the plains-with some estimates placing their historic
numbers as high as 5 billion. Due to a combination of factors
including habitat destruction, hunting, plague, and poisoning
programs, the black-tailed prairie dog may now be threatened
with extinction across its entire range. In this paper, a tentative
prairie dog conservation strategy consisting of core reserves,
buffer areas, and corridors is proposed.
Key Words: Great Plains, rangeland policy, extinction, prairie
dog conservation strategy
We tend to think of extinction as affecting only species that are
numerically rare, with narrow habitat preferences, or limited dis-
tribution. Yet, the black-tailed prairie dog
(Cynomys
ludoviciunus), a species that once numbered in the “billions” of
individuals, and ranged from Mexico to Canada, may be heading
toward extinction. Due to human-caused factors, black-tailed
prairie dog populations are now highly fragmented, and isolated
(Miller et al. 1994). Most colonies are small and subject to poten-
tial extirpation due to inbreeding, population fluctuations, and
other problems that affect long term population viability
(Primack 1993, Meffe and Carroll 1994, Noss and Cooperrider
1994). An additional threat is posed by sylvatic plague (Cully
1989) which, combined with other human-caused mortality, may
hasten the extirpation of the rodent from the Great Plains. Since
the turn of the century, it is estimated that prairie dog numbers
have been reduced by 98-99% of their former numbers across the
West (Miller et al. 1994). Furthermore, the loss of the prairie dog,
a keystone species, may accelerate the extinction of a host of
other dependent species (Reading et al. 1989, Miller et al. 1994,
Knowles and Knowles 1994). Even if small populations of black-
tailed prairie dogs manage to persist, their ecological-evolution-
The author wishes to thank Carolyn Cartier, Mollie Matteson, and 2 anonymous
reviewers for helpful comments on the manuscript. I also thank Tim Clark. Richard
Reading, Greg Schenbeck, Glen Plumb, Jon Shaps, and Craig Knowles for their insights
into prairie dog ecology.
Manuscript accepted 24 Aug. 19%.
JOURNAL OF RANGE MANAGEMENT 50(5), September 1997
ary influence on grassland ecosystems is now greatly diminished.
Although a number of studies document the ecological influence
of prairie dogs upon grassland ecosystems (Coppock et al. 1983a,
1983b, Hansen and Gold 1977, Koford 1958, Krueger 1986,
O’Meilia et al. 1982, Whicker and Detling 1988, Reading et al.
1989, Knowles and Knowles 1994), it is difficult to quantify how
much the present decline in prairie dog numbers has negatively
affected Great Plains ecosystem function in terms of nutrient
cycling, and plant community structure. Given their past num-
bers, prairie dogs must have been an ecological disturbance factor
at least equal to that attributed to wildfire and bison.
Noss and Cooperrider (1994) suggest that preventing “biological
impoverishment” is the goal of biological diversity preservation.
They define biodiversity as the variety of life and its processes.
Biodiversity includes the variety of living organisms, the genetic
differences among them, the communities and ecosystems in
which they occur, and the ecological and evolutionary processes
that keep them functioning, yet ever changing and adapting.
Preservation of biodiversity emphasizes native species over
exotics, and preservation of biodiversity is more than preserving
some representative individuals of a species (Noss and
Cooperrider 1994). Species must be protected in such numbers so
as to ensure they can function and participate in maintaining evo-
lutionary and ecological processes. By this definition of biodiver-
sity, black-tailed prairie dog ecosystems are already endangered,
and if current trends are not reversed, the potential even exists for
the extinction of the species altogether. Clearly, then, the dimin-
ishment of the rodent’s influence upon the Great Plains landscape
is contributing to the biological impoverishment of these grassland
ecosystems. To ensure the continuing ecological influence of
prairie dogs upon grassland ecosystems, and long-term viability of
black-tailed prairie dog populations and associated species, I pro-
pose the establishment of a prairie dog reserve system network
consisting of cores, buffers, and linkage corridors.
Basic Ecology and Description
The black-tailed prairie dog is a burrowing rodent that feeds
primarily on grasses. It is 1 of 5 prairie dog species in North
America. The 4 other species include the Mexican prairie dog
(Cynomys mexicanus),
white-tailed prairie dog (Cynomys
leucu-
rus), Gunnison’s prairie dog
(Cynomys gunnisoni),
and Utah
prairie dog
(Cynomys pan&fens).
Of the 5, the black-tailed
prairie dog is the only one found on the short and mid-grass
459
plains east of the Rockies. Black-tail prairie dogs avoid areas
with tall grass, heavy sagebrush, and other thick vegetative cover
which interfere with detection of predators (Krueger 1986, Clark
and Stromberg 1987). Historically, the species ranged from the
southern Alberta and Saskatchewan in Canada south through the
plains states to northern Mexico (Clark and Stromberg 1987).
Black-tailed prairie dogs live in family groups, protecting indi-
vidual group territories within a larger colony matrix. Although
most prairie dogs are somewhat colonial, black-tailed prairie dogs
form the largest colonies, and achieve the highest densities of the
5 species (Knowles and Knowles 1994).
Burrows are the key to prairie dog survival. They provide pro-
tection from weather, predators, and a den for young. Most social
interactions center on burrows. Burrows tend to be regularly
spaced within a colony (Knowles 1982). Prairie dog burrows are
also an extremely valuable resource for other species including
swift fox
(Vulpes
v&x), black-footed ferret (Musrelu nigripes),
burrowing owl
(Athene cunicularia),
among others, providing
shelter from weather and protection from predators. Indeed, the
occurrence of prairie dog burrows may be a key element for the
survival of many other species (Knowles and Knowles 1994).
