Prairie-Thunder

Prairie Dogs

General Prairie Dog Facts

Identification

Prairie dogs are stocky burrowing rodents that live in colonies called “towns.” French explorers called them “little dogs”
because of the barking noise they make. Their legs are short and muscular, adapted for digging. The tail and other
extremities are short. Their hair is rather coarse with little underfur, and is sandy brown to cinnamon in color with
grizzled black and buff-colored tips. The belly is light cream to white.

Five species of prairie dogs are found in North America: the black-tailed (Cynomys ludovicianus), Mexican (C.
mexicanus), white-tailed (C. leucurus), Gunnison’s (C. gunnisoni), and Utah prairie dog (C. parvidens). The most
abundant and widely distributed of these is the black-tailed prairie dog, which is named for its black-tipped tail. Adult
black-tailed prairie dogs weigh 2 to 3 pounds (0.9 to 1.4 kg) and are 14 to 17 inches (36 to 43 cm) long. The Mexican
prairie dog also has a black-tipped tail, but is smaller than its northern relative. White-tailed, Gunnison’s, and Utah prairie
dogs all have white-tipped tails. White-tailed prairie dogs are usually smaller than blacktailed prairie dogs, weighing
between 1 1/2 and 2 1/2 pounds (0.7 to 1.1 kg). The Gunnison’s prairie dog is the smallest of the five species.

Range

Prairie dogs occupied up to 700 million acres of western grasslands in the early 1900s. The largest prairie dog colony on
record, in Texas, measured nearly 25,000 square miles (65,000 km2) and contained an estimated 400 million prairie dogs.
Since 1900, prairie dog populations have been reduced by as much as 98% in some areas and eliminated in others. This
reduction is largely the result of cultivation of prairie soils and prairie dog control programs implemented in the early and
mid-1900s. Population increases have been observed in the 1970s and 1980s, possibly due to the increased restrictions
on and reduced use of toxicants.

Habitat

All species of prairie dogs are found in grassland or short shrubland habitats. They prefer open areas of low vegetation.
They often establish colonies near intermittent streams, water impoundments, homestead sites, and windmills. They do
not tolerate tall vegetation well and avoid brush and timbered areas. In tall, mid- and mixed-grass rangelands, prairie
dogs have a difficult time establishing a colony unless large grazing animals (bison or livestock) have closely grazed
vegetation. Once established, prairie dogs can maintain their habitat on mid- and mixed-grass rangelands. In shortgrass
prairies, where moisture is limited, prairie dogs can invade and maintain acceptable habitat without assistance.

Food Habits

Prairie dogs are active above ground only during the day and spend most of their time foraging. In the spring and
summer, individuals consume up to 2 pounds (0.9 kg) of green grasses and forbs (broad-leafed, nonwoody plants) per
week. Grasses are the preferred food, making up 62% to 95% of their diet. Common foods include western wheatgrass,
blue grama, buffalo grass, sand dropseed, and sedges. Forbs such as scarlet globe mallow, prickly pear, kochia,
peppergrass, and wooly plantain are common in prairie dog diets and become more important in the fall, as green grass
becomes scarce. Prairie dogs also eat flowers, seeds, shoots, roots, and insects when available.

General Biology, Reproduction, and Behavior

Prairie dogs are social animals that live in towns of up to 1,000 acres (400 ha) or more. Larger towns are often divided
into wards by barriers such as ridges, lines of trees, and roads. Within a ward, each family or “coterie” of prairie dogs
occupies a territory of about 1 acre (0.4 ha). A coterie usually consists of an adult male, one to four adult females, and
any of their offspring less than 2 years old. Members of a coterie maintain unity through a variety of calls, postures,
displays, grooming, and other forms of physical contact.

