USE OF NATURAL VEGETATIVE BA RRIERS TO LIMIT BLACK-TAILED PRAIRIE DOG TOWN EXPANSION IN WESTERN SOUTH DAKOTA

BY DAVID F. TERRALL

A thesis submitted in partial fulfillment of the requirements for the Master of Science Major in Wildlife and Fisheries Sciences Wildlife Specialization South Dakota State University
2006ii

USE OF NATURAL VEGETATIVE BA RRIERS TO LIMIT BLACK-TAILED PRAIRIE DOG TOWN EXPANTION IN WESTERN SOUTH DAKOTA

This thesis is approved as a credita ble and independent investigation by a candidate for the Master of Science degr ee and is acceptable for meeting the thesis requirements for this degree. Acceptance of this thesis does not imply that the conclusions reached by the candidate are ne cessarily the conclusions of the major department.

_______________________________ Dr. Jonathan A. Jenks Date Thesis Advisor

_______________________________ Dr. Charles G. Scalet Date Department Head of Wildlife And Fisheries Sciencesiii
Acknowledgements

I would like to thank my advisor Dr. Joha than A. Jenks for providing me with the opportunity to work on this project. I apprec iate all of the patien ce and guidance he has shown throughout the rough spots in this proj ect, as well as the additional opportunities to learn and grow in this fiel d outside of my thesis researc h. I would also like to thank Dr. Daniel E. Hubbard (Wildlife and Fisher ies Department), Dr. Dwight Galster (Math and Statistics Department), and Dr. Allen Branum (Graduate School) for serving on my committee and for the comments that they made on this thesis. I would also like to thank the agency personnel that helped me throughout this project. I would like to thank Art Smith, Wildlife Damage Management Program Administrator, for all of the opportunities he shared with me , especially in the field of wildlife damage management. I also tha nk Robert Hodorff, USDA Forest Service Biologist, for all of the help you gave in finding study sites and the heads up on the constantly changing prairie dog policies and landowner issues that were encountered during this project. This study would not have been possible without the help and cooperation of the landowners that participated in this study; J. Sides, E. Br unson, G. Schueth, M. Sheets, L. Hall, and J. Gilespie. These landowners understood the importance of looking for solutions to difficult problems and went out of there way to let prai rie dogs stay on their property during a difficult time in western South Dakota.iv I would like to thank my technician K. Herman for help during my first field season. The help she gave in setting up the st udy sites was truly appreciated, as well as the company on the long drives, and hot summe r days in the field. Many of graduate students at South Dakota Stat e University also deserve thanks for their comments, suggestions, inspiration, a nd intellectual stimulation. Lastly I would like to th ank my family. The va lue of their support is immeasurable. I thank my parents for allowing me to stay with them when I was in the southwest portion of the state and being understanding when I came and went throughout the summers of this project. I would fina lly like to thank my wife, Amy and my two daughters, Gracie and Carlie. They were strong and understanding when daddy had to be away during the summer, and long hours at scho ol. They are an inspiration for me to do better everyday. Funding for this project was provided by Federal Aid to Wildlife Restoration (Study No. 75120) administered by the South Dakota Department of Game, Fish and Parks, and South Dakota State University.v

Abstract

USE OF NATURAL VEGETATIVE BA RRIERS TO LIMIT BLACK-TAILED PRAIRIE DOG TOWN EXPANTION IN WESTERN SOUTH DAKOTA David F. Terrall July 2006

Prairie dog ( Cynomys ludovicianus ) control has historically consisted of lethal methods to maintain, reduce, or eliminate popul ations. Non-lethal methods of control for prairie dogs are desired to meet changing management objectives. Use of naturally occurring buffer strips as ve getative barriers may be effec tive in limiting prairie dog town expansion. Objectives of this study were to evaluate effective width of vegetative barriers in limiting prairie dog town expansi on, document characteristics of natural vegetation that affect expansion of pr airie dog towns, and examine vegetation characteristics associated with prairie dog to wns in western South Dakota. Five study sites were established in western South Dakota on rangelands containing prairie dog towns of adequate size ( ≥ 10 ha). Electric fences were constructed to exclude cattle and create buffer strips of naturally occurring gr asses and shrubs. Buff er strips were 100 m long and 10, 25, and 40 m wide. Zero meter c ontrols were included on all study sites. Prairie dogs were poisoned to create prairie dog free buffer zone s within cont rol areas. Grazing was allowed on both sides of buffer strips. When grazing pressure was not sufficient, mowing was used to simulate grazi ng. To quantify vegeta tion characteristics,vi quadrats (25) were randomly distributed th roughout buffer strips. Evaluation of study sites included visual obstruction (VOR), vegetation cover (%), vegetation frequency, vegetation height, and vegetation identificati on. Burrow density adjacent to buffers was quantified as an index to prairie dog populat ion. Barrier penetra tion was evaluated by presence of new active burrows behind vegeta tive barriers (Breakth rough). Breakthrough was minimized with 40-cm vegetation height and 10-cm VOR. The predictive model for vegetation height and buffe r width was Breakthrough=exp (2.410-0.004*Veg Height-0.036*Buffer

Width) . The predictive model for VOR and buffer width was Breakthrough=exp (2.48-

0.048*VOR-0.031*Buffer Width) . Percent grass cover, percent forb cover, percent bare ground, percent litter cover, and burro w density did not add significan tly to the model. Models were used to predict buffer width needed to prevent breakthroughs. Estimated buffer width to minimize breakthroughs ranged from 85.1 – 103.1 m. Vegetation characteristics indicated that visual obstruc tion was greater on buffers th an on controls. Vegetation height was higher on treatment than control plots, and higher on eastern sites than western sites. Western wheatgrass ( Pascopyrum smithii ) was greater on eastern than western site. Bare ground was significantly gr eater on control areas compared to buffer areas. Vegetation characteristics associated w ith relative percent gra ss cover, forb cover, and litter indicated minor or no differences be tween controls and buffer, and eastern sites and western sites. Plant species richness wa s not different from control to buffer area, but was greater on eastern s ites than western sites.vii

Table of Contents Acknowledgements............................................................................................................ iii Abstract....................................................................................................................... .........v Table of Contents.............................................................................................................. vii List of Tables ................................................................................................................. .... ix List of Figures ............................................................................................................... .......x List of Appendices ............................................................................................................. xi Chapter 1. General Introduction .........................................................................................1
Status .......................................................................................................................1 Natural History ........................................................................................................4 Literature Review ....................................................................................................6 Literature Cited......................................................................................................10 Chapter 2. Use of natural vegetative barriers to limit expansion of blacktailed prairie dog towns...................................................................................13 Introduction ...........................................................................................................13 Study Area .............................................................................................................14 Methods .................................................................................................................16 Results ..................................................................................................................18 Discussion..............................................................................................................19 Literature Cited......................................................................................................26 Chapter 3. Vegetation characteristics associated with black-tailed prairie dog town expansion .........................................................................................39viii

Introduction ...........................................................................................................39 Study Area .............................................................................................................40 Methods .................................................................................................................41 Results ...................................................................................................................43 Discussion..............................................................................................................45 Literature Cited......................................................................................................50 Chapter 4. Management Implications and Conclusions ...................................................59 Literature Cited......................................................................................................62ix

List of Tables Table 2.1. Mean (SE) of vegetati on characteristics and breakthroughs (new active burrows) associat ed with prairie dog town expansion measured from five study sites in western South Dakota, August 2004 and 2005......................................................................30

