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B-85 PRAIRIE DOGS Scott E. Hygnstrom Extension Wildlife Damage Specialist Department of Forestry, Fisheries and Wildlife University of Nebraska Lincoln, NE 68583-0819 Dallas R. Virchow Extension Assistant-Wildlife Damage Panhandle Research and Extension Center University of Nebraska Scottsbluff, NE 69361 Fig. 1. Black-tailed prairie dogs, Cynomys ludovicianus Damage Prevention and Control Methods Exclusion Wire mesh fences can be installed but they are usually not practical or cost-effective. Visual barriers of suspended burlap, windrowed pine trees, or snow fence may be effective. Cultural Methods Modify grazing practices on mixed and mid-grass rangelands to exclude or inhibit prairie dogs. Cultivate, irrigate, and establish tall crops to discourage prairie dog use. Frightening No methods are effective. Repellents None are registered. Toxicants Zinc phosphide. Fumigants Aluminum phosphide. Gas cartridges. Trapping Box traps. Snares. Conibear® No. 110 (body-gripping) traps or equivalent. Shooting Shooting with .22 rimfire or larger rifles. Other Methods Several home remedies have been used but most are unsafe and are not cost-effective. PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994 Cooperative Extension Division Institute of Agriculture and Natural Resources University of Nebraska - Lincoln United States Department of Agriculture Animal and Plant Health Inspection Service Animal Damage Control Great Plains Agricultural Council Wildlife Committee

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B-85

PRAIRIE DOGSScott E. HygnstromExtension Wildlife Damage SpecialistDepartment of Forestry, Fisheries

and WildlifeUniversity of NebraskaLincoln, NE 68583-0819

Dallas R. VirchowExtension Assistant-Wildlife DamagePanhandle Research and

Extension CenterUniversity of NebraskaScottsbluff, NE 69361

Fig. 1. Black-tailed prairie dogs, Cynomysludovicianus

Damage Prevention andControl Methods

Exclusion

Wire mesh fences can be installed butthey are usually not practical orcost-effective.

Visual barriers of suspended burlap,windrowed pine trees, or snowfence may be effective.

Cultural Methods

Modify grazing practices on mixedand mid-grass rangelands toexclude or inhibit prairie dogs.

Cultivate, irrigate, and establish tallcrops to discourage prairie dog use.

Frightening

No methods are effective.

Repellents

None are registered.

Toxicants

Zinc phosphide.

Fumigants

Aluminum phosphide.

Gas cartridges.

Trapping

Box traps.

Snares.

Conibear® No. 110 (body-gripping)traps or equivalent.

Shooting

Shooting with .22 rimfire or largerrifles.

Other Methods

Several home remedies have beenused but most are unsafe and arenot cost-effective.

PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994

Cooperative Extension DivisionInstitute of Agriculture and Natural ResourcesUniversity of Nebraska - Lincoln

United States Department of AgricultureAnimal and Plant Health Inspection ServiceAnimal Damage Control

Great Plains Agricultural CouncilWildlife Committee

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Fig. 2a. Distribution of the black-tailed (light),and Gunnison’s prairie dogs (dark) in NorthAmerica.

Fig. 2b. Distribution of the white-tailed (light),Utah (medium), and Mexican prairie dogs(dark) in North America.

Identification

Prairie dogs (Fig. 1) are stocky burrow-ing rodents that live in colonies called“towns.” French explorers called them“little dogs” because of the barkingnoise they make. Their legs are shortand muscular, adapted for digging.The tail and other extremities areshort. Their hair is rather coarse withlittle underfur, and is sandy brown tocinnamon in color with grizzled blackand buff-colored tips. The belly is lightcream to white.

Five species of prairie dogs are foundin North America: the black-tailed(Cynomys ludovicianus), Mexican (C.mexicanus), white-tailed (C. leucurus),Gunnison’s (C. gunnisoni), and Utahprairie dog (C. parvidens). The mostabundant and widely distributed ofthese is the black-tailed prairie dog,which is named for its black-tippedtail. Adult black-tailed prairie dogsweigh 2 to 3 pounds (0.9 to 1.4 kg) andare 14 to 17 inches (36 to 43 cm) long.The Mexican prairie dog also has ablack-tipped tail, but is smaller than itsnorthern relative. White-tailed, Gunni-son’s, and Utah prairie dogs all havewhite-tipped tails. White-tailed prairiedogs are usually smaller than black-tailed prairie dogs, weighing between1 1/2 and 2 1/2 pounds (0.7 to 1.1 kg).The Gunnison’s prairie dog is thesmallest of the five species.

Range

Prairie dogs occupied up to 700 millionacres of western grasslands in the early1900s. The largest prairie dog colonyon record, in Texas, measured nearly25,000 square miles (65,000 km2) andcontained an estimated 400 millionprairie dogs. Since 1900, prairie dogpopulations have been reduced by asmuch as 98% in some areas and elimi-nated in others. This reduction islargely the result of cultivation of prai-rie soils and prairie dog control pro-grams implemented in the early andmid-1900s. Population increases havebeen observed in the 1970s and 1980s,possibly due to the increased restric-tions on and reduced use of toxicants.

Today, about 2 million acres of prairiedog colonies remain in North America.

The black-tailed prairie dog lives indensely populated colonies (20 to 35per acre [48 to 84/ha]) scattered acrossthe Great Plains from northern Mexicoto southern Canada (Fig 2). Occasion-ally they are found in the RockyMountain foothills, but rarely at eleva-tions over 8,000 feet (2,438 m). TheMexican prairie dog occurs only inMexico and is an endangered species.White-tailed prairie dogs live insparsely populated colonies in aridregions up to 10,000 feet (3,048 m). TheGunnison’s prairie dog inhabits opengrassy and brushy areas up to 12,000feet (3,658 m). Utah prairie dogs are athreatened species, limited to centralUtah.

Habitat

All species of prairie dogs are found ingrassland or short shrubland habitats.They prefer open areas of low vege-tation. They often establish coloniesnear intermittent streams, waterimpoundments, homestead sites, andwindmills. They do not tolerate tallvegetation well and avoid brush andtimbered areas. In tall, mid- andmixed-grass rangelands, prairie dogshave a difficult time establishing acolony unless large grazing animals(bison or livestock) have closelygrazed vegetation. Once established,prairie dogs can maintain their habitaton mid- and mixed-grass rangelands.In shortgrass prairies, where moistureis limited, prairie dogs can invade andmaintain acceptable habitat withoutassistance.

Food Habits

Prairie dogs are active above groundonly during the day and spend most oftheir time foraging. In the spring andsummer, individuals consume up to 2pounds (0.9 kg) of green grasses andforbs (broad-leafed, nonwoody plants)per week. Grasses are the preferredfood, making up 62% to 95% of theirdiet. Common foods include westernwheatgrass, blue grama, buffalo grass,sand dropseed, and sedges. Forbs suchas scarlet globe mallow, prickly pear,kochia, peppergrass, and wooly plan-tain are common in prairie dog dietsand become more important in the fall,as green grass becomes scarce. Prairiedogs also eat flowers, seeds, shoots,roots, and insects when available.

