Endangered and Threatened Wildlife and Plants; 12-Month Finding for a Petition To List the Black-Tailed Prairie Dog as Threatened

Note: EPA no longer updates this information, but it may be useful as a reference or resource.
 




[Federal Register: February 4, 2000 (Volume 65, Number 24)]
[Proposed Rules]
[Page 5476-5488]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr04fe00-29]

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17


Endangered and Threatened Wildlife and Plants; 12-Month Finding
for a Petition To List the Black-Tailed Prairie Dog as Threatened

AGENCY:  Fish and Wildlife Service, Interior.

ACTION:  Notice of 12-month petition finding.

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SUMMARY:  We, the Fish and Wildlife Service, announce a 12-month
finding for a petition to list the black-tailed prairie dog (Cynomys
ludovicianus) as threatened throughout its range under the Endangered
Species Act of 1973, as amended (Act). After reviewing all available
scientific and commercial information, we have determined that listing
this species is warranted but precluded by other higher priority
actions to amend the Lists of Endangered and Threatened Wildlife and
Plants. Upon publication of this notice of 12-month petition finding,
the black-tailed prairie dog will be added to our candidate species
list.
    This decision is based on--the number, variety, and significance of
threats affecting the species, especially sylvatic plague (an exotic
disease to which the species has no resistance) and inadequate
regulatory mechanisms (some areas mandate eradication); evidence of
recent general population declines in a significant portion of the
species' range; and cumulative rangewide population data indicating
overall population declines since 1980.

DATES:  The finding announced in this document was made on February 4,
2000.

ADDRESSES:  You may submit data, information, comments, or questions
concerning this finding to the Field Supervisor, U.S. Fish and Wildlife
Service, 420 South Garfield, Suite 400, Pierre, South Dakota 57501. You
may inspect the petition finding, supporting data, and comments by
appointment during normal business hours at the above address. The
petition finding also will be available at the Service's Region 6
website at www.r6.fws.gov/btprairiedog>.

FOR FURTHER INFORMATION CONTACT:  Pete Gober, Field Supervisor, South
Dakota Field Office (see ADDRESSES section), telephone (605) 224-8693,
extension 24, or facsimile (605) 224-9974.

SUPPLEMENTARY INFORMATION:

[[Page 5477]]

Background

    On July 31, 1998, we received a petition dated July 30, 1998, from
the National Wildlife Federation (National Wildlife Federation 1998).
The Petitioner requested that we list the black-tailed prairie dog as
threatened throughout its range. The Petitioner also requested that the
species be afforded emergency listing. Section 4 of the Act and
regulations at 50 CFR 424 do not provide for petitions to request the
listing of species on an emergency basis. However, section (4)(b)(7) of
the Act and the Service's Listing Priority Guidance (63 FR 25502)
direct that all petitions are to be reviewed to determine if an
emergency listing is appropriate. We determined and advised the
Petitioner by letter dated August 27, 1998, that it would be
inappropriate to list this species on an emergency basis given its then
known status. On September 16, 1999, the Petitioner requested that we
readdress this issue based on reports of increased control efforts
(Graber, National Wildlife Federation, in litt. 1999). We have
reevaluated information available regarding this subject and determined
that emergency listing of the species is not appropriate at this time.
    Section 4(b)(3)(A) of the Act requires that, for any petition to
revise the List of Threatened and Endangered Species containing
substantial scientific and commercial information that listing may be
warranted, we make a positive 90-day finding and initiate a status
review of the species. We published a notice of a positive 90-day
finding on the subject petition in the Federal Register on March 25,
1999 (64 CFR 14425). Accordingly, the subject petition requires a 12-
month administrative finding pursuant to section 4(b)(3)(B) on whether
the petitioned action is--(I) not warranted, (ii) warranted, or (iii)
warranted but precluded from immediate proposal by other higher
priority efforts to revise the List of Threatened and Endangered
Species. When we find a petition to list a species is warranted but
precluded, the species is designated a candidate species.
    We believe that sufficient information is currently available to
support a finding that listing the black-tailed prairie dog as
threatened is warranted, but that a proposed rule at this time is
precluded by work on other higher priority listing actions. We will
reevaluate the status of the species in 1 year. The information
contained in this notice is a summary of the information in the 12-
month finding.
    The National Wildlife Federation petition presented extensive
information regarding the biology of the black-tailed prairie dog. This
information included a description of the species and its range, as
well as comments related to its population biology and trend. The
Petitioner noted that the species still occurs intermittently
throughout most of its historic range, although much reduced in numbers
and in the amount of habitat that it occupies. The Petitioner
contrasted reports that the black-tailed prairie dog once occupied as
much as 100-200 million acres (ac) (40-80 million hectares (ha)) of the
western North American prairie with current estimates of occupied
habitat and concluded that the species' habitat has been reduced by at
least 99 percent. The Petitioner attributed reductions in occupied
habitat to habitat loss and degradation related to the conversion of
prairie grasslands to farmland, extensive control, disease, urban
development, unregulated shooting, and other factors.
    On August 26, 1998, we received another petition regarding the
black-tailed prairie dog from the Biodiversity Legal Foundation, the
Predator Project, and Jon C. Sharps (Biodiversity Legal Foundation et
al. 1998). They requested that we list the black-tailed prairie dog as
threatened throughout its known historic range in the contiguous United
States. We accepted this second request as supplemental information to
the National Wildlife Federation petition. The Biodiversity Legal
Foundation et al. (1998) provided estimates of historic and current
distribution of the black-tailed prairie dog, both regionally and by
State. They noted that the species' populations are impacted by
eradication programs, sylvatic plague, recreational shooting, land
conversion, and natural predation. The Biodiversity Legal Foundation
(1999) also developed and submitted a potential plan for black-tailed
prairie dog conservation.
    The notice of a 90-day finding that a petition to list the black-
tailed prairie dog presented substantial information that appeared in
the Federal Register on March 25, 1999 (64 FR 14424). In this notice,
we requested that any additional scientific information relevant to a
proposed 12-month administrative finding be submitted to us by May 24,
1999. We published a notice in the Federal Register on June 4, 1999 (64
FR 29983), that reopened this period for an additional 45 days, through
July 19, 1999. On October 4, 1999, we again published a notice that we
would accept additional information, especially pertaining to a draft
black-tailed prairie dog Conservation Assessment and Strategy
(Strategy) developed by various States and its effect on the status of
the species (64 FR 53655). This information collection period closed
November 3, 1999.
    We received approximately 14,500 comment letters during the
development of this finding. The following summarizes the sources and
general content of information we received.
    All State wildlife agencies within the historic range of the black-
tailed prairie dog provided written comments on the petition. Two State
agriculture departments (New Mexico and Wyoming) and two State
Legislatures (North Dakota and Wyoming) also provided comments. In
general, the States opposed listing the black-tailed prairie dog but
supported the development of conservation measures for the species.
Most information provided by the States focused on policy and
jurisdictional concerns rather than on information related to the
biological status of the species.
    State wildlife agencies and other interested parties also developed
a Strategy for conservation of the black-tailed prairie dog (Van Pelt
in prep.). The actions identified in the current draft of this Strategy
remain tentative and do not at this time confer any improved status for
the species. Eight of the 11 participating State wildlife agencies have
signed a Memorandum of Understanding for the purpose of implementing
the States' Strategy for the black-tailed prairie dog. At this time,
the strategy does not include participation by the States of New
Mexico, North Dakota, and Colorado, other State (non-wildlife)
agencies, Federal agencies, Tribal agencies, or any private interests.
We recognize the significant effort that went into the development of
this strategy, and we believe that the strategy is a positive step in
addressing the conservation needs of the black-tailed prairie dog. At
this early stage in development of the strategy, the document lacks
commitments to specific immediate actions that would affect the status
of the species. We will continue working with the States and other
interested parties to support the coordinated conservation efforts of
the States.
    Three Tribes in South Dakota provided written comments on the
petition--the Cheyenne River Sioux Tribe, the Crow Creek Sioux Tribe,
and the Rosebud Sioux Tribe. Information was provided by these Tribes
regarding distribution and abundance and existing regulatory mechanisms
on and adjoining their respective Tribal lands.
    Several Federal agencies provided written comments on the petition.
The Bureau of Indian Affairs (BIA) supported conservation measures and

[[Page 5478]]

acknowledged a possible need to list the species. The U.S. Forest
Service provided supplemental information regarding the current status
of black-tailed prairie dogs on National Grasslands (Sidle, U.S. Forest
Service, in litt. 1999). The National Park Service provided information
on its control efforts and noted its preference for the development and
implementation of cooperative management strategies among State,
Tribal, and Federal agencies rather than a listing of the species. The
Corps of Engineers Omaha District also reviewed information provided in
the petition, but had no specific comments.
    Twenty-three county agencies (county commissions and weed/pest
councils) in Colorado, Montana, Nebraska, South Dakota, and Wyoming
provided written comments on the petition. All county agencies were
opposed to listing the species. Economic considerations were a common
concern in these comment letters. Because the Act directs that only
biological considerations are to be addressed in the listing process,
we cannot address economic considerations in review of this petition.
    One hundred forty-four organizations (wildlife/conservation or
livestock/land management organizations) provided written comments on
the petition. Forty-two wildlife/conservation organizations supported
listing of the black-tailed prairie dogs. Eighty-seven livestock/land
management organizations were opposed to listing the species. Fifteen
organizations provided recommendations but did not indicate a position.
    Over 14,300 individuals provided written comments on the petition.
Approximately 90 percent of all individuals supported listing the
black-tailed prairie dog as threatened. The issues most frequently
noted in these letters were impacts from the loss of 99 percent of the
species' habitat, recreational shooting, control, and disease.
Individuals opposed to listing the species most frequently expressed
the view that adequate numbers of the species exist, the species is
able to reproduce rapidly in response to adverse impacts, sport
shooting does not impact the species, and adverse economic impacts can
occur if the species is not controlled.
    We received approximately 9,000 letters during the third comment
period (October 4 to November 3, 1999). Of these, 84 mentioned the
States' Strategy, 25 of which opposed the States' Strategy, mostly due
to a perceived lack of specific conservation measures and reliance on
future, voluntary actions. Fifty-six letters supported the States'
Strategy, most expressing the view that the proposed measures were
sufficient to avoid listing and that State management was preferable to
Federal management. The remaining 3 of the 84 commenters did not
express a position.