Today, about 2 million acres of prairie dog colonies remain in North America. The black-tailed prairie dog lives in densely
populated colonies (20 to 35 per acre [48 to 84/ha]) scattered across the Great Plains from northern Mexico to southern
Canada (Fig 2). Occasionally they are found in the Rocky Mountain foothills, but rarely at elevations over 8,000 feet (2,438
m). The Mexican prairie dog occurs only in Mexico and is an endangered species. White-tailed prairie dogs live in
sparsely populated colonies in arid regions up to 10,000 feet (3,048 m). The Gunnison’s prairie dog inhabits open grassy
and brushy areas up to 12,000 feet (3,658 m). Utah prairie dogs are a threatened species, limited to central Utah.

Black-tailed prairie dog towns typically have 30 to 50 burrow entrances per acre, while Gunnison’s and whitetailed prairie
dog towns contain less than 20 per acre. Most burrow entrances lead to a tunnel that is 3 to 6 feet (1 to 2 m) deep and
about 15 feet (5 m) long. Prairie dogs construct crater- and dome-shaped mounds up to 2 feet (0.6 m) high and 10 feet (3
m) in diameter. The mounds serve as lookout stations. They also prevent water from entering the tunnels and may
enhance ventilation of the tunnels. Prairie dogs are most active during the day. In the summer, during the hottest part of
the day, they go below ground where it is much cooler. Black-tailed prairie dogs are active all year, but may stay
underground for several days during severe winter weather. The white-tailed, Gunnison’s, and Utah prairie dogs
hibernate from October through February.

Black-tailed prairie dogs reach sexual maturity after their second winter and breed only once per year. They can breed as
early as January and as late as March, depending on latitude. The other four species of prairie dogs reach sexual
maturity after their first winter and breed in March. The gestation period is about 34 days and litter sizes range from 1 to 6
pups. The young are born hairless, blind, and helpless. They remain underground for the first 6 weeks of their lives. The
pups emerge from their dens during May or June and are weaned shortly thereafter. By the end of fall, they are nearly full
grown. Survival of prairie dog pups is high and adults may live from 5 to 8 years. Even with their sentries and
underground lifestyle, predation is still a major cause of mortality for prairie dogs. Badgers, weasels, and blackfooted
ferrets are efficient predators. Coyotes, bobcats, foxes, hawks, and eagles also kill prairie dogs. Prairie rattlesnakes and
bull snakes may take young, but rarely take adult prairie dogs. Accidents, starvation, weather, parasites, and diseases
also reduce prairie dog populations, but human activities have had the greatest impact. Prairie dog colonies attract a
wide variety of wildlife. One study identified more than 140 species of wildlife associated with prairie dog towns. Vacant
prairie dog burrows serve as homes for cottontail rabbits, small rodents, reptiles, insects, and other arthropods. Many
birds, such as meadowlarks and grasshopper sparrows, appear in greater numbers on prairie dog towns than in
surrounding prairie. The burrowing owl is one of several uncommon or rare species that frequent prairie dog towns.
Others include the golden eagle, prairie falcon, ferruginous hawk, mountain plover, swift fox, and endangered
black-footed ferret.

Damage and Damage Identification

Several independent studies have produced inconsistent results regarding the impacts of prairie dogs on livestock
production. The impacts are difficult to determine and depend on several factors, such as the site conditions, weather,
current and historic plant communities, number of prairie dogs, size and age of prairie dog towns, and the intensity of
site use by livestock and other grazers. Prairie dogs feed on many of the same grasses and forbs that livestock feed on.
Annual dietary overlap ranges from 64% to 90%. Prairie dogs often begin feeding on pastures and rangeland earlier in
spring than cattle do and clip plants closer to the ground. Up to 10% of the aboveground vegetation may be destroyed
due to their burrowing and mound-building activities. Overall, prairie dogs may remove 18% to 90% of the available
forage through their activities. The species composition of pastures occupied by prairie dogs may change dramatically.
Prairie dog activities encourage shortgrass species, perennials, forbs, and species that are resistant to grazing. Annual
plants are selected against because they are usually clipped before they can produce seed. Several of the succeeding
plant species are less palatable to livestock than the grasses they replace.