General Biology,Reproduction, andBehavior

Prairie dogs are social animals that livein towns of up to 1,000 acres (400 ha)or more. Larger towns are oftendivided into wards by barriers such asridges, lines of trees, and roads. Withina ward, each family or “coterie” ofprairie dogs occupies a territory ofabout 1 acre (0.4 ha). A coterie usuallyconsists of an adult male, one to four

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adult females, and any of their off-spring less than 2 years old. Membersof a coterie maintain unity through avariety of calls, postures, displays,grooming, and other forms ofphysical contact.

Black-tailed prairie dog towns typi-cally have 30 to 50 burrow entrancesper acre, while Gunnison’s and white-tailed prairie dog towns contain lessthan 20 per acre. Most burrowentrances lead to a tunnel that is 3 to 6feet (1 to 2 m) deep and about 15 feet(5 m) long. Prairie dogs constructcrater- and dome-shaped mounds upto 2 feet (0.6 m) high and 10 feet (3 m)in diameter. The mounds serve aslookout stations. They also preventwater from entering the tunnels andmay enhance ventilation of the tunnels.

Prairie dogs are most active during theday. In the summer, during the hottestpart of the day, they go below groundwhere it is much cooler. Black-tailedprairie dogs are active all year, butmay stay underground for severaldays during severe winter weather.The white-tailed, Gunnison’s, andUtah prairie dogs hibernate fromOctober through February.

Black-tailed prairie dogs reach sexualmaturity after their second winter andbreed only once per year. They can breedas early as January and as late as March,depending on latitude. The other fourspecies of prairie dogs reach sexualmaturity after their first winter and breedin March. The gestation period is about34 days and litter sizes range from 1 to6 pups. The young are born hairless,blind, and helpless. They remainunderground for the first 6 weeks oftheir lives. The pups emerge from theirdens during May or June and areweaned shortly thereafter. By the endof fall, they are nearly full grown. Sur-vival of prairie dog pups is high andadults may live from 5 to 8 years.

Even with their sentries and under-ground lifestyle, predation is still amajor cause of mortality for prairiedogs. Badgers, weasels, and black-footed ferrets are efficient predators.Coyotes, bobcats, foxes, hawks, andeagles also kill prairie dogs. Prairierattlesnakes and bull snakes may take

young, but rarely take adult prairiedogs. Accidents, starvation, weather,parasites, and diseases also reduceprairie dog populations, but humanactivities have had the greatest impact.

Prairie dog colonies attract a widevariety of wildlife. One study identi-fied more than 140 species of wildlifeassociated with prairie dog towns.Vacant prairie dog burrows serve ashomes for cottontail rabbits, smallrodents, reptiles, insects, and otherarthropods. Many birds, such asmeadowlarks and grasshopper spar-rows, appear in greater numbers onprairie dog towns than in surroundingprairie. The burrowing owl is one ofseveral uncommon or rare species thatfrequent prairie dog towns. Othersinclude the golden eagle, prairie fal-con, ferruginous hawk, mountainplover, swift fox, and endangeredblack-footed ferret (see Appendix A ofthis chapter).

Damage and DamageIdentification

Several independent studies have pro-duced inconsistent results regarding theimpacts of prairie dogs on livestock pro-duction. The impacts are difficult todetermine and depend on several fac-tors, such as the site conditions, weather,current and historic plant communities,number of prairie dogs, size and age ofprairie dog towns, and the intensity ofsite use by livestock and other grazers.Prairie dogs feed on many of the samegrasses and forbs that livestock feed on.Annual dietary overlap ranges from 64%to 90%. Prairie dogs often begin feedingon pastures and rangeland earlier inspring than cattle do and clip plantscloser to the ground. Up to 10% of theaboveground vegetation may be de-stroyed due to their burrowing andmound-building activities. Overall, prai-rie dogs may remove 18% to 90% of theavailable forage through their activities.

The species composition of pasturesoccupied by prairie dogs may changedramatically. Prairie dog activitiesencourage shortgrass species, perenni-als, forbs, and species that are resistantto grazing. Annual plants are selectedagainst because they are usually

clipped before they can produce seed.Several of the succeeding plant speciesare less palatable to livestock than thegrasses they replace.

Other studies, however, indicate thatprairie dogs may have little or no sig-nificant effect on livestock production.One research project in Oklahoma re-vealed that there were no differencesin annual weight gains between steersusing pastures inhabited by prairiedogs and steers in pastures withoutprairie dogs. Reduced forage avail-ability in prairie dog towns may bepartially compensated for by theincreased palatability and crude pro-tein of plants that are stimulated bygrazing. In addition, prairie dogssometimes clip and/or eat plants thatare toxic to livestock. Bison, elk, andpronghorns appear to prefer feeding inprairie dog colonies over uncolonizedgrassland.

Prairie dog burrows increase soil erosionand are a potential threat to livestock,machinery, and horses with riders. Dam-age may also occur to ditch banks,impoundments, field trails, and roads.

Prairie dogs are susceptible to severaldiseases, including plague, a severeinfectious disease caused by the bacte-rium Yersinia pestis. Plague, which isoften fatal to humans and prairie dogs,is most often transmitted by the bite ofan infected flea. Although plague hasbeen reported throughout the westernUnited States, it is uncommon. Symp-toms in humans include swollen andtender lymph nodes, chills, and fever.The disease is curable if diagnosed andtreated in its early stages. It is impor-tant that the public be aware of the dis-ease and avoid close contact withprairie dogs and other rodents. Publichealth is a primary concern regardingprairie dog colonies that are in closeproximity to residential areas andschool yards.

Rattlesnakes and black widow spidersalso occur in prairie dog towns, butcan be avoided. Rattlesnakes often restin prairie dog burrows during the dayand move through towns at night insearch of food. Black widow spidersare most often found in abandonedprairie dog holes where they form

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webs and raise their young. Bites fromthese animals are rare, but are a threatto human health.

Legal Status

Black-tailed, white-tailed, and Gunni-son’s prairie dogs are typically classi-fied as unprotected or nuisanceanimals, allowing for their controlwithout license or permit. Most statesrequire purchase of a small gamelicense to shoot prairie dogs. If theshooter is acting as an agent for thelandowner to reduce prairie dog num-bers, a license may not be required.The Utah and Mexican prairie dogs areclassified as threatened and endan-gered species, respectively. Contactyour local wildlife agency for moreinformation.

