Scott E. Hygnstrom Extension Wildlife Damage Specialist Department of Forestry, Fisheries PRAIRIE DOGS 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 Frightening Conibear® No. 110 (body-gripping) traps or equivalent. Control Methods No methods are effective. Shooting Repellents Exclusion Shooting with .22 rimfire or larger None are registered. Wire mesh fences can be installed but rifles. they are usually not practical or Toxicants Other Methods cost-effective. Zinc phosphide. Several home remedies have been Visual barriers of suspended burlap, Fumigants used but most are unsafe and are windrowed pine trees, or snow not cost-effective. fence may be effective. Aluminum phosphide. Cultural Methods Gas cartridges. Modify grazing practices on mixed Trapping and mid-grass rangelands to Box traps. exclude or inhibit prairie dogs. Snares. Cultivate, irrigate, and establish tall crops to discourage use.

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 and Plant Health Inspection Service Animal Damage Control B-85 Great Plains Agricultural Council Wildlife Committee

Identification Habitat

Prairie dogs (Fig. 1) are stocky - All species of prairie dogs are found in ing that live in colonies called grassland or short shrubland habitats. “towns.” French explorers called them They prefer open areas of low vege- “little dogs” because of the barking tation. They often establish colonies noise they make. Their legs are short near intermittent streams, water and muscular, adapted for digging. impoundments, homestead sites, and The tail and other extremities are windmills. They do not tolerate tall short. Their hair is rather coarse with vegetation well and avoid brush and little underfur, and is sandy brown to timbered areas. In tall, mid- and cinnamon in color with grizzled black mixed-grass rangelands, prairie dogs and buff-colored tips. The belly is light have a difficult time establishing a cream to white. colony unless large grazing Fig. 2a. Distribution of the black-tailed (light), (bison or livestock) have closely Five species of prairie dogs are found and Gunnison’s prairie dogs (dark) in North grazed vegetation. Once established, America. in North America: the black-tailed prairie dogs can maintain their habitat

(Cynomys ludovicianus), Mexican (C. on mid- and mixed-grass rangelands. mexicanus), white-tailed (C. leucurus), In shortgrass prairies, where moisture Gunnison’s (C. gunnisoni), and Utah is limited, prairie dogs can invade and prairie dog (C. parvidens). The most maintain acceptable habitat without abundant and widely distributed of assistance. these is the black-tailed prairie dog, which is named for its black-tipped Food Habits tail. Adult black-tailed prairie dogs weigh 2 to 3 pounds (0.9 to 1.4 kg) and Prairie dogs are active above ground are 14 to 17 inches (36 to 43 cm) long. only during the day and spend most of The also has a their time foraging. In the spring and black-tipped tail, but is smaller than its summer, individuals consume up to 2 northern relative. White-tailed, Gunni- pounds (0.9 kg) of green grasses and son’s, and Utah prairie dogs all have forbs (broad-leafed, nonwoody plants) white-tipped tails. White-tailed prairie per week. Grasses are the preferred dogs are usually smaller than black- Fig. 2b. Distribution of the white-tailed (light), food, making up 62% to 95% of their tailed prairie dogs, weighing between Utah (medium), and Mexican prairie dogs diet. Common foods include western 1 1/2 and 2 1/2 pounds (0.7 to 1.1 kg). (dark) in North America. wheatgrass, blue grama, buffalo grass, The Gunnison’s prairie dog is the sand dropseed, and sedges. Forbs such smallest of the five species. as scarlet globe mallow, prickly pear, Today, about 2 million acres of prairie kochia, peppergrass, and wooly plan- Range dog colonies remain in North America. tain are common in prairie dog diets The black-tailed prairie dog lives in and become more important in the fall, Prairie dogs occupied up to 700 million densely populated colonies (20 to 35 as green grass becomes scarce. Prairie acres of western grasslands in the early per acre [48 to 84/ha]) scattered across dogs also eat flowers, seeds, shoots, 1900s. The largest prairie dog colony the Great Plains from northern Mexico roots, and when available. on record, in Texas, measured nearly to southern Canada (Fig 2). Occasion- 25,000 square miles (65,000 km2) and ally they are found in the Rocky General Biology, contained an estimated 400 million Mountain foothills, but rarely at eleva- Reproduction, and prairie dogs. Since 1900, prairie dog tions over 8,000 feet (2,438 m). The Behavior populations have been reduced by as Mexican prairie dog occurs only in much as 98% in some areas and elimi- Mexico and is an endangered species. Prairie dogs are social animals that live nated in others. This reduction is White-tailed prairie dogs live in in towns of up to 1,000 acres (400 ha) largely the result of cultivation of prai- sparsely populated colonies in arid or more. Larger towns are often rie soils and prairie dog control pro- regions up to 10,000 feet (3,048 m). The divided into wards by barriers such as grams implemented in the early and Gunnison’s prairie dog inhabits open ridges, lines of trees, and roads. Within mid-1900s. Population increases have grassy and brushy areas up to 12,000 a ward, each family or “coterie” of been observed in the 1970s and 1980s, feet (3,658 m). Utah prairie dogs are a prairie dogs occupies a territory of possibly due to the increased restric- threatened species, limited to central about 1 acre (0.4 ha). A coterie usually tions on and reduced use of toxicants. Utah. consists of an adult male, one to four