Table 2.2. Predicted buffer width needed (meters) to minimize prairie dog breakthrough (new active burrows) based upon visual obstruction readings (VOR) and vegetation height from sites with breakthroughs in western South Dakota during 2004 and 2005 .................................................................................................................31 Table 2.3. Precipitation as registered by the nearest weather station within 25 km of study sites for 2004 and 2005..........................................................32 Table 3.1. Mean (SE) of vegetation char acteristics measured at five study sites in western South Dakota during August 2004 and 2005 a . .....................54 Table 3.2. Relative percent canopy cover for top three most abundant species on five study sites in western South Dakota in August 2005. ................................................................................................................55 Table 3.3. Precipitation as registered by the nearest weather station within 25 km of study sites for 2004 and 2005...........................................................57x List of Figures Figure 2.1. Locations of study areas us ed in vegetative barrier study in western South Dakota in 2004 and 2005. .....................................................33 Figure 2.2. Schematic of buffer strips used to reduce prairie dog town expansion for five study site s in western South Dakota in 2004 and 2005................................................................................................34 Figure 2.3. Non-linear mode l of breakthroughs (Breakout) of new, active prairie dog burrows versus visual obstruction (VOR, [cm]) for five study sites in western South Dakota during August 2004 and 2005.........................................................................................................35 Figure 2.4. Non-linear model of br eakthroughs (BREAKOUT) of new, active prairie dog burrows ve rsus vegetation height (VEGHEIGHT, [cm]) for five st udy sites in western South Dakota during August 2004 and 2005. ..........................................................36 Figure 2.5. Non-linear model of br eakthroughs (BREAKOUT) of new, active prairie dog burrows vers us visual obstruction (VOR, [cm]) and buffer width (BUFFW IDTH, [m]) for five study sites in western South Dakota during August 2004 and 2005. ......................37 Figure 2.6. Non-linear model of br eakthroughs (BREAKOUT) of new, active burrows versus vege tation height (VEGHEIGHT, [cm]) and buffer width (BUFFWIDTH [M]) for five study sites in western South Dakota during August 2004 and 2005. ......................38 Figure 3.1. Location of st udy areas used in vegetative barrier study in western South Dakota in 2004 and 2005. ......................................................58xi
List of Appendices Appendix A. Plant species identifie d on the Bad River Road study site, 2004 and 2005.............................................................................................64 Appendix B. Plant species identified on the Custer county site, 2004. ............................65 Appendix C. Plant species identified on the Custer county site, 2005. ............................66 Appendix D. Plants identified on Fall River county site, 2004 and 2005. .......................67 Appendix E. Plant species identified on Fort Pierre study site, 2004 and 2005...............68 Appendix F. Plant species identif ied on Winner study site, 2004 and 2005 ....................69 Appendix G. Breakthroughs of new, active burrows, and vegetation characteristics associated with five study sites in west ern South Dakota, August 2004 and 2005. ......................................................................................................701
Chapter 1

General Introduction

Status In 1998, the United States Fish and W ildlife Service (USFWS) received two petitions to list the black-tailed prairie dog ( Cynomys ludovicianus ) as threatened throughout its range; one petition from the Natio nal Wildlife Federation filed in July, and one petition from the Biodiversity Legal F oundation, the Predator Project, and Jon C. Sharps filed in August (U. S. Fish and W ildlife Service 2000). A positive, 90-day finding led to an investigation by the USFWS. Th e 12-month administrative finding found that the listing of the black-tailed prairie d og was warranted, but precluded due to other species of greater importance (U. S. Fish and Wildlife Service 2000). The 12-month finding found three major fact ors that were impacting black-tailed prairie dog populations. The first major impact was the loss and destruction of habitat, mainly caused by the conversion of native pr airie grasslands to cropland. Extensive conversion of the eastern portion of the blac k-tailed prairie dog range into cropland occurred during the 1880’s and 90’s (U. S. Fish and Wildlife Service 2000). This conversion continued duri ng the beginning of the 20 th century and still continues to some extent today. Improved dry-land farm ing techniques and new crop hybrids have contributed to habitat loss by making farming profitable in ar eas previously unsuitable for cultivation (U. S. Fish a nd Wildlife Service 2000).2 The second major impact was large scale control efforts to reduce or eliminate large populations of prairie dogs. Due to co mpetition with livestock, extensive control efforts of prairie dogs have occurred on range land including federal, state, tribal, and private lands (U. S. Fish and Wildlife Service 2000). Control efforts have often led to the complete loss of some populations of prai rie dogs. Prairie dog control in South Dakota dates back to 1914 (Hanson 1988). Contro l of prairie dogs in South Dakota was conducted on a county by county basis using strychnine oat bait (Hanson 1988). Zinc phosphide oat bait and fumigants, such as aluminum phosphide, are currently used in South Dakota. In 2004, the South Dakota Game , Fish and Parks Department controlled just fewer than 11,000 ha, and Buffalo Gap National Grassland poisoned approximately 3,200 ha of land along the border between federa l and private lands in southwest South Dakota (South Dakota Department of Game Fish and Parks 2004). The third major factor found by USFWS to affect prairie dog populations was sylvatic plague. Sylvatic plague is caused by the transfer of the bacterium Yersinia pestis from infected fleas to the host organism. Black-tailed prairie dogs are highly susceptible to outbreaks of sylvatic plague and Cully (1993) reported near 100% mortality for blacktailed prairie dogs from plague. Sylvatic pl ague is an exotic disease for which prairie dogs develop no antibodies or immunity agai nst (Cully 1993). The near complete mortality from sylvatic pla gue results in epizootic outbreaks being short lived (Cully 1993). South Dakota had its first recorded cas e of sylvatic plague in 2004 (South Dakota Department of Game, Fish and Parks 2004). Plague outbreaks expanded in 2005 in the3 southwest portion of the state with the focal point of the outbreak located on the western side of Shannon County. Other factors that contributed to the candi date status of the black-tailed prairie dog included concerns over exploitation due to recreational shooting and the inadequacy of existing regulatory mechanisms. At the time of petitioning, South Dakota categorized the black-tailed prairie dog as a state designated pest. Presence of prairie dogs was considered an infestation and control was required (U. S. Fish and Wildlife Service 2000). South Dakota did require residents and non-residents to acquire a license to hunt prairie dogs, however, no limits were placed on the number harvested. The designation of the black-tailed prairi e dog angered landowners, elevated the controversy surrounding prairie dog control on rangelands, and prompted South Dakota, as well as other states and agencies, to m odify or create prairie dog management plans (Cooper and Gabriel 2005). Following the pe tition, the South Dakota Game, Fish and Parks Department, and the USDA Forest Servic e suspended control operations for prairie dogs. South Dakota entered into a multi-state , multi-agency cooperative effort to develop a comprehensive management strategy that woul d ensure that management and control of black-tailed prairie dogs remained the res ponsibility of states and not the federal government (Cooper and Gabriel 2005). Efforts were designed to remove or minimize threats to ensure the long-term conservati on of the black-tailed prairie dog (Cooper and Gabriel 2005). South Dakota’s manage ment plan included six objectives: 1-Determine statewide preliminary population goals and special management areas.4 2-Develop effective tools to monito r changes in prairie dog populations. 3-Develop disease monitoring protocol s including a contingency plan for sylvatic plague outbreaks in South Dakota. 4-Determine and accommodate conservation needs for black-footed ferrets. 5-Use public involvement techniques to gather input on management goals, objectives, and strategies. 6-Use adaptive management to eval uate progress and make needed adjustments to reach program goals. Public opinion over the listing included concerns over landowner rights, control responsibilities, and other speci es associated with prairie dog towns, including the blackfooted ferret ( Mustela nigripes ), swift fox ( Vulpes velox ), and burrowing owl ( Athene
cunicularia ). In August 2004, the USFWS remove d the black-tailed prairie dog as a candidate species for listing as threatened and stated that the black-tailed prairie dog was not likely to become endangered due to new in formation indicating the species ability to exist over time, and increased management ef forts by states within the prairie dog’s range (Cooper and Gabriel 2005).

Natural History Black-tailed prairie dogs are small, ground dwelling members of the family Sciuridae. Five species of prairie dogs are found in North America; black-tailed, whitetailed ( Cynomys leucurus ), Utah ( Cynomys parvidens ), Gunnison’s ( Cynomys gunnisoni ),5 and Mexican ( Cynomys mexicanus ). Of the five species of prairie dogs, the black-tailed is the most numerous, has the largest geogra phic distribution, and is the most colonial (Hoogland 1995). Black-tailed pr airie dogs range from norther n Mexico in the south to southern Canada in the north, and from the eas tern edge of the Ro cky Mountains in the west, east into the mixed grass prairies of central North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, and Texas (Hoogland 1995). Current distribution of prairie dogs in South Dakota includes the mixed- and short-gr ass prairies of the western two-thirds of the state (Sidle et al. 20 01). Prairie dogs currently occupy approximately 1,665 km 2 of land in South Dakota (Cooper and Gabriel 2005). One of the most striking aspects of the black-tailed prairie dog is the extensive social and colonial tendenci es that are characteristic of the species (Hoogland 1995). Prairie dogs live in groups cal led colonies or towns (Ki ng 1955, Hoogland 1995). Within these colonies are subgroups called wards that are often se parated by unsuitable habitat (Hoogland 1995). Harem-polygynous, territorial family groups found within colonies are termed coteries, and generally contain one br eeding male, two to three adult females, and one or two yearlings of each sex (Hoogland 1995). Burrows that prairie dogs excavate and live in can have one to many holes and can be several meters in length and depth (Hoogland 1995). Female prairie dogs tend to remain in their natal coterie, while juvenile males will disperse to other ar eas (Hoogland 1995). Coterie members do not show territoriality towards other members, but will defend the cote rie territory from nonmembers.6 Prairie dogs give birth to one litter of pups in the spring of each year in a single underground burrow that is defended by the female. Male and female prairie dogs typically reach sexual maturity at 2 years of age. Hoogland (1995) observed that only 50% of females will bring a litte r of pups to the surface. Th e leading cause of juvenile mortality is infanticide and can result in th e partial or total loss of 39% of litters. Average size of litters that reach first emer gence is 3-4. Larger groups of pups seen outside of burrow entrances are likely due to communal nursing (Hoogland 1995). First year mortality rate for both sexes is 50%; how ever, female prairie dogs that live past the first year can live up to eight years a nd males up to five years (Hoogland 1995). Black-tailed prairie dogs clip and ma intain short vegetation throughout the colony. Short vegetation enhances predat or detection within the colony (Hoogland 1995). Maintenance of short vegetation in to wns is seen as direct competition with livestock for range resources in areas where prairie dogs and cattle occur sympatrically. There is evidence that the use of buffer strips of native vegetation that is allowed to grow free of grazing pressure by livestock or prai rie dogs may be an effective barrier in limiting prairie dog expansion.