Taxonomy

    Five species of prairie dogs occur in North America. Prairie dogs
are rodents within the squirrel family (Sciuridae) and include the
black-tailed prairie dog, the white-tailed prairie dog (Cynomys
leucurus), the Gunnison's prairie dog (C. gunnisoni), the Utah prairie
dog (C. parvidens), and the Mexican prairie dog (C. mexicanus)
(Pizzimenti 1975). The Utah and Mexican prairie dogs are currently
listed as threatened (49 FR 22339) and endangered (35 FR 8495),
respectively. Generally the black-tailed prairie dog occurs east and
north of the other four species in less arid habitat.
    Some scientific literature describes a subspecies (Cynomys
ludovicianus arizonensis) of the black-tailed prairie dog. This
subspecies, found in northeastern Mexico (Ceballos et al. 1993), is
extirpated in Arizona (Alexander 1932; Bureau of Sport Fisheries and
Wildlife 1961; Van Pelt, Arizona Game and Fish Department, in litt.
1998) and has a remnant population in southwestern New Mexico (Hall and
Kelson 1959) and in the Trans-Pecos region of Texas (Davis 1974, Hall
and Kelson 1959). A complex of this subspecies in Chihuahua, Mexico,
comprises the largest remaining prairie dog complex of any prairie dog
species (Ceballos and Pacheco 1997).
    The remainder of the species is found in eastern Montana, eastern
Wyoming, eastern Colorado, eastern New Mexico, southwestern North
Dakota, western and central South Dakota, western and central Nebraska,
western and central Kansas, western and central Oklahoma, northwestern
Texas, and southwestern Canada. Although some literature describes a
subspecies, the research that has focused on evolutionary divergence
(genetic segregation and differentiation within a taxon) supports
categorizing the black-tailed prairie dog as a monotypic species. Based
on this research we do not consider this subspecies separation to be
valid. We consider the species as being monotypic. For the remainder of
this notice, the use of the common name ``black-tailed prairie dog''
includes both varieties discussed above.

Biology

    Prairie dogs are small, stout ground squirrels. The total length of
an adult black-tailed prairie dog is approximately 14-17 inches. The
weight of an individual ranges from 1 to 3 pounds. Individual
appearances within the species vary in mixed colors of brown, black,
gray, and white. The black-tipped tail is characteristic (Hoogland
1995). Black-tailed prairie dogs are diurnal, burrowing animals and
spend most of the day above ground. They do not hibernate as do white-
tailed, Gunnison's, and Utah prairie dogs (Hoogland 1995, Tileston and
Lechleitner 1966). The species is very social, living in population
aggregations called colonies, towns, or villages (King 1955). Groups of
colonies comprise a complex. Historically, they generally occurred in
large colonies that contained thousands of individuals, covered
hundreds of thousands of acres, and extended for miles (Bailey 1905).
This description is no longer accurate for existing black-tailed
prairie dog populations; most colonies are now much smaller.
    The colonial behavior of prairie dogs, especially the black-tailed
prairie dog, is a significant characteristic of the species. Colonial
behavior offers an effective defense mechanism by aiding in the
detection of predators and deterring predators through mobbing
behavior. It increases reproductive success through cooperative rearing
of juveniles and aids parasite removal via shared grooming. However, it
also has been noted that this behavior promotes the transmission of
disease, which can significantly suppress populations (Olsen 1981,
Hoogland 1995).
    Several biological factors determine the reproductive potential of
the black-tailed prairie dog. Females usually do not breed until their
second year and live 3-4 years (Hoogland 1995, King 1955, Knowles and
Knowles 1994). Females of the species produce a single litter, usually
4-5 pups, annually (Hoogland 1995, Knowles and Knowles 1994). Prairie
dog dispersal is usually limited to approximately 3 miles (5
kilometers) or less, and individuals dispersing from home colonies
generally move into an established colony rather than attempting to
initiate a new colony (Garrett and Franklin 1988, Hoogland 1995). These
limitations could restrict recruitment of animals into small and
declining isolated populations and favor the reestablishment of
individuals in nearby, recently abandoned colonies over the
establishment of new, more distantly located colonies.

Ecology

    The extent to which the black-tailed prairie dog is affected by
other species, particularly ungulates, is largely unknown. The black-
footed ferret (Mustela nigripes), swift fox (Vulpes

[[Page 5479]]

velox), mountain plover (Charadrius montanus), ferruginous hawk (Buteo
regalis), burrowing owl (Athene cunicularia), and numerous other
species are dependent upon prairie dogs to varying degrees. Although
reports vary as to those species that require prairie dogs for their
survival, at least 9 species depend directly on prairie dogs or their
activities to some extent, and another 137 species are associated
opportunistically (Kotliar et al. 1999). The most obligatory species of
this group is the endangered black-footed ferret. Probably no other
species has a more clearly documented dependence on another species
than does the black-footed ferret on the prairie dog (Anderson et al.
1986, Biggins et al. 1986, Clark 1989, Forrest et al. 1988, Henderson
et al. 1974, Hillman 1968, Miller et al. 1996).

Rangewide Distribution

    The historic range of the black-tailed prairie dog included
portions of 11 States, Canada, and Mexico. Today it occurs from extreme
southern Canada to northeastern Mexico and from approximately the 100th
meridian west to the Rocky Mountains. The species is currently present
in 10 States including Colorado, Kansas, Montana, Nebraska, New Mexico,
North Dakota, Oklahoma, South Dakota, Texas, and Wyoming. It has been
extirpated in Arizona since as early as 1932 (Alexander 1932). We
believe that significant range contractions have occurred in the
southwestern portion of the species' historic range in Arizona, western
New Mexico and western Texas, and in the eastern portion of the
species' historic range in Kansas, Nebraska, Oklahoma, South Dakota,
and Texas. These range contractions represent approximately 20 percent
of the species' original range. Only a few individuals or none remain
in these areas. Approximately 37 percent of the species' potential
habitat in the United States has been converted to cropland (Black-
footed Ferret Recovery Foundation, in litt. 1999). This habitat loss is
essentially permanent and not considered a range contraction in the
usual sense occurring at the periphery of a species' range. Although
the species will occupy abandoned tilled ground, these lands are
generally unavailable for use by the species because the land is
continuously disturbed and thus the habitat is lost permanently.

Rangewide Abundance

    Historically, black-tailed prairie dogs were one of the most
conspicuous and characteristic residents of the short-grass and mixed-
grass prairies of the United States. Seton (1953) estimated that, in
the late 1800s, 5 billion black-tailed prairie dogs existed over their
entire range of 600,000 square miles (384 million ac or 155.5 million
ha). Miller et al. (1996) and Mulhern and Knowles (1995) provided a
range for historic occupied habitat by all species of prairie dogs of
99 million-247 million ac (40 million-100 million ha). Anderson et al.
(1986) noted that, as a conservative estimate for the early 1900s, 104
million ac (42 million ha) of rangeland may have been occupied by all
species of prairie dogs. Black-tailed prairie dogs had the most
extensive range of all the species of prairie dogs and probably
occupied more area than all other species combined (Hoogland 1995).
Estimates of historic black-tailed prairie dog occupied habitat of
approximately 79 million ac (32 million ha) in the United States by the
Black-footed Ferret Recovery Foundation (in litt. 1999) and of
approximately 111 million ac (45 million ha ) by Knowles (1998) provide
a reasonable historic range for black-tailed prairie dog occupied
habitat. It is apparent that regardless of which estimate is
considered, tens of millions of acres of occupied habitat once existed
in the United States.
    At present, the black-tailed prairie dog may be found scattered in
remnant populations throughout much of the range that it once occupied.
A significant portion of existing occupied habitat rangewide occurs in
a few large complexes. Approximately 36 percent of the remaining
occupied habitat for the species in North America occurs in seven
complexes, each larger than 10,000 ac (4,000 ha). We believe that
approximately 768,000 ac (311,000 ha) of occupied habitat currently
exists rangewide. This estimate is based on the sum of Service
estimates from various States, from Canada, and from Mexico, as
discussed under the ``Statewide Distribution, Trends, and Abundance''
section of this document.