B-86 adult females, and any of their off- young, but rarely take adult prairie clipped before they can produce seed. spring less than 2 years old. Members dogs. Accidents, starvation, weather, Several of the succeeding plant species of a coterie maintain unity through a parasites, and diseases also reduce are less palatable to livestock than the variety of calls, postures, displays, prairie dog populations, but human grasses they replace. grooming, and other forms of activities have had the greatest impact. Other studies, however, indicate that physical contact. Prairie dog colonies attract a wide prairie dogs may have little or no sig- Black-tailed prairie dog towns typi- variety of wildlife. One study identi- nificant effect on livestock production. cally have 30 to 50 burrow entrances fied more than 140 species of wildlife One research project in Oklahoma re- per acre, while Gunnison’s and white- associated with prairie dog towns. vealed that there were no differences tailed prairie dog towns contain less Vacant prairie dog serve as in annual weight gains between steers than 20 per acre. Most burrow homes for cottontail rabbits, small using pastures inhabited by prairie entrances lead to a tunnel that is 3 to 6 rodents, reptiles, insects, and other dogs and steers in pastures without feet (1 to 2 m) deep and about 15 feet arthropods. Many birds, such as prairie dogs. Reduced forage avail- (5 m) long. Prairie dogs construct meadowlarks and grasshopper spar- ability in prairie dog towns may be crater- and dome-shaped mounds up rows, appear in greater numbers on partially compensated for by the to 2 feet (0.6 m) high and 10 feet (3 m) prairie dog towns than in surrounding increased palatability and crude pro- in diameter. The mounds serve as prairie. The is one of tein of plants that are stimulated by lookout stations. They also prevent several uncommon or rare species that grazing. In addition, prairie dogs water from entering the tunnels and frequent prairie dog towns. Others sometimes clip and/or eat plants that may enhance ventilation of the tunnels. include the golden eagle, prairie fal- are toxic to livestock. Bison, elk, and Prairie dogs are most active during the con, ferruginous , mountain pronghorns appear to prefer feeding in day. In the summer, during the hottest plover, swift fox, and endangered prairie dog colonies over uncolonized part of the day, they go below ground black-footed ferret (see Appendix A of grassland. where it is much cooler. Black-tailed this chapter). Prairie dog burrows increase soil erosion prairie dogs are active all year, but and are a potential threat to livestock, may stay underground for several Damage and Damage machinery, and horses with riders. Dam- days during severe winter weather. Identification age may also occur to ditch banks, The white-tailed, Gunnison’s, and impoundments, field trails, and roads. Utah prairie dogs hibernate from Several independent studies have pro- Prairie dogs are susceptible to several October through February. duced inconsistent results regarding the impacts of prairie dogs on livestock pro- diseases, including plague, a severe Black-tailed prairie dogs reach sexual duction. The impacts are difficult to infectious disease caused by the bacte- maturity after their second winter and determine and depend on several fac- rium Yersinia pestis. Plague, which is breed only once per year. They can breed tors, such as the site conditions, weather, often fatal to humans and prairie dogs, as early as January and as late as March, current and historic plant communities, is most often transmitted by the bite of depending on latitude. The other four number of prairie dogs, size and age of an infected flea. Although plague has species of prairie dogs reach sexual prairie dog towns, and the intensity of been reported throughout the western maturityafter their first winter and breed site use by livestock and other grazers. United States, it is uncommon. Symp- in March. The gestation period is about Prairie dogs feed on many of the same toms in humans include swollen and 34 days and litter sizes range from 1 to grasses and forbs that livestock feed on. tender lymph nodes, chills, and fever. 6 pups. The young are born hairless, Annual dietary overlap ranges from 64% The disease is curable if diagnosed and blind, and helpless. They remain to 90%. Prairie dogs often begin feeding treated in its early stages. It is impor- underground for the first 6 weeks of on pastures and rangeland earlier in tant that the public be aware of the dis- their lives. The pups emerge from their spring than do and clip plants ease and avoid close contact with dens during May or June and are closer to the ground. Up to 10% of the prairie dogs and other rodents. Public weaned shortly thereafter. By the end aboveground vegetation may be de- health is a primary concern regarding of fall, they are nearly full grown. Sur- stroyed due to their burrowing and prairie dog colonies that are in close vival of prairie dog pups is high and mound-building activities. Overall, prai- proximity to residential areas and adults may live from 5 to 8 years. rie dogs may remove 18% to 90% of the school yards. Even with their sentries and under- available forage through their activities. Rattlesnakes and black widow spiders ground lifestyle, predation is still a The species composition of pastures also occur in prairie dog towns, but major cause of mortality for prairie occupied by prairie dogs may change can be avoided. Rattlesnakes often rest dogs. , , and black- dramatically. Prairie dog activities in prairie dog burrows during the day footed ferrets are efficient predators. encourage shortgrass species, perenni- and move through towns at night in , , foxes, , and als, forbs, and species that are resistant search of food. Black widow spiders eagles also kill prairie dogs. Prairie to grazing. Annual plants are selected are most often found in abandoned rattlesnakes and bull may take against because they are usually prairie dog holes where they form