The black-footed ferret is an endan-gered species that lives almost exclu-sively in prairie dog towns, and allactive prairie dog colonies are poten-tial black-footed ferret habitat. It is aviolation of federal law to willfully killa black-footed ferret or poison prairiedog towns where ferrets are present.Federal agencies must assess their ownactivities to determine if they “mayaffect” endangered species. Some pes-ticides registered for prairie dog con-trol require private applicators toconduct ferret surveys before toxicantscan be applied. Detailed informationon identifying black-footed ferrets andtheir sign is included in Appendix A ofthis chapter. To learn more about fed-eral and state guidelines regardingprairie dog control, black-footed ferretsurveys, and block clearance proce-dures, contact personnel from yourlocal Cooperative Extension, USDA-APHIS-ADC, US Fish and WildlifeService, or state wildlife agency office.

Damage Prevention andControl Methods

Exclusion

Fencing. Exclusion of prairie dogs israrely practical, although they may bediscouraged by tight-mesh, heavy-gauge, galvanized wire, 5 feet (1.5 m)wide with 2 feet (60 cm) buried in theground and 3 feet (90 cm) remaining

8

aboveground. A slanting overhang atthe top increases the effectiveness ofthe fence.

Visual Barriers. Prairie dogs grazeand closely clip vegetation to providea clear view of their surroundings andimprove their ability to detect preda-tors. Fences, hay bales, and otherobjects can be used to block prairiedogs’ view and thus reduce suitabilityof the habitat. Franklin and Garrett(1989) used a burlap fence to reduceprairie dog activity over a two-monthperiod. Windrows of pine trees alsoreduced prairie dog activity. Unfortu-nately, the utility of visual barriers islimited because of high constructionand maintenance costs. Tensar snowfences (2 feet [60 cm] tall) are lesscostly, at about $0.60 per foot($1.97/m) for materials. Unfortunately,they were inconsistent in reducingreinvasion rates of prairie dog townsin Nebraska (Hygnstrom andVirchow, unpub. data).

Cultural Methods

Grazing Management. Proper rangemanagement can be used to controlprairie dogs. Use stocking rates thatmaintain sufficient stand density andheight to reduce recolonization of pre-viously controlled prairie dog townsor reduce occupation of new areas.The following general recommenda-tions were developed with the assis-tance of extension range managementspecialists and research scientists.

Stocking Rate. Overgrazed pasturesare favorable for prairie dog townestablishment or expansion. If present,prairie dogs should be included instocking rate calculations. At a conser-vative population density of 25 prairiedogs per acre (60/ha) and dietaryoverlap of 75%, it takes 6 acres (2.4 ha)of prairie dogs to equal 1 Animal UnitMonth (AUM) (the amount of foragethat one cow and calf ingest per monthduring summer [about 900 pounds;485 kg]).

Rest/Rotation Grazing. Rest pas-tures for a period of time during thegrowing season to increase grassheight and maintain desired grass spe-cies. Instead of season-long continuous

grazing, use short duration or rapidrotation grazing systems, or even totaldeferment during the growing season.Livestock can be excluded from vacantprairie dog towns with temporaryfencing to help vegetation regain vigorand productivity. Mid- to tallgrassspecies should be encouraged wherethey are a part of the natural vegeta-tion. In semiarid and shortgrass prairiezones, grazing strategies may havelittle effect on prairie dog town expan-sion or establishment.

Grazing Distribution. Prairie dogsoften establish towns in areas wherelivestock congregate, such as at water-ing sites or old homesteads. Movewatering facilities and place salt andminerals on areas that are under-utilized by livestock to distribute live-stock grazing pressure more evenly.Prescribed burns in spring mayenhance regrowth of desirable grassspecies.

Cultivation. Prairie dog numbers canbe reduced by plowing or diskingtowns and leaving the land fallow for1 to 2 years, where soil erosion is not aproblem. Establish tall grain cropsafter the second year to further dis-courage prairie dogs. Burrows can beleveled and filled with a tractor-mounted blade to help slow reinva-sion. Flood irrigation may discourageprairie dogs.

Frightening

Frightening is not a practical means ofcontrol.

Repellents

None are registered.

Toxicants

Safety Precautions. Use pesticidessafely and comply with all label rec-ommendations. Only use productsthat are registered for prairie dog con-trol by the Environmental ProtectionAgency. Some pesticides registered forprairie dog control require that privateapplicators conduct ferret surveysbefore toxicants can be applied.Detailed information on identifyingblack-footed ferrets and their sign isincluded in Appendix A of this

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Bait6"

Fig. 3. Prebait and toxic bait should be scattered over a 6-inch (15-cm) circle at each burrow entrance.

chapter. Seek assistance from yourlocal extension agent or from theUSDA-APHIS-ADC if needed.

Toxic Bait. The only toxic baits currentlyregistered and legal for use to controlprairie dogs are 2% zinc phosphide-treated grain bait and pellet formulations.Zinc phosphide baits are effective andrelatively safe regarding livestock andother wildlife in prairie dog towns, ifused properly. These baits are availablethrough national suppliers (see Suppliesand Materials), USDA-APHIS-ADC,and local retail distributors.

Toxic baits are most effective when prai-rie dogs are active and when there is nogreen forage available. Therefore, it isbest to apply baits in late summer andfall. Zinc phosphide baits can only beapplied from July 1 through January31.

Prebaiting. Prairie dog burrows must beprebaited before applying toxic bait.Prebaiting will accustom prairie dogs toeating grain and will make the toxic baitconsiderably more effective when it isapplied. Use clean rolled oats as a prebaitif you are using 2% zinc phosphide-treated rolled oats. Drop a heaping tea-spoon (4 g) of untreated rolled oats on thebare soil at the edge of each prairie dogmound or in an adjacent feeding area.The prebait should scatter, forming abouta 6-inch (15-cm) circle (Fig. 3). Do notplace the prebait in piles or inside bur-rows, on top of mounds, among prairiedog droppings, or in vegetation far fromthe mound.

Apply toxic bait only after the prebaithas been readily eaten, which usuallytakes 1 to 2 days. If the prebait is notaccepted immediately, wait until it iseaten readily before applying the toxicbait. More than one application ofprebait may be necessary if rain orsnow falls on the prebait. Prohibitshooting and other disturbance of thecolony at least 6 weeks prior to andduring treatment.

Prebait and toxic bait can be appliedby hand on foot, but mechanical baitdispensers attached to all-terrain ve-hicles are more convenient and cost-ef-fective for towns greater than 20 acres(8 ha). Motorcycles and horses can alsobe used to apply prebait and toxic bait.See Supplies and Materials for infor-mation on bait dispensers.

Bait Application. Apply about 1 heap-ing teaspoon (4 g) of grain bait per bur-row in the same way that the prebaitwas applied. About 1/3 pound ofprebait and 1/3 pound of zinc phos-phide bait are needed per acre (0.37kg/ha). Excess bait that is not eaten byprairie dogs can be a hazard to nontar-get wildlife or livestock. It is best to re-move livestock, especially horses,sheep, or goats, from the pasture be-fore toxic bait is applied; however, re-moval is not required. Apply toxic baitearly in the day for best results andrestrict any human disturbance for 3days following treatment. Alwayswear rubber gloves when handlingzinc phosphide-treated baits. Followall label directions and observe warn-

ings regarding bait storage andhandling.