Historical Accounts
Early historical records suggest black-tailed prairie dogs may
have been the most abundant mammals in North America at the
time of first Euro-American explorations of the West. In 1805,
while skirting the Missouri River near its confluence with the
Marias River, Meriwether Lewis, crossed a town of “barking
squirrels” or prairie dogs more than 7 miles wide. The expedition
leaders described prairie dog numbers encountered along their
journey as “infinite” (Coues 1893). Messiter (1890), traveling
through northern Montana, recorded a prairie dog colony he esti-
mated to be 3&40 miles long. One colony in the Texas panhan-
dle reported by Vernon Bailey of the U.S. Biological Survey was
an estimated 250 miles long by 100 miles wide, and may have
been home to more than 400 million prairie dogs (Davis 1974).
Merriam calculated that prairie dogs occupied some 700 million
acres of the West in the late 1800’s (Cully 1989). Seton (1929)
judged that the combined North American population of all
prairie dogs exceeded 5 billion individuals. As late as 1900, 100
million acres were occupied by prairie dogs (Knowles and
Knowles 1994).
Whether all of these estimates are accurate is not important.
Almost no one disputes that prairie dogs were once extremely
common, and found throughout the plains. And today, in many
parts of the West you can survey hundreds of miles of potential
prairie dog habitat, and never see a single individual.
Relationships to Other Herbivores
Prairie
dogs
are considered “pests” by some agricultural inter-
ests. They qualify as “varmints” in nearly all states where they are
found, and most states provide no legal protection. Thus far, 2 of
the 5 prairie dog species have achieved some protection under the
Endangered Species Act, but only after they had approached the
brink of extinction.
Ever since Merriam (1902) estimated that prairie dogs reduced
range productivity X&75%, there has been a perception among
livestock producers that prairie dogs compete with domestic live-
stock for forage (Clark 1989). Areas in and around prairie dog
colonies often look “overgrazed” with an abundance of bare soil,
little litter, and a carpet of short, heavily cropped vegetation.
Long term occupancy on a site by prairie dogs can shift vegeta-
tive communities from dominance by climax perennial grasses to
early serial stages characterized by forbs and annuals. This con-
tributes to the impression among livestock operators that prairie
dogs degrade rangelands (Knowles and Knowles 1994).
Ironically, heavy grazing by livestock, as well as some facets of
livestock production, can lead to an expansion in prairie dog
numbers (Knowles 1985, Knowles 1986a). The shorter grasses
and bare dirt that result from heavy grazing favors prairie dog
colony enlargement by removing tall vegetation which otherwise
limits the rodent’s ability to see predators (Coppock et al. 1983a,
1983b).
However, even where prairie dog numbers do increase, they
may not pose a threat to livestock production as presumed.
Continual cropping by prairie dogs, particularly on recently colo-
nized sites, tends to maintain high forage quality, and produces
plants with greater palatability than non-prairie dog sites
(Krueger 1986, Whicker and Detling 1988). Such sites are attrac-
tive to cattle as well as a host of other grazing species such as
bison (Bison) elk (Cervus e&&us), and antelope
(Antilocupra
americana)
(Coppock et al. 1983a, 1983b, Knowles 1986a,
Krueger 1986).
Whether or not prairie dogs are actually competitors with
domestic animals, there is overlap in diet. Under normal circum-
stances, prairie dogs consume 18-37% of the vegetation in the
immediate vicinity of their colonies (Hansen and Gold 1977,
O’Meilia et al. 1982, Knowles 1986a), although there are a few
cases where herbivory can reach 80% vegetation loss by the end
of the summer (Knowles and Knowles 1994). In extreme cases,
cattle herbivory, combined with cropping of plants by prairie
dogs, can remove a substantial portion of the vegetation on small
vegetation patches, achieving a utilization level of 90% by the
end of a growing season (Knowles 1986a). Other studies have
shown that forage consumption of 300 prairie dogs equal that of 1
cow and calf (Miller et al. 1994). Hansen and Gold (1977) con-
cluded prairie dogs within a short grass ecosystem may depress
habitat suitability for cattle grazing. Although there may be less
forage left on a prairie dog town, the higher nutritional level typi-
cally results in no net loss of weight or decline in weight gains
among livestock utilizing such areas (O’Meilia et al. 1982).
In a review of prairie dog literature, Knowles and Knowles
(1994) could find no documented evidence that prairie dogs com-
pete with domestic livestock under densities typically encoun-
tered on the Great Plains (~10% of the area occupied), and they
conclude that competition in rangeland situations would be
minor.
Whatever forage competition may exist between prairie dogs
and domestic livestock must be balanced against the fact that the
plains once supported an untold number of bison, antelope, elk,
deer
(Odocoileus
sp.), and bighorn sheep
(Ovis cunudensis
sp.),
not to mention other smaller herbivores, in spite of, or perhaps
because of, the presence of billions of prairie dogs.
Prior to their eradication from the plains, there appears to have
been a mutually beneficial relationship between bison and prairie
dogs, and to a lesser degree, antelope (Krueger 1986), and elk
(Knowles 1986a). Bison tend to forage on the edges of active
prairie dog towns (Krueger 1986) where they focus grazing on
460 JOURNAL OF RANGE MANAGEMENT 50(5), September 1997
the succulent, nutritious growth found there (Coppock et al.
1983b), while antelope selected the centers of dog towns
(Krueger 1986), thus spatially dividing up forage resources. The
grazing of coarse tall grasses by bison on the fringes of colonies
increased prairie dog habitat and aided dispersal (Coppock et al.
1983b). There is even evidence that suggests the decline of bison
brought about a reduction and even extirpation of some prairie
dog colonies in tall grass locations (Osbom and Allan 1949).
However, on short-grass plains, prairie dogs persist even in the
absence of cattle or bison.