Rangewide Trends

    Most estimates of prairie dog population trends are not based on
numbers of individuals, but on the amount of occupied habitat for the
species. The actual number of animals present depends upon the density
of animals in that locality. Estimates of black-tailed prairie dog
density across the species' range vary seasonally, but range from 2 to
18 individuals per ac (5 to 45 individuals per ha) (Fagerstone and
Ramey 1996, Hoogland 1995, King 1955, Koford 1958, Miller 1996). Most
prairie dog surveys do not estimate density because of the high effort
and cost involved. We believe that a review of various estimates of
occupied habitat area provides the best available and most reasonable
means of determining population trends for the species.
    The U.S. Geological Survey estimated that the black-tailed prairie
dog may occupy less than 0.5 percent of its original range and has
experienced an estimated 98 percent decline in population abundance
throughout North America (Mac et al. 1998). It notes that the amount of
occupied habitat has declined from approximately 100 million ac (40.5
million ha) in the late 1800s to less than 1 million ac (0.4 million
ha) at present; a decline of over 99 percent. Barko (1997), Fagerstone
and Ramey (1996), Knowles (1998), Mulhern and Knowles (1995), and
Wuerthner (1997) concluded that a reduction of approximately 94-99
percent in the amount of occupied habitat within this range has
occurred since about 1900. State wildlife agencies generally confirm
this decline, but some point out that disproportionately more occupied
habitat remains in some areas than in others.
    Some increases in the amount of occupied habitat in some areas
occurred subsequent to the Executive Order banning the use of compound
1080 (a toxicant) in 1972. These increases appear to have been limited
in later years by the use of other toxicants such as zinc phosphide,
the continuing spread of sylvatic plague, and other factors (Knowles
1998). Moreover, the majority of these increases (approximately 85
percent) occurred in areas (Montana, South Dakota, and Wyoming) where
significant impacts due to disease had not yet occurred.
    Survey efforts in some areas have noted significant declines in the
amount of black-tailed prairie dog occupied habitat over the last few
decades. For example, the U.S. Forest Service has mapped black-tailed
prairie dog colonies within the Northern Great Plains National
Grasslands in North Dakota, South Dakota, Wyoming, and Nebraska. These
grasslands, covering approximately 3.7 million ac (1.5 million ha),
included a maximum of 86,220 ac (34,890 ha) of black-tailed prairie dog
occupied habitat in the 1970s to the 1990s. In 1997, the U.S. Forest
Service mapped 39,420 ac (15,965 ha) of occupied habitat in the same
areas, indicating a 54 percent decline (U.S. Forest Service 1998). Data
provided by the U.S. Forest Service in 1999 confirmed losses in
occupied habitat for the National Grasslands with a 58 percent decline
from the 1970s to the present (Sidle, U.S. Forest Service, in litt.
1999).

[[Page 5480]]

    Lockhart (U.S. Fish and Wildlife Service, in litt. 1998) reported
that the recovery program for the black-footed ferret has identified
large prairie dog complexes potentially useful for reintroduction of
the ferret. Both black-tailed and other prairie dog species are
considered. One necessary criteria for these sites is that they contain
approximately 10,000 ac (4,000 ha) of occupied habitat. In the late
1980s, the Black-footed Ferret Interstate Coordinating Committee
identified dozens of potential sites that may have qualified as
suitable for ferret recovery. Black-tailed prairie dog populations at
these sites appear to have been reduced by as much as 90 percent within
the last 15 years. By 1994 only 16 sites were identified, and by 1998
this number was reduced to 10 sites (7 being black-tailed prairie dog
sites). Although the overall trend is a large-scale reduction,
population increases have been observed at some locales. These declines
have occurred largely in the western portion of the species' range and
are generally attributed to sylvatic plague. These declines may be
representative of the overall population dynamics of the species in
many areas. However, populations in some other areas in the eastern
portion of the species' range where plague is mostly absent have
increased marginally or remained generally constant during the same
period.
    Approximately 66 percent, or 300 million ac (122 million ha), of
the black-tailed prairie dog range in the United States is affected by
sylvatic plague (Black-footed Ferret Recovery Foundation, in litt.
1999). This area includes the western portions of the species' range.
Another important factor that has affected the species is the
conversion of rangeland to cropland, especially in the eastern portion
of the species' range. Conversion of native prairie to cropland has
largely progressed across the species' range from east to west with
more cropland occurring in the eastern portion of the species' range.
In the plague-free portion of the species' range, less than 33 percent
of the species' historic range is available to the species (Black-
footed Ferret Recovery Foundation, in litt. 1999). Therefore, only
approximately 10 percent of the black-tailed prairie dog historic range
is both plague-free and available (not cropland) to the species. The
majority of plague-free, suitable range occurs in South Dakota.

Statewide Distribution, Abundance, and Trends

    In some parts of the species' range, statewide population increases
were noted after 1972. However, in most western States, populations
have declined since the 1980s, most likely due to sylvatic plague. In
the eastern part of the range, where plague has not yet occurred,
similar declines have not been observed. These trends are discussed
below by State. We have evaluated all historic and current data and
information available on the species' abundance and trends. Several
estimates of black-tailed prairie dog occupied habitat were available
for each State. The dates, methodologies, and ultimately the
reliability of these estimates varied. Generally, our estimate of
current occupied habitat for each State is the most recently reported
estimate with the most reliable methodology (Arizona, Montana,
Nebraska, North Dakota, Oklahoma, South Dakota, Canada, and Mexico).
For States where a range (Wyoming) or two reliable estimates were
available (Kansas), we used the midpoint. For States where no recent
estimate with adequate methodology was available (Colorado, New Mexico,
and Texas), we extrapolated from older estimates. We rounded all our
estimates to the nearest 1,000 ac.
    In Arizona, black-tailed prairie dogs existed in the southeastern
portion of the State prior to eradication efforts (Hall and Kelson
1959). The species is extirpated at present in the State. Approximately
2 percent of occupied habitat in the United States may have existed in
Arizona historically. We believe that intensive grazing at the turn of
the last century may have caused occupied habitat to expand in Arizona
and that control may have been the principal factor that subsequently
suppressed populations. Shrub invasion also may have limited recovery.
The species largely disappeared from the State prior to the documented
occurrence of sylvatic plague in the State (Shroufe, Arizona Game and
Fish Department, in litt. 1999). However, plague is an additional
factor that could affect the future viability of the species in
Arizona.
    In Colorado, black-tailed prairie dogs historically occurred on
suitable habitat east of the Rocky Mountain foothills (Hall and Kelson
1959, Torres 1973). Presently, the species appears to be scattered in
remnant populations throughout the same area. Statewide estimates of
occupied habitat noted for Colorado range from 7 million ac (2.8
million ha) historically to 44,000 ac (18,000 ha) in 1998 (Knowles
1998).
    We believe that occupied habitat in Colorado has declined
significantly from historic estimates. There is a large disparity in
recent statewide estimates of remnant occupied habitat. However, we
believe that trends at specific locations within the State (a 50
percent decline in Denver Metropolitan Area from 1994 to 1998 (Seery,
U.S. Fish and Wildlife Service, pers. comm. 1998), a 70 percent decline
at Rocky Mountain Arsenal National Wildlife Refuge from 1988-1999
(Seery and Matiatos, in press), and a 90 percent decline at Comanche
National Grasslands from 1995 to 1998 (Cully 1998), indicate that there
has likely been a statewide decline in recent years (despite periodic
limited recovery) and that these declines may continue. These declines
have largely been attributed to sylvatic plague. We estimate that
93,000 ac (43,000 ha) of black-tailed prairie dog occupied habitat
currently exist statewide.
    In Kansas, black-tailed prairie dogs historically occurred on
suitable habitat throughout the western two-thirds of the State (Hall
and Kelson 1959, Smith 1958). Presently, the species appears to be
scattered throughout generally the same area, except that the eastern
limit of the range appears to have shifted westward approximately 30-50
miles (50-80 kilometers) (Vanderhoof and Robel 1992). Statewide
estimates of occupied habitat for Kansas range from 2.5 million ac (1
million ha) historically to 36,000 ac (15,000 ha) in 1998 (Knowles
1998). We estimate that 42,000 ac (17,000 ha) of black-tailed prairie
dog occupied habitat currently exist statewide.
    We believe that occupied habitat in Kansas has declined
significantly from historic estimates, but has likely been stable to
slightly declining in recent years. The most recent statewide survey is
from 1992 (Vanderhoof and Robel 1992). However, in 1996 sylvatic plague
was documented in Kansas on the Cimarron National Grasslands (Cully,
U.S. Geological Survey, Biological Resources Division, pers. comm.
1998). Therefore, occupied habitat may decline if sylvatic plague
impacts continue and/or spread to other areas of the State.
    In Montana, black-tailed prairie dogs historically occurred on
suitable habitat in the eastern two-thirds of the State (Flath and
Clark 1986), with the exception of the northeastern corner of the State
(Hall and Kelson 1959). One of the seven large remaining black-tailed
prairie dog complexes occurs in Montana. Statewide estimates of
occupied habitat for Montana range from 6 million ac (2.4 million ha)
historically (Knowles 1998) to 28,286 ac (11,456 ha) in 1961 (Bureau of
Sport Fisheries and Wildlife 1961). The Montana Department of Fish,
Wildlife, and Parks believes that historic estimates are inaccurate
(Graham,

[[Page 5481]]