Apply prebait and bait during periodsof settled weather, when vegetation isdry and dormant. Avoid baiting onwet, cold, or windy days. Bait accep-tance is usually best after August 1stor when prairie dogs are observedfeeding on native seeds and grains. Donot apply zinc phosphide to a prairiedog town more than once per year. Ifdesired, survivors can be removed byfumigation or shooting. Treatmentwith toxic baits, followed by a fumi-gant cleanup, is most cost-effective forareas of more than 5 acres (2 ha).

Inspection and evaluation. Inspecttreated prairie dog towns 2 to 3 daysafter treatment. Remove and burn orbury any dead prairie dogs that areaboveground to protect any other ani-mals from indirect poisoning. Successrates of 75% to 85% can usually be ob-tained with zinc phosphide if it is ap-plied correctly.

To evaluate the success of a treatment,mark and plug 100 burrows 3 daysprior to treatment. Count the reopenedburrows 24 hours later. Replug thesame 100 burrows 3 days after treat-ment and again count the reopenedburrows 24 hours later. Divide thenumber of reopened burrows (post-treatment) by the number of reopenedburrows (pretreatment) to determinethe survival rate. Abandoned burrowsare usually filled with spider webs,vegetation, and debris. Active burrowsare clean and surrounded by tracks,diggings, and fresh droppings at theentrances.

Zinc phosphide is a Restricted Use Pes-ticide, available for sale to and use bycertified pesticide applicators or theirdesignates. Contact your county exten-sion office for information on acquiringEPA certification. Treatment of a prairiedog town with zinc phosphide-treatedbaits cost about $10 per acre ($25/ha)(includes materials and labor).

Fumigants

Fumigants, including aluminum phos-phide tablets and gas cartridges, canprovide satisfactory control of prairiedogs in some situations. We do not

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recommend fumigation as the primarymeans of control for large numbers ofprairie dogs because it is costly, time-consuming, and usually more hazard-ous to desirable wildlife species thantoxic baits. Fumigants cost about 5 to10 times more per acre (ha) to applythan toxic baits. Therefore, fumigationis usually used during spring as afollow-up to toxic bait treatment. Suc-cess rates of 85% to 95% can usually beobtained if fumigants are applied cor-rectly.

For best results, apply fumigants inspring when soil moisture is high andsoil temperature is greater than 60o F(15o C). Fumigation failures are mostfrequent in dry, porous soils. Springapplications are better than fall appli-cations because all young prairie dogsare still in their natal burrows.

Do not use fumigants in burrowswhere nontarget species are thought tobe present. Black-footed ferrets, bur-rowing owls, swift fox, cottontail rab-bits, and several other species of wild-life occasionally inhabit prairie dogburrows and would likely be killed byfumigation. Be aware of sign andavoid fumigating burrows that are oc-cupied by nontarget wildlife. Somemanufacturers’ labels now requireprivate applicators to conduct black-footed ferret surveys before applica-tion. Detailed information on identify-ing black-footed ferrets and their signis included in Appendix A of thischapter. Burrows used by burrowingowls often have feathers, pellets, andwhitewash nearby. Natal burrows areoften lined with finely shredded cowmanure. Migratory burrowing owlsusually arrive in the central GreatPlains in late April and leave in earlyOctober. Fumigate before late April tominimize the threat to burrowingowls.

Aluminum Phosphide. Aluminumphosphide is a Restricted Use Pesti-cide, registered as a fumigant for thecontrol of burrowing rodents. The tab-lets react with moisture in prairie dogburrows, and release toxic phosphinegas (PH3). Use a 4-foot (1.2-m) sectionof 2-inch (5-cm) PVC pipe to improveplacement of the tablets. Insert the

0

pipe into a burrow and roll the tabletsdown the pipe. Place crumpled news-paper and/or a slice of sod in the bur-row to prevent loose soil from smoth-ering the tablets and tightly pack theburrow entrance with soil. To increaseefficiency, work in pairs, one persondispensing and one plugging burrows.

Always wear cotton gloves while han-dling aluminum phosphide. Aim con-tainers away from the face whenopening and work into the wind toavoid inhaling phosphine gas from thecontainer and the treated area. Alumi-num phosphide should be stored in awell-ventilated area, never inside avehicle or occupied building. Alumi-num phosphide is classified as a flam-mable solid. Check with your localdepartment of transportation for regu-lations regarding transportation ofhazardous materials.

Aluminum phosphide can be pur-chased by certified pesticide applica-tors through national suppliers (seeSupplies and Materials) or local retaildistributors. It typically provides an85% to 95% reduction in prairie dogpopulations when applied correctlyand costs about $25 per acre ($63/ha)to apply. It is typically more cost-effec-tive to use than gas cartridges becauseof the reduced handling time.

Gas Cartridges. Gas cartridges havebeen used for many years to controlprairie dogs. When ignited, they burnand produce carbon monoxide, carbondioxide, and other gases. To prepare agas cartridge for use, insert a nail orsmall screwdriver in the end atmarked points and stir the contentsbefore inserting and lighting the fuse.Hold the cartridge away from youuntil it starts burning, then place itdeep in a burrow. Burrows should beplugged immediately in the same wayas with aluminum phosphide. Be care-ful when using gas cartridges becausethey can cause severe burns. Do notuse them near flammable materials orinside buildings. Gas cartridges are aGeneral Use Pesticide, availablethrough USDA-APHIS-ADC. Theyprovide up to 95% control when ap-plied correctly and cost about $35 peracre ($88/ha) to apply.

Trapping

Cage traps can be used to captureindividual animals, but the process istypically too expensive and time con-suming to be employed for prairie dogcontrol. Best results are obtained bytrapping in early spring after snow-melt and before pasture green up. Baittraps with oats flavored with corn oilor anise oil.

It may be difficult to find release sites forprairie dogs. Releasing prairie dogs intoan established colony will increase stresson resident and released prairie dogs.

Body-gripping traps, such as theConibear® No. 110, are effective whenplaced in burrow entrances. No. 1Gregerson snares can be used to removea few prairie dogs, but the snares areusually rendered useless after each catch.Prairie dogs also can be snared by hand,using twine or monofilament line. Thesetraps and snares may be effective for 1- to5-acre (0.4- to 2-ha) colonies where timeis not a consideration.

Shooting

Shooting is very selective and not haz-ardous to nontarget wildlife. It is mosteffective in spring because it can dis-rupt prairie dog breeding. Continuousshooting can remove 65% of the popu-lation during the year, but it usually isnot practical or cost-effective. Prairiedogs often become wary and gun-shyafter extended periods of shooting.They can be conditioned to loud noisesby installing a propane cannon or old,mis-timed gasoline engine in the townfor 3 to 4 days before shooting.