Trampling and grazing of taller vegetation by livestock can aid
dispersal and expansion of prairie dog colonies (Knowles 1985,
Knowles 1986a). Livestock are not, however, an ecological ana-
logue for bison under most conditions. Bison utilize the land-
scape in profoundly different w,ays than cattle. Bison move more
frequently (Norland 1984). and are less likely to spend time in
riparian areas (Van Vuren 1984). Bison originally ranged in huge
herds over vast areas, thus distributing grazing pressure different-
ly than continuous, confined grazers can. Bison tend to utilize dry
uplands-the preferred habitat of prairie dogs-more than cattle,
and wander further from water supplies (Plumb and Dodd 1993,
Peden et al. 1974, Lott 1991). Hence, bison may create more
prairie
dog
habitat than water-dependent cattle in the prairie dog’s
preferred short-grass environment as well as aid in creation of
dispersal corridors. A shifting mosaic of disturbed habitat patches
created by the interaction of periodic wildfires, often combined
with intense localized grazing by bison and prairie dogs most
likely existed in the pre-settlement era (Coppock and Detling
1986) that is not emulated by most current livestock grazing sys-
tems.
Factors Responsible for Prairie Dog Decline
There are 3 major factors implicated in prairie dog decline
across their range: rodent poisoning programs, habitat loss, and
sylvatic plague. In many areas, all 3 work synergistically to place
prairie dog populations at risk.
Control Programs
The widespread perception among livestock operators that
prairie dogs compete with domestic animals for forage has led to
control programs throughout their range for nearly a century. The
primary control mechanism is poisoning, however, there is evi-
dence to suggest such control programs are not cost-effective
(Collins et al. 1984).
In the past the favored control method was the use of grain
soaked in strychnine. Between .1903 and 1912, strychnine soaked
grain reduced Colorado’s prairie dog population by an estimated
91% (Clark 1989). But that was just the beginning of extermina-
tion efforts. Clark (1989) recounts that ranchers in Colorado dis-
tributed enough poison between 1912 and 1923 to kill an addi-
tional 31 million prairie dogs. More than 400,ooO ha of prairie
dog colonies were poisoned in eastern Wyoming between 1915
and 1927 (Clark 1989).
The favored poison of today i.s zinc phosphide. After treatment
with zinc phosphide, a 95% reduction in active prairie dog bur-
rows was achieved in one South Dakota study (Apa et al. 1990)
and in Montana Knowles (1986b) reported an 85% reduction in
prairie dog numbers after poison treatment.
In some states such as Nebraska and Kansas, landowners are
forced to carry out control efforts or suffer fines. Poisoning is
usually carried out under supervision of Animal Damage Control
(Animal Damage Control Program 1990). Control is pursued on
both private lands as well as federal holdings. Prairie dog extirpa-
tion efforts are not confined to multiple use BLM and Forest
Service lands. Poisoning is also common on Indian reservations,
wildlife refuges, and in some national parks. For example,
between 1980 and 1984 some 185,600 ha of prairie dog towns on
the Pine Ridge Indian Reservation in South Dakota were poi-
soned (Hansen 1988). Poisoning programs are also an on-going
effort in national park units such as Wind Cave, Devil’s Tower,
and others (NPS personal comm. 1994). Prairie
dogs
were poi-
soned in Badlands National Park until 1993-the year prior to the
recent reintroduction of the black-footed ferret (Wilkinson 1994).
Habitat Losses
The plowing of millions of acres of the plains for wheat and
other grain production has also destroyed prairie dog colonies
(Knowles and Knowles 1994). For example, in Montana approxi-
mately 18 million acres, much of it former grassland, is reported
as cropland (Montana Ag. Statistics 1992). Similar habitat losses
have occurred in other Great Plains states as a consequence of
farming.
Sylvatic Plague
A third factor contributing to population decline has been syl-
vatic plague (Yersinia pestis). Fleas carry the bacterial disease
and spread it through prairie dog colonies. Deer mice, among
other species, are suspected to be the maintenance host for the
disease (Cully 1989).
The disease was first documented in the United States in 1899
(Cully 1989). Prairie dogs are highly susceptible to the plague
(Lechleitner et al. 1968). Even isolated colonies can suffer sub-
stantial declines as a consequence of plague (Zeveloff and Collett
1988, Clark 1989, Cully 1989). There appears to be little or no
immunity to the disease among prairie dogs and mortality is near-
ly 100% (Knowles and Knowles 1994).
Consequences of Population Fragmentation and
Potential Extinction
Not only is the long term viability of black-tailed prairie dog in
jeopardy, but due to the close dependency of a host of other
species, the demise of the prairie dog could bring about the
reduction or even extinction of many associated species
(Knowles and Knowles 1994, Biodiversity Legal Foundation
1994, Miller et al. 1994).
Many other species are dependent upon prairie dogs and their
burrow systems for habitat (Clark et al. 1982). Clark (1989)
reports that more than 163 vertebrate wildlife species depend on,
or are found in close association with prairie dog colonies. No
one has yet attempted to determine how many invertebrate
species also depend upon prairie dog ecosystems, although 1
study concluded that harvester ants appeared to be slightly
JOURNAL OF RANGE MANAGEMENT 50(5), September 1997 461
favored by the presence of prairie dogs (O’Meilia et al. 1982).
Grasslands ecosystems with prairie dogs had higher numbers of
small mammals, more terrestrial predators, higher avian species
diversity, and higher avian density than found on grasslands with-
out (Hansen and Gold 1977, O’Meilia et al. 1982, Reading et al.
1989, Miller et al. 1994). Thus the documented extirpation and/or
decline of prairie dog populations across the West has resulted in
a significant biological impoverishment and loss in the biological
diversity of grasslands ecosystems.
Of even greater concern, is the mounting evidence that prairie
dogs
are a “keystone species”. Their decline and potential extinc-
tion may cause secondary extinctions among other species whose
existence hinges on maintaining viable prairie dog populations
throughout its range (Knowles and Knowles 1994, Miller et al.
1994).
Among the most endangered of prairie dog dependent species
is the black-footed ferret (Mustela
nigripes),
classified as an
endangered species and 1 of the rarest mammals in the world.
Today fewer than 400 ferrets remain. To give an indication of
how severe the decline in ferrets has been, Clark (1989) estimates
that given the population densities found in relict wild popula-
tions in the early 1980’s, as many as 1 million ferrets may have
lived on the plains at the turn of the century.