B-87 webs and raise their young. Bites from aboveground. A slanting overhang at grazing, use short duration or rapid these animals are rare, but are a threat the top increases the effectiveness of rotation grazing systems, or even total to human health. the fence. deferment during the growing season. Livestock can be excluded from vacant Visual Barriers. Prairie dogs graze prairie dog towns with temporary Legal Status and closely clip vegetation to provide fencing to help vegetation regain vigor a clear view of their surroundings and Black-tailed, white-tailed, and Gunni- and productivity. Mid- to tallgrass improve their ability to detect preda- son’s prairie dogs are typically classi- species should be encouraged where tors. Fences, hay bales, and other fied as unprotected or nuisance they are a part of the natural vegeta- objects can be used to block prairie animals, allowing for their control tion. In semiarid and shortgrass prairie dogs’ view and thus reduce suitability without license or permit. Most states zones, grazing strategies may have of the habitat. Franklin and Garrett require purchase of a small game little effect on prairie dog town expan- (1989) used a burlap fence to reduce license to shoot prairie dogs. If the sion or establishment. shooter is acting as an agent for the prairie dog activity over a two-month landowner to reduce prairie dog num- period. Windrows of pine trees also Grazing Distribution. Prairie dogs bers, a license may not be required. reduced prairie dog activity. Unfortu- often establish towns in areas where The Utah and Mexican prairie dogs are nately, the utility of visual barriers is livestock congregate, such as at water- classified as threatened and endan- limited because of high construction ing sites or old homesteads. Move gered species, respectively. Contact and maintenance costs. Tensar snow watering facilities and place salt and your local wildlife agency for more fences (2 feet [60 cm] tall) are less minerals on areas that are under- information. costly, at about $0.60 per foot utilized by livestock to distribute live- ($1.97/m) for materials. Unfortunately, stock grazing pressure more evenly. The black-footed ferret is an endan- they were inconsistent in reducing Prescribed burns in spring may gered species that lives almost exclu- reinvasion rates of prairie dog towns enhance regrowth of desirable grass sively in prairie dog towns, and all in Nebraska (Hygnstrom and species. active prairie dog colonies are poten- Virchow, unpub. data). tial black-footed ferret habitat. It is a Cultivation. Prairie dog numbers can violation of federal law to willfully kill Cultural Methods be reduced by plowing or disking towns and leaving the land fallow for a black-footed ferret or poison prairie Grazing Management. Proper range dog towns where ferrets are present. 1 to 2 years, where soil erosion is not a management can be used to control problem. Establish tall grain crops Federal agencies must assess their own prairie dogs. Use stocking rates that activities to determine if they “may after the second year to further dis- maintain sufficient stand density and courage prairie dogs. Burrows can be affect” endangered species. Some pes- height to reduce recolonization of pre- ticides registered for prairie dog con- leveled and filled with a tractor- viously controlled prairie dog towns mounted blade to help slow reinva- trol require private applicators to or reduce occupation of new areas. conduct ferret surveys before toxicants sion. Flood irrigation may discourage The following general recommenda- prairie dogs. can be applied. Detailed information tions were developed with the assis- on identifying black-footed ferrets and tance of extension range management Frightening their sign is included in Appendix A of specialists and research scientists. this chapter. To learn more about fed- Frightening is not a practical means of eral and state guidelines regarding Stocking Rate. Overgrazed pastures control. prairie dog control, black-footed ferret are favorable for prairie dog town surveys, and block clearance proce- establishment or expansion. If present, Repellents dures, contact personnel from your prairie dogs should be included in None are registered. local Cooperative Extension, USDA- stocking rate calculations. At a conser- APHIS-ADC, US Fish and Wildlife vative population density of 25 prairie Toxicants Service, or state wildlife agency office. dogs per acre (60/ha) and dietary overlap of 75%, it takes 6 acres (2.4 ha) Safety Precautions. Use pesticides Damage Prevention and of prairie dogs to equal 1 Animal Unit safely and comply with all label rec- ommendations. Only use products Control Methods Month (AUM) (the amount of forage that one cow and calf ingest per month that are registered for prairie dog con- trol by the Environmental Protection Exclusion during summer [about 900 pounds; 485 kg]). Agency. Some pesticides registered for Fencing. Exclusion of prairie dogs is prairie dog control require that private . Rest pas- rarely practical, although they may be Rest/Rotation Grazing applicators conduct ferret surveys tures for a period of time during the discouraged by tight-mesh, heavy- before toxicants can be applied. growing season to increase grass gauge, galvanized wire, 5 feet (1.5 m) Detailed information on identifying height and maintain desired grass spe- wide with 2 feet (60 cm) buried in the black-footed ferrets and their sign is cies. Instead of season-long continuous ground and 3 feet (90 cm) remaining included in Appendix A of this

B-88

ings 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 accep- tance 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 6" with toxic baits, followed by a fumi- Bait gant cleanup, is most cost-effective for areas of more than 5 acres (2 ha). Fig. 3. Prebait and toxic bait should be scattered over a 6-inch (15-cm) circle at each burrow entrance. Inspection and evaluation. Inspect chapter. Seek assistance from your Apply toxic bait only after the prebait treated prairie dog towns 2 to 3 days local extension agent or from the has been readily eaten, which usually after treatment. Remove and burn or USDA-APHIS-ADC if needed. takes 1 to 2 days. If the prebait is not bury any dead prairie dogs that are accepted immediately, wait until it is aboveground to protect any other ani- Toxic Bait. The only toxic baits currently eaten readily before applying the toxic mals from indirect poisoning. Success registered and legal for use to control bait. More than one application of rates of 75% to 85% can usually be ob- prairie dogs are 2% zinc phosphide- prebait may be necessary if rain or tained with zinc phosphide if it is ap- treated grain bait and pellet formulations. snow falls on the prebait. Prohibit plied correctly. Zinc phosphide baits are effective and shooting and other disturbance of the relatively safe regarding livestock and To evaluate the success of a treatment, colony at least 6 weeks prior to and other wildlife in prairie dog towns, if mark and plug 100 burrows 3 days during treatment. used properly. These baits are available prior to treatment. Count the reopened through nationalsuppliers (see Supplies Prebait and toxic bait can be applied burrows 24 hours later. Replug the and Materials), USDA-APHIS-ADC, by hand on foot, but mechanical bait same 100 burrows 3 days after treat- and local retail distributors. dispensers attached to all-terrain ve- ment and again count the reopened hicles are more convenient and cost-ef- burrows 24 hours later. Divide the Toxic baits are most effective when prai- fective for towns greater than 20 acres number of reopened burrows (post- rie dogs are active and when there is no (8 ha). Motorcycles and horses can also treatment) by the number of reopened green forage available. Therefore, it is be used to apply prebait and toxic bait. burrows (pretreatment) to determine best to apply baits in late summer and See Supplies and Materials for infor- the survival rate. Abandoned burrows fall. Zinc phosphide baits can only be mation on bait dispensers. are usually filled with spider webs, applied from July 1 through January vegetation, and debris. Active burrows 31. Bait Application. Apply about 1 heap- are clean and surrounded by tracks, ing teaspoon (4 g) of grain bait per bur- Prebaiting. Prairie dog burrows must be diggings, and fresh droppings at the row in the same way that the prebait prebaited before applying toxic bait. entrances. was applied. About 1/3 pound of Prebaiting will accustom prairie dogs to prebait and 1/3 pound of zinc phos- Zinc phosphide is a Restricted Use Pes- eating grain and will make the toxic bait phide bait are needed per acre (0.37 ticide, available for sale to and use by considerably more effective when it is kg/ha). Excess bait that is not eaten by certified pesticide applicators or their applied. Use clean rolled oats as a prebait prairie dogs can be a hazard to nontar- designates. Contact your county exten- if you are using 2% zinc phosphide- get wildlife or livestock. It is best to re- sion office for information on acquiring treated rolled oats. Drop a heaping tea- move livestock, especially horses, EPA certification. Treatment of a prairie spoon (4 g) of untreated rolled oats on the sheep, or goats, from the pasture be- dog town with zinc phosphide-treated bare soil at the edge of each prairie dog fore toxic bait is applied; however, re- baits cost about $10 per acre ($25/ha) mound or in an adjacent feeding area. moval is not required. Apply toxic bait (includes materials and labor). The prebait should scatter, forming about early in the day for best results and a 6-inch (15-cm) circle (Fig. 3). Do not restrict any human disturbance for 3 Fumigants place the prebait in piles or inside bur- days following treatment. Always rows, on top of mounds, among prairie Fumigants, including aluminum phos- wear rubber gloves when handling dog droppings, or in vegetation far from phide tablets and gas cartridges, can zinc phosphide-treated baits. Follow the mound. provide satisfactory control of prairie all label directions and observe warn- dogs in some situations. We do not