Literature Review Previous studies on the use of barriers to prairie dog town expansion have focused mainly on artificial barriers. Franklin a nd Garrett (1989) used 1-m high burlap fencing and cut ponderosa pine ( Pinus ponderosa ) trees as a method to control prairie dog town expansion on a study site at Wind Cave Nati onal Park, South Dakota. Use of control7 areas by prairie dogs was 3 times greater than on the treatment area using burlap fencing. The area of expansion was 54% on the control areas while only 8% on the treated area (Franklin and Garrett 1989). Cut pine trees were used as a visual barrier on a large colony in the Park and were successful at re ducing the use and expansion of prairie dogs into the treated area (F ranklin and Garrett 1989). Plastic snow fence was ineffective at reducing the expansion of black-tailed prai rie dogs in central Nebraska (Hygnstrom 1995). This study indicated that visual barriers with lowe r porosity or solid barriers might prove more effective. Additionally, barriers that were more durable and less vulnerable to environmental damage, and secu red in trenches to prevent movement of prairie dogs under barriers might increase effec tiveness of artificial barriers. Robinette (1992) unsuccessfully used electrified fenci ng and metal flashing to prevent prairie dogs from returning to burrows. Similarly, galvan ized roofing material failed to prevent expansion of prairie dog towns in New Mexico (Merriman et al. 2004). Use of vegetation as a barrier to expans ion of black-tailed prairie dog towns has focused on controlling grazing patterns of liv estock to influence vegetative condition on rangeland. In 1977, a 44.5-ha prairie dog town in Kansas was reduced to 4.9 ha following four successive seasons of reduced grazing during the growing season (Snell and Hlavachick 1980). Methods to attract predators and incr ease vegetation growth with fertilizer also were utilized on this site ; however, the most beneficial treatment at reducing prairie dogs was attributed to the re duction in grazing pre ssure. Following this time period, cattle were allowed back into th is pasture during the growing season. The town expanded to 8.1 ha in two years. Cattle were removed and the town was reduced to8 2.3 ha by fall (Snell 1985). Lack of grazing by livestock following the termination of private grazing permits on the Wichita M ountains Wildlife Ref uge in southwest Oklahoma is credited with the disappearance of a protected prairie dog town (Osborn and Allan 1949). Following the creation of the Wichita Mountains Wildlife Refuge, all grazing permits were cancelled and fences that contained a resident heard of bison ( Bison bison ) were removed. The resulting lack of grazing on the Grace Mountain prairie dog colony (20.2 ha) was credited with the di sappearance of the town within 11 years (Osborn and Allan 1949). Cable and Timm (1988) observed a similar trend in reduction of prairie dog town expansion during the s econd year of a deferred grazing study. The first year of the study found no difference betw een control and treatm ent sites. Second year results of the study indicated reducti ons in natality and population growth on deferred sites when compared to grazed sites. Data collected duri ng the second year also indicated that 4 of 5 deferred sites decreased in size and 6 of 8 grazed sites increased in size. High visibility through adjacent vege tation was a significant factor influencing prairie dog colonization of adjacent prairie (Cincotta et al. 1988) Use of a buffer strip of natural vegetati on as a barrier to limit the expansion of black-tailed prairie dog towns ma y prove effective. Quantif ication of effective buffer width and vegetation structural characteristics (vegetation he ight and visual obstruction) to reduce prairie dog town expansion has not been done. The objectives of this study were to evaluate effective width of ve getative barriers in lim iting prairie dog town expansion, and to document effect of vegeta tion height and visual obstruction of native vegetation on expansion of prairie dog to wns. We also studied the vegetation9

characteristics associated with black-taile d prairie dog towns in western South Dakota and the post treatment response of vegetati on to removal of grazing by prairie dogs and cattle. Knowledge gained in this study will supplement existing non-lethal methods for managing prairie dogs and further our unde rstanding of prairie dog impacts on the environment.10

Literature Cited Cable, K. A., and R. M. Timm. 1988. E fficacy of deferred grazing in reducing prairie dog reinfestation rates. Pages 46-49 in D. W. Uresk, G. L. Schenbeck, and R. Cefkin, Technical Coordinators. Eighth Great Plains Wildlife Damage Control Workshop Proceedings, 28-30 April 1987, Rapid City, South Dakota. USDA Forest Service General Technical Report RM-154. Cincotta, R. P., D. W. Uresk, and R. M. Ha nsen. 1988. A statistical model of expansion in a colony of black-tailed prairie dogs. Pages 30-32 in D. W. Uresk, G. L. Schenbeck, and R. Cefkin, Technical Coordi nators. Eighth Great Plains Wildlife Damage Control Workshop Proceedings , 28-30 April 1987, Rapid City, South Dakota. USDA Forest Service General Technical Report RM-154. Cooper, J, and L. Gabriel. 2005. South Da kota black-tailed prairi e dog conservation and management plan. Final Draft-Februa ry 2005. South Dakota Department of Game, Fish and Parks, Pierre, South Dakota. Cully, J. F. 1993. Plague, prairie dogs, and black-footed ferrets. Pages 38-49 in J. Oldemeyer, D. Biggins, B. Miller, and R. Crete, Editors. Management of prairie dog complexes for the reintroduction of the black-footed ferret. U. S. Fish and Wildlife Service Biological Report No. 13. Franklin, W. L., and M. G. Garrett. 1989. Nonlethal control of prairie dog colony expansion with visual barriers. Wildlife Society Bulletin 17:426-430.11 Hanson R. 1988. A chronology of prairi e dog control operations and related developments in South Dakota. Pages 121- 122 in D. W. Uresk, G. L. Schenbeck, and R. Cefkin, Technical Coordinators. Eighth Great Plains Wildlife Damage Control Workshop Proceedings, 28-30 Ap ril 1987, Rapid City, South Dakota. USDA Forest Service Genera l Technical Report RM-154. Hoogland, J. L. 1995. The black-tailed prairie dog: social life of a burrowing mammal. University of Chicago Press. Chicago, Illinois. 557pp. Hygnstrom, S. E. 1995. Plastic visual barriers were ineffective at reducing recolonization rates of prairie dogs. Pages 74-76 in R. E. Masters, and J. G. Huggins, Editors. Twelfth Great Plains Wildlife Damage Control Workshop Proceedings, 10-13 April 1995, Tulsa, Okla homa. National Wildlife Research Center, Fort Collins, Co. King, J. A. 1955. Social behavior, social organization, and population dynamic in a black-tailed prairie dog town in the Black Hills of South Dakota. Contributions from the Laboratory of Vertebrate Biol ogy Number 67. University of Michigan, Ann Arbor, Michigan. Merriman J. W., P. J. Zwank, C. W. Boal, a nd T. L. Bashore. 2004. Efficacy of visual barriers in reducing black-tailed prairi e dog colony expansion. Wildlife Society Bulletin 32:1316-1320. Osborn, B., and P. F. Allan. 1949. Vegetation of an abandoned prairie-dog town in tall grass prairie. Ecology 30:322-332.12
Robinette, K. W. 1992. Black-t ailed prairie dog management: tr anslocation and barriers. M.S. Thesis, Colorado State University, Fort Collins, Colorado. 39pp. Sidle, J. G., D. H. Johnson, and B. R. Euliss. 2001. Estimated areal extent of colonies of black-tailed prairie dogs in the Northern Great Plains. Journal of Mammalogy
82:928-936. Snell, G. P. 1985. Results of cont rol of prairie dogs . Rangelands 7:30. Snell, G. P., and B. D. Hlavachick. 1980. Control of prairie dogs-the easy way. Rangelands 2:239-240. South Dakota Game, Fish and Parks. 2004. Division of Wildlife 2004 Annual Report. South Dakota Game, Fish and Parks, Pierre, South Dakota. U. S. Fish and Wildlife Service. 2000. E ndangered and threatened wildlife and plants; 12-month finding for a petition to list the black-tailed prairie dog as threatened. Federal Register 65(24):5476-5488. Depart ment of the Interior, Washington,
D.C.13
Chapter 2

Use of natural vegetative ba rriers to limit expansion of Black-tailed prairie dog towns.