The ferret is intricately tied to prairie dogs. Prairie dogs make
up 90% of the ferret’s diet (Knowles and Knowles 1994). Equally
important for black-footed ferret survival are the availability of
prairie dog burrows as shelter from the weather and as escape
cover. The ferret is totally dependent upon a high density of bur-
rows for escape from other predators (Clark 1989).
A similar decline has occurred in swift fox, once common on
grasslands throughout the plains. The fox is now extinct in
Montana, and rare in much of its former range (Knowles and
Knowles 1991). Poisoning programs aimed at coyotes (Canis
latruns),
along with the conversion of native habitat to croplands,
are likely the major factors originally responsible for the foxes’
decline (Knowles and Knowles 1991), but the loss of prairie dogs
has had ecological consequences for the fox as well. Foxes con-
sume prairie dogs, and rely upon the abundance of burrows to
hide from predators such as coyotes. In areas where prairie dogs
or other burrowing animals are absent, reintroduced swift foxes
have never successfully maintained themselves (Knowles and
Knowles 1994).
Burrowing owls also depend upon prairie dogs not only for
food, but their burrows for shelter. Early travelers on the Great
Plains continuously remarked about the abundance and close
association between these small owls and prairie dog colonies.
Owl numbers have declined significantly throughout the region
where prairie dogs have disappeared (Knowles and Knowles
1994).
Mountain plover
(Charudrius montunus),
currently a candidate
for listing under the Endangered Species Act (ESA), relies upon
prairie dogs for creation of the short grass nesting habitat
(Knowles and Knowles 1994). Knowles and Knowles (1984)
found that the continued existence of the mountain plover in
Montana was dependent upon availability of native grasslands
with areas of low growing vegetation such as that afforded by
prairie dog towns. There also may be a relationship between the
insects this bird consumes and dog colonies. Some scientists
speculate that insect abundance is greater, or insects are more
easily captured
by
mountain plover due to high visibility on
prairie dog colonies (Olson 1985).
The ferruginous hawk
(Buteo regalis)
is another ESA category
2 candidate species linked to prairie dogs. The hawk specializes
in hunting ground dwelling rodents including prairie dogs. The
hawk sits next to a burrow waiting for an animal to emerge and
then captures it (Knowles and Knowles 1994).
Current Status of Prairie Dogs
The most southerly species is the Mexican prairie dog
(Cynomys mexicanus).
It is distributed south of the border in
Mexico. Little is known of its status.
The Utah prairie dog
(Cynomys parvidens),
found only in
southwest Utah, historically had the most restricted distribution.
In 1920 there was an estimated population of 95,000 of this
species. However by 1976 poisoning programs, along with dis-
ease, had reduced them to only 3,500 individuals (Zeveloff and
Collett 1988).
Gunnison’s prairie dog
(Cynomys gunnisoni),
has a center of
distribution located in the Four Comer’s region of New Mexico,
Colorado, Utah and Arizona. Due to poisoning programs and
plague, their numbers also have declined precipitously (Zeveloff
and Collett 1988).
The white-tailed prairie dog
(Cynomys leucurus),
is the largest
of the prairie dogs. It sports a short, white-tipped tail that looks as
if it were “dipped in paint.” The white-tailed prairie dog inhabited
much of western Wyoming and adjacent portions of northeast
Utah and northwest Colorado. A small part of its range also
extended into southern Montana just south of Billings, Montana
(Zeveloff and Collett 1988).
Status of the Black-tailed Prairie Dog by State
Arizona
The black-tailed and Gunnison’s prairie dogs both inhabited
Arizona. Historically, the black-tailed prairie dog ranged from the
Sulphur Springs Valley to the Mexican border in the southeast
comer of the state. Black-tailed were completely extirpated from
the state by 1938. The Arizona Game and Fish has considered
reintroduction of the species, but thus far has been stymied in its
efforts by opposition from the livestock industry (Biodiversity
Legal Foundation 1994).
Colorado
Colorado was one of the few western states to have 3 of the 5
species of prairie dogs recorded within its borders. The white-
tailed prairie dog was found in the northwest part of the state,
Gunnison’s was distributed in the southwest comer, and black-
tailed prairie dogs were found on the eastern plains (Zeveloff and
Collett 1988, Clark 1989).
According to Clark (1989) poisoning efforts were widespread
and successful in Colorado. In 1903 an estimated 1.2 million ha
of the state’s plains were inhabited by black-tailed prairie dogs.
By 1912, the prairie dogs were reduced by 91%. There are no
current state-wide population estimates, although it is thought
that prairie dog numbers are significantly reduced from earlier
estimates (Biodiversity Legal Foundation 1994).
Colorado still allows recreational and competition shooting of
prairie dogs, and provides directions to prairie dog towns
(Biodiversity Legal Foundation 1994). Poisoning efforts continue
in the state as well (Miller et al. 1994).
462 JOURNAL OF RANGE MANAGEMENT 50(5), September 1997
KaIlS3.S
Prairie dogs once ranged across most of western Kansas.
However their numbers have been severely reduced. Vanderhoof
and Robe1 (1992) report: “Lantz (1903) estimated that prairie dog
towns covered 1 million ha of Kansas in 1902 whereas
Henderson and Little (1973) estimated that only 15,000 ha of
prairie dog towns existed in Kansas in 1973. Despite this decline
some Kansas counties still conduct mandatory control programs
(Kansas Dept. Wildlife and Parks 1994).
Montana
In Montana the black-tailed prairie dog was once found
throughout the high plains east of the Continental Divide.
Populations have been significantly reduced throughout the state,
although there are no current estimates of numbers. The largest
prairie dog complex in the state lies north of the Missouri River
on the Charles M. Russell National Wildlife Refuge, and adjacent
BLM lands. However, the recent spread of plague throughout the
state has led to documented declines in affected colonies
(Knowles and Knowles 1994).