Long range, flat trajectory rifles are themost efficient for shooting prairiedogs. Rifles of .22 caliber or slightlylarger are most commonly used.Bipods and portable shooting benches,telescopic sights, and spotting scopesare also useful equipment for efficientshooting. Contact a local extensionoffice or state wildlife agency for listsof shooters and receptive landowners.

Other Methods

An amazing variety of home remedieshave been tried in desperate attemptsto control prairie dogs. Engine

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exhaust, dry ice, butane, propane,gasoline, anhydrous ammonia, insecti-cides, nonregistered rodenticides,water, and dilute cement are allunregistered for prairie dog control.None have proven to be as cost-effective or successful as registeredrodenticides, and most are hazardousto applicators and/or nontarget spe-cies. In addition, those methods thathave been observed by the authors(exhaust, propane, ammonia, nonreg-istered rodenticides, and water) weresubstantially more expensive than reg-istered and recommended methods.

A modified street sweeper vacuum hasrecently been used to suck prairie dogsout of their burrows. Inventor GayBalfour of Cortez, Colorado, reports thatthe “Sucker Upper” can typically cleara range of 5 to 20 acres (2 to 8 ha) perday at a cost of $1,000 per day, notincluding travel expenses. This device,unfortunately, has not been indepen-dently tested. Although relativelyexpensive, this method may provide anonlethal approach to dealing withprairie dogs where conventionalmethods are not appropriate or accept-able. The prairie dogs can either beeuthanized with carbon dioxide gas orrelocated if a suitable site can be found.

Integrated Pest Management

An integrated pest managementapproach dictates the timely use of avariety of cost-effective managementoptions to reduce prairie dog damage toa tolerable level. We recommend theapplication of toxic bait in the fall, fol-lowed by the application of aluminumphosphide in the spring. If possible,defer grazing on the treated area duringthe next growing season to allow grassesand other vegetation to recover. A com-puter program was produced by Coxand Hygnstrom in 1993 to determinecost-effective options and economicreturns of prairie dog control (see ForAdditional Information).

Economics of Damageand Control

Prairie dogs play an important role inthe prairie ecosystem by creatingislands of unique habitat that increase

plant and animal diversity. Prairiedogs are a source of food for severalpredators and their burrows providehomes for several species, includingthe endangered black-footed ferret.Burrowing mixes soil types and incor-porates organic matter, both of whichmay benefit soil. It also increases soilaeration and decreases compaction.Prairie dogs provide recreationalopportunities for nature observers,photographers, and shooters. Thepresence of large, healthy prairie dogtowns, however, is not always compat-ible with agriculture and other humanland-use interests.

Prairie dogs feed on many of the samegrasses and forbs that livestock do.Annual dietary overlap has been esti-mated from 64% to 90%. One cow andcalf ingest about 900 pounds (485 kg)of forage per month during the sum-mer (1 AUM). One prairie dog eatsabout 8 pounds (17.6 kg) of forage permonth during the summer. At a con-servative population density of 25prairie dogs per acre (60/ha) anddietary overlap of 75%, it takes 6 acres(2.4/ha) of prairie dogs to equal 1AUM. Small, rather widely dispersedcolonies occupying 20 acres (8 ha) orless are tolerated by many landownersbecause of the sport hunting andaesthetic opportunities they provide.Colonies that grow larger than 20 acres(8 ha) often exceed tolerance levelsbecause of lost AUMs, taxes, andincreasing control costs.

The South Dakota Department ofAgriculture (1981) reported that730,000 acres (292,000 ha) were inhab-ited by prairie dogs in 1980, with a lossof $9,570,000 in production. The SouthDakota livestock grazing industrysimilarly estimated losses of up to$10.29 per acre ($25.43/ha) on pastureand rangeland inhabited by prairiedogs and $30.00 per acre ($74.10/ha)for occupied hay land. Prairie dogsinhabited about 73,000 acres (29,200ha) in Nebraska in 1987, with a lossestimated at $200,000. A reported 1/2to 1 million acres (200,000 to 400,000ha) are occupied in Colorado. A com-mittee of the National Academy of Sci-ences (1970) concluded that “thenumerous eradication campaigns

against prairie dogs and other smallmammals were formerly justified be-cause of safety for human health andconflicts with livestock for forage.”

On the other hand, Collins et al. (1984)found it was not economically feasible totreat prairie dogs on shortgrass range-land with zinc phosphide in SouthDakota because the annual control costsexceeded the value of forage gained.Seventeen acres (6.8 ha) would have tobe treated to gain 1 AUM. Uresk (1985)reported that South Dakota prairie dogtowns treated with zinc phosphideyielded no increase in production after 4years. The cost-effectiveness of prairiedog control depends greatly on the age,density, and size of the prairie dog colony;soil and grassland type; rainfall; andcontrol method employed.

Acknowledgments

We acknowledge M. J. Boddicker and F. R.Henderson, who authored the “Prairie Dogs”and “Black-footed Ferrets” chapters,respectively, in the 1983 edition of Preventionand Control of Wildlife Damage.

Figure 1 by Emily Oseas Routman.

Figure 2 by Dave Thornhill, University ofNebraska.

Figure 3 by Renee Lanik, University of Nebraska.

For AdditionalInformation

Agnew, W., D. W. Uresk, and R. M. Hansen.1986. Flora and fauna associated with prairiedog colonies and adjacent ungrazed mixed-grass prairie in western South Dakota. J.Range. Manage. 39:135-139.

Bonham, C.D., and A. Lerwick. 1976. Vegetationchanges induced by prairie dogs on shortgrassrange. J. Range Manage. 29:217-220.

Cable, K. A., and R. M. Timm. 1988. Efficacy ofdeferred grazing in reducing prairie dogreinfestation rates. Proc. Great Plains Wildl.Damage Control Workshop 8:46-49.

Cincotta, R. P., D. W. Uresk, and R. M. Hansen.1987. Demography of black-tailed prairie dogpopulations reoccupying sites treated withrodenticide. Great Basin Nat. 47:339-343.

Clark, T. W. 1986. Annotated prairie dogbibliography 1973 to 1985. Montana BureauLand Manage. Tech. Bull. No. 1. Helena. 32 pp.

Clark, T. W., T. M. Campbell, III, M. H.Schroeder, and L. Richardson. 1983.Handbook of methods for locating black-footed ferrets. Wyoming Bureau LandManage. Tech. Bull. No. 1. Cheyenne. 55 pp.

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Committee. 1970. Vertebrate Pests: Problemsand Control. Natl. Acad. of Science.Washington, DC. 153 pp.

Collins, A. R., J. P. Workman, and D. W. Uresk.1984. An economic analysis of black-tailedprairie dog (Cynomys ludovicianus) control.J. Range Manage. 37:358-361.