B-89 recommend fumigation as the primary pipe into a burrow and roll the tablets Trapping means of control for large numbers of down the pipe. Place crumpled news- Cage traps can be used to capture prairie dogs because it is costly, time- paper and/or a slice of sod in the bur- individual animals, but the process is consuming, and usually more hazard- row to prevent loose soil from smoth- typically too expensive and time con- ous to desirable wildlife species than ering the tablets and tightly pack the suming to be employed for prairie dog toxic baits. Fumigants cost about 5 to burrow entrance with soil. To increase control. Best results are obtained by 10 times more per acre (ha) to apply efficiency, work in pairs, one person trapping in early spring after snow- than toxic baits. Therefore, fumigation dispensing and one plugging burrows. melt and before pasture green up. Bait is usually used during spring as a Always wear cotton gloves while han- traps with oats flavored with corn oil follow-up to toxic bait treatment. Suc- dling aluminum phosphide. Aim con- or anise oil. cess rates of 85% to 95% can usually be tainers away from the face when obtained if fumigants are applied cor- It may be difficult to find release sites for opening and work into the wind to rectly. prairie dogs. Releasing prairie dogs into avoid inhaling phosphine gas from the an established colony will increase stress For best results, apply fumigants in container and the treated area. Alumi- on resident and released prairie dogs. spring when soil moisture is high and num phosphide should be stored in a soil temperature is greater than 60o F well-ventilated area, never inside a Body-gripping traps, such as the (15o C). Fumigation failures are most vehicle or occupied building. Alumi- Conibear® No. 110, are effective when frequent in dry, porous soils. Spring num phosphide is classified as a flam- placed in burrow entrances. No. 1 applications are better than fall appli- mable solid. Check with your local Gregerson snares can be used to remove cations because all young prairie dogs department of transportation for regu- a few prairie dogs, but the snares are are still in their natal burrows. lations regarding transportation of usually rendered useless after each catch. hazardous materials. Prairie dogs also can be snared by hand, Do not use fumigants in burrows using twine or monofilament line. These where nontarget species are thought to Aluminum phosphide can be pur- traps and snares may be effective for 1- to be present. Black-footed ferrets, bur- chased by certified pesticide applica- 5-acre (0.4- to 2-ha) colonies where time rowing owls, swift fox, cottontail rab- tors through national suppliers (see is not a consideration. bits, and several other species of wild- Supplies and Materials) or local retail life occasionally inhabit prairie dog distributors. It typically provides an Shooting burrows and would likely be killed by 85% to 95% reduction in prairie dog fumigation. Be aware of sign and populations when applied correctly Shooting is very selective and not haz- avoid fumigating burrows that are oc- and costs about $25 per acre ($63/ha) ardous to nontarget wildlife. It is most cupied by nontarget wildlife. Some to apply. It is typically more cost-effec- effective in spring because it can dis- manufacturers’ labels now require tive to use than gas cartridges because rupt prairie dog breeding. Continuous private applicators to conduct black- of the reduced handling time. shooting can remove 65% of the popu- footed ferret surveys before applica- lation during the year, but it usually is Gas Cartridges. Gas cartridges have tion. Detailed information on identify- not practical or cost-effective. Prairie been used for many years to control ing black-footed ferrets and their sign dogs often become wary and gun-shy prairie dogs. When ignited, they burn is included in Appendix A of this after extended periods of shooting. and produce carbon monoxide, carbon chapter. Burrows used by burrowing They can be conditioned to loud noises dioxide, and other gases. To prepare a owls often have feathers, pellets, and by installing a propane cannon or old, gas cartridge for use, insert a nail or whitewash nearby. Natal burrows are mis-timed gasoline engine in the town small screwdriver in the end at often lined with finely shredded cow for 3 to 4 days before shooting. marked points and stir the contents manure. Migratory burrowing owls before inserting and lighting the fuse. Long range, flat trajectory rifles are the usually arrive in the central Great Hold the cartridge away from you most efficient for shooting prairie Plains in late April and leave in early until it starts burning, then place it dogs. Rifles of .22 caliber or slightly October. Fumigate before late April to deep in a burrow. Burrows should be larger are most commonly used. minimize the threat to burrowing plugged immediately in the same way Bipods and portable shooting benches, owls. as with aluminum phosphide. Be care- telescopic sights, and spotting scopes Aluminum Phosphide. Aluminum ful when using gas cartridges because are also useful equipment for efficient phosphide is a Restricted Use Pesti- they can cause severe burns. Do not shooting. Contact a local extension cide, registered as a fumigant for the use them near flammable materials or office or state wildlife agency for lists control of burrowing rodents. The tab- inside buildings. Gas cartridges are a of shooters and receptive landowners. lets react with moisture in prairie dog General Use Pesticide, available burrows, and release toxic phosphine through USDA-APHIS-ADC. They Other Methods

gas (PH3). Use a 4-foot (1.2-m) section provide up to 95% control when ap- An amazing variety of home remedies of 2-inch (5-cm) PVC pipe to improve plied correctly and cost about $35 per have been tried in desperate attempts placement of the tablets. Insert the acre ($88/ha) to apply. to control prairie dogs. Engine