Other studies, however, indicate that prairie dogs may have little or no significant effect on livestock production. One
research project in Oklahoma revealed that there were no differences in annual weight gains between steers using
pastures inhabited by prairie dogs and steers in pastures without prairie dogs. Reduced forage availability in prairie dog
towns may be partially compensated for by the increased palatability and crude protein of plants that are stimulated by
grazing. In addition, prairie dogs sometimes clip and/or eat plants that are toxic to livestock. Bison, elk, and pronghorns
appear to prefer feeding in prairie dog colonies over uncolonized grassland.

Prairie dog burrows increase soil erosion and are a potential threat to livestock, machinery, and horses with riders.
Damage may also occur to ditch banks, impoundments, field trails, and roads. Prairie dogs are susceptible to several
diseases, including plague, a severe infectious disease caused by the bacterium Yersinia pestis. Plague, which is often
fatal to humans and prairie dogs, is most often transmitted by the bite of an infected flea. Although plague has been
reported throughout the western United States, it is uncommon. Symptoms in humans include swollen and tender lymph
nodes, chills, and fever. The disease is curable if diagnosed and treated in its early stages. It is important that the public
be aware of the disease and avoid close contact with prairie dogs and other rodents. Public health is a primary concern
regarding prairie dog colonies that are in close proximity to residential areas and school yards.

Rattlesnakes and black widow spiders also occur in prairie dog towns, but can be avoided. Rattlesnakes often rest in
prairie dog burrows during the day and move through towns at night in search of food. Black widow spiders are most
often found in abandoned prairie dog holes where they form webs and raise their young. Bites from these animals are
rare, but are a threat to human health.

Legal Status

Black-tailed, white-tailed, and Gunnison’s prairie dogs are typically classified as unprotected or nuisance animals,
allowing for their control without license or permit. Most states require purchase of a small game license to shoot prairie
dogs. If the shooter is acting as an agent for the landowner to reduce prairie dog numbers, a license may not be required.
The Utah and Mexican prairie dogs are classified as threatened and endangered species, respectively. Contact your
local wildlife agency for more information.

The black-footed ferret is an endangered species that lives almost exclusively in prairie dog towns, and all active prairie
dog colonies are potential black-footed ferret habitat. It is a violation of federal law to willfully kill a black-footed ferret or
poison prairie dog towns where ferrets are present. Federal agencies must assess their own activities to determine if
they “may affect” endangered species. Some pesticides registered for prairie dog control require private applicators to
conduct ferret surveys before toxicants can be applied. Detailed information on identifying black-footed ferrets and their
sign is included in Appendix A of this chapter. To learn more about federal and state guidelines regarding prairie dog
control, black-footed ferret surveys, and block clearance procedures, contact personnel from your local Cooperative
Extension, USDAAPHIS- ADC, US Fish and Wildlife Service, or state wildlife agency office.

DAMAGE PREVENTION AND CONTROL METHODS

Exclusion

Fencing. Exclusion of prairie dogs is rarely practical, although they may be discouraged by tight-mesh, heavygauge,
galvanized wire, 5 feet (1.5 m) wide with 2 feet (60 cm) buried in the ground and 3 feet (90 cm) remaining aboveground. A
slanting overhang at the top increases the effectiveness of the fence.

Visual Barriers

Prairie dogs graze and closely clip vegetation to provide a clear view of their surroundings and improve their ability to
detect predators. Fences, hay bales, and other objects can be used to block prairie dogs’ view and thus reduce
suitability of the habitat. Franklin and Garrett (1989) used a burlap fence to reduce prairie dog activity over a two-month
period. Windrows of pine trees also reduced prairie dog activity. Unfortunately, the utility of visual barriers is limited
because of high construction and maintenance costs. Tensar snow fences (2 feet [60 cm] tall) are less costly, at about
$0.60 per foot ($1.97/m) for materials. Unfortunately, they were inconsistent in reducing reinvasion rates of prairie dog
towns in Nebraska (Hygnstrom and Virchow, unpub. data).