Nebraska
Prairie dogs once ranged across most of Nebraska and today
are found in the western half. Prairie dogs are found in 60 of
Nebraska’s 93 counties (Nebraska Game and Parks Commission
1993). Conversion of lands to crops, as well as poisoning efforts,
have drastically reduced their numbers.
New Mexico
Both the Gunnison and black-tailed prairie dog are found in
New Mexico. The Gunnison is confined to the northwest comer,
while the black-tailed was found across the eastern and southern
portions of the state and was particularly numerous east of the
Rio Grande River. In 1908, Vernon Bailey, working for the US
Biological Survey traveled between Deming and Hachita, by way
of the Animas and Playas valleys, and reported encountering 1
continuous prairie dog town. Bailey estimated the town contained
6.4 million animals (Findley 1987). In numerous trips through the
region between 1955 and 1972, biologists working for the
Museum of Southwestern Biology failed to record a single prairie
dog (Findley 1987).
The species is still found in northeastern New Mexico in small
numbers, but has apparently been extirpated from southwestern
New Mexico due to poison programs (Biodiversity Legal
Foundation 1994).
North Dakota
Prairie dogs once were numerous across North Dakota. Control
efforts began in the early 1900’s and have continued into the pre-
sent. Bishop and Culbertson (1976) conducted a study of prairie
dog town size in the western part of the state between 1933 and
1972 using air photos and reported an 89% decline during this
period. The largest prairie dog populations are centered on the
Little Missouri National Grassland and adjacent parts of
Theodore Roosevelt National Park.
Oklahoma
Prairie dogs once ranged throughout the western half of the
state, although today most towns are in the panhandle region.
Conversion of lands to crops, along with poisoning programs and
plague, are the main threat to prairie dogs in the state (Oklahoma
Dept. of Wildlife Conservation 1993).
South Dakota
Prairie dogs once occupied millions of hectares in South
Dakota and currently occupy about 100,000 ha in the state (South
Dakota Dept. of Game, Fish and Parks 1993). The largest
colonies are found on the Buffalo Gap National Grassland and
adjacent parts of Badlands National Park. Sizable colonies also
exist on the Pine Ridge Indian Reservation.
In South Dakota, prairie dogs are classified as a “pest” and if a
colony expands onto adjoining lands, the owner of the spreading
colony can be forced to poison the prairie dogs (Biodiversity
Legal Foundation 1994).
Texas
Prairie dogs were found across the Trans Pecos, Edwards
Plateau, and Panhandle regions of Texas. Vernon Bailey recorded
a nearly continuous prairie dog town at the turn of the century
that stretched for 100 miles by 250 miles that had an estimated
400 million inhabitants (Davis 1974). In total, Bailey thought
there might be 800 million of the rodents in Texas (Biodiversity
Legal Foundation 1994). By 1975 approximately 2.2 million
black-tailed prairie dogs were estimated to remain in Texas.
Wyoming
The original range of the black-tailed prairie dog in Wyoming
encompassed most of the eastern portion of the state. Cheyenne is
built on an old prairie dog colony (Clark and Stromberg 1987).
According to the Bureau of Land Management, the black-tailed
prairie dog still occurs throughout its historic range but in signiti-
cantly reduced numbers (Biodiversity Legal Foundation 1994).
Clark and Stromberg (1987) estimated that black-tailed prairie
dogs had been reduced by 80% across their Wyoming range. The
largest prairie dog colonies are found on the Thunder Basin
National Grassland. The state of Wyoming manages the black-
tailed prairie dog as a regulated non-game species.
Protection Efforts
Some biologists are speculating that without remedial action,
the black-tailed prairie dog may be headed towards extinction
(Miller et al. 1994). In late 1994, the Biodiversity Legal
Foundation, and wildlife biologist Jon Sharp, filed a petition with
the U.S. Fish and Wildlife Service to list the black-tailed prairie
dog as a category 2 Candidate species under the Endangered
Species Act (Biodiversity Legal Foundation 1994). The USFWS
recently rejected the petition listing, however, the petitioners plan
to challenge the finding in court (Per. corn. Biodiversity Legal
Foundation 1996).
The black-tailed soon may join the fate of the other 4 prairie
dog species, which are already so reduced in numbers and distrib-
ution that both the Mexican and the Utah prairie dogs are listed
under the Endangered Species Act, and some biologists believe
the white-tailed and Gunnison’s also qualify for listing
JOURNAL OF RANGE MANAGEMENT 50(5), September 1997 463
(Biodiversity Legal Fund 1994). Even if the species doesn’t dwin-
dle to extinction, given their past influences upon grasslands
ecosystems, it can be argued that the dramatic decline of black-
tailed prairie dogs across their formal ranges has already led to
biological impoverishment of the grassland ecosystem.
Conservation Strategies
Traditionally we have focused our wildlife conservation efforts
on too small temporal and spatial scales. This wasn’t a problem
when human influences on the ecosystem and wildlife numbers
were minimal. However, human impacts now limit the number
and size of prairie dogs populations. Many barriers prevent dis-
persal. This, coupled with continued prairie dog control, has
resulted in population fragmentation that now threatens black-
tailed prairie dog viability across its historic range (Miller et al.
1994).
Small, isolated populations are more susceptible to a variety of
extinction factors, including decreased genetic variability
(Wilcove et al. 1986, Schonewald-Cox and Bayless 1986, Noss
and Cooperrider 1994, Meffe and Carroll 1994). Small popula-
tions, because of random variability in demographics are more
likely to become extinct than larger populations (Meffe and
Carroll 1994). The cumulative effects of all these variables
increases the likelihood of extinction (Noss and Cooperrider
1994).
At present there is no coordinated effort to preserve prairie
dogs. Indeed, most current public policy can be characterized as
detrimental to the long-term viability of prairie dog ecosystems.
An important immediate research need is the development of
population viability analysis for prairie dogs, as well as depen-
dent species like the black-footed ferret (Meffe and Carroll
1994). Determination of a “minimum dynamic area” (Noss and
Cooperrider 1994) defined as the smallest area which maintains
internal recolonization sources, should be defined for colony
complexes.