B-90 exhaust, dry ice, butane, propane, plant and animal diversity. Prairie against prairie dogs and other small gasoline, anhydrous ammonia, insecti- dogs are a source of food for several were formerly justified be- cides, nonregistered rodenticides, predators and their burrows provide cause of safety for human health and water, and dilute cement are all homes for several species, including conflicts with livestock for forage.” unregistered for prairie dog control. the endangered black-footed ferret. On the other hand, Collins et al. (1984) None have proven to be as cost- Burrowing mixes soil types and incor- found it was not economically feasible to effective or successful as registered porates organic matter, both of which treat prairie dogs on shortgrass range- rodenticides, and most are hazardous may benefit soil. It also increases soil land with zinc phosphide in South to applicators and/or nontarget spe- aeration and decreases compaction. Dakota because the annual control costs cies. In addition, those methods that Prairie dogs provide recreational exceeded the value of forage gained. have been observed by the authors opportunities for nature observers, Seventeen acres (6.8 ha) would have to (exhaust, propane, ammonia, nonreg- photographers, and shooters. The be treated to gain 1 AUM. Uresk (1985) istered rodenticides, and water) were presence of large, healthy prairie dog reported that South Dakota prairie dog substantially more expensive than reg- towns, however, is not always compat- towns treated with zinc phosphide istered and recommended methods. ible with agriculture and other human yielded no increase in production after 4 land-use interests. A modified street sweeper vacuum has years. The cost-effectiveness of prairie recently been used to suck prairie dogs Prairie dogs feed on many of the same dog control depends greatly on the age, out of their burrows. Inventor Gay grasses and forbs that livestock do. density, and size of the prairie dog colony; Balfour of Cortez, Colorado, reports that Annual dietary overlap has been esti- soil and grassland type; rainfall; and the “Sucker Upper” can typically clear mated from 64% to 90%. One cow and control method employed. a range of 5 to 20 acres (2 to 8 ha) per calf ingest about 900 pounds (485 kg) day at a cost of $1,000 per day, not of forage per month during the sum- Acknowledgments including travel expenses. This device, mer (1 AUM). One prairie dog eats unfortunately, has not been indepen- about 8 pounds (17.6 kg) of forage per We acknowledge M. J. Boddicker and F. R. Henderson, who authored the “Prairie Dogs” dently tested. Although relatively month during the summer. At a con- and “Black-footed Ferrets” chapters, expensive, this method may provide a servative population density of 25 respectively, in the 1983 edition of Prevention nonlethal approach to dealing with prairie dogs per acre (60/ha) and and Control of Wildlife Damage. prairie dogs where conventional dietary overlap of 75%, it takes 6 acres Figure 1 by Emily Oseas Routman. methods are not appropriate or accept- (2.4/ha) of prairie dogs to equal 1 Figure 2 by Dave Thornhill, University of able. The prairie dogs can either be AUM. Small, rather widely dispersed Nebraska. euthanized with carbon dioxide gas or colonies occupying 20 acres (8 ha) or relocated if a suitable site can be found. less are tolerated by many landowners Figure 3 by Renee Lanik, University of Nebraska. because of the sport hunting and Integrated Pest Management aesthetic opportunities they provide. For Additional An integrated pest management Colonies that grow larger than 20 acres Information approach dictates the timely use of a (8 ha) often exceed tolerance levels variety of cost-effective management because of lost AUMs, taxes, and Agnew, W., D. W. Uresk, and R. M. Hansen. increasing control costs. 1986. Flora and fauna associated with prairie options to reduce prairie dog damage to dog colonies and adjacent ungrazed mixed- a tolerable level. We recommend the The South Dakota Department of grass prairie in western South Dakota. J. application of toxic bait in the fall, fol- Agriculture (1981) reported that Range. Manage. 39:135-139. lowed by the application of aluminum 730,000 acres (292,000 ha) were inhab- Bonham, C.D., and A. Lerwick. 1976. Vegetation phosphide in the spring. If possible, ited by prairie dogs in 1980, with a loss changes induced by prairie dogs on shortgrass defer grazing on the treated area during of $9,570,000 in production. The South range. J. Range Manage. 29:217-220. the next growing season to allow grasses Dakota livestock grazing industry Cable, K. A., and R. M. Timm. 1988. Efficacy of and other vegetation to recover. A com- deferred grazing in reducing prairie dog similarly estimated losses of up to reinfestation rates. Proc. Great Plains Wildl. puter program was produced by Cox $10.29 per acre ($25.43/ha) on pasture Damage Control Workshop 8:46-49. and Hygnstrom in 1993 to determine and rangeland inhabited by prairie Cincotta, R. P., D. W. Uresk, and R. M. Hansen. cost-effective options and economic dogs and $30.00 per acre ($74.10/ha) 1987. Demography of black-tailed prairie dog returns of prairie dog control (see For for occupied hay land. Prairie dogs populations reoccupying sites treated with Additional Information). inhabited about 73,000 acres (29,200 rodenticide. Great Basin Nat. 47:339-343. ha) in Nebraska in 1987, with a loss Clark, T. W. 1986. Annotated prairie dog bibliography 1973 to 1985. Montana Bureau Economics of Damage estimated at $200,000. A reported 1/2 Land Manage. Tech. Bull. No. 1. Helena. 32 pp. to 1 million acres (200,000 to 400,000 and Control Clark, T. W., T. M. Campbell, III, M. H. ha) are occupied in Colorado. A com- Schroeder, and L. Richardson. 1983. Prairie dogs play an important role in mittee of the National Academy of Sci- Handbook of methods for locating black- the prairie ecosystem by creating ences (1970) concluded that “the footed ferrets. Wyoming Bureau Land Manage. Tech. Bull. No. 1. Cheyenne. 55 pp. islands of unique habitat that increase numerous eradication campaigns