Cultural Methods

Grazing Management

Proper range management can be used to control prairie dogs. Use stocking rates that maintain sufficient stand density
and height to reduce recolonization of previously controlled prairie dog towns or reduce occupation of new areas. The
following general recommendations were developed with the assistance of extension range management specialists
and research scientists. Stocking Rate. Overgrazed pastures are favorable for prairie dog town establishment or
expansion. If present, prairie dogs should be included in stocking rate calculations. At a conservative population density
of 25 prairie dogs per acre (60/ha) and dietary overlap of 75%, it takes 6 acres (2.4 ha) of prairie dogs to equal 1 Animal
Unit Month (AUM) (the amount of forage that one cow and calf ingest per month during summer [about 900 pounds; 485
kg]).

Rest/Rotation Grazing

Rest pastures for a period of time during the growing season to increase grass height and maintain desired grass
species. Instead of season-long continuous grazing, use short duration or rapid rotation grazing systems, or even total
deferment during the growing season. Livestock can be excluded from vacant prairie dog towns with temporary fencing
to help vegetation regain vigor and productivity. Mid- to tallgrass species should be encouraged where they are a part of
the natural vegetation. In semiarid and shortgrass prairie zones, grazing strategies may have little effect on prairie dog
town expansion or establishment.

Grazing Distribution

Prairie dogs often establish towns in areas where livestock congregate, such as at watering sites or old homesteads.
Move watering facilities and place salt and minerals on areas that are underutilized by livestock to distribute livestock
grazing pressure more evenly. Prescribed burns in spring may enhance regrowth of desirable grass species.

Cultivation

Prairie dog numbers can be reduced by plowing or disking towns and leaving the land fallow for 1 to 2 years, where soil
erosion is not a problem. Establish tall grain crops after the second year to further discourage prairie dogs. Burrows can
be leveled and filled with a tractormounted blade to help slow reinvasion. Flood irrigation may discourage prairie dogs.

Frightening

Frightening is not a practical means of control.

Repellents

None are registered.

Toxicants

Safety Precautions.

Use pesticides safely and comply with all label recommendations. Only use products that are registered for prairie dog
control by the Environmental Protection Agency. Some pesticides registered for prairie dog control require that private
applicators conduct ferret surveys before toxicants can be applied. Detailed information on identifying black-footed
ferrets and their sign is included in Appendix A of this chapter. Seek assistance from your local extension agent or from
the USDA-APHIS-ADC if needed. Toxic Bait. The only toxic baits currently registered and legal for use to control prairie
dogs are 2% zinc phosphidetreated grain bait and pellet formulations. Zinc phosphide baits are effective and relatively
safe regarding livestock and other wildlife in prairie dog towns, if used properly. These baits are available through
national suppliers (see Supplies and Materials), USDA-APHIS-ADC, and local retail distributors. Toxic baits are most
effective when prairie dogs are active and when there is no green forage available. Therefore, it is best to apply baits in
late summer and fall. Zinc phosphide baits can only be applied from July 1 through January 31.

Prebaiting

Prairie dog burrows must be prebaited before applying toxic bait. Prebaiting will accustom prairie dogs to eating grain
and will make the toxic bait considerably more effective when it is applied. Use clean rolled oats as a prebait if you are
using 2% zinc phosphidetreated rolled oats. Drop a heaping teaspoon (4 g) of untreated rolled oats on the bare soil at
the edge of each prairie dog mound or in an adjacent feeding area. The prebait should scatter, forming about a 6-inch
(15-cm) circle. Do not place the prebait in piles or inside burrows, on top of mounds, among prairie dog droppings, or in
vegetation far from the mound.