Montana Department of Fish, Wildlife, and Parks, in litt. 1998). The
most recent estimate of occupied habitat is 66,000 ac (26,000 ha)
(Montana Department of Fish, Wildlife and Parks in prep.). We estimate
that 65,000 ac (26,000 ha) of black-tailed prairie dog occupied habitat
currently exist statewide.
    We believe that occupied habitat in Montana has declined
significantly from historic estimates. Following a major reduction in
occupied habitat from approximately 1900 to 1961, black-tailed prairie
dog populations in the State apparently expanded from 1961 to 1986 and
then experienced significant declines due to sylvatic plague. The
Montana Department of Fish, Wildlife, and Parks (1998) noted that
occupied habitat declined by approximately 50 percent from the
estimates of the late 1980s, largely due to sylvatic plague.
    In Nebraska, black-tailed prairie dogs historically occurred on
suitable habitat throughout most of the State west of the 97th meridian
(Hall and Kelson 1959, Knowles 1995). Presently, the species appears to
be scattered throughout the same area, but at much reduced numbers,
especially east of the 99th meridian. Statewide estimates of occupied
habitat noted for Nebraska range from 6 million ac (2.4 million ha)
historically (Knowles 1998) to 30,000 ac (12,000 ha) in 1961 (Bureau of
Sport Fisheries and Wildlife 1961). The most recent estimate of
occupied habitat is 60,000 ac (24,000 ha) (Knowles 1998). We estimate
that 60,000 ac (24,000 ha) of black-tailed prairie dog occupied habitat
currently exist statewide.
    We believe that occupied habitat in Nebraska has declined
significantly from historic estimates and has likely been stable to
slightly declining in recent years (Amack, Nebraska Game and Parks
Commission, in litt. 1999). This stability may be due to the fact that
sylvatic plague does not appear to be widespread in the State, although
it has been documented in the northwestern portion of the State where
it has impacted some black-tailed prairie dog populations (Virchow et
al. 1992).
    In New Mexico, black-tailed prairie dogs historically occurred on
suitable habitat throughout the southern and eastern two-thirds of the
State (Bailey 1932, Hall and Kelson 1959). Presently, the species
appears to exist in remnant populations in scattered locations,
generally east of the Pecos River (Findley et al. 1975). Statewide
estimates of occupied habitat noted for New Mexico range from over
6,640,000 ac (2,690,000 ha) historically (Bailey 1932) to 15,000 ac
(6,000 ha) in 1998 (Knowles 1998). We estimate that 39,000 ac (16,000
ha) of black-tailed prairie dog occupied habitat currently exist
statewide.
    We believe that occupied habitat in New Mexico has declined
significantly from historic estimates. Following the toxicant ban in
1972, increases in occupied habitat appear to have occurred. However,
declines in occupied habitat have likely occurred in more recent years
(Maracchini, New Mexico Department of Game and Fish, in litt. 1998).
    In North Dakota, black-tailed prairie dogs historically occurred on
suitable habitat in the southwestern third of the State, west of the
Missouri River (Hall and Kelson 1959). Presently, the species appears
to be scattered throughout the same area. Statewide estimates of
occupied habitat for North Dakota range from 2 million ac (810,000 ha)
historically (Knowles 1998) to approximately 7,000 ac (2,800 ha) as a
conservative estimate in 1973 (Grondahl 1973). The most recent estimate
of occupied habitat is a preliminary estimate of approximately 25,000
ac (10,000 ha), based on aerial surveys (Sidle, U.S. Forest Service,
pers. comm. 1999). We estimate that 25,000 ac (10,000 ha) of black-
tailed prairie dog occupied habitat currently exist Statewide.
    We believe that occupied habitat in North Dakota has declined
significantly from historic estimates, but has likely been fairly
stable to increasing (McKenna, North Dakota Game and Fish Department,
in litt. 1999) in recent years. The amount of occupied habitat in North
Dakota is relatively small compared to other States in the northern
Great Plains.
    In Oklahoma, black-tailed prairie dogs historically occurred on
suitable habitat in the western two-thirds of the State (Hall and
Kelson 1959). Presently, the species is largely limited to the
panhandle (Shaw et al. 1993, Tyler 1968, Wuerthner 1997), although
scattered remnant populations occur in the western half of the State
outside of the panhandle (Shackford et al. 1990). Statewide estimates
of occupied habitat noted for Oklahoma range from 950,000 ac (385,000
ha) historically (Knowles 1998) to less than 8,600 ac (3,500 ha) in
1998 (Lomolino, University of Oklahoma, in litt. 1999). We estimate
that 9,000 ac (3,600 ha) of black-tailed prairie dog occupied habitat
currently exist Statewide.
    Populations in the panhandle have experienced significant declines
in the past 10 years, although with limited recovery (Lomolino,
University of Oklahoma, in litt. 1999). These declines were likely due
to plague. The amount of occupied habitat in the remainder of the State
has experienced a slow, steady decline (Shackford et al. 1990).
Statewide, populations have been reduced by 50 percent in the last 10
years (Lomolino, in litt. 1999).
    In South Dakota, black-tailed prairie dogs historically were found
throughout all but the eastern one-fourth of the State (Hall and Kelson
1959, Linder et al. 1972). Presently the species appears to be
scattered throughout the same area, with the majority of occupied
habitat on Tribal or Federal lands west of the Missouri River and small
scattered populations elsewhere. Four of the seven remaining large
black-tailed prairie dog complexes occur in South Dakota. Statewide
estimates of occupied habitat for South Dakota range from more than
1,757,000 ac (712,000 ha) historically, following the initiation of
intensive control efforts in 1918 (Linder et al. 1972), to 33,000 ac
(13,000 ha) in 1961 (Bureau of Sport Fisheries and Wildlife 1961). The
most recent estimate of occupied habitat in the State is a preliminary
estimate of 147,000 ac (60,000 ha), based on aerial surveys (Sidle,
U.S. Forest Service, pers. comm. 1999). We estimate that 147,000 ac
(60,000 ha) of black-tailed prairie dog occupied habitat currently
exist Statewide.
    We believe that occupied habitat in South Dakota has declined
significantly from historic estimates, with notable recovery from 1961-
1980 (Bureau of Sport Fisheries and Wildlife 1961, Tschetter 1988).
Thereafter, extensive control efforts at Pine Ridge Reservation and
elsewhere in the 1980s resulted in a significant decline in occupied
habitat. Subsequently, occupied habitat has remained fairly stable.
More unoccupied, but available, habitat appears to remain in South
Dakota than in other States.
    In Texas, black-tailed prairie dogs historically occurred on
suitable habitat throughout the northwestern one-third of the State
(Bailey 1905, Hall and Kelson 1959). Presently, the species occurs
largely in the western portion of the panhandle. Some scattered remnant
populations exist in the Trans-Pecos Region of western Texas. Statewide
estimates of occupied habitat range from 58 million ac (23 million ha)
historically to 23,000 ac (9,000 ha ) in 1998 (Knowles 1998). We
estimate that 71,000 ac (29,000 ha) of black-tailed prairie dog
occupied habitat currently exist Statewide.
    We believe that occupied habitat in Texas has declined
significantly from historic estimates. However, based upon the limited
amount of information available, we believe that occupied habitat
increased following the toxicant

[[Page 5482]]

ban in 1972 and that populations may have remained fairly stable since
the late 1970s (Cheatheam 1977, Lair and Mecham 1991).
    In Wyoming, black-tailed prairie dogs historically occurred on
suitable habitat east of the Rocky Mountain foothills (Clark 1973, Hall
and Kelson 1959) below approximately 5,500 feet (1,676 meters)
elevation (Van Pelt in prep.). Presently, the species appears to be
scattered throughout the same area. One of the seven remaining large
black-tailed prairie dog complexes occurs in Wyoming. Statewide
estimates of occupied habitat for Wyoming range from 16 million ac (6.5
million ha) historically (Knowles 1998) to 49,000 ac (20,000 ha) in
1961 (Bureau of Sport Fisheries and Wildlife 1961). The most recent
estimate is 70,000-180,000 ac (28,000-73,000 ha) in 1998 (Knowles
1998). We estimate that 125,000 ac (51,000 ha) of black-tailed prairie
dog occupied habitat currently exist Statewide.
    We believe that occupied habitat in Wyoming has declined
significantly from historic estimates. Increases in occupied habitat
occurred following the toxicant ban in 1972. However, we believe that
recent declines, largely due to impacts from sylvatic plague, are
likely to continue.

Canada Distribution, Abundance, and Trends

    Historically, black-tailed prairie dogs occurred on suitable
habitat in southernmost Saskatchewan (Hall and Kelson 1959). Presently
the species is found in a small area along the Frenchman River Valley.
Many of these colonies are in Canada's Grasslands National Park (Laing
1986). Canada represents a very small percentage (approximately 0.3
percent) of the rangewide population. Estimates of occupied habitat in
Canada range from 1,244 ac (503 ha) in 1970 (Millson 1976) to 2,318 ac
(938 ha) in 1996 (Fargey, Grasslands National Park, pers. comm. 1998).
We estimate that 2,000 ac (800 ha) of black-tailed prairie dog occupied
habitat currently exists in Canada.
    We believe that occupied habitat in Canada has remained at
approximately 2,000 ac (800 ha) and, in the absence of sylvatic plague,
will likely remain stable.

Mexico Distribution, Abundance, and Trends

    Historically, black-tailed prairie dogs occurred on suitable
habitat throughout the northern portion of the Mexican States of
Chihuahua and Sonora (Hall and Kelson 1959). Presently, most
individuals appear to be limited to a small region in northern
Chihuahua. The largest remaining black-tailed prairie dog complex
occurs in Mexico. Estimates of occupied habitat in Mexico range from
1,384,000 ac (560,000 ha) historically (Mearns 1907 as cited in
Ceballos et al. 1993) to 90,000 ac (36,000 ha) in 1996 (List et al.
1997). We believe that the List et al. (1997) estimate of 90,000 ac
(36,000 ha) of currently existing black-tailed prairie dog occupied
habitat in Mexico is accurate.
    We believe that occupied habitat in Mexico has declined
significantly from historic estimates and that this decline continues.
Decline appears to be due primarily to cropland conversion. From 1988
to 1996, the geographic range of the species in Mexico contracted 80
percent and the amount of occupied habitat decreased by 34 percent
(List et al. 1997). Colony fragmentation has occurred in previously
surveyed black-tailed prairie dog colonies, reducing the size of towns
and increasing their isolation.