B-91 Committee. 1970. Vertebrate Pests: Problems Hygnstrom, S. E., and P. M. McDonald. 1989. Snell, C. P., and B. D. Hlavachick. 1980. Control and Control. Natl. Acad. of Science. Efficacy of three formulations of zinc of prairie dogs - the easy way. Rangelands Washington, DC. 153 pp. phosphide for black-tailed prairie dog 2:239-240. control. Proc. Great Plains Wildl. Damage Collins, A. R., J. P. Workman, and D. W. Uresk. Control Workshop 9:181. South Dakota Department of Agriculture. 1981. 1984. An economic analysis of black-tailed Vertebrate economic loss, South prairie dog (Cynomys ludovicianus) control. Hygnstrom, S. E., and D. R. Virchow. 1988. Prairie Dakota 1980. US Dep. Agric. Stat. Rep. Serv. J. Range Manage. 37:358-361. dogs and their control. Univ. Nebraska-Coop. Sioux Falls. 4 pp. Ext. NebGuide No. C80-519. Lincoln. 4 pp. Cox, M. K., and S. E. Hygnstrom. 1991. Prairie dog Uresk, D. W. 1985. Effects of controlling black- control: a computer model for prairie dog Knowls, C. J. 1986. Population recovery of black tailed prairie dogs on plant production. management on rangelands. Proc. Great Plains tailed prairie dogs following control with zinc J. Range Manage. 38:466-468. Wildl. Damage Control Workshop 10:68-69. phosphide. J. Range Manage. 39:249-251. Uresk, D. W. 1987. Relation of black-tailed Dobbs, T. L. 1984. Economic losses due to prairie Koford, C. B. 1958. Prairie dogs, whitefaces and prairie dogs and control programs to dogs inSouth Dakota. South Dakota Dep. Agric. blue grama. Wildl. Mono. 3:1-78. vegetation, livestock, and wildlife. Pages Div. Agric. Regs. Inspect. Pierre. 15 pp. 312-322 in J. L. Caperinera, ed. Integrated Merriam, C. H. 1902. The prairie dog of the Great pest management on rangeland: a shortgrass Fagerstone, K. A. 1982. A review of prairie dog Plains. Pages257-270 in Yearbook ofthe USDA. prairie perspective. Westview Press. diet and its variability among animals and US Govt. Print. Office. Washington, DC. Boulder, Colorado. colonies. Proc. Great Plains Wildl. Damage Control Workshop 5:178-184. O’Meilia, M. E., F. L. Knopf, and J. C. Lewis. Uresk, D. W., J. G. MacCracken, and A. J. 1982. Some consequences of competition Bjugstad. 1982. Prairie dog density and cattle Franklin, W. L., and M. G. Garrett. 1989. between prairie dogs and beef cattle. grazing relationships. Great Plains Wildl. Nonlethal control of prairie dog colony J. Range Manage. 35:580-585. Damage Control Workshop. 5:199-201. expansion with visual barriers. Wildl. Soc. Bull. 17:426-430. Schenbeck, G. L. 1981. Management of black- Whicker, A. D., and J. K. Detling. 1988. tailed prairie dogs on the National Ecological consequences of prairie dog Foster-McDonald, N. S., and S. E. Hygnstrom. Grasslands. Proc. Great Plains Wildl. disturbances. BioSci. 38:778-785. 1990. Prairie dogs and their ecosystem. Univ. Damage Control Workshop 5:207-213. Nebraska. Dep. For., Fish. Wildl. Lincoln. 8 pp. Sharps, J. C., and D. W. Uresk. 1990. Ecological Computer Software Hansen, R. M., and I. Gold. 1977. Blacktail review of black-tailed prairie dogs and Cox, M. K., and S. E. Hygnstrom. 1993. Prairie prairie dogs, desert cottontails and cattle associated species in western South Dakota. dog control: An educational guide, trophic relations on shortgrass range. Great Basin Nat. 50:339-345. population model, and cost-benefit analysis J. Range Manage. 30:210-214. for prairie dog control. Available from 105 ACB IANR-CCS, University of Nebraska, Lincoln, NE 68583-0918.

BLACK-FOOTED FERRETS Appendix A

Fig. 4. Black-footed ferret, Mustela nigripes

Introduction dogs. The reduction in prairie dog Identification numbers in the last 100 years and the The black-footed ferret (Mustela isolation and disappearance of many Black-footed ferrets are members of nigripes, Fig. 4) is the most rare and large towns has led to the decline of the family and are the only fer- endangered in North the ferret population. Large and ret native to North America. The most America. Black-footed ferrets establish healthy prairie dog towns are needed obvious distinguishing feature is the their dens in prairie dog burrows and to ensure that black-footed ferrets sur- striking black mask across the face. feed almost exclusively on prairie vive in the wild. The feet, legs, and tip of the tail are

B-92 been released in north-central Wyo-

ming. For the past 10 years, biologists

have intensively searched for and in-

vestigated hundreds of reports of black-footed ferrets, but no new popu- lations have been found. In addition, a public reward of $5,000 to $10,000 was Domestic (fitch) ferret available during the 1980s for sightings of black-footed ferrets, but none were confirmed. Current efforts are being made to identify black-footed ferret habitat and potential reproduction sites. Captive breeding populations are held at Wheatland, Wyoming, at the Wyoming Game and Fish Depart-

ment’s Sybille Conservation and Edu-

cation Center, and at zoos in Omaha, Mink Nebraska; Washington, DC; Louisville, Kentucky; Colorado Springs, Colo- rado; Phoenix, Arizona; and Toronto, Ontario.

Habitat

Black-footed ferrets rely on prairie

dogs for both food and shelter. There-

fore, all active prairie dog colonies are considered potential black-footed fer- ret habitat. Resident ferrets have only been found in prairie dog towns. Tran- Fig. 5. Three animals that may be mistaken for Bridled weasel sient and dispersing ferrets may cross the black-footed ferret. areas that are not occupied by prairie dogs.

General Biology, also black. The remaining coat is pale longtail weasel. It occurs in southwest Reproduction, and yellow-brown, becoming lighter on the Kansas, parts of Oklahoma, Texas, and Behavior under parts of the body and nearly New Mexico. The bridled weasel has a white on the forehead, muzzle, and mask or dark markings on its face, but Normally 4 young ferrets are born per throat. The top of the head and middle is smaller than a black-footed ferret. It litter in May and June. The mother of the back are a darker brown. Ferrets does not have black feet, and it has a alone cares for the young and directs have short legs, long, well-developed tail that is longer in relation to its total their activities until they disperse in claws on the front paws, large pointed body length. Mink are about the same mid-September. The young are first ears, and relatively large eyes. size as black-footed ferrets but are observed aboveground during day- dark brown and occasionally have Ferrets are similar in size and weight light hours in July. white markings on the throat. to wild mink. Adult male ferrets are 21 From June to mid-July, the ferret fam- to 23 inches (53.3 to 58.4 cm) long and ily remains in the same general area of weigh 2 to 2 1/2 pounds (0.9 to 1.2 kg). Range the prairie dog town. Around the mid- Females are slightly smaller. dle of July, after the young are active The native black-footed ferret may be The original range of the black-footed aboveground at night, the family confused with the domestic European ferret included most of the Great extends its area of activity. By the fitch ferret, long-tailed weasel, bridled Plains area. Its current range within middle of July the young ferrets are weasel, or wild mink (Fig. 5). The the Great Plains is unknown, although weaned at nearly one-half adult size. it is assumed to be greatly reduced domestic fitch ferret has longer and By early August, the mother ferret from the original range. Currently the darker pelage on the back, yellowish separates the young and places them only known wild ferret population is underfur, and an entirely black tail. in different burrows. At this time some The bridled weasel is a variant of the an experimental population that has