Apply toxic bait only after the prebait has been readily eaten, which usually takes 1 to 2 days. If the prebait is not
accepted immediately, wait until it is eaten readily before applying the toxic bait. More than one application of prebait may
be necessary if rain or snow falls on the prebait. Prohibit shooting and other disturbance of the colony at least 6 weeks
prior to and during treatment.

Prebait and toxic bait can be applied by hand on foot, but mechanical bait dispensers attached to all-terrain vehicles are
more convenient and cost-effective for towns greater than 20 acres (8 ha). Motorcycles and horses can also be used to
apply prebait and toxic bait. See Supplies and Materials for information on bait dispensers.

Bait Application. Apply about 1 heaping teaspoon (4 g) of grain bait per burrow in the same way that the prebait was
applied. About 1/3 pound of prebait and 1/3 pound of zinc phosphide bait are needed per acre (0.37 kg/ha). Excess bait
that is not eaten by prairie dogs can be a hazard to nontarget wildlife or livestock. It is best to remove livestock,
especially horses, sheep, or goats, from the pasture before toxic bait is applied; however, removal is not required. Apply
toxic bait early in the day for best results and restrict any human disturbance for 3 days following treatment. Always wear
rubber gloves when handling zinc phosphide-treated baits. Follow all label directions and observe warnings regarding
bait storage and handling.

Apply prebait and bait during periods of settled weather, when vegetation is dry and dormant. Avoid baiting on wet, cold,
or windy days. Bait acceptance is usually best after August 1st or when prairie dogs are observed feeding on native
seeds and grains. Do not apply zinc phosphide to a prairie dog town more than once per year. If desired, survivors can
be removed by fumigation or shooting. Treatment with toxic baits, followed by a fumigant cleanup, is most cost-effective
for areas of more than 5 acres (2 ha). Inspection and evaluation. Inspect treated prairie dog towns 2 to 3 days after
treatment. Remove and burn or bury any dead prairie dogs that are aboveground to protect any other animals from
indirect poisoning. Success rates of 75% to 85% can usually be obtained with zinc phosphide if it is applied correctly.

To evaluate the success of a treatment, mark and plug 100 burrows 3 days prior to treatment. Count the reopened
burrows 24 hours later. Replug the same 100 burrows 3 days after treatment and again count the reopened burrows 24
hours later. Divide the number of reopened burrows (posttreatment) by the number of reopened burrows (pretreatment)
to determine the survival rate. Abandoned burrows are usually filled with spider webs, vegetation, and debris. Active
burrows are clean and surrounded by tracks, diggings, and fresh droppings at the entrances.

Zinc phosphide is a Restricted Use Pesticide, available for sale to and use by certified pesticide applicators or their
designates. Contact your county extension office for information on acquiring EPA certification. Treatment of a prairie
dog town with zinc phosphide-treated baits cost about $10 per acre ($25/ha) (includes materials and labor).

Fumigants

Fumigants, including aluminum phosphide tablets and gas cartridges, can provide satisfactory control of prairie dogs in
some situations. We do not recommend fumigation as the primary means of control for large numbers of prairie dogs
because it is costly, timeconsuming, and usually more hazardous to desirable wildlife species than toxic baits.
Fumigants cost about 5 to 10 times more per acre (ha) to apply than toxic baits. Therefore, fumigation is usually used
during spring as a follow-up to toxic bait treatment. Success rates of 85% to 95% can usually be obtained if fumigants
are applied correctly. For best results, apply fumigants in spring when soil moisture is high and soil temperature is
greater than 60o F (15o C). Fumigation failures are most frequent in dry, porous soils. Spring applications are better than
fall applications because all young prairie dogs are still in their natal burrows.