It would be prudent to develop a system of biological reserves
across the prairie dog’s historic range modeled after Noss and
Cooperrider (1994). A reserve system of prairie dog colony com-
plexes may reverse the downward decline of black-tailed prairie
dog populations, avoiding ecological “train wrecks” in the future.
Implementation of such a reserve system would be a pro-active
response to the current threats to the species population viability,
and may preclude future listing of the black-tailed prairie dog
under the ESA.
Core Reserves
A conservation strategy for black-tailed prairie dog should
include protected core reserves as described by Noss, (1992) con-
sisting of several interconnected prairie dog colony complexes.
Core reserves must be of sufficient size to maintain viable popula-
tions of prairie dogs as ecologically and evolutionary functional
units over a time frame of at least a hundred years (Meffe and
Carroll, 1994.) Core areas should be maintained in their natural
state with natural disturbance events permitted or mimicked
through management (Noss and Cooperrider 1994). This will
require core reserves large enough to maintain a minimum dynam-
ic area of continuously shifting patches of disturbance associated
with wildfire, heavy grazing by large herbivores like bison, prairie
dog colony abandonment, expansion, and colonization.
Size and density of colonies is critical. Large colony complexes
should be encouraged. Research has demonstrated a direct corre-
lation between species richness among associated vertebrate
species and colony size. Regional colony density also influences
the abundance of prairie dog associated species (Reading et al.
1989). For example, more bird species were sighted on larger
colonies than smaller ones, and among higher density colony
complexes (Reading et al. 1989).
Core reserves should be located within national parks, wildlife
refuges, BLM lands, National Forest lands, National Grasslands,
and other federal and state holdings. Coordination and coopera-
tion between various agencies will be necessary.
Given the reciprocal relationship between prairie dogs and larg-
er native herbivores, reintroduction of associated ungulates like
bison, elk, and antelope should be given serious consideration.
By definition the absence of these important ecological processes
and species from most grasslands equates to a loss in biodiversity
(Noss and Cooperrider 1994).
We should eliminate all poisoning programs or other human-
caused sources of mortality until populations recover to viable
levels for prairie dogs and dependent species.
The needs of dependent species such as the black-footed ferret
must be considered. Colony complexes large enough to maintain
metapopulations of prairie dogs, may not be of sufficient size to
maintain viable populations of predators like black-footed ferrets.
Predators occur at much lower densities than herbivores like
prairie dogs, and maintaining viable populations may require core
areas much larger than all but a few remaining natural grassland
ecosystems in the West.
Buffer Areas
Core areas should be surrounded by appropriately managed
buffer zones (Noss and Cooperrider, 1994). Some human-activi-
ties, such as limited livestock production, oil and gas develop-
ment, and other human resource use may be permitted in buffer
zones, but should be compatible with the long term viability of
prairie dog populations and native biodiversity concerns. Under
certain circumstances, grazing by livestock may be used as a tool
to enhance prairie dog colony expansion (Knowles 1986b).
Noss (1992) identified 4 major functions for buffer zones.
1. Ameliorate physical and biotic edge effects.
2. Protect core reserves from hunting, poisoning, and other
harmful human activities that would otherwise be intense
near reserve boundaries.
3. Provide supplementary habitat to native species to increase
population size and viability.
4. Provide connectivity for movement among reserves.
Even within buffer zones, prairie dog control efforts and other
negative human intrusions should be limited.
Connecting Linkages
Corridors are designed to provide dispersal and movement
between core areas. They may also provide critical habitat require-
ments. Prairie dogs typically use trails, roadways, and other linear
pathways for dispersal (Knowles 1985, Knowles 1986b). Ideally,
some corridors will be maintained by native species such as bison
whose trails historically facilitated movement between prairie dog
colonies. However, roadways with mowed right-of-ways may also
serve as functional dispersal corridors.
464 JOURNAL OF RANGE MANAGEMENT 50(5), September 1997
Table 1 Potentially suitable for black-tailed prairie dog core reserve
complexes.
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
Little Missouri National Grasslands and Theodore Roosevelt
National Park, North Dakota.
Buffalo Gap National Grassland, Badlands National Park, and Pine
Ridge Indian Reservation, South Dakota.
Wind Cave National Park, Custer State Park, Black Hills National
Forest, South Dakota.
Thunder Basin National Grasslands, Black Hills National Forest,
and Devil’s Tower National Monument, Wyoming.
Oglala National Grassland and Nebraska National Forest in
Nebraska.
Pawnee National Grassland, Colorado.
Comanche National Grassland, Colorado.
Cimarron National Grassland, Kansas.
Kiowa National Grassland, Colorado and Rita Blanca National
Grassland, Texas.
Black Kettle National Grassland, Oklahoma.
Charles M. Russell National Wildlife Refuge, adjacent BLM lands,
and Fort Belnap Indian Reservation in central Montana.
Ashland District of Custer National Forest, adjacent BLM lands,
Crow Indian Reservation, and Northern Cheyenne Indian
Reservation in Southeast Montana. M. Wichita Mountains National
Wildlife Refuge, Oklahoma. Cooperation of individual Indian
Tribes would he necessary on reservation lands.
Major highways and interstates present a significant barrier to
dispersal. At present, the amount of traffic on most of the region’s
interstate highways may not hinder movement by rodents.
Nevertheless, it is possible that the day will come when even the
wide-open spaces of the plains will experience increased traffic.
The placement of bridges over suitable natural habitat may permit
continued movement, despite the barrier posed by highways as
has been done in Florida to allow for movement of the Florida
panther and other wildlife. However, in some areas it may be nec-
essary to physically transport prairie dogs across such barriers to
facilitate genetic exchange between metapopulations.