Introduction In 2000, the U. S. Fish and Wildlife Serv ice designated the black-tailed prairie dog ( Cynomys ludovicianus ) a candidate species for listing as threatened (U. S. Fish and Wildlife Service 2000). This designation a ngered ranchers, elevated the controversy surrounding prairie dog control on rangelands, an d prompted South Dakota, as well as other states and agencies, to modify or cr eate prairie dog management plans (Cooper and Gabriel 2005). Public opinion over the lis ting included concerns over landowner rights, control responsibilities, and other species associated with prairie dog towns including the black-footed ferret ( Mustela nigripes ), swift fox ( Vulpes velox ), and burrowing owl ( Athene cunicularia ). Black-tailed prairie dogs ar e small burring rodents ( ≈ 700g) that live in colonies called towns (Hoogland 1995). The extensive social and colonial tendencies of the blacktailed prairie dog are characteristic of the spec ies. Of the five species of prairie dog, the black-tailed is the most numerous and has the largest geographic distribution. Blacktailed prairie dogs range from northern Mexico in the south to southern Canada in the north, and from the eastern edge of the Rocky Mountains in the west, east into the mixed grass prairies of central No rth Dakota, South Dakota, Nebr aska, Kansas, Oklahoma, and14 Texas (Hoogland 1995). The current distri bution of prairie dogs in South Dakota includes the mixed- and short-gra ss prairies of the western two-th irds of the state (Sidle et al. 2001). Prairie dogs currently occupy approximately 1665 km 2 of land in South Dakota (Cooper and Gabriel 2005). Black-tailed prairie dogs clip and ma intain short vegetation throughout the colony. Short vegetation enhances predat or detection within the colony (Hoogland 1995). Maintenance of short vegetation in to wns is seen as direct competition with livestock for range resources in areas where prairie dogs and grazing occur sympatrically. There is evidence that the use of buffer strips of native vegetation that is allowed to grow free of grazing pressure by livesto ck or prairie dogs may be effective in limiting prairie dog expansion (Osborn and Allan 1949, Sne ll and Hlavachick 1980, Franklin and Garrett 1989). Use and success rate of a naturally occu rring vegetative buffer strip as a barrier to prairie dog town expansion has not been quantif ied. The objectives of this study were: 1) to evaluate effective width of vegetative ba rriers in limiting prairie dog town expansion; 2) to document effect of height and visual obstruction of native vegetation on expansion of prairie dog towns. Knowledge gained in this study will supplement existing non-lethal methods for managing prairie dogs.

Study Area We selected five study sites on rang elands containing prairie dog towns ≥ 10-ha west of the Missouri River in South Dakota during 2004 and 2005. Study areas where located on rangelands in Custer, Fall River, Stanley, and Tripp Counties (Figure 2.1). A15

new site located 3.2 km NE of the 2004 site was established due to access issues. Study site locations were: Custer County (2 004 - N43o38.2’ W103o 4.1’, 2005 - N43o39.5’ W103o2.5’); Fall River Count y (N43o20.7’ W103o5.0’), Ba d River Road (N44o14.1’ W100o55.7’), Fort Pierre (N 44o23.0’ W100o31.6’), and Winne r (N43o36.7’ W099o55.7’) Study areas where located in the Pierre Hills and Southern Plateaus physiographic regions in western South Dakot a (Johnson et al. 1995). The Pierre Hills physiographic region is characterized by eroded rounded hi lls and ridges composed of primarily clay soils. The Southern Plateaus physiographi c region is underlined by sandstone and mudstone containing mostly loam and silt lo am soils that form highland benches and buttes (Johnson et al. 1995). Mean annual te mperatures ranged from 8.3oC at the Fall River County site to 10.0oC at the Winner site (South Dakota Office of Climatology 2006). Monthly mean temperatures ranged from a low of -7.7oC in January to a high of 24.6oC in July. Mean annual rainfall ranged from 42.6 cm at Fort Pierre to 60.3 cm at the Winner site (South Dakota Office of Climatology 2006). Primary land use of the area was past ure and rangeland livestock grazing intermixed with crop production, which included wheat ( Triticum aestivum ), alfalfa ( Medicago sativa ), corn ( Zea mays ), and soybeans ( Glycine max ). Johnson and Larson (1999) classified the region as northern wh eatgrass-needlegrass plains. Dominant vegetation in this area includes western wheatgrass ( Pascopyrum smithii ), Japanese brome ( Bromus japonicus ), needleandthread ( Stipa comata ), green needlegrass ( Stipa viridula ), blue grama ( Bouteloua gracilis ), buffalograss ( Buchloe dactyloides ), scarlet16 globemallow ( Sphaeralcea coccinea ), western wallflower ( Erysimum asperum ), and prickly pear ( Opuntia macrorhiza ) (Johnson and Larson 1999).

Methods Study sites were established and monito red from 1 March 2004 to 30 October 2005. We constructed electric fences for the purpose of excluding cattle and creating buffer strips of native grasses and shrubs. At the beginning of the study, we poisoned prairie dogs to create a prairi e dog free buffer zone adjacent to active prairie dog towns. Grazing was allowed on both sides of the buffer st rips. This created strips of naturally occurring vegetation between an area that c ontained both grazing and prairie dogs and an area with grazing only (Figure 2.2). Buffer strips were 100-m long and 10, 25, and 40 m in width. A zero m control was included on all study sites. Initial poisoning efforts took place in sp ring 2004 prior to the first emergence of young prairie dogs (Franklin and Garrett 1989). We used aluminum phosphide (Weevelcide, United Phosphorus Inc., Trenton, NJ) fumigant tablets (60% concentration) for the initial spring applica tion. This was conducted by placing tw o to three tablets within all open burrow entrances; burrows were then sealed with sod or dirt. Fumigants, such as aluminum phosphide, are the only poisoning method approved for controlling prairie dogs in South Dakota during spring. Follow-up applications were conducted to establish a prairie dog free buffer. Poisoning for th e 2005 field season was conducted the previous fall using zinc phosphide treated oats a nd aluminum phosphide tablets. Follow up applications of aluminum phosphi de were done in spring of 2005.17 We evaluated study sites using visual obs truction (0.2 dm), vegetation cover (%), vegetation height (cm), vege tation composition, and burrow density adjacent to buffer strips. We established three transect lines to facilitate random dist ribution of quadrats. Transects extended the length of the buffer stri p and were systematically spaced at 25, 50, and 75% positions across the width of buffer strips. Transects were separated into 1-m increments to establish potential quadrat locations. End points of transects were eliminated to reduce effect of buffer edge. We randomly chose 25 non-consecutive points along the total length of transects for evaluation. We measured visual obstruction (to nearest 0.2 dm) at each quadrat site usi ng a modified Robel pole (Robel et al. 1970). Cover measurements for grasses, forbs, ba re ground, and litter were estimated at sampling points (Daubenmire 1959). Quadrat size was 30 cm wide and 75 cm long. Modified cover classes were 0 (not present), 1 (trace-5%), 2 (6-25%), 3 (26-50%), 4 (51- 75%), 5 (76-95%), and 6 (96-100%). Median values for cover cla sses where used to calculate relative percent canopy coverage for ve getation classes, bare ground, and litter. Vegetation was grouped into two broad categories, graminoids and forbs. Graminoids were classified as members of the families Gramineae , Cyperaceae , and Juncaceae

. Forbs were classified as all other broa d-leaved herbaceous vegetation excluding the preceding three families of graminoids a nd any woody vegetation (Johnson and Larson 1999). Vegetation height was obtained for each of the sampling points using a clear 30- cm disc lowered until the bottom side of th e disc was first touched by leafy vegetation (Higgins and Barker 1982). Vegetation id entification followed that of Johnson and Larson (1999) and Stubbendieck et al. (2003). Burrow density was estimated by18 counting the number of burrows in three random ly spaced 1-ha plots adjacent to the study site. Mean burrow density wa s then used as an index to population density. We evaluated barrier penetration using the presence of new active burrows behind vegetative buffers. Burrow counts were completed in Oc tober and November to ensure all prairie dog breakthroughs were counted for that seas on. We used negative binomial regression models to analyze vege tation characteristics.