Do not use fumigants in burrows where nontarget species are thought to be present. Black-footed ferrets, burrowing
owls, swift fox, cottontail rabbits, and several other species of wildlife occasionally inhabit prairie dog burrows and
would likely be killed by fumigation. Be aware of sign and avoid fumigating burrows that are occupied by nontarget
wildlife. Some manufacturers’ labels now require private applicators to conduct blackfooted ferret surveys before
application. Detailed information on identifying black-footed ferrets and their sign is included in Appendix A of this
chapter. Burrows used by burrowing owls often have feathers, pellets, and whitewash nearby. Natal burrows are often
lined with finely shredded cow manure. Migratory burrowing owls usually arrive in the central Great Plains in late April
and leave in early October. Fumigate before late April to minimize the threat to burrowing owls.

Aluminum Phosphide

Aluminum phosphide is a Restricted Use Pesticide, registered as a fumigant for the control of burrowing rodents. The
tablets react with moisture in prairie dog burrows, and release toxic phosphine gas (PH3). Use a 4-foot (1.2-m) section of
2-inch (5-cm) PVC pipe to improve placement of the tablets. Insert the pipe into a burrow and roll the tablets down the
pipe. Place crumpled newspaper and/or a slice of sod in the burrow to prevent loose soil from smothering the tablets and
tightly pack the burrow entrance with soil. To increase efficiency, work in pairs, one person dispensing and one
plugging burrows. Always wear cotton gloves while handling aluminum phosphide. Aim containers away from the face
when opening and work into the wind to avoid inhaling phosphine gas from the container and the treated area.
Aluminum phosphide should be stored in a well-ventilated area, never inside a vehicle or occupied building. Aluminum
phosphide is classified as a flammable solid. Check with your local department of transportation for regulations
regarding transportation of hazardous materials.

Aluminum phosphide can be purchased by certified pesticide applicators through national suppliers (see Supplies and
Materials) or local retail distributors. It typically provides an 85% to 95% reduction in prairie dog populations when
applied correctly and costs about $25 per acre ($63/ha) to apply. It is typically more cost-effective to use than gas
cartridges because of the reduced handling time.

Gas Cartridges

Gas cartridges have been used for many years to control prairie dogs. When ignited, they burn and produce carbon
monoxide, carbon dioxide, and other gases. To prepare a gas cartridge for use, insert a nail or small screwdriver in the
end at marked points and stir the contents before inserting and lighting the fuse. Hold the cartridge away from you until it
starts burning, then place it deep in a burrow. Burrows should be plugged immediately in the same way as with
aluminum phosphide. Be careful when using gas cartridges because they can cause severe burns. Do not use them
near flammable materials or inside buildings. Gas cartridges are a General Use Pesticide, available through
USDA-APHIS-ADC. They provide up to 95% control when applied correctly and cost about $35 per acre ($88/ha) to apply.

Trapping

Cage traps can be used to capture individual animals, but the process is typically too expensive and time consuming to
be employed for prairie dog control. Best results are obtained by trapping in early spring after snowmelt and before
pasture green up. Bait traps with oats flavored with corn oil or anise oil.

It may be difficult to find release sites for prairie dogs. Releasing prairie dogs into an established colony will increase
stress on resident and released prairie dogs. Body-gripping traps, such as the Conibear® No. 110, are effective when
placed in burrow entrances. No. 1 Gregerson snares can be used to remove a few prairie dogs, but the snares are
usually rendered useless after each catch. Prairie dogs also can be snared by hand, using twine or monofilament line.
These traps and snares may be effective for 1- to 5-acre (0.4- to 2-ha) colonies where time is not a consideration.

Shooting

Shooting is very selective and not hazardous to nontarget wildlife. It is most effective in spring because it can disrupt
prairie dog breeding. Continuous shooting can remove 65% of the population during the year, but it usually is not
practical or cost-effective. Prairie dogs often become wary and gun-shy after extended periods of shooting. They can be
conditioned to loud noises by installing a propane cannon or old, mis-timed gasoline engine in the town for 3 to 4 days
before shooting. Long range, flat trajectory rifles are the most efficient for shooting prairie dogs. Rifles of .22 caliber or
slightly larger are most commonly used. Bipods and portable shooting benches, telescopic sights, and spotting scopes
are also useful equipment for efficient shooting. Contact a local extension office or state wildlife agency for lists of
shooters and receptive landowners.