While linkages between major prairie dog colonies is generally
desirable, corridors can also facilitate the transfer of sylvatic
plague from colony to colony. Thus, maintaining some physically
isolated colonies within core reserves and buffer zones may be
desirable. There is also value in maintaining some isolated popu-
lations which may have genetic and evolutionary significance for
the species (Noss and Cooperrider 1994).
In order to create such a reserve network, all existing public
and private lands should be inventoried for the existence of
prairie dog colonies, and/or their potential ability to support
viable prairie dog populations. Suitable buffer
zones and corri-
dors should be mapped and protected. Since concerns over the
effect of prairie dogs upon private lands is a major driving force
behind control programs, checkerboard ownership patterns of
mixed public and private lands hinder conservation efforts.
Acquisition of critical private holdings within or adjacent to large
public land by trade or from willing sellers should be pursued.
All of this will require a change in current prairie dog manage-
ment including the elimination of most poisoning programs, a
reduction in hunting, and protection of suitable habitat in core
and buffer areas from further destruction by agriculture, highway
construction, and other unsuitable development.
There is evidence that some other rodent species have devel-
oped resistance to plague (Cully 1989). It may be possible to has-
ten the evolution of plague-immune prairie dogs through labora-
tory intervention and captive breeding programs. Due to the rapid
reproduction capacity of prairie dogs, the introduction of geneti-
cally immune individuals into prairie dog populations would
eventually confer a degree of resistance to this disease to prairie
dog populations throughout the West. This, more than any other
factor, might be key to protecting the long-term viability of
prairie dog ecosystems in the West.
Given the current status of the black-tailed prairie dog, failure
to act will likely result in the extirpation of the species across
most of its range, not to mention the extinction of numerous
dependent species. A pro-active establishment of a reserve net-
work can reverse this trend, and ultimately provide for the preser-
vation of the Great Plains Ecosystem.
Literature Cited
Animal Damage Control Program. 1990. Animal Damage Control
Program Draft Environmental Impact Statement. USDA Animal and
Plant Health Inspection Service. Washington, D.C.
Apa, A.D., D.W. Uresk, and R.L. Lander. 1990. Black-tailed prairie
dog populations one year after treatment with rodenticides. Great
Basin Natur. 50:107-l 13.
Biodiversity Legal Foundation. 1994. Petition to classify the black-
tailed prairie dog (Cynomys ludovicianus) as a Category 2 Candidate
species. Office of Endangered Species. U.S. Fish and Wildl. Service.
Washington, D.C.
Bishop, N.G. and J.L. Culbertson. 1976. Decline of prairie dog towns
in southwestern North Dakota. J. Range Manage. 29:217-220.
Clark, T.W., T.M. Campbell, D.G. Socha, and D.E. Casey. 1982.
Prairie dog colony attributes and associated vertebrate species. Great
Basin Natur. 42572-582.
Clark, T.W. 1989. Conservation Biology of the Black-footed Ferret.
Wildlife Preservation Trust International. Philadelphia, Penn.
Clark, T.W. and M.R. Stromberg. 1987. Mammals in Wyoming.
University Press of Kansas, Lawrence, Kan. 3 14pp.
Collius, A.R., J.P. Workman, and D.W. Uresk. 1984. An economic
analysis of black-tailed prairie (Cynomys
ludovicianus)
control. J.
Range Manage. 37:358-361.
Coppock, D.L., J. F. EUis, J.K. DetIing, and M.I. Deyer. 1983a Plant-
herbivore interactions in a North American mixed grass prairie.1.
Effects of black-tailed prairie dogs on intraseasonal above ground plant
biomass and nutrient dynamics and plant species diversity. Oecologia
56: 1-9.
Coppock, D.L., J.F. EIIis, J.K. Detting, and M.I. Deyer. 1983b. Plant-
herbivore interactions in a North American mixed-grass prairie. II.
Responses of bison to modification of vegetation by prairie dogs.
Oecologia 56:1&15.
Coppock, D.L. and J.K. Detting. 1986. Alteration of bison and black-
tailed prairie dog grazing interaction by prescribed burning. J. Wildl.
Manage. 50~452-455.
Coues, E. 1893. The History of the Lewis and Clark Expedition. Vol. 1.
Ed. by Elliot Coues. Dover Books. N.Y.
Gully, J.F. 1989. Plague in prairie dog ecosystems: Importance for
black-footed ferret management. In The prairie dog ecosystem:
Managing for Biol. Diversity. Montana BLM Wild]. Tech. Bull. No. 2.
Davis, W.B. 1974. The Mammals of Texas. Texas Parks and Wildlife
Dept. Bull. 41. Austin, Tex.
Findley, J.S. 1987. The Natural History of New Mexican Mammals.
Univ. of New Mexico Press. Albuquerque, N.M.
Hansen, R. M. and I. K. Gold. 1977. Black-tail prairie dogs, desert cot-
tontails and cattle tropic relations on short grass range. J. of Range
Manage. 30:21&213.
JOURNAL OF RANGE MANAGEMENT 50(5), September 1997 465
Hansen, R. 1988. A chronology of prairie dog control operations and
related developments in South Dakota. Eight Great Plains Wildlife
Damage Control Workshop Proc. Rapid City, S.D. US Forest Service;
Washington, D.C.
Kansas Dept. of Wildlife and Parks. 1994. Petition to classify the
Black-tailed Prairie Dog (Cynomys ludovicianus) as a Category 2
Candidate species. In Biodiversity Legal Foundation; Boulder, Colo.
Knowles, CJ. 1982. Habitat affinity, populations, and control of black-
tailed prairie dogs on the Charles M. Russell National Wildlife Refuge.
Ph.D. Dissertation. Univ.of Montana. Missoula, Mont.
Knowles, CJ. 1985. Observations on prairie dog dispersal in Montana.
Prairie Nat. 17:334.
Knowles, C J. 1986a. Some relationships of black-tailed prairie dogs to
livestock grazing. Great Basin Nat. 46202-206.
Knowles, C J. 1986b. Population recovery of black-tailed prairie dogs
following control with zinc phosphide. J. Range Manage. 39:249-251.