B-93 of the young occasionally hunt at night law to conduct surveys unless their A white-tailed prairie dog town or by themselves. By mid-August, they activities are associated with federal complex of less than 200 acres (81 ha) can be seen during daylight hours, programs or if they are specifically having no neighboring prairie dog peering out of their burrow, playing directed by pesticide labels. Compli- towns may be cleared without a ferret near the entrance, and sometimes fol- ance with or disregard for black-footed survey. White-tailed prairie dog towns lowing the adult female. ferret survey guidelines does not, of or complexes greater than 200 acres itself, show compliance with or viola- (81 ha) but less than 1,000 acres (400 By late August or early September, tion of the Endangered Species Act or ha), may be cleared after completion of when the young are as large as the any derived regulations. a survey for black-footed ferrets, pro- adult, the ferret family starts to dis- vided that no ferrets or their sign were perse and is no longer seen as a closely found during the survey. knit group. The young ferrets are soli- Guidelines for Black- tary during the late fall, winter, and footed Ferret Surveys Contact the US Fish and Wildlife Ser- early spring. In December, ferrets vice before any federally funded or become active just after sunset and are Any actions that kill prairie dogs or permitted activities are conducted on active at least until midnight. alter their habitat could prove detri- black-tailed or white-tailed prairie dog mental to ferrets occupying affected towns or complexes greater than 1,000 Legal Status prairie dog towns. The US Fish and acres, to determine the status of the Wildlife Service guidelines should area for future black-footed ferret The black-footed ferret is classified as assist agencies or their authorized rep- reintroductions. an endangered species and receives resentatives in designing surveys to full protection under the Federal “clear” prairie dog towns prior to ini- Defining a Prairie Dog Town/ Endangered Species Act of 1973 (PL tiation of construction projects, prairie Complex dog control projects, or other actions 93-205). The act, as amended, requires For the purpose of this document a that affect prairie dogs. If these guide- federal agencies to ensure that any ac- prairie dog town is defined as a group lines are followed by individuals con- tion authorized, funded, or carried out of prairie dog holes in which the den- ducting black-footed ferret surveys, by them is not likely to jeopardize the sity meets or exceeds 20 burrows per agency personnel can be reasonably continued existence of a threatened or hectare (8 burrows/acre). Prairie dog confident in results that indicate black- endangered species or their habitat. holes need not be active to be counted footed ferrets are not occupying a pro- Regulations implementing Section 7 of but they should be recognizable and posed project area. the act require that federal agencies intact; that is, not caved in or filled determine if any actions they propose Delineation of Survey Areas. Until with debris. A prairie dog complex “may affect” any threatened or endan- the time that wildlife agencies are able consists of two or more neighboring gered species. If it is determined that a to identify reintroduction areas and to prairie dog towns, each less than 4.3 proposed action “may affect,” then the classify other areas as being free of fer- miles (7 km) from the other. agency is required to request formal rets, surveys for black-footed ferrets Section 7 consultation with the US Fish will usually be recommended. During Timing of Surveys and Wildlife Service. Section 9 of the this interim period the following The US Fish and WIldlife Service rec- act prohibits any person (including the approach is recommended to deter- ommends that surveys for black- federal government) from the “taking” mine where surveys are needed. of a listed species. The term take means footed ferrets be conducted as close to to harass, harm, pursue, hunt, shoot, A black-tailed prairie dog town or the initiation of a project construction wound, kill, capture, or collect, or to complex of less than 80 acres (32 ha) date as possible but not more than 1 attempt to engage in any such conduct. having no neighboring prairie dog year before the start of a proposed Habitat destruction constitutes the tak- towns may be developed or treated action. This is recommended to mini- ing of a listed species. without a ferret survey. A neighboring mize the chance that a ferret might prairie dog town is defined as one less move into an area during the period Guidelines for black-footed ferret than 4.3 miles (7 km) from the nearest between completion of a survey and searches have been developed by the edge of the town being affected by a the start of a project. US Fish and Wildlife Service (Black- project. footed Ferret Survey Guidelines for Project Type Black-tailed prairie dog towns or com- Compliance with the Endangered Spe- Construction projects (buildings, facili- plexes greater than 80 acres (32 ha) but cies Act, 1989). Federal agencies are ties, surface coal mines, transmission less than 1,000 acres (400 ha) may be required by the US Fish and Wildlife lines, major roadways, large pipelines, cleared after a survey for black-footed Service to conduct black-footed ferret impoundments) that permanently alter ferrets has been completed, provided surveys if their proposed actions may prairie dog towns should be surveyed. that no ferrets or ferret sign have been affect ferrets or their habitat. Although Projects of a temporary nature and found. encouraged to do so, private landown- those that involve only minor distur- ers and applicators are not required by bances (fences, some power lines,