Other Methods

A modified street sweeper vacuum has recently been used to suck prairie dogs out of their burrows. Inventor Gay
Balfour of Cortez, Colorado, reports that the “Sucker Upper” can typically clear a range of 5 to 20 acres (2 to 8 ha) per
day at a cost of $1,000 per day, not including travel expenses. This device, unfortunately, has not been independently
tested. Although relatively expensive, this method may provide a nonlethal approach to dealing with prairie dogs where
conventional methods are not appropriate or acceptable. The prairie dogs can either be euthanized with carbon dioxide
gas or relocated if a suitable site can be found. Integrated Pest Management An integrated pest management approach
dictates the timely use of a variety of cost-effective management options to reduce prairie dog damage to a tolerable
level. We recommend the application of toxic bait in the fall, followed by the application of aluminum phosphide in the
spring. If possible, defer grazing on the treated area during the next growing season to allow grasses and other
vegetation to recover. A computer program was produced by Cox and Hygnstrom in 1993 to determine cost-effective
options and economic returns of prairie dog control (see For Additional Information).

Economics of Damage and Control

Prairie dogs play an important role in the prairie ecosystem by creating islands of unique habitat that increase plant and
animal diversity. Prairie dogs are a source of food for several predators and their burrows provide homes for several
species, including the endangered black-footed ferret. Burrowing mixes soil types and incorporates organic matter, both
of which may benefit soil. It also increases soil aeration and decreases compaction. Prairie dogs provide recreational
opportunities for nature observers, photographers, and shooters. The presence of large, healthy prairie dog towns,
however, is not always compatible with agriculture and other human land-use interests.

Prairie dogs feed on many of the same grasses and forbs that livestock do. Annual dietary overlap has been estimated
from 64% to 90%. One cow and calf ingest about 900 pounds (485 kg) of forage per month during the summer (1 AUM).
One prairie dog eats about 8 pounds (17.6 kg) of forage per month during the summer. At a conservative population
density of 25 prairie dogs per acre (60/ha) and dietary overlap of 75%, it takes 6 acres (2.4/ha) of prairie dogs to equal 1
AUM. Small, rather widely dispersed colonies occupying 20 acres (8 ha) or less are tolerated by many landowners
because of the sport hunting and aesthetic opportunities they provide. Colonies that grow larger than 20 acres (8 ha)
often exceed tolerance levels because of lost AUMs, taxes, and increasing control costs. The South Dakota Department
of Agriculture (1981) reported that 730,000 acres (292,000 ha) were inhabited by prairie dogs in 1980, with a loss of
$9,570,000 in production. The South Dakota livestock grazing industry similarly estimated losses of up to $10.29 per acre
($25.43/ha) on pasture and rangeland inhabited by prairie dogs and $30.00 per acre ($74.10/ha) for occupied hay land.
Prairie dogs inhabited about 73,000 acres (29,200 ha) in Nebraska in 1987, with a loss estimated at $200,000. A reported
1/2 to 1 million acres (200,000 to 400,000 ha) are occupied in Colorado. A committee of the National Academy of Sciences
(1970) concluded that “the numerous eradication campaigns against prairie dogs and other small mammals were
formerly justified because of safety for human health and conflicts with livestock for forage.” On the other hand, Collins
et al. (1984) found it was not economically feasible to treat prairie dogs on shortgrass rangeland with zinc phosphide in
South Dakota because the annual control costs exceeded the value of forage gained. Seventeen acres (6.8 ha) would
have to be treated to gain 1 AUM. Uresk (1985) reported that South Dakota prairie dog towns treated with zinc phosphide
yielded no increase in production after 4 years. The cost-effectiveness of prairie dog control depends greatly on the age,
density, and size of the prairie dog colony; soil and grassland type; rainfall; and control method employed.