Knowles, C J. and P.R. Knowles. 1984. Additional records of mountain
plovers using prairie dog towns in Montana. Prairie Nat. 16: 183-l 86.
Knowles CJ. and P.R. Knowles. 1991. Au ecological and taxonomic
review of the swift fox (Vulpes velox), with special reference to
Montana. Montana Dept. of Fish, Wiidl. and Parks. Helena,Mont.
Knowles CJ. and P.R. Knowles. 1994. A review of Black-tailed prairie
dog literature in relation to rangelands administered by the Custer
National Forest. USDA Custer National Forest; Billings, Mont.
Koford, C.B. 1958. Prairie dogs, whitefaces, and blue grama. Wildl.
Mono. 3.
Krneger, Khxten. 1986. Feeding relationships among bison, pronghom,
and prairie dogs: an experimental analysis. Ecol. 67:760-770.
Lechleitner, RR., I. Kartman, M.I. Goldenherg and B.W. Hudson.
1968. An epizootic of plague in Gunnison’s prairie dogs (Cynomys
gzmnisoni) in south-central Colomdo. Ecol. 49:734-743.
Lott, D.F. 1991. American bison so&ecology. Applied Animal Behav.
Sci. 29135-145.
Me&, G.K. and CR. CarrotI. 1994. Principles of conservation biology.
Sinauer Associates. Sunderland, Mass.
Merriam, C.H. 1982. The prairie dog of the Great Plains p. 257-270 In:
Yearbook of the U.S. Department of Agriculture 1901. U.S.
Government Printing Office; Washington, D.C.
Messiter, C.A. 1898. Sport and adventure among the North American
Indians. R.H. Porter, London.
Miller, B., G. Cehallos, and R. Reading. 1994. The prairie dog and
biotic diversity. Conservation Biol. 8:677481.
Montana Agricultural Statistics. 1992. Montana Dept. of Agr. Helena,
Mom.
Nebraska Game and Parks Commission. 1993. Petition to classify the
Black-tailed Prairie Dog (Cynomys ludovicianus) as a Category 2
Candidate species. In: Biodiversity Legal Foundation. Boulder, Colo.
Not-land, J.E. 1984. Habitat use and distribution of bison in Theodore
Roosevelt National Park. M.S. Thesis. Montana State Univ., Bozeman,
Mont.
Nom, RF. 1992. The Wildlands Project land conservation strategy. p.
10-25 In: Wild Earth (special issue), plotting a North American
Wilderness Recovery Strategy. The Wildlands Project. Richmond, Vt.
NW, RF. and A.Y. Cooperrider. 1994. Saving natme’s legacy-pto-
tecting and restoring biodiversity. Defenders of Wildlife and Island
Press, Washington, D.C.
Oklahoma Dept. of Wildlife Conservation. 1993. Petition to classify
the Black-tailed Prairie Dog (Cynomys hdoviciunus) as a Category 2
Candidate species. B&diversity Legal Foundation Boulder, Colo.
Olson, S.C. 1985. Mountain plover food items on and adjacent to a
prairie dog town. Prairie Nat. 17:83-90.
O’Meilia, M.E. , F.L. Knopf, and J.C. Lewis. 1982. Some conse-
quences of competition between prairie dogs and beef cattle. J. Range
Manage. 35:58@-585.
O&torn, B. and P.F. Allan. 1949. Vegetation of an abandoned prairie-
dog town in tall grass prairie. Ecol.. 30:322-332.
Peden, D.G., G.M. Van Dyne, R.W. Rice, and R.M. Hansen. 1974.
The tropic ecology of Bison bison on short grass plains. J. Appl. Ecol.
11:489498.
Plumb, G.E. and J.L. Dodd. 1993. Foraging ecology of bison and cattle
on a mixed prairie: implications for natural area management. Ecol.
Appl. 3:631-643.
Primack, R.B. 1993. Essentials of Conservation Biology. Sinauer
Associates inc. Sunderland, Mass.
Reading, RP., JJ. Grenston, S.R Beiisinger, and T.W. Clark. 1989.
Attributes of black-tailed prairie dog colonies in north central
Montana, with management recommendations for the conservation of
biodivemity. Wildlife Technical Bulletin 2. Montana Bureau of Land
Management, Billings, Mont.
Schonewald-Cox, C.M. and J.W. Bayless. 1986. The boundary model:
a geological analysis of design and conservation of nature reserves.
Biol. Conserv. 38:305-322.
Seton, KT. 1929. Lives of game animals. Doubleday, Dovan, and Co.
Inc. Garden City, N.Y.
South Dakota Dept. of Game, Fish, and Parks. 1993. Petition to classi-
fy the Black-tailed Prairie Dog (Cynomys 1udovicianus)as a Category 2
Candidate species. Biodiversity Legal Foundation. Boulder, Colo.
Vanderhoof, J.L. and RJ. Robe1 1992. Numbers and extent of black-
tailed prairie dog towns in western Kansas. Kansas State Univ., Cont.
No. 221. Kansas Dept. of Wildl. and Parks.
Van Vnren, D. 1984. Summer diets of bison and cattle in southern Utah.
JRange Manage. 37:260-261.
Whicker, April D. and James K. Detling. 1988. Ecological conse-
quences of prairie dog disturbances. Bioscience 38:77&785.
Wilcove, D.S., C.H. MeLeEan, and A.P. Dobson. 1986. Habitat frag-
mentation in the temperate zone. p. 237-256 In: M.E. Soule (ed.)
Conservation biology: the science of scarcity and diversity. Sinauer
Associates, Sunderland, Mass.
Win, T. 1994. Back to the badlands. National Parks Magazine.
68:3842.
Zeveloff, S.L and F.R Collett. 1988. Mammals of the inter-mountain
west. Univ.of Utah Press, Salt Lake City, Ut.
466 JOURNAL OF RANGE MANAGEMENT SO(5), September 1997