Cox, M. K., and S. E. Hygnstrom. 1991. Prairie dogcontrol: a computer model for prairie dogmanagement on rangelands. Proc. Great PlainsWildl. Damage Control Workshop 10:68-69.

Dobbs, T. L. 1984. Economic losses due to prairiedogs in South Dakota. South Dakota Dep. Agric.Div. Agric. Regs. Inspect. Pierre. 15 pp.

Fagerstone, K. A. 1982. A review of prairie dogdiet and its variability among animals andcolonies. Proc. Great Plains Wildl. DamageControl Workshop 5:178-184.

Franklin, W. L., and M. G. Garrett. 1989.Nonlethal control of prairie dog colonyexpansion with visual barriers. Wildl. Soc.Bull. 17:426-430.

Foster-McDonald, N. S., and S. E. Hygnstrom.1990. Prairie dogs and their ecosystem. Univ.Nebraska. Dep. For., Fish. Wildl. Lincoln. 8 pp.

Hansen, R. M., and I. Gold. 1977. Blacktailprairie dogs, desert cottontails and cattletrophic relations on shortgrass range.J. Range Manage. 30:210-214.

2

Appendix A

Fig. 4. Black-footed ferret, Mustela nigripes

Hygnstrom, S. E., and P. M. McDonald. 1989.Efficacy of three formulations of zincphosphide for black-tailed prairie dogcontrol. Proc. Great Plains Wildl. DamageControl Workshop 9:181.

Hygnstrom, S. E., and D. R. Virchow. 1988. Prairiedogs and their control. Univ. Nebraska-Coop.Ext. NebGuide No. C80-519. Lincoln. 4 pp.

Knowls, C. J. 1986. Population recovery of blacktailed prairie dogs following control with zincphosphide. J. Range Manage. 39:249-251.

Koford, C. B. 1958. Prairie dogs, whitefaces andblue grama. Wildl. Mono. 3:1-78.

Merriam, C. H. 1902. The prairie dog of the GreatPlains. Pages 257-270 in Yearbook of the USDA.US Govt. Print. Office. Washington, DC.

O’Meilia, M. E., F. L. Knopf, and J. C. Lewis.1982. Some consequences of competitionbetween prairie dogs and beef cattle.J. Range Manage. 35:580-585.

Schenbeck, G. L. 1981. Management of black-tailed prairie dogs on the NationalGrasslands. Proc. Great Plains Wildl.Damage Control Workshop 5:207-213.

Sharps, J. C., and D. W. Uresk. 1990. Ecologicalreview of black-tailed prairie dogs andassociated species in western South Dakota.Great Basin Nat. 50:339-345.

BLACK-FOOTED FERRETS

Snell, C. P., and B. D. Hlavachick. 1980. Controlof prairie dogs - the easy way. Rangelands2:239-240.

South Dakota Department of Agriculture. 1981.Vertebrate rodent economic loss, SouthDakota 1980. US Dep. Agric. Stat. Rep. Serv.Sioux Falls. 4 pp.

Uresk, D. W. 1985. Effects of controlling black-tailed prairie dogs on plant production.J. Range Manage. 38:466-468.

Uresk, D. W. 1987. Relation of black-tailedprairie dogs and control programs tovegetation, livestock, and wildlife. Pages312-322 in J. L. Caperinera, ed. Integratedpest management on rangeland: a shortgrassprairie perspective. Westview Press.Boulder, Colorado.

Uresk, D. W., J. G. MacCracken, and A. J.Bjugstad. 1982. Prairie dog density and cattlegrazing relationships. Great Plains Wildl.Damage Control Workshop. 5:199-201.

Whicker, A. D., and J. K. Detling. 1988.Ecological consequences of prairie dogdisturbances. BioSci. 38:778-785.

Computer Software

Cox, M. K., and S. E. Hygnstrom. 1993. Prairiedog control: An educational guide,population model, and cost-benefit analysisfor prairie dog control. Available from 105ACB IANR-CCS, University of Nebraska,Lincoln, NE 68583-0918.

Introduction

The black-footed ferret (Mustelanigripes, Fig. 4) is the most rare andendangered mammal in NorthAmerica. Black-footed ferrets establishtheir dens in prairie dog burrows andfeed almost exclusively on prairie

dogs. The reduction in prairie dognumbers in the last 100 years and theisolation and disappearance of manylarge towns has led to the decline ofthe ferret population. Large andhealthy prairie dog towns are neededto ensure that black-footed ferrets sur-vive in the wild.

Identification

Black-footed ferrets are members ofthe weasel family and are the only fer-ret native to North America. The mostobvious distinguishing feature is thestriking black mask across the face.The feet, legs, and tip of the tail are

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Bridled weasel

Domestic (fitch) ferret

Mink

Fig. 5. Three animals that may be mistaken forthe black-footed ferret.

also black. The remaining coat is paleyellow-brown, becoming lighter on theunder parts of the body and nearlywhite on the forehead, muzzle, andthroat. The top of the head and middleof the back are a darker brown. Ferretshave short legs, long, well-developedclaws on the front paws, large pointedears, and relatively large eyes.

Ferrets are similar in size and weightto wild mink. Adult male ferrets are 21to 23 inches (53.3 to 58.4 cm) long andweigh 2 to 2 1/2 pounds (0.9 to 1.2 kg).Females are slightly smaller.

The native black-footed ferret may beconfused with the domestic Europeanfitch ferret, long-tailed weasel, bridledweasel, or wild mink (Fig. 5). Thedomestic fitch ferret has longer anddarker pelage on the back, yellowishunderfur, and an entirely black tail.The bridled weasel is a variant of the

longtail weasel. It occurs in southwestKansas, parts of Oklahoma, Texas, andNew Mexico. The bridled weasel has amask or dark markings on its face, butis smaller than a black-footed ferret. Itdoes not have black feet, and it has atail that is longer in relation to its totalbody length. Mink are about the samesize as black-footed ferrets but aredark brown and occasionally havewhite markings on the throat.

Range

The original range of the black-footedferret included most of the GreatPlains area. Its current range withinthe Great Plains is unknown, althoughit is assumed to be greatly reducedfrom the original range. Currently theonly known wild ferret population isan experimental population that has

been released in north-central Wyo-ming. For the past 10 years, biologistshave intensively searched for and in-vestigated hundreds of reports ofblack-footed ferrets, but no new popu-lations have been found. In addition, apublic reward of $5,000 to $10,000 wasavailable during the 1980s for sightingsof black-footed ferrets, but none wereconfirmed. Current efforts are beingmade to identify black-footed ferrethabitat and potential reproductionsites. Captive breeding populations areheld at Wheatland, Wyoming, at theWyoming Game and Fish Depart-ment’s Sybille Conservation and Edu-cation Center, and at zoos in Omaha,Nebraska; Washington, DC; Louisville,Kentucky; Colorado Springs, Colo-rado; Phoenix, Arizona; and Toronto,Ontario.