Results VOR and vegetation height were highly correlated (r 2 = 0.86) and therefore, both variables were not used in the same model. Significant relationships were documented for both VOR and vegetation height. The pr edictive model for VOR was Breakthrough =
exp (4.274 – 0.573*VOR) ; mean corrected r 2 was 0.71 (P<0.01) (Figure 2.3). The predictive model for vegetation height was Breakthrough = exp (4.883 – 0.143*vegetation height) ; mean corrected r 2 was 0.61 (P<0.01) (Figure 2. 4). Br eakthrough was minimized with 40-cm (SE = 0.021) vegetation height and 10-cm (SE = 0.064) VOR. Additional vegetation characteristics such as grass cover, forb cove r, litter cover, and ba re ground increased the mean corrected R 2 by less than 2% and thus, were not included in models. Burrow density adjacent to buffer strips also di d not add significantly to the model. Breakthroughs decreased across sites from 2004 to 2005, ranging from a 36.4% decrease in controls between years to 69.4% decrease in the 40-m buffer between years (Table 2.1). Visual obstruction increased across st udy sites from 2004 to 2005 and ranged from 13.6% in the 10-m buffer to 52.2% in the 40-m buffer (Table 2.1). Vegetation height19 decreased in the control from 2004 to 2005 by 7.2%, but increased in the buffers from 4.0% in the 10-m buffer to 40.7% in the 40-m buffer (Table 2.1). Bad River Road and Winner sites had no breakthroughs in 2005 at the 40-m buffer width. Analysis of variance indicated that a significant difference ( F 1,38 =5.459, P =0.025) of new active prairie dog burrows occurred between breakth roughs between successful sites and the unsuccessful sites. Predictive models from th ese two sites were used to develop models that included buffer width. Models were used to estimate the buffer width needed given vegetation height and VOR measurements for unsuccessful sites. The predictive model for VOR with buffer width was Breakthrough=exp ( 2.48-0.048*VOR-0.031*Buffer Width ); mean corrected R 2 was 0.86 (P<0.01) (Figure 2.5). The pr edictive model for vegetation height was Breakthrough=exp ( 2.410-0.004*Veg Height-0.036*Buffer Width ); mean corrected R 2 was 0.85 (P<0.01) (Figure 2.6). Based on the models, predicted buffer width necessary for zero breakthroughs ranged from 85.1 m to 103.1 m with means ranging from 91.3 m (SE=2.08) to 100.7 m (SE=0.92) (Table 2.2). Rainfall measurements were taken from nearest weather stations within 25 km of study sites (Table 2.3). Annual rainfall ranged from 37.95 cm at Fort Pierre to 48.82 cm at Bad River Road and Fall River county sites. Growing season rainfall wa s calculated from 1 April to 31 August for 2004 and 2005 (Table 2.3).

Discussion Our models indicated that both visual obstruction through the barrier and vegetation height were the most important factors limiting black ta iled prairie dog town20 expansion. Visual obstructi on alone, however, explained more of the variation (mean corrected r 2 =0.71, P<0.01) in the data than did vegetation height (mean corrected r 2 =0.61, P<0.01). The addition of buffer width in th e model increased the mean corrected R 2 of both models. Models had similar mean corrected R 2 values (0.86 and 0.85) when buffer width was added to the model. Previous barrier studies have mainly focu sed on the use of artificial barriers to limit the expansion of prairie dog towns (Franklin and Garrett 1989, Robinette 1992, Hygnstrom 1995, Merriman et al. 2004). These studies have shown mixed results as to their effectiveness in controlling prairie dog town expansion. Our models indicated a decreasing trend in prairie dog expansion with increased visual obs truction. This is consistent with the findings of Franklin and Garrett (1989) who noted a significant decrease in the use of areas with visual barr iers made from burlap cloth or cut ponderosa pine ( Pinus ponderosa ). Hygnstrom ( 1995), however, repor ted that visual barriers made from plastic snow fence material were in effective at controlling prairie dog town expansion. Exclosures made of a polyweave ma terial in Colorado also proved ineffective at keeping prairie dogs from returning to burrows (Robinette 1992). Merriman et al. (2004) used silt fence and galvanized steel sh eeting as an artifici al visual barrier. Presence of the visual barriers did no t prevent prairie dog town expansion. One possible explanation for the success of our study and that of Franklin and Garrett (1989) was the inclusion of a depth co mponent to the visual barrier. Our models indicated an increase in the mean corrected r 2 from 0.71 with just vi sual obstruction to 0.86 with the addition of buffer width. Buff er width increased the mean corrected R 2 of21 the model with vegetation height from 0.61 to 0.85. Franklin and Garrett (1989) study design called for three parallel ro ws of visual barriers. Burlap visual barriers were placed 10-m apart for a total barrier width of 20-m and ponderosa pine tree barriers were placed 16.7-m apart for a total barrier width of 33.4- m. The addition of a third dimension, barrier depth, may be necessary to fully dete r prairie dogs that would otherwise dig under or climb over a two-dimensional visual barr ier. These studies also reported that maintenance of artificial barriers was high a nd that regular attention was needed to maintain the integrity of arti ficial barriers. Climactic c onditions in western South Dakota can include extreme temperatures, high winds, and precipitation in the form of snow and ice. Establishing permanent buffer strips usi ng barbed wire fences to exclude cattle could reduce many maintenance issues. High visibility through adjacent vegetati on was a significant factor influencing prairie dog colonization of adj acent prairie (Cincotta et al. 1988). Our models indicated that there was a reduction in barrier penetr ation with increasing vegetation height. The use of naturally occurring vegetation as a dete rrent to prairie dog town expansion also has been utilized on rangelands by controlling the timing and intensity of grazing. Reductions in grazing were associ ated with increases in vegeta tion height and density. In 1977, a 44.5-ha prairie dog town in Kansas was reduced to 4.9 ha following four successive seasons of reduced grazing during the growing season (Snell and Hlavachick 1980). Methods to attract pred ators and increase vegetation gr owth with fertilizer also were utilized on this site, however, the most beneficial treatment at reducing prairie dogs in this area was attributed to the reducti on in grazing pressure. Following this time22 period, cattle were allowed back into this pasture during the growing season. The town expanded to 8.1 ha in two years. Cattle were removed and the town was reduced to just 2.3 ha by the fall (Snell 1985). L ack of grazing by livestock following the termination of private grazing permits on the Wichita M ountains Wildlife Ref uge in southwest Oklahoma was credited with the disappearance of a protected prairie dog town (Osborn and Allan 1949). Cable and Timm (1988) obser ved a similar trend in the reduction of prairie dog town expansion during the second ye ar of a deferred grazing study. The first year of the study found no difference between co ntrol and treatment sites. Second year results indicated reductions in natality, and population growth on deferred sites when compared to grazed sites. The second year also indicated that 4 of 5 deferred sites decreased in size and 6 of 8 grazed sites increased in size. Decreases in above ground primary producti on and biomass have been associated with low soil moisture and reduced precip itation (Heitschmidt et al. 1999, Knapp and Smith 2001). Mean annual precipitation was a strong predictor of above ground net primary production (Knapp and Smith 2001). Cable and Timm (1988) suggested that precipitation may have played a role in the expansion of prairie dog towns. The first year of their study was a dry year in the Nebraska panhandle and sites received below average rainfall. The second year of the study ha d higher precipitation w ith sites receiving average or above average rainfall. Our study showed similar patterns in that none of the buffer strips was successful at preventing breakthroughs during the first year with drought conditions and below average rainfa ll. The second year of our study had precipitation during the growing s eason that was near or above average, which resulted in23 a decrease in the number of breakthroughs across study sites. C ontrolled burns and woody shrub removal were used to facilitate the expansion of prairie dog towns at Theodore Roosevelt National Park, North Dakot a (Milne-Laux and Sweitzer 2006). The increases of prairie dog activity and expans ion were observed on areas were vegetation height was reduced through burns and shrub removal. This is consistent with our results indicating the importance of vegetation structure on prai rie dog town expansion. Methodology in our study, however, differed fr om the Milne-Laux and Sweitzer (2006) study in that our buffer strips were establis hed within the boundaries of an active colony, while their treatment and control sites were es tablished in unoccupied areas adjacent to prairie dog towns. Soil type and composition ha s been shown to be a factor influencing prairie dog colonization success in uncoloni zed areas (Sheets et al. 1971, Reading and Matchett 1997, Roe and Roe 2003). Placing ou r buffer strips on active colony sites increased our confidence that vegetation char acteristics influenced prairie dog expansion and not other abiotic factors. Our models indicated a trend towards a d ecreased in breakthroughs with increased VOR, vegetation height, and buffer width. Model results indicate that barrier breakthroughs are minimized at vegetation heights of ≈ 40 cm and visual obstruction measuring ≈ 10 cm. During 2004, we noted that ba rriers were unable to prevent the movement of prairie dogs through barriers. Drought was prevalent during the first year of the study and no barriers were able to m eet the minimum 40-cm vegetation height and 10-cm visual obstruction requirement. Ho wever, 2005 had increased precipitation and two of the eastern sites did have vegetation characteristics that approached or exceeded24 the necessary requirements. No breakthroughs were observed on these sites in 2005. The increase in vegetation height and visual obstruction may be due to a combination of precipitation and plant species . The Bad River Road and Fall River county sites had similar annual precipitation, and Fall River County had higher growing season precipitation than did the Bad River Road site. Bad River Road, which had no breakthroughs in 2005, had a higher percen tage (21.4%) of western wheatgrass ( Pascopyrum smithii ) in 2005 than did Fall River C ounty (Chapter 2). Western wheatgrass has the potential to reach greater heights than buffalo grass ( Buchloe dactyloides ). Winner site also had high percen tages of western wheatgrass (46.4%) in 2005 and no breakthroughs. Fort Pierre is an eastern site th at had 31.9% western wheatgrass, but was unsuccessf ul at preventing breakthrough s by prairie dogs in 2005. The Fort Pierre site had lower annual precip itation (37.95 cm) compared to the successful eastern sites (Bad River Road-48.82 cm, Wi nner-60.25 cm). This indicates that the combination of high precipitation and plant sp ecies capable of growing tall and dense is required to establish successful vegetativ e barriers. When conditions allow for ≈ 40 cm vegetation height and ≈ 10 cm VOR, a 40-m buff er strip is likely adequate at reducing black-tailed prairie dog expansion through barriers. Under less than ideal conditions or in areas where vegetation charac teristics do not allow for th e minimum VOR and vegetation height, a 100-m buffer strip is recommended. Further tes ting of the model should be conducted to determine if the predicted dist ance is sufficient to stop prairie dog town expansion. Cincotta et al. (1988) reported that distan ce from the colony edge was important. No new burrows further than 55-m from the existing colony edge where25