Summary of Factors Affecting the Species

    Section 4 of the Act and regulations (50 CFR part 424) promulgated
to implement the listing provisions of the Act set forth the procedures
for adding species to the Federal lists. A species may be determined to
be an endangered or threatened species due to one or more of the five
factors described in section 4(a)(1). These factors and their
application to the black-tailed prairie dog are as follows:

A. The Present or Threatened Destruction, Modification, or Curtailment
of the Species' Habitat or Range

    We believe that habitat loss due to cropland conversion,
urbanization, habitat modification, and fragmentation is a factor
adversely affecting black-tailed prairie dog populations rangewide.
    In the United States, approximately 37 percent of the suitable
habitat within the range of the black-tailed prairie dog has been
converted to cropland (Black-footed Ferret Recovery Foundation, in
litt. 1999). This land use change resulted in significant destruction
of black-tailed prairie dog habitat, particularly in eastern portions
of the species' range where adequate precipitation favors farming.
Cropland conversion continues, but the amount of occupied habitat
converted annually is unknown. In some areas cropland conversion occurs
due to continuing improvements in intensive agricultural techniques,
for example, dryland wheat farming in Montana (Knowles et al. 1996,
Lessica 1995) and irrigated croplands in Mexico (List et al. 1997).
List et al. (1997) reported that occupied habitat in Mexico declined by
34 percent between 1988 and 1996, in part due to conversion to
cropland.
    Habitat loss also has occurred due to urbanization. One example of
the present and threatened destruction of black-tailed prairie dog
occupied habitat due to urban development is apparent along the Front
Range of Colorado near Denver. In 1994, 42,500 ac (17,200 ha) of
occupied habitat were mapped in the Denver/Boulder/Fort Collins
metropolitan area (Skiba, Colorado Division of Wildlife, pers. comm.
1999). Knowles (1998) estimated that occupied habitat has declined by
approximately 8,000 ac (3,200 ha) since the initial mapping effort, due
to urbanization. An evaluation of the specific impact of urbanization
is difficult because sylvatic plague also has significantly affected
populations in this area in recent years (Weber, Colorado Division of
Wildlife, pers. comm. 1998).
    Habitat modification and loss due to the absence of black-tailed
prairie dogs can be anticipated in the prairie ecosystem where
populations have been extirpated or significantly reduced in number.
Weltzin et al. (1997) determined that black-tailed prairie dogs, and
the herbivores and granivores associated with their colonies, probably
maintained grassland and savanna historically by preventing woody
species such as mesquite from establishing or attaining dominance. List
et al. (1997) reported that control of black-tailed prairie dogs in
Mexico resulted in the invasion of mesquite shrubs that rendered the
landscape unsuitable for reoccupation by the species. Davis (1974) also
noted that the removal of the species from some sites in Texas resulted
in the invasion of brush. The fragmented nature of remaining prairie
dog colonies, barriers to immigration and emigration, and the lack of
fire and native ungulate herds that historically denuded the landscape
and provided opportunities for prairie dog colonies to expand (Miller
et al. 1994) accentuate habitat loss due to vegetative succession. The
degree to which this type of grassland change and other landscape
alterations affect black-tailed prairie dog populations across their
range is unknown. Nevertheless, these subtle habitat changes may be a
major factor in precluding the utilization of habitat or recolonization
of former habitat by the species.
    North American grasslands have suffered among the most extensive
fragmentation and transformation of any

[[Page 5483]]

biome on the continent (Groombridge 1992). More fragmented, more
isolated, and less connected populations usually have higher extinction
rates (Clark 1989, Gilpin and Soule 1986, MacArthur and Wilson 1967,
Shaffer 1981, Wilcove et al. 1986, Wilcox and Murphy 1985). List et al.
(1997) suggested that fragmented black-tailed prairie dog colonies in
Mexico were prone to extirpation. Miller et al. (1996) described
existing prairie dog populations as small, disjunct, and geographically
isolated. Dispersal has been limited by barriers created by human
development that preclude immigration or emigration. Fragmentation and
extirpation of small, isolated colonies will result in the loss of
additional genotypes, as occurred with the complete extirpation of the
species in portions of the eastern and southwestern areas of its
historic range. Lost genetic diversity will inherently be detrimental
to the long-term survival of the species.

B. Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes

    We believe that overutilization of the black-tailed prairie dog via
the pet trade is not a significant factor affecting black-tailed
prairie dog populations rangewide. Herron (Texas Parks and Wildlife
Department, pers. comm. 1999) and others have reported that black-
tailed prairie dogs are removed from the wild for sale as pets. Herron
was aware of 3 commercial operators who collectively removed
approximately 5,000 individuals from the Texas panhandle and other
States annually in recent years. Miscellaneous reports indicate that
this practice occurs elsewhere in the species' range, but the extent of
removal of individuals from the wild for use as pets is unknown.
    Recreational (sport or varmint) shooting is impacting black-tailed
prairie dog populations in some local areas. At present, we do not
believe that this factor is responsible for significant rangewide
declines in the species' population; however, it may be important
locally. The popularity of shooting has increased appreciably in recent
years. Many States do not require hunting licenses and have no bag
limits or seasonal restrictions for taking prairie dogs. Some areas
administered by the Bureau of Land Management and the U. S. Forest
Service have been closed to recreational shooting over the past two
years, but recreational shooting is still allowed on other areas
administered by these agencies. Recreational shooting is not allowed on
on lands administered by the National Park Service or the Fish and
Wildlife Service. Knowles (1988) reported that shooting on two black-
tailed prairie dog colonies removed 69 percent of the adults. He
thought that the reduction of prairie dog populations below a certain
threshold number might have a further negative consequence because
fewer prairie dogs were available to watch for predators and keep the
vegetation clipped around burrows to improve detection of predators.
Vosburgh (1996) reported that intensive shooting can have a
statistically significant impact on the density of local black-tailed
prairie dog colonies. He observed that during the summer, species
density declined 33 percent on colonies with shooting and 15 percent on
colonies without shooting. Prairie dogs also spent more time in alert
postures and less time foraging on colonies where shooting occurred.
    Large, healthy populations appear to be able to withstand
considerable removal by shooting and remain viable (Bourland and
Dupris, Cheyenne River Sioux Tribe, in litt. 1998; Finnegan et al.,
Rosebud Sioux Tribe, in litt. 1998). Accordingly, the shooting of
hundreds of thousands of individuals across the extensive range of the
black-tailed prairie dog where millions of individuals occur will not
likely adversely impact the overall population of a species where each
female can produce an average of four young annually. Conversely, small
local populations already depressed by disease and other adverse
influences may suffer additive losses from shooting impacts. Shooting
impacts also may contribute to population fragmentation and preclude or
delay recovery of colonies reduced by other factors, such as sylvatic
plague.

C. Disease or Predation

    We believe that sylvatic plague is likely the most important factor
in recent reductions of many black-tailed prairie dog populations
throughout a significant portion of the range of the species.
Approximately 66 percent of the species' range has been affected by
plague (Black-footed Ferret Recovery Foundation, in litt. 1999). Plague
is an exotic disease foreign to the evolutionary history of North
American species (Gage, Center for Disease Control, pers. comm. 1999).
Plague was first observed in wild rodents in North America near San
Francisco, California, in 1908 (Eskey and Haas 1940). It spread
eastward across the continent in subsequent years and still appears to
be expanding its range, although not as rapidly as in its early years.
The first reported incidences of plague in black-tailed prairie dogs
occurred in the 1940s (Gage, Center for Disease Control, pers. comm.
1999, Miles et al. 1952). Black-tailed prairie dogs show neither
effective antibodies nor immunity to the disease. This disease is
caused by the bacterium Yersinia pestis, which fleas acquire from
biting infected rodents and other species and then transmit via a bite.
Plague also can be transmitted directly between animals. Cully (1989)
summarized plague reports in 76 species of 5 mammalian orders in the
United States, although plague is primarily a rodent disease. It can
seriously affect humans, although it responds well to modern treatment
(Center for Disease Control 1997). Rodent species vary in their
susceptibility to plague, with some species acting as hosts or carriers
of the disease or infected fleas and showing little or no symptoms.
Black-tailed and Gunnison's prairie dog populations demonstrate nearly
100 percent mortality when exposed to plague (Barnes 1993, Cully 1993)
and cannot be considered carriers.
    Plague, once established in an area, becomes persistent and
periodically erupts, with the potential to extirpate local black-tailed
prairie dog populations. After several epizootics (an eruption of the
disease that attacks a large number of animals at the same time),
black-tailed prairie dogs at the Rocky Mountain Arsenal National
Wildlife Refuge have neared extirpation (Seery, U.S. Fish and Wildlife
Service, pers. comm. 1998). This phenomenon may be occurring at other
formerly large black-tailed prairie dog complexes across much of the
western portion of the species' range. At Northern Cheyenne Reservation
in southeastern Montana, a plague epizootic started in 1991 and
continued through 1996 (Young 1997), removing 97 percent of the black-
tailed prairie dog population (Fourstar, Bureau of Indian Affairs,
pers. comm. 1998). The population has begun to recover and has
increased from a low of 378 ac (153 ha) of occupied habitat to 963 ac
(390 ha). However, Young (University of Arizona, pers. comm. 1998) does
not believe that this complex will recover to its former status. The
effects of plague on prairie dogs may be exacerbated in smaller,
isolated colonies where populations are not buffered by large numbers
(where some individuals may escape infection by chance) and where
recovery may be hampered by limited immigration from other colonies.
    We believe that predation is not likely a major factor affecting
overall black-tailed prairie dog populations, but it may be important
locally or contribute to the effects of other factors. Little

[[Page 5484]]

information is available to quantify the impact of predators on prairie
dog populations.