Habitat

Black-footed ferrets rely on prairiedogs for both food and shelter. There-fore, all active prairie dog colonies areconsidered potential black-footed fer-ret habitat. Resident ferrets have onlybeen found in prairie dog towns. Tran-sient and dispersing ferrets may crossareas that are not occupied by prairiedogs.

General Biology,Reproduction, andBehavior

Normally 4 young ferrets are born perlitter in May and June. The motheralone cares for the young and directstheir activities until they disperse inmid-September. The young are firstobserved aboveground during day-light hours in July.

From June to mid-July, the ferret fam-ily remains in the same general area ofthe prairie dog town. Around the mid-dle of July, after the young are activeaboveground at night, the familyextends its area of activity. By themiddle of July the young ferrets areweaned at nearly one-half adult size.

By early August, the mother ferretseparates the young and places themin different burrows. At this time some

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of the young occasionally hunt at nightby themselves. By mid-August, theycan be seen during daylight hours,peering out of their burrow, playingnear the entrance, and sometimes fol-lowing the adult female.

By late August or early September,when the young are as large as theadult, the ferret family starts to dis-perse and is no longer seen as a closelyknit group. The young ferrets are soli-tary during the late fall, winter, andearly spring. In December, ferretsbecome active just after sunset and areactive at least until midnight.

Legal Status

The black-footed ferret is classified asan endangered species and receivesfull protection under the FederalEndangered Species Act of 1973 (PL93-205). The act, as amended, requiresfederal agencies to ensure that any ac-tion authorized, funded, or carried outby them is not likely to jeopardize thecontinued existence of a threatened orendangered species or their habitat.Regulations implementing Section 7 ofthe act require that federal agenciesdetermine if any actions they propose“may affect” any threatened or endan-gered species. If it is determined that aproposed action “may affect,” then theagency is required to request formalSection 7 consultation with the US Fishand Wildlife Service. Section 9 of theact prohibits any person (including thefederal government) from the “taking”of a listed species. The term take meansto harass, harm, pursue, hunt, shoot,wound, kill, capture, or collect, or toattempt to engage in any such conduct.Habitat destruction constitutes the tak-ing of a listed species.

Guidelines for black-footed ferretsearches have been developed by theUS Fish and Wildlife Service (Black-footed Ferret Survey Guidelines forCompliance with the Endangered Spe-cies Act, 1989). Federal agencies arerequired by the US Fish and WildlifeService to conduct black-footed ferretsurveys if their proposed actions mayaffect ferrets or their habitat. Althoughencouraged to do so, private landown-ers and applicators are not required by

4

law to conduct surveys unless theiractivities are associated with federalprograms or if they are specificallydirected by pesticide labels. Compli-ance with or disregard for black-footedferret survey guidelines does not, ofitself, show compliance with or viola-tion of the Endangered Species Act orany derived regulations.

Guidelines for Black-footed Ferret Surveys

Any actions that kill prairie dogs oralter their habitat could prove detri-mental to ferrets occupying affectedprairie dog towns. The US Fish andWildlife Service guidelines shouldassist agencies or their authorized rep-resentatives in designing surveys to“clear” prairie dog towns prior to ini-tiation of construction projects, prairiedog control projects, or other actionsthat affect prairie dogs. If these guide-lines are followed by individuals con-ducting black-footed ferret surveys,agency personnel can be reasonablyconfident in results that indicate black-footed ferrets are not occupying a pro-posed project area.

Delineation of Survey Areas. Untilthe time that wildlife agencies are ableto identify reintroduction areas and toclassify other areas as being free of fer-rets, surveys for black-footed ferretswill usually be recommended. Duringthis interim period the followingapproach is recommended to deter-mine where surveys are needed.

A black-tailed prairie dog town orcomplex of less than 80 acres (32 ha)having no neighboring prairie dogtowns may be developed or treatedwithout a ferret survey. A neighboringprairie dog town is defined as one lessthan 4.3 miles (7 km) from the nearestedge of the town being affected by aproject.

Black-tailed prairie dog towns or com-plexes greater than 80 acres (32 ha) butless than 1,000 acres (400 ha) may becleared after a survey for black-footedferrets has been completed, providedthat no ferrets or ferret sign have beenfound.

A white-tailed prairie dog town orcomplex of less than 200 acres (81 ha)having no neighboring prairie dogtowns may be cleared without a ferretsurvey. White-tailed prairie dog townsor complexes greater than 200 acres(81 ha) but less than 1,000 acres (400ha), may be cleared after completion ofa survey for black-footed ferrets, pro-vided that no ferrets or their sign werefound during the survey.

Contact the US Fish and Wildlife Ser-vice before any federally funded orpermitted activities are conducted onblack-tailed or white-tailed prairie dogtowns or complexes greater than 1,000acres, to determine the status of thearea for future black-footed ferretreintroductions.

Defining a Prairie Dog Town/Complex

For the purpose of this document aprairie dog town is defined as a groupof prairie dog holes in which the den-sity meets or exceeds 20 burrows perhectare (8 burrows/acre). Prairie dogholes need not be active to be countedbut they should be recognizable andintact; that is, not caved in or filledwith debris. A prairie dog complexconsists of two or more neighboringprairie dog towns, each less than 4.3miles (7 km) from the other.

Timing of Surveys

The US Fish and WIldlife Service rec-ommends that surveys for black-footed ferrets be conducted as close tothe initiation of a project constructiondate as possible but not more than 1year before the start of a proposedaction. This is recommended to mini-mize the chance that a ferret mightmove into an area during the periodbetween completion of a survey andthe start of a project.

Project Type

Construction projects (buildings, facili-ties, surface coal mines, transmissionlines, major roadways, large pipelines,impoundments) that permanently alterprairie dog towns should be surveyed.Projects of a temporary nature andthose that involve only minor distur-bances (fences, some power lines,

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underground cables) may be exempt-ed from surveys when project activi-ties are proposed on small prairie dogtowns or complexes of less than 1,000acres (400 ha), do not impact thoseareas where ferret sightings have beenfrequently reported, or occur on areaswhere no confirmed sightings havebeen made in the last 10 years.

The US Fish and Wildlife Service rec-ommends that before any actioninvolving the use of a toxicant in ornear a prairie dog town begins, a sur-vey for ferrets should be conducted. Iftoxicants or fumigants are to be used,and the town proposed for treatmentis in a complex of less than 1,000 acres(400 ha), the town should be surveyedusing the nocturnal survey technique30 days or less before treatment.Prairie dog towns or complexes great-er than 1,000 acres (400 ha) should notbe poisoned without first contactingyour local US Fish and Wildlife Serviceoffice.

Survey Methods

Method 1 — Daylight surveys forferrets are recommended if surveysare conducted between December 1and March 31. This type of survey isused to locate signs left by ferrets.During winter months, ferret scats,prairie dog skulls, and diggings aremore abundant because prairie dogsare less active and less likely to disturbor destroy ferret sign. When there issnow cover, both ferret tracks andfresh diggings are more obvious anddetectable.