observed at Badlands National Park. However, this may be attributable to increased visual obstruction from plan ts outside the maintained vegetational boundaries of the colony. Our results indicate that burrow density next to buffer strips did not add significantly to the models. Increased activ e burrows, as an indicator to population density, was a significant parameter in predic ting the colonization of adjacent prairie by prairie dogs in Badlands Nati onal Park, South Dakota (Cincott a et al. 1988). Severson and Plumb (1998) however, showed that burrow counts were not good indicators to population density when compared with ma rk recapture population counts, and that maximum visual counts should be used as an indicator to population density. This could explain why burrow density did not add significantly to our models. New prairie dogs found on the colony edge are often times immigrants that have undergone long-distance (inter-colony) disp ersals from nearby colonies (Knowles 1985, Cincotta et al. 1988). Mean st raight line distance traveled by radio-collared prairie dogs at Wind Cave National Park was 2.4-km (Garre tt and Franklin 1988). Dispersing prairie dogs from adjacent towns may colonize areas on the other side of the buffer strips. The effectiveness of buffer strips as deterrence, th erefore, may be influenced by proximity to other prairie dog towns.26

Literature Cited

Cable, K. A., and R. M. Timm. 1988. E fficacy of deferred grazi ng in reducing prairie dog reinfestation rates. Pages 46-49 in D. W. Uresk, G. L. Schenbeck, and R. Cefkin, Technical Coordinators. Eighth Great Plains Wildlife Damage Control Workshop Proceedings, 28-30 April 1987, Rapid City, South Dakota. USDA Forest Service General Technical Report RM-154. Cincotta, R. P., D. W. Uresk, and R. M. Ha nsen. 1988. A statistical model of expansion in a colony of black-tailed prairie dogs. Pages 30-32 in D. W. Uresk, G. L. Schenbeck, and R. Cefkin, Technical Coordi nators. Eighth Great Plains Wildlife Damage Control Workshop Proceedings , 28-30 April 1987, Rapid City, South Dakota. USDA Forest Service General Technical Report RM-154. Cooper, J, and L. Gabriel. 2005. South Da kota black-tailed prairi e dog conservation and management plan. Final Draft-Februa ry 2005. South Dakota Department of Game, Fish and Parks, Pierre, South Dakota. Daubenmire, R. F. 1959. A canopy-covera ge method of vegetational analysis. Northwest Science 33:43-64. Franklin, W. L., and M. G. Garrett. 1989. Nonlethal control of prairie dog colony expansion with visual barriers. Wildlife Society Bulletin 17:426-430. Garrett, M. G., and W. L. Fr anklin. 1988. Behavioral ecolo gy of dispersal in the blacktailed prairie dog. Jour nal of Mammalogy 69:236-250.27 Heitschmidt, R. K., M.R. Haferkamp, M. G. Karl, and A. L. Hild. 1999. Drought and grazing: I. Effects on quantity of forage produced. Journal of Range Management
52:440-446. Higgins, K. F., and W. T. Barker. 1982. Changes in vegetation structure in seeded nesting cover in the prairi e pothole region. Special Sc ientific Report-Wildlife 242 U. S. Fish and Wildlife Service, Washington, D. C. 27pp. Hoogland, J. L. 1995. The black-tailed prairie dog: social life of a burrowing mammal. University of Chicago Press. Chicago, Illinois. 557pp. Hygnstrom, S. E. 1995. Plastic visual barriers were ineffective at reducing recolonization rates of prairie dogs. Pages 74-76 in R. E. Masters, and J. G. Huggins, Editors. Twelfth Great Plains Wildlife Damage Control Workshop Proceedings, 10-13 April 1995, Tulsa, Okla homa. National Wildlife Research Center, Fort Collins, Co. Johnson, J. R., and G. E. Larson. 1999. Gr assland plants of South Dakota and the Northern Great Plains. S outh Dakota State University College of Agriculture and Biological Sciences, South Dakota Agricu ltural Experiment Station, Brookings, South Dakota. 288pp. Johnson, R. R., K. F. Higgins, and D. E. H ubbard. 1995. Using soils to delineate South Dakota physiographic regions. Gr eat Plains Research 5:309-322. Knapp, A. K., and M. D. Smith. 2001. Variation among biomes in temporal dynamics of aboveground primary production. Science 291:481-484.28 Knowles C. J. 1985. Observation on prairi e dog dispersal in Montana. The Prairie Naturalist 17:33-44. Merriman J. W., P. J. Zwank, C. W. Boal, a nd T. L. Bashore. 2004. Efficacy of visual barriers in reducing black-tailed prairi e dog colony expansion. Wildlife Society Bulletin 32:1316-1320. Milne-Laux, S., and R. A. Sweitzer. 2006. Experimentally induced colony expansion by black-tailed prairie dogs ( Cynomys ludovicianus ) and implications for conservation. Journal of Mammalogy 87:296-303. Osborn, B., and P. F. Allan. 1949. Vegetation of an abandoned prairie-dog town in tall grass prairie. Ecology 30:322-332. Reading, R. P., and R. Matchett. 1997. Attrib utes of black-tailed prairie dog colonies in northcentral Montana. Journal of Wildlife Management 61:664-673. Robel, R. J., J. N. Briggs, A. D. Dayton, and L. C. Hulbert. 1970. Relationships between visual obstruction measurements and weight of grassland vegetation. Journal of Range Management 23:295-297. Roe, K. A., and C. M. Roe. 2003. Habitat selection guidelines fo r black-tailed prairie dog relocations. Wildlife Society Bulletin 31:1246-1253. Robinette, K. W. 1992. Black-t ailed prairie dog management: tr anslocation and barriers. M.S. Thesis, Colorado State University, Fort Collins, Colorado. 39 pp. Severson, K. E., and G. E. Plumb. 1988. Comparison of methods to estimate population densities of black-tailed prairie dogs. Wildlife So ciety Bulletin 26:859-86629
Sheets, R. G., R. L. Linder, and R. B. Da hlgran. 1971. Burrow systems of prairie dogs in South Dakota. Journal of Mammalogy 52:451-453. Sidle, J. G., D. H. Johnson, and B. R. Euliss. 2001. Estimated areal extent of colonies of black-tailed prairie dogs in the Northern Great Plains. Journal of Mammalogy
82:928-936. Snell, G. P. 1985. Results of cont rol of prairie dogs . Rangelands 7:30. Snell, G. P., and B. D. Hlavachick. 1980. Control of prairie dogs-the easy way. Rangelands 2:239-240. South Dakota Office of Climatology. 2006. Te mperature and Precipitation Archives. South Dakota State University . Brookings, South Dakota. http://climate.sdstate.edu/climate_site /archive_data.htm. Accessed 7 June 2006. Stubbendieck, J. L., M. J. Coffin, and L. M. Landholt. 2003. Weeds of the Great Plains. Nebraska Department of Agricu lture, Lincoln, Nebraska. 605pp. U. S. Fish and Wildlife Service. 2000. E ndangered and threatened wildlife and plants; 12-month finding for a petition to list the black-tailed prairie dog as threatened. Federal Register 65(24):5476-5488. Depart ment of the Interior, Washington,
D.C. Uresk, D. W., R. M. King, A. D. Apa, and R. L. Linder. 1987. Efficacy of zinc phosphide and strychnine for black-tailed prairie dog control. Journal of Range management 39:298-299.Table 2.1. Mean (SE) of vegetation characteristics and breakthroughs (new active burrows) associated with prairie dog townexpansion measured from five study sitesin western South Dakota, August 2004 and 2005.Control 10m 25m 40m2004 2005 2004 2005 2004 2005 2004 2005Break through28.6(11.57)18.2(5.77)23.4(12.6)13.80(3.71)25.0(10.9)12.00(4.51)21.6(7.69)6.60(3.34)VOR (cm)1.78(0.47)2.48(0.41)3.42(1.67)3.96(0.95)3.1(1.2)5.22(1.50)4.1(1.87)8.58(1.92)Vegetation Height (cm)12.76(2.11)11.84(1.34)17.36(3.02)18.08(3.84)14.58(2.57)20.18(4.03)17.1(3.74)28.84(6.44)Graminoid cover (%)36.48(11.72)42.30(8.27)51.34(10.99)67.34(5.75)49.2(14.48)62.98(8.23)51.5(14.04)67.40(6.55)Forb cover (%)11.66(6.04)10.74(5.04)6.62(2.42)7.00(2.20)9.8(5.69)11.60(4.39)12.1(5.97)11.12(4.97)Liter cover (%)21.14(6.70)16.74(5.19)26.3(12.70)10.78(2.50)24.0(13.07)10.62(2.36)22.1(12.16)8.30(2.54)Bare ground (%)30.68(6.76)30.20(5.51)15.76(2.94)14.90(5.86)17.0(4.29)14.80(5.70)14.26(3.67)30.68(6.76) 3031 Table 2.2. Predicted buffer width needed (met ers) to minimize prai rie dog breakthrough (new active burrows) based upon visual obs truction readings (VOR) and vegetation height from sites with breakthroughs in western South Dakota during 2004 and 2005.
Mean Max Min
Fort Pierre 91.3m 100.1m 85.1m Visual Obstruction Cust er County 98.6m 100.4m 97.8m Fall River County 100.7m 103.1m 95.2m