D. The Inadequacy of Existing Regulatory Mechanisms

    We believe that inadequate regulatory mechanisms are a contributing
factor affecting overall black-tailed prairie dog populations. Many
States, Tribes, and Federal agencies recognize the historic decline and
ecological significance of the black-tailed prairie dog, but few use
available regulatory mechanisms to conserve the species. At least one
government entity in most States promotes their reduction. However,
some limited regulatory mechanisms exist for conservation of the
species.

States

    In Arizona, the Game and Fish Department classifies all prairie
dogs native to the State as nongame mammals. Although the species has
been extirpated in Arizona, a hunting season was open until 1999, when
it was closed (Shroufe, Arizona Game and Fish Department, in litt.
1999). Arizona does not require the eradication of prairie dogs for
agricultural purposes or promote recreational shooting of prairie dogs
(Shroufe, Arizona Game and Fish Department, in litt. 1998). The black-
tailed prairie dog is listed as endangered on the Arizona Game and Fish
Department ``Threatened Native Wildlife'' list (Arizona Game and Fish
Department 1988).
    In Colorado, the Division of Wildlife requires a resident or
nonresident hunting license for prairie dog shooting unless the animals
are on land owned by the shooter. The season is year-round, with no bag
or possession limit. However, for hunt contests, no participant may
take more than five prairie dogs during the contest. In 1999, the
Colorado State Legislature passed a bill prohibiting the translocation
of prairie dogs and other species into a county without the consent of
the county's commissioners (Van Pelt in prep.).
    The State of Kansas considers black-tailed prairie dogs as
agricultural pests and mandates control if an adjoining landowner files
a complaint (Knowles 1995). In recent years, some counties have invoked
``Home Rule'' to take over authority for prairie dog control from the
townships and impose mandatory control requirements on landowners. The
landowner is given the opportunity to control prairie dogs on his land
and if he fails to do so it is done by the county at the landowner's
expense (Van Pelt in prep.). Shooting of prairie dogs in Kansas is
somewhat restricted since a resident or nonresident hunting license is
required and established methods of take are listed (Williams, Kansas
Department of Wildlife and Parks, in litt. 1998).
    In Montana, the Department of Fish, Wildlife, and Parks requires no
license to shoot prairie dogs, and no limits on take or season exist.
Prairie dogs are protected on two State parks as important features of
those parks (Graham, Montana Department of Fish, Wildlife and Parks, in
litt. 1998). The Department of Fish, Wildlife, and Parks identifies the
black-tailed prairie dog as a State ``species of special concern''
(Flath 1998). The Department of Fish, Wildlife, and Parks is developing
a species conservation plan for black- and white-tailed prairie dogs in
Montana (Montana Department of Fish, Wildlife and Parks in prep.).
However, the Montana Department of Agriculture classifies prairie dogs
as ``rodents'' and ``vertebrate pests.'' The Montana Department of
Agriculture assists landowners in control of prairie dogs if requested,
but such assistance is not mandated (Sullins, Montana Department of
Agriculture, pers. comm. 1999).
    In Nebraska, the Game and Parks Commission currently considers the
black-tailed prairie dog an unprotected nongame species that can be
taken in any manner, without restrictions on shooting or control
activities. Permits are not required for residents; nonresidents must
have a small-game hunting permit. The Game and Parks Commission
recognizes prairie dog shooting as an acceptable recreational activity,
but suggests that shooting be avoided when prairie dogs have dependent
young and that shooters take responsible measures to avoid disturbance
of other wildlife species that use prairie dog colonies (Amack,
Nebraska Game and Parks Commission, in litt. 1998).
    In New Mexico, the Department of Game and Fish requires a license
to shoot prairie dogs, but there are no bag limits or restrictions
(Knowles 1998). The Petitioner reports that New Mexico considers the
prairie dog as a ``rodent pest'' and mandates that landowners destroy
prairie dogs on notice (National Wildlife Federation 1998).
    In North Dakota, the Game and Fish Department classifies the black-
tailed prairie dog as a nongame wildlife species. A resident is not
required to purchase a hunting license to shoot prairie dogs; however,
nonresidents are required to purchase one. The State sets no bag limits
or seasons for prairie dogs. The North Dakota Game and Fish Department
has published a guidebook to aid prairie dog shooters in finding
colonies (North Dakota Game and Fish Department undated). The State of
North Dakota considers the black-tailed prairie dog a pest, although
the Game and Fish Department considers it a nongame species. The North
Dakota Department of Agriculture and the county weed boards have
regulatory authority over control efforts (Van Pelt in prep.).
    In Oklahoma, the Department of Wildlife Conservation classifies the
black-tailed prairie dog as a Category II Mammal Species of Special
Concern. Prairie dog eradication is no longer mandatory in Oklahoma but
is assisted by some State agencies and local governments. Control and
recreational shooting of the species can occur on private land, but the
Department of Wildlife Conservation does not promote either activity
(Duffy, Oklahoma Department of Wildlife Conservation, in litt. 1998). A
license for recreational shooting is required by residents and
nonresidents. The Department of Wildlife Conservation requires that a
permit be obtained prior to any control. Prairie dogs cannot be reduced
in any county to fewer than 1,000 individuals, and control is not
permitted on public lands (Van Pelt in prep.).
    In South Dakota, the Department of Game, Fish, and Parks classifies
the black-tailed prairie dog as a predator/varmint and requires that a
resident or nonresident acquire a license to shoot prairie dogs. No
seasons or bag limits have been established. The South Dakota Weed and
Pest Control Statute designates the species as a statewide declared
pest. Therefore, the existence of prairie dogs constitutes an
infestation, giving the State authority to enter private land and
exterminate the animals. If a county declares an infestation,
landowners are responsible for the costs to control prairie dogs on
their land whether they want control or not (Van Pelt in prep.).
    In Texas, the Parks and Wildlife Department designates black-tailed
prairie dogs as a nongame species and is prohibited by State statute
from listing them as a State endangered species. A license is required
to hunt prairie dogs, but no season or bag limits have been
established. In 1999, the State established a regulation that requires
a nongame collection or dealer's permit to possess more than 10 live
prairie dogs or to sell prairie dogs (Van Pelt in prep.). This law does
not regulate the killing of prairie dogs for recreational,
agricultural, or nuisance purposes (Sansom, Texas Parks and Wildlife
Department, in litt. 1998). The Texas Health and Safety Code authorizes

[[Page 5485]]

counties to control prairie dogs and gives the Texas Department of
Agriculture responsibility for providing information regarding control
to requesting counties (Van Pelt in prep.).
    The Wyoming Game and Fish Department regards the black-tailed
prairie dog as a nongame wildlife species and has listed it as a
Species of Special Concern. No license is required to hunt prairie
dogs, and no seasons, bag limits, or restrictions on method of take
have been established (Van Pelt in prep.). The Game and Fish Department
supports development of seasons and bag limits for the black-tailed
prairie dog (Wichers, Wyoming Game and Fish Department, in litt. 1998).
The Wyoming Department of Agriculture lists the species as a pest. The
Wyoming Weed and Pest Control Act of 1973 authorizes counties to enter
private property to control prairie dogs if damage has been documented
to neighboring landowners (Knowles 1995).

Tribal

    Mulhern and Knowles (1995) estimated that 30 percent of black-
tailed prairie dog colonies occur on Tribal lands. Four of the seven
remaining large complexes (those with 10,000 acres or more) (Cheyenne
River, Fort Belknap, Pine Ridge, and Rosebud) occur on Tribal lands.
Two Tribes (Cheyenne River Sioux Tribe in South Dakota and Fort Belknap
in Montana) have prairie dog management plans in place (Knowles 1995).
No extensive control of prairie dogs has occurred on Cheyenne River
Sioux Tribe, Fort Belknap, or Rosebud Sioux Tribe (in South Dakota) in
recent years due to concerns related to the conservation of black-
footed ferrets. However, active recreational shooting programs on these
and other Tribal lands exist. The Cheyenne River Sioux Tribe does not
classify the prairie dog as a pest and does not require or encourage
their eradication; however, shooting of black-tailed prairie dogs
occurs year-round and without limits (Bourland and Dupris, Cheyenne
River Sioux Tribe, in litt. 1998). Recreational shooting is also
allowed on the Crow Creek Sioux Tribe in South Dakota, but chemical
control is not allowed. The Tribe states that shooting appears to have
no effect on black-tailed prairie dog numbers, and they report the
species as abundant (Miller, Crow Creek Sioux Tribe, in litt. 1998). In
1998, the Rosebud Sioux Tribe Department of Natural Resources
implemented a new licensing system for black-tailed prairie dogs in an
attempt to reduce the number of shooters. License sales were reduced by
approximately 50 percent from approximately 4,000 licenses in 1997 to
2,000 licenses in 1998 (Finnegan, Rosebud Sioux Tribe, pers. comm.
1999).