Daylight searches for ferret signshould meet the following criteria tofulfill the minimum standards of theseguidelines:

1. Three searches must be made oneach town. Conduct each searchwhen fresh snow has been presentfor at least 24 hours and after 10 ormore days have passed betweeneach search period.

2. Vehicles driven at less than 5 milesper hour (8.3 km/hr) may be usedto search for tracks or ferret dig-gings, but complete visual inspec-tions of each part of the town being

surveyed is required (that is, visu-ally overlapping transects).

3. If ferret sign is observed, photo-graph the sign and make drawingsand measurements of diggingsbefore contacting the US Fish andWildlife Service and state wildlifeagency.

Method 2 — Nighttime surveysinvolve the use of spotlighting tech-niques for locating ferrets. This surveymethod is designed to locate ferretswhen the maximum population andthe longest periods of ferret activityare expected to occur.

Minimum standards should be fol-lowed as recommended below:

1. Conduct surveys between July 1and October 31.

2. Continuously survey the prairiedog town using spotlights. Beginsurveys at dusk and continue untildawn on each of at least 3 consecu-tive nights. Divide large prairie dogcolonies into tracts of 320 acres (130ha) and search each tract systemati-cally throughout 3 consecutivenights. Rough uneven terrain andtall dense vegetation may requiresmaller tracts to result in effectivecoverage of a town.

3. Begin observations on each prairiedog town or tract at a differentstarting point on each successivenight to maximize the chance ofoverlapping nighttime activityperiods of ferrets.

4. A survey crew should consist ofone vehicle and two observersequipped with two 200,000 to300,000 candlepower (lumen) spot-lights. In terrain not suitable forvehicles, a crew should consist oftwo individuals working on footwith battery-powered 200,000 to300,000 candlepower (lumen) spot-lights. To estimate the number ofcrew nights for a survey, divide thetotal area of prairie dog town to besurveyed by 320 acres (130 km) andmultiply by 3. One or both of theobservers in each survey crewshould be a biologist trained in fer-ret search techniques.

Additional information on data collec-tion, reporting, and training work-shops are included in Black-footed FerretSurvey Guidelines for Compliance with theEndangered Species Act, 1989, availablefrom the US Fish and Wildlife Service.

Black-footed Ferret Sign

To determine if black-footed ferrets areliving in a given area, some sign mustbe found or a ferret observed. Evi-dence such as tracks, diggings, ordroppings is uncommon, even whereferrets occur. They are secretive, noc-turnal, and inactive for long periods oftime, and therefore are very seldomseen by people.

Prairie dogs compact the soil aroundtheir burrows, making it difficult tofind ferret tracks. Most ferret tracksare observed when snow covers theground. The average distance betweeneach “twin print” track in the normalbounding gait is 12 to 16 inches (30.5 to40.6 cm) (Fig. 6). The track of a ferret isvery similar to that of a mink or wea-sel. In Wyoming, ferrets are mostactive between December and earlyMarch, sometimes covering up to 5miles (8 km) per night. Scent marks,scrapes, and scratches in the snowmay be noticeable. Ferret droppingsare rarely found above ground. Theyare long and thin, taper on both ends,and consist almost entirely of prairiedog hair and bones.

Ferrets sometimes form “trenches” or“ramps” when they excavate prairiedog burrows. Prairie dogs occasionallyplug the entrances to their burrow sys-tems with soil. When excavating sucha plug in a burrow, the ferret backs outwith the soil held against its chest withits front paws. It generally comes outof the burrow in the same path eachtime. This usually occurs when snowcovers the ground. After repeatedtrips, a ramp from 3 to 5 inches (7.6 to12.7 cm) wide and from 1 to 9 feet (0.3to 2.7m) long is formed (Fig. 7). Bad-gers, foxes, and weasels occasionallyform similar ramps.

Prairie dogs generally deposit exca-vated soil around the burrow entranceto form a mound, building it higher by

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16" apart Direction of travel

Fig. 7. Ramp made by a black-footed ferret excavating a prairie dog burrow.

Fig. 6. Black-footed ferret tracks left in the snow.

adding soil from outside the mound.The movement of soil toward themound is in the opposite direction ofthat done by a ferret.

Ferrets sometimes dig in fresh snow.These “snow trenches” are narrowtrough-like depressions in the snowthat extend away from prairie dog

6

burrow entrances. Snow trenches arerelatively rare compared to trenches inthe soil.

If you observe a black-footed ferret oridentify ferret sign while conductingsurveys, notify your local US Fish andWildlife Service or state wildlife repre-sentative within 24 hours.

Acknowledgments

Figures 4 and 5 by Emily Oseas Routman.

Figure 6 courtesy of Thomas M. Campbell III,Biota Research and Consulting Service.

Figure 7 courtesy of Walt Kittams.

For AdditionalInformation

Biggins, P.E., and R.A. Crete. 1989. Black-footedferret recovery. Proc. Great Plains Wildl.Damage Control Workshop 9:59-63.

Clark, T.W., T.M. Campbell, III, M.H. Schroeder,and L. Richardson. 1984. Handbook ofmethods for location of black-footed ferrets.Wyoming BLM Wildl. Tech. Bull. No. 1. USBureau Land Manage., in coop. withWyoming Game Fish Comm. Cheyenne.47 pp.

Hall, E.R. 1981. The mammals of NorthAmerica. John Wiley and Sons, New York.1181 pp.

Hillman, C.N. 1968. Field observations of black-footed ferrets in South Dakota. Trans. NorthAm. Wildl. Nat. Resour. Conf. 33:346-349.

Hillman, C.N. 1974. Status of the black-footedferret. Pages 75-81 in Proc. symp.endangered and threatened species of NorthAmerica. Wild Canid Survival Res. Center.St. Louis, Missouri.

Hillman, C.N., and T.W. Clark. 1980. Mustelanigripes. Mammal. Species 126:1-3.

Hillman, C.N., and R.L. Linder. 1973. The black-footed ferret. Pages 10-23 in R. L. Linder andC. N. Hillman, eds. Proc. black-footed ferretand prairie dog workshop. South DakotaState Univ., Brookings.

Sheets, R.C., R.L. Linder, and R.B. Dahlgren.1972. Food habits of two litters of black-footed ferrets in South Dakota. Am. Midl.Nat. 87:249-251.

US Fish and Wildlife Service. 1988. Black-footedferret recovery plan. US Fish Wildl. Serv.,Denver, Colorado. 154 pp.

US Fish and Wildlife Service. 1989. Black-footedferret survey guidelines for compliance withthe endangered species act. US Fish Wildl.Serv. Denver, Colorado, 15 pp.

EditorsScott E. HygnstromRobert M. TimmGary E. Larson