Fort Pierre 97.5m 98.9m 96.1m Vegetation Height Cust er County 97.9m 98.8m 95.0m Fall River County 99.5m 100.2m 98.7m32 Table 2.3. Precipitation as regi stered by the nearest weathe r station within 25 km of study sites for 2004 and 2005. Growing season includes rainfall from 1 April to 31 August. Rainfall Total (cm) Site Average Annual Growing Season Ave. Growing Season 2004 Growing Season 2005 Bad River Rd 48.82 30.15 22.04 28.6 Fort Pierre 37.95 26.95 23.34 22.05 Winner 60.25 38.94 32.99 41.43 Custer Cty 42.14 30.12 24.31 26.57 Fall River Cty 48.82 29.69 11.48 42.2933

Figure 2.1. Locations of study areas used in vegetative barrier study in western South Dakota in 2004 and 2005. 0 75 150 225 300 37.5 Kilometers Fall River

Custer Stanley

Tripp34

Figure 2.2. Schematic of buffer strips used to reduce prairie dog town expansion for five study sites in western South Dakota in 2004 and 2005.

Cattle and Prairie dogs Cattle with no prairie dogs

No cattle, No prairie dogs

Control35

0 5 10 15 VOR 0 20 40 60 80

B R E A K O U T

Figure 2.3. Non-linear model of breakthroughs (Breakout) of new, active prairie dog burrows versus visual obstru ction (VOR, [cm]) for five study sites in western South Dakota during August 2004 and 2005.36

0 10 20 30 40 50 VEGHEIGHT 0 20 40 60 80

B R E A K O U T

Figure 2.4. Non-linear model of breakthroughs (BREAKOUT) of new, active prairie dog burrows versus vegetation height (VEGHEIG HT, [cm]) for five study sites in western South Dakota during August 2004 and 2005.37

0 1 0 2 0 3 0 4 0 5 0

B

U

F

F

W

I D

T

H
0 5 1

0 1 5 V O

R 4 8 1 2

B R E A K O U T

Figure 2.5. Non-linear model of breakthroughs (BREAKOUT) of new, active prairie dog burrows versus visual obstru ction (VOR, [cm]) and buffer width (BUFFWIDTH, [m]) for five study sites in western South Dakota during August 2004 and 2005.38

0 1 0 2 0 3 0 4 0 5 0

B

U

F

F

W

I D

T

H 10 2

0 3

0 4

0 5

0 V

E

G

H

E

I G

H

T 4 8 1 2

B R E A K O U T

Figure 2.6. Non-linear model of breakthroughs (BREAKOUT) of new, active burrows versus vegetation height (V EGHEIGHT, [cm]) and buffer width (BUFFWIDTH [M]) for five study sites in western South Dakota during August 2004 and 2005.39
Chapter 3

Vegetation characteristics associated with black-tailed prairie dog towns in western South Dakota.

Introduction The black-tailed prairie dog ( Cynomys ludovicianus ) is considered by some to be a keystone species of the prairie ecosystem (Kotliar et al. 1999, Miller et al. 2000). Prairie dogs serve as prey to a wide variety of predators including black-footed ferrets ( Mustela nigripes ), coyotes ( Canis latrans ), bobcats ( Felis rufus ), and badgers ( Taxidea

taxus ), as well as a many birds of prey (Hoogland 1995, Kotliar et al. 1999). Prairie dogs can drastically alter their envi ronment providing nesting habita t, foraging, and shelter for many species (Kotliar et al. 1999). Plant co mmunity structure and composition, nutrient cycling, and ecosystem processes can be aff ected by prairie dog activities (Whicker and Detling 1988). Black-tailed prairie dogs ar e small burring rodents ( ≈ 700g) that live in colonies called towns (Hoogland 1995). The extensive soci al and colonial tende ncies of the blacktailed prairie dog are characteristic of the spec ies. Of the five species of prairie dog, the black-tailed is the most numerous and has the largest geographic distribution. Blacktailed prairie dogs range from northern Mexico in the south to southern Canada in the north, and from the eastern edge of the Rocky Mountains in the west, east into the mixed grass prairies of central No rth Dakota, South Dakota, Nebr aska, Kansas, Oklahoma, and40 Texas (Hoogland 1995). South Dakota lies alon g the northeastern edge of the prairie dog’s range. Current distribu tion of prairie dogs in Sout h Dakota includes the mixedand short-grass prairies of the western two-thirds of the stat e (Sidle et al. 2001). Prairie dogs currently occupy approximately 1665 km 2 of land in South Dakota (Cooper and Gabriel 2005). The objective of this study is to examine vegetation characteristics associated with prairie dog towns in western South Da kota. Results of this study will provide managers with a better unde rstanding of post-treatment re sponses of vegetation following the elimination of prairie dogs and cattle from rangelands. Study Area We selected five study sites on rang elands containing prairie dog towns ≥ 10-ha west of the Missouri River in South Da kota in 2004 and 2005. Western study areas where located on rangelands in Custer and Fa ll River counties, while eastern study areas where located in Stanley, and Tripp coun ties (Figure 3.1). In 2005, the Custer County site was established at a new location 3.2 km NE of the 2004 site due to access issues. Study site locations were: Custer Co unty (2004 - N43o38.2’ W103o4.1’, 2005 - N43o39.5’ W103o2.5’); Fall Ri ver County (N43o20.7’ W103o 5.0’), Bad River Road (N44o14.1’ W100o55.7’), Fort Pierre (N44o23.0’ W100o31.6’), and Winner (N43o36.7’ W099o55.7’) Study areas where located in th e Pierre Hills and Southern Plateaus physiographic regions in western South Dakot a (Johnson et al. 1995). The Pierre Hills physiographic region is characterized by er oded rounded hills and ridges composed of primarily clay soils. The Southern Plat eaus physiographic region is underlined by41 sandstone and mudstone containing mostly loam and silt loam soils that form highland benches and buttes (Johnson et al. 1995). M ean annual temperatures ranged from 8.3oC at the Fall River County site to 10.0oC at the Winner si te (South Dakota Office of Climatology 2006). Monthly mean temperatures ranged from a low of -7.7oC in January to a high of 24.6oC in July. Mean annual rainfall ranged from 42.6 cm at the Fort Pierre to 60.3 cm at the Winner site (South Dakota Office of Climatology 2006). Primary land use of study areas was pa sture and rangeland livestock grazing intermixed with crop production, which included wheat ( Triticum aestivum ), alfalfa ( Medicago sativa ), corn ( Zea mays ), and soybeans ( Glycine max ). Johnson and Larson (1999) classified the region as northern wh eatgrass-needlegrass plains. Dominant vegetation in this area includes western wheatgrass ( Pascopyrum smithii ), Japanese brome ( Bromus japonicus ), needleandthread ( Stipa comata ), green needlegrass ( Stipa viridula ), blue grama ( Bouteloua gracilis ), buffalograss ( Buchloe dactyloides ), scarlet globemallow ( Sphaeralcea coccinea ), western wallflower ( Erysimum asperum ), and prickly pear ( Opuntia macrorhiza ) (Johnson and Larson 1999).