Federal Agencies

    The BIA has a trust responsibility to oversee management of Tribal
lands. The BIA's involvement in prairie dog control efforts has been
principally through management of funding for prairie dog control
programs on Tribal lands. In the northern Great Plains, from 1978-1992,
BIA funding was responsible for the control of more prairie dog habitat
than any other Federal agency in the country (Roemer and Forrest 1996).
    The Bureau of Land Management (BLM) manages prairie dogs to meet
multiple-use resource objectives including production of livestock
forage and preventing prairie dog movement to adjacent State or private
lands. Although BLM no longer actively conducts control, it still
allows control to occur by other agencies on its lands and it still
allows significant levels of unregulated sport shooting (Knowles 1995).
In a memorandum dated June 23, 1999, and expiring September 30, 2000,
the BLM instructed all of its State Directors within the range of the
black-tailed prairie dog to ``ensure that all actions authorized,
funded or carried out by their respective field offices do not
contribute to the need to list this species'' (Colby, Bureau of Land
Management, in litt. 1999). The BLM also anticipates implementing a
mandatory restriction on prairie dog hunting in portions of south
Phillips County, Montana, due to the lack of success of current
voluntary closures in the area (October 18, 1999; 64 FR 56213).
    We manage over 500 National Wildlife Refuges and their satellites,
but only about 15 refuges, satellites, or Waterfowl Production Areas
have black-tailed prairie dogs. Only two refuges have any significant
amount of occupied habitat. On the Charles M. Russell and UL Bend
National Wildlife Refuges in Montana, we manage 5,150 ac (2,090 ha) of
black-tailed prairie dog occupied habitat. We have treated burrows with
insecticide in an attempt to reduce fleas and disease transmission, and
we have moved prairie dogs to recolonize vacant or low-density towns
(Matchett 1997). The Rocky Mountain Arsenal National Wildlife Refuge in
Colorado is attempting to recover its populations subsequent to
repeated plague epizootics (U.S. Fish and Wildlife Service 1998).
Shooting of prairie dogs is currently prohibited on all National
Wildlife Refuges and satellites. Limited control has occurred on a few
wildlife refuges, primarily as a measure to prevent the spread of
prairie dogs onto adjacent private lands. At this time, all control
efforts regarding the species have been suspended on Service lands
(Clark, U.S. Fish and Wildlife Service, in litt. 1999).
    The U.S. Forest Service manages approximately 3.7 million ac (1.5
million ha) of National Grasslands, which support approximately 42,460
ac (17,200 ha) of black-tailed prairie dog occupied habitat,
approximately 1.1 percent of the National Grasslands (Sidle, U.S.
Forest Service, in litt. 1999). In response to a request from the
National Wildlife Federation and the positive 90-day finding, the U.S.
Forest Service issued a moratorium on control of black-tailed prairie
dogs during the current status review period on all lands administered
by the U.S. Forest Service. The U.S. Forest Service also noted their
intention to manage for larger prairie dog populations via new planning
efforts subject to completion and approval (Manning, U.S. Forest
Service, in litt. 1999).
    The National Park Service is involved with prairie dog control
programs through integrated pest management guidelines. During 1982-
1992, four National Parks in the northern Great Plains were involved in
prairie dog control--Badlands National Park, South Dakota; Wind Cave
National Park, South Dakota; Theodore Roosevelt National Park, North
Dakota; and Devils Tower National Monument, Wyoming (Roemer and Forrest
1996). In a memorandum dated January 14, 1999, the National Park
Service instructed Superintendents of National Parks within the Midwest
Region where prairie dogs occur (Badlands, Fort Larned, Scotts Bluff,
Theodore Roosevelt, and Wind Cave units) to suspend further treatment
of prairie dog colonies (with few exceptions) until a final
determination is made on their status (Schenk, National Park Service,
in litt. 1999).
    The U.S. Department of Agriculture's Animal and Plant Health
Inspection Service-Wildlife Services influences prairie dog control
programs through its grant-in-aid program to States, which provides
technical assistance to other State, Tribal, and Federal agencies, and
private landowners, and its distribution of prairie dog toxicants.
Roemer (1997) reported that during 1990-1994, the Animal and Plant
Health Inspection Service-Wildlife Services was involved in control of
prairie dogs over 101,660 ac (41,140 ha). Additionally, they were
involved in control programs in the early 1980s at the Pine Ridge
Indian Reservation (Oglala Sioux Tribe), South

[[Page 5486]]

Dakota. The Animal and Plant Health Inspection Service-Wildlife
Services has directed and conducted research related to the efficiency
of prairie dog and other rodent control.
    The Environmental Protection Agency deals indirectly with prairie
dog control through pesticide labeling programs including restrictions
to protect wildlife. Presently, labeling does not restrict prairie dog
control, but does address concerns for the endangered black-footed
ferret.
    In Canada, the black-tailed prairie dog is designated as vulnerable
by the Committee on the Status of Endangered Wildlife in Canada.
Control is prohibited, and only private landowners are permitted to
shoot prairie dogs (Fargey, Grasslands National Park, pers. comm.
1998).
    In Mexico, the black-tailed prairie dog is listed as threatened by
the Lista de las Especies Amerzadas, the official threatened and
endangered species list of the Mexican Government (SEMARNAP 1994). List
et al. (1997) reported that in Mexico, laws exist to stop control, but
are often not enforced, and extensive control occurs. There are no
protected areas for the black-tailed prairie dog in Mexico (Ceballos et
al. 1993).

E. Other Natural or Manmade Factors Affecting the Species' Continued
Existence

Control Effort
    We believe that control efforts have limited black-tailed prairie
dog populations, especially large-scale, well-organized efforts
conducted early in the century. These control programs were conducted
in response to concerns regarding potential forage competition with
domestic livestock. Current control efforts are limited compared to
historic efforts, but still impact a significant portion of occupied
habitat annually. A well-documented control effort has occurred over
most of the range of the black-tailed prairie dog (Anderson et al.
1986, Bell 1921, Cain et al. 1972, Forrest and Proctor in prep., Hanson
1993, Hubbard and Schmitt 1983, Lantz 1903, Lewis and Hassien 1973,
Linder et al. 1972, Merriam 1902, Roemer and Forrest 1996, Shriver
1965). Control efforts resulted in extirpation of the black-tailed
prairie dog in Arizona (Alexander 1932). Similar control efforts in
Texas resulted in the persistence of only remnant populations in areas
where, historically, the largest known populations of the species
occurred (Bureau of Sport Fisheries and Wildlife 1961, Cheatheam 1977,
Cottam and Caroline 1965).
    Prairie dog control occurred repeatedly in most areas, and figures
cited for acreage controlled may include retreatment of the same areas
in subsequent years. Therefore, annual estimates of lands treated do
not always equate to total loss of habitat. However, control (usually
in conjunction with other factors) has led to the complete loss of
occupied habitat in many areas. Organized prairie dog control gained
momentum from 1916 to 1920 when prairie dogs were controlled on tens of
millions of acres of western rangeland (Bell 1921). Federal programs
were responsible for much of this effort (Cain et al. 1972). From 1937
to 1968, 30,447,355 ac (12,331,178 ha) of prairie dog occupied habitat
were controlled (Cain et al. 1972). In the 1960s, several States
reached their lowest estimates of occupied habitat (Bureau of Sport
Fisheries and Wildlife 1961). In 1972, Compound 1080, which was used
extensively in prairie dog control efforts, was banned by Presidential
Executive Order II 11643. Although prairie dog control continued via
other toxicants, it was at a reduced rate.
    The most extensive control efforts in recent years have been
conducted in the Northern Great Plains (U.S. Forest Service 1998).
Roemer and Forrest (1996) summarized recent Federal and State control
efforts on approximately 1,045,524 ac (423,437 ha) in South Dakota,
Montana, and Wyoming. From 1978 to 1992, an average of 69,701 ac
(28,229 ha) were treated annually in these three States. These
estimates did not include estimates for private control or control
involving indirect State or Federal assistance. Forrest and Proctor (in
prep.) estimated that in recent years control conducted at the local
level probably affected ``tens of thousands'' of black-tailed prairie
dog occupied habitat on an annual basis. The BIA administered the last
large-scale control effort for black-tailed prairie dogs on the Pine
Ridge Reservation in South Dakota in the early 1980s. This effort
resulted in the eradication of most prairie dogs on approximately
458,618 ac (185,740 ha) from 1980 to 1984. From 1985 to 1986, 240,000
ac (97,000 ha) were retreated (Roemer and Forrest 1996). In 1987, after
these efforts, 57,281 ac (23,199 ha) of occupied habitat remained
(Tschetter 1988). Current estimates of occupied habitat range from
20,000 to 30,000 ac (8,000 to 12,000 ha) (Yellowhair, Pine Ridge Sioux
Tribe, pers. comm. 1999). Following control efforts on Pine Ridge,
three additional extensive control efforts targeted for the Cheyenne
River and Rosebud Reservations in South Dakota and Fort Belknap
Reservation in Montana were halted due to concerns regarding the lack
of available black-footed ferret reintroduction sites.

Vulnerability of the Species in Perspective

    Three major impacts have had a substantial influence on black-
tailed prairie dog populations. The first major impact on the species
was the initial conversion of prairie grasslands to cropland in the
eastern portion of its range from approximately the 1880s-1920s. The
conversion of native prairie to cropland likely reduced black-tailed
prairie dog occupied habitat in the United States from about 80 million
ac (32 million ha) to about 50 million ac (20 million ha) or less. The
second major impact on the species was large-scale control efforts
conducted from approximately 1918-1972 in efforts to reduce competition
between prairie dogs and domestic livestock. Repeated control efforts
likely reduced black-tailed prairie dog occupied habitat in the United
States from about 50 million ac (20 million ha) to approximately
364,000 ac (147,000 ha) by 1961 (Bureau of Sport Fisheries and Wildlife
1961). Some limited recovery and subsequent declines have since
occurred in these remnant populations. The third major impact on the
species was the inadvertent introduction of an exotic disease from the
Old World, sylvatic plague, into North American ecosystems in 1908,
with the first recorded impacts on the black-tailed prairie dog in the
1940s. These three factors, as well as other additional factors
impacting the species, are discussed below.
    We believe that many factors, alone, in combination with each
other, and synergistically, have influenced and continue to influence
black-tailed prairie dog populations. Historically, large black-tailed
prairie dog populations successfully coped with various depressant
factors, except plague, on a different scale; populations were large
and robust, while threats were few with only short-term effects.
Presently, most populations are significantly reduced and must cope
with many persistent influences that depress populations, both
temporally and permanently. Based upon our review of the available
information, we conclude that a general long-term, rangewide decline
has occurred, in addition to more recent population declines in some
areas.
    The persistence of the black-tailed prairie dog as a species may
appear secure to some observers because it is relatively abundant in
absolute numbers when compared with many other