B-94 underground cables) may be exempt- surveyed is required (that is, visu- Additional information on data collec- ed from surveys when project activi- ally overlapping transects). tion, reporting, and training work- ties are proposed on small prairie dog Black-footed Ferret 3. If ferret sign is observed, photo- shops are included in Survey Guidelines for Compliance with the towns or complexes of less than 1,000 graph the sign and make drawings Endangered Species Act, 1989, available acres (400 ha), do not impact those and measurements of diggings areas where ferret sightings have been from the US Fish and Wildlife Service. before contacting the US Fish and frequently reported, or occur on areas Wildlife Service and state wildlife where no confirmed sightings have agency. Black-footed Ferret Sign been made in the last 10 years. Method 2 — Nighttime surveys The US Fish and Wildlife Service rec- To determine if black-footed ferrets are involve the use of spotlighting tech- living in a given area, some sign must ommends that before any action niques for locating ferrets. This survey involving the use of a toxicant in or be found or a ferret observed. Evi- method is designed to locate ferrets dence such as tracks, diggings, or near a prairie dog town begins, a sur- when the maximum population and vey for ferrets should be conducted. If droppings is uncommon, even where the longest periods of ferret activity ferrets occur. They are secretive, noc- toxicants or fumigants are to be used, are expected to occur. and the town proposed for treatment turnal, and inactive for long periods of is in a complex of less than 1,000 acres Minimum standards should be fol- time, and therefore are very seldom (400 ha), the town should be surveyed lowed as recommended below: seen by people. using the nocturnal survey technique 1. Conduct surveys between July 1 Prairie dogs compact the soil around 30 days or less before treatment. and October 31. their burrows, making it difficult to Prairie dog towns or complexes great- 2. Continuously survey the prairie find ferret tracks. Most ferret tracks er than 1,000 acres (400 ha) should not dog town using spotlights. Begin are observed when snow covers the be poisoned without first contacting surveys at dusk and continue until ground. The average distance between your local US Fish and Wildlife Service dawn on each of at least 3 consecu- each “twin print” track in the normal office. tive nights. Divide large prairie dog bounding gait is 12 to 16 inches (30.5 to 40.6 cm) (Fig. 6). The track of a ferret is Survey Methods colonies into tracts of 320 acres (130 ha) and search each tract systemati- very similar to that of a mink or wea- Method 1 — Daylight surveys for cally throughout 3 consecutive sel. In Wyoming, ferrets are most ferrets are recommended if surveys nights. Rough uneven terrain and active between December and early are conducted between December 1 tall dense vegetation may require March, sometimes covering up to 5 and March 31. This type of survey is smaller tracts to result in effective miles (8 km) per night. Scent marks, used to locate signs left by ferrets. coverage of a town. scrapes, and scratches in the snow During winter months, ferret scats, may be noticeable. Ferret droppings prairie dog skulls, and diggings are 3. Begin observations on each prairie are rarely found above ground. They more abundant because prairie dogs dog town or tract at a different are long and thin, taper on both ends, are less active and less likely to disturb starting point on each successive and consist almost entirely of prairie or destroy ferret sign. When there is night to maximize the chance of dog hair and bones. overlapping nighttime activity snow cover, both ferret tracks and Ferrets sometimes form “trenches” or fresh diggings are more obvious and periods of ferrets. “ramps” when they excavate prairie detectable. 4. A survey crew should consist of dog burrows. Prairie dogs occasionally Daylight searches for ferret sign one vehicle and two observers plug the entrances to their burrow sys- should meet the following criteria to equipped with two 200,000 to tems with soil. When excavating such fulfill the minimum standards of these 300,000 candlepower (lumen) spot- a plug in a burrow, the ferret backs out guidelines: lights. In terrain not suitable for with the soil held against its chest with vehicles, a crew should consist of its front paws. It generally comes out 1. Three searches must be made on two individuals working on foot of the burrow in the same path each each town. Conduct each search with battery-powered 200,000 to time. This usually occurs when snow when fresh snow has been present 300,000 candlepower (lumen) spot- covers the ground. After repeated for at least 24 hours and after 10 or lights. To estimate the number of trips, a ramp from 3 to 5 inches (7.6 to more days have passed between crew nights for a survey, divide the 12.7 cm) wide and from 1 to 9 feet (0.3 each search period. total area of prairie dog town to be to 2.7m) long is formed (Fig. 7). Bad- 2. Vehicles driven at less than 5 miles surveyed by 320 acres (130 km) and gers, foxes, and weasels occasionally per hour (8.3 km/hr) may be used multiply by 3. One or both of the form similar ramps. to search for tracks or ferret dig- observers in each survey crew Prairie dogs generally deposit exca- gings, but complete visual inspec- should be a biologist trained in fer- vated soil around the burrow entrance tions of each part of the town being ret search techniques. to form a mound, building it higher by

B-95 Acknowledgments

Figures 4 and 5 by Emily Oseas Routman. 16" apart Direction of travel Figure 6 courtesy of Thomas M. Campbell III, Biota Research and Consulting Service. Figure 7 courtesy of Walt Kittams.

For Additional Information

Biggins, P.E., and R.A. Crete. 1989. Black-footed ferret recovery. Proc. Great Plains Wildl. Fig. 6. Black-footed ferret tracks left in the snow. Damage Control Workshop 9:59-63. Clark, T.W., T.M. Campbell, III, M.H. Schroeder, and L. Richardson. 1984. Handbook of methods for location of black-footed ferrets. Wyoming BLM Wildl. Tech. Bull. No. 1. US Bureau Land Manage., in coop. with Wyoming Game Fish Comm. Cheyenne. 47 pp. Hall, E.R. 1981. The mammals of North America. John Wiley and Sons, New York. 1181 pp. Hillman, C.N. 1968. Field observations of black- footed ferrets in South Dakota. Trans. North Am. Wildl. Nat. Resour. Conf. 33:346-349. Hillman, C.N. 1974. Status of the black-footed ferret. Pages 75-81 in Proc. symp. endangered and threatened species of North America. Wild Canid Survival Res. Center. St. Louis, Missouri. Hillman, C.N., and T.W. Clark. 1980. Mustela nigripes. Mammal. Species 126:1-3. Hillman, C.N., and R.L. Linder. 1973. The black- footed ferret. Pages 10-23 in R. L. Linder and C. N. Hillman, eds. Proc. black-footed ferret and prairie dog workshop. South Dakota State Univ., Brookings. Sheets, R.C., R.L. Linder, and R.B. Dahlgren. 1972. Food habits of two litters of black- Fig. 7. Ramp made by a black-footed ferret excavating a prairie dog burrow. footed ferrets in South Dakota. Am. Midl. Nat. 87:249-251. US Fish and Wildlife Service. 1988. Black-footed adding soil from outside the mound. burrow entrances. Snow trenches are ferret recovery plan. US Fish Wildl. Serv., Denver, Colorado. 154 pp. The movement of soil toward the relatively rare compared to trenches in mound is in the opposite direction of the soil. US Fish and Wildlife Service. 1989. Black-footed that done by a ferret. ferret survey guidelines for compliance with If you observe a black-footed ferret or the endangered species act. US Fish Wildl. Ferrets sometimes dig in fresh snow. identify ferret sign while conducting Serv. Denver, Colorado, 15 pp. These “snow trenches” are narrow surveys, notify your local US Fish and

trough-like depressions in the snow Wildlife Service or state wildlife repre- Editors that extend away from prairie dog sentative within 24 hours. Scott E. Hygnstrom Robert M. Timm Gary E. Larson

B-96