Methods Study sites were established and monito red from 1 March 2004 to 30 October 2005. We constructed electric fences for the purpose of excluding cattle and creating treatment areas of native grasses and shrubs. At the beginning of the study, we poisoned prairie dogs to create a prai rie dog free zone adjacent to ac tive prairie dog towns. Livestock grazing was allowed outside of the treatment area. Pois oning created a 100-m42 long and 40-m wide treatment area of naturally occurring vegetation adjacent to a control area that contained both grazing and prairie dogs. Initial poisoning efforts took place in sp ring 2004 prior to the first emergence of young prairie dogs (Franklin and Garrett 1989). We used aluminum phosphide (Weevelcide, United Phosphorus Inc., Trenton, NJ) fumigant tablets (60% concentration) for the initial spring applica tion. This was conducted by placing tw o to three tablets within all open burrow entrances; burrows were then sealed with sod or dirt. Fumigants, such as aluminum phosphide, are the only poisoning method approved for controlling prairie dogs in South Dakota during spring. Follow-up applications were conducted to establish a prairie dog free treatment area. Poisoni ng for the 2005 field season was conducted the previous fall using zinc phosphi de treated oats and aluminum phosphide tablets. Follow up applications of aluminum phosphi de were conducted in spring 2005. We evaluated study sites using visual obs truction (0.2 dm increments), vegetation cover (%), vegetation height (cm), and ve getation composition. We established three transect lines to facilitate random distribution of quadrats. Transects extended the length of the treatment area and c ontrol areas, and were equally spaced at 25, 50, and 75% positions across the width of the treatment area. Transects were separated into 1-m increments to establish potential quadrat locations. End points of transects were eliminated to reduce the effect of the tr eatment area edge. We randomly chose 25 nonconsecutive points along the tota l length of transects for evaluation. We measured visual obstruction (to nearest 0.2 dm) at each quadrat site using a modified Robel pole (Robel et al. 1970). Cover measurements for graminoi ds, forbs, bare ground, and litter were43 estimated at sampling points (Daubenmire 1959). Quadrat size was 30-cm-wide and 75- cm-long. Modified cover classes were 0 (not present), 1 (trace-5%), 2 (6-25%), 3 (26- 50%), 4 (51-75%), 5 (76-95%), and 6 (96-100%). Median values fo r cover classes where used to calculate relative percent canopy coverage for vegetation classes, bare ground, and litter. Vegetation was gr ouped into two broad categories; graminoids and forbs. Graminoids were classified as members of the families Gramineae , Cyperaceae , and
Juncaceae . Forbs were classified as all ot her broad-leaved herbaceous vegetation excluding the preceding three families of gr aminoids and any woody vegetation (Johnson and Larson 1999). Vegetation height was obtai ned for each of the sampling points using a clear 30-cm disc lowered unt il the bottom side of the disc was first touched by leafy vegetation (Higgins and Barker 1982). Ve getation identification followed that of Johnson and Larson (1999), and Stubbendieck et al. (2003). A 2-f actor Analysis of Variance was used to detect significant differe nces between the main effects of treatment (prairie dogs vs. no prairie dogs), location ( east vs. west), and the interaction between factors.

Results Vegetation characteristics were obtai ned from control and 40-m x 100-m treatment areas for three eastern sites (Fort Pierre, Bad River Road, and Winner) and two western study sites (Custer county, and Fa ll River county) in western South Dakota during August 2004 and 2005 (Table 3.1). A 2-factor Analysis of Varian ce indicated that there was a significant ( F 1,16 =4.046, P =0.061) interaction effect between treatment and44

location for visual obstruction. Visual obs truction was higher in the treatment than control plots for eastern sites, but not western s ites. No significant ( P >0.10) interaction between the main effects (treatment and location) was found for vegetation height, relative percent graminoid cover, forb cover, bare ground, or litter cover. Vegetation height was signi ficantly higher in treatmen t than in control plots ( F 1,16 =8.243, P =0.011) and in east versus west sites ( F 1,16 =10.805, P =0.005). We recorded an increase ( F 1,16 =3.754, P =0.071) in relative percent grass cover from the control to the treatment. Relative pe rcent graminoid cover did not differ ( F 1,16 =2.506,
P =0.133) between locations. Forb relative percent canopy coverage did not differ by treatment ( F 1,16 =0.007, P =0.934), or location ( F 1,16 =1.127, P =0.304). Bare ground was greater ( F 1,16 =11.339, P =0.004) in control than treat ment plots, and greater ( F 1,16 =3.732,
P =0.071) on western than eastern sites. Rela tive percent litter cover did not differ between control and treatment plots ( F 1,16 =0.149, P =0.704), or east versus west sites ( F 1,16 =2.850, P =0.111). There was no difference ( F 1,36 <0.000, P =1.000) in the number of species of plants identified between the tr eatment and control plots. Eastern sites contained 33% more plant species ( F =11.958, P =0.001) than in western sites. Western wheatgrass ( Pascopyrum smithii ) had higher relative percent grass cover on eastern than western sites (Table 3.2). Scarlet globemallow ( Sphaeralcea coccinea ) was the dominant forb on both western sites, while kochia ( Kochia scoparia ) was the only forb to rank in the top three species on an eastern s ite (Table 3.2). Japanese brome ( Bromus japonicus ) was similar in relative canopy cover for Bad River Road (41.0%) and Fall River County (39.4%) sites. Annual rainfall ranged from 37.95 cm at Fort Pierre to 48.82 cm at Bad45 River Road and Fall River county sites. Gr owing season rainfall was calculated from 1 April to 31 August for 2004 and 2005 (Table 3.3).

Discussion Visual obstruction can be ut ilized as an indicator of above ground biomass for plant species on rangelands. Robel et al . (1970) showed that visual obstruction measurements taken from a distance of 4 m and a height of 1 m explained 95.5% of the variation in the weight of vegetation collect ed from rangelands. Similar results were found by Vermeire and Gillen (2001) who obser ved a linear relationship between visual obstruction and standing crop biomass with at least 90% of the variation in biomass explained by visual obstruction. Many studies on prairie dog impacts have focused on the amount of above ground biomass. Because of the relationship between visual obstruction and plant biomass, our study is dire ctly comparable to studies that measured above ground and standing crop plant biomass. Our study indicated that there was higher visual obstruction in treatment than control plots on eastern s ites. Visual obstruction was 3.7 times greater on treatment plots in the eas t. Our results from eastern sites are supported by Johnson-Nistler et al. (2004) who found total standing crop biomass was 2 times greater on uncolonized sites as compar ed to colonized sites in north central Montana. Total above ground plant bioma ss was always greater off colony when compared to on colony sites during a three- year study conducted at Badlands National Park, South Dakota (Fahnestock and Detling 2002). Total live biomass was similarly higher on uncolonized sites than on recently co lonized sites at Wind Cave National Park,46 South Dakota, but was not significantly differe nt for areas colonized for longer than 26 years. (Coppock et al.1983). This finding was attributed to similar