[[Page 5487]]

species with smaller populations that are not thought to be vulnerable.
Many wildlife species in North America that have experienced
significant population declines remain viable (e.g., various game
species such as the pronghorn (Antilocapra americana)). However, the
black-tailed prairie dog is a highly social species that, for the most
part, responds to major factors causing population reductions (e.g.,
plague and control) on the basis of entire colonies rather than on an
individual basis. Additionally, adequate regulatory mechanisms are not
in place to protect or manage populations of the black-tailed prairie
dog, as they are with most game species. Therefore, populations are
likely not as viable as their absolute numbers might suggest.
    A significant portion of existing black-tailed prairie dog occupied
habitat rangewide occurs in a few large complexes. Approximately 36
percent of the remaining occupied habitat for the species in North
America occurs in seven complexes, each larger than 10,000 ac (4,000
ha). These complexes include--Buffalo Gap National Grassland/Conata
Basin, South Dakota; Cheyenne River Reservation, South Dakota; Fort
Belknap Reservation, Montana; Janos Nuevo Casas Grandes, Mexico; Pine
Ridge Reservation, South Dakota; Rosebud Reservation, South Dakota; and
Thunder Basin National Grassland, Wyoming. These complexes are
potentially vulnerable to control efforts or plague.
    Extant populations of black-tailed prairie dogs may or may not be
large enough to be resilient to ongoing or future environmental
challenges and related potential declines. Quammen (1996) provided
examples of species that were abundant, but suddenly became very rare.
For example, he reported that the passenger pigeon (Ectopistes
migratorius) numbered in the billions around 1810 and in the low
millions by the 1880s, yet was extinct in the wild by 1900. Habitat
destruction and over-harvesting depressed passenger pigeon numbers to a
few million, a level too low for a highly social and colonial species
to function (Halliday 1980). The black-tailed prairie dog numbered in
the billions around 1900, exists as a few million at present, and
appears to be declining in a significant portion of its range. The
advantages of sociality (e.g., breeding, feeding, predator defense) may
no longer offset its modern disadvantages (e.g., vulnerability to an
exotic disease and control efforts). Accordingly, the vulnerability of
the black-tailed prairie dog to population reductions is likely related
less to its absolute numbers than to the number of colonies in which it
exists, their size, their geospatial relationship, existing barriers to
immigration and emigration, and ultimately the number and nature of the
remaining direct threats to the species.

Finding

    After a thorough review of the best available scientific and
commercial information, we find that sufficient information is
currently available to support a determination that listing the black-
tailed prairie dog as threatened is warranted. This action is
appropriate because of the number and variety of threats that act in
concert to adversely affect the species. A significant recent decline
in occupied habitat has occurred due to several factors, the most
influential of which is the widespread occurrence of plague, an exotic
and lethal disease to the species. In concert with plague, the loss of
suitable habitat and inadequate regulatory mechanisms have adversely
affected remnant fragmented populations. The available information
indicates that the species is likely to become endangered throughout
all or a significant portion of its range in the foreseeable future.
    A major decline in historic black-tailed prairie dog occupied
habitat has occurred (perhaps as much as 99 percent). Sixty percent of
the species' remnant occupied habitat is vulnerable or very vulnerable
to the effects of habitat loss or modification, disease, inadequate
regulatory mechanisms, and other factors (Black-footed Ferret Recovery
Foundation, in litt. 1999). Based on our review of the available
distribution data, we estimate that approximately 30 percent of the
historic range no longer supports any appreciable number of black-
tailed prairie dogs, and that these reductions occurred at the
periphery of the historic range. However, reductions in occupied
habitat have also occurred throughout the historic range; approximately
37 percent of the suitable habitat within the historic range in the
United States has been fundamentally modified via conversion to
cropland and is not available for use by the species (Black-footed
Ferret Recovery Foundation, in litt. 1999). Additionally, habitat in
approximately 66 percent of the historic range of the species has been
degraded by the occurrence of plague (Black-footed Ferret Recovery
Foundation, in litt. 1999). These estimates are not additive inasmuch
as several factors can affect any given portion of the range.
    Recent, widely separated, site-specific declines across the area
where 60 percent of the current occupied black-tailed prairie dog
habitat now exists appear to be indicative of a general population
decline. The overall decline may be similar to the specific decline
observed across the State of Montana from 1986 to 1998 when
approximately 50 percent of all occupied habitat was lost, largely due
to plague (Montana Department of Fish, Wildlife, and Parks 1998).
Plague has incrementally extended its range and impacts on black-tailed
prairie dogs since it was first documented in the species. It may
likely continue to expand into the eastern portions of the species'
range in the immediate future, as evidenced by recent reports of
predator species' exposure to plague in previously unaffected portions
of the black-tailed prairie dog range. A decline of similar magnitude
has occurred with populations in Mexico (12 percent of current occupied
habitat); however, the decline in Mexico is due to cropland conversion,
not plague.
    At present, occupied habitat has decreased over the past century by
two orders of magnitude (or 99 percent, from approximately 100 million
ac to less than 1 million ac). If the magnitude of decline that we have
observed due to plague or cropland conversion persists in western
portions of the species' range, and manifests itself in eastern
portions of the species' range, over the next 30 years existing
occupied habitat could decline another order of magnitude to as low as
approximately 10 percent of current estimates, or approximately 0.1
percent of historic estimates.
    We have evaluated the magnitude and immediacy of threats to the
black-tailed prairie dog. The following provides a summary of these
evaluations.
    Habitat loss and fragmentation are considered a threat of moderate
magnitude. The species has lost an estimated 99 percent of its historic
occupied habitat, much of it through cropland conversion, largely in
the eastern portion of the species' range. However, a considerable
amount of potential unoccupied habitat remains, especially in the
western portion of the species' range. This unoccupied habitat could be
utilized if other factors such as disease and control efforts were not
present or were carefully managed via adequate regulatory mechanisms.
This threat is considered imminent because habitat loss continues at
present in various parts of the species' range from a variety of
activities, including cropland conversion, urbanization, change in
vegetative communities, and fragmentation.
    Overutilization via commercial use of the species as a pet is not
considered a threat because of the apparent low

[[Page 5488]]

number of individuals utilized. Overutilization via recreational
shooting is considered a threat of low magnitude. Local populations may
be impacted by shooting; however, significant rangewide population
declines due to this factor are not likely. This threat is considered
imminent because it is ongoing.
    Disease is considered a threat of moderate magnitude. Plague has
markedly reduced some populations, but has not affected all populations
at once. Some population recovery may occur, largely via unaffected
adjacent populations, before plague reoccurrence. Plague has impacted
the species and its conspecifics throughout a significant portion of
their ranges. Black-tailed prairie dog populations demonstrate nearly
100 percent mortality when exposed to plague. An epizootic may affect
an entire complex similar to a pathogen affecting an individual animal.
The spread of plague in black-tailed prairie dog populations
underscores the likelihood that areas as yet unaffected may experience
outbreaks in the future. This threat is considered imminent because it
is ongoing. Predation is not considered a threat.
    Existing regulatory mechanisms are inadequate and considered a
threat of moderate magnitude. All States within the current range of
the black-tailed prairie dog classify the species as a pest for
agricultural purposes and either allow or require its eradication
(Mulhern and Knowles 1995). Few regulatory mechanisms exist to aid in
conserving the species. This threat is considered imminent because it
is ongoing. State wildlife agencies and other interested parties are
developing a conservation plan for the species. While we support the
States' efforts and will cooperate in conservation actions for the
black-tailed prairie dog, at this early stage of development, the
conservation assessment and strategy document lacks commitments to
specific immediate actions that would affect the status of the species.
    Control programs conducted largely in response to concerns related
to potential forage competition with domestic livestock are considered
a threat of moderate magnitude. Control programs have had significant
impacts on population levels in the past. Control efforts resulted in
extirpation of the black-tailed prairie dog from Arizona and
significant reductions in other States. Current control efforts may
impact 10-20 percent of the species' overall population annually
(Forrest and Proctor, in prep.). This threat is considered imminent
because it is ongoing. Control efforts in some areas could likely be
accommodated if adequate regulatory mechanisms were in place that
balanced agricultural and wildlife conservation interests.
    We conclude that the overall magnitude of threats to the black-
tailed prairie dog throughout its range is moderate and the overall
immediacy of these threats is imminent. The black-tailed prairie dog is
considered a species without subspecies classification. Pursuant to the
Service's Listing Priority Guidance (48 FR 43098), a species for which
threats are moderate and imminent is assigned a Listing Priority Number
of 8. Region 6 currently has nine Candidate species or subspecies that
have lower Listing Priority Numbers and, therefore, are in more
immediate need of protection. Region 6 also has four species proposed
as endangered or threatened, and two species for which proposed rules
are under review. Therefore, while we have concluded that the listing
of the black-tailed prairie dog as threatened is warranted, an
immediate proposal to list is precluded by other, higher priority
actions to amend the Lists of Endangered and Threatened Wildlife and
Plants.

References Cited

    A complete list of references cited in this notice is available
upon request from the South Dakota Field Office (see ADDRESSES
section).
    Author: The primary author of this document is Pete Gober (see
ADDRESSES section).

    Authority: The authority for this action is the Endangered
Species Act of 1973 as amended (16 U.S.C. 1532 et seq.).

    Dated: February 1, 2000.
Jamie Rappaport Clark,
Director, Fish and Wildlife Service.
[FR Doc. 00-2593 Filed 2-3-00; 8:45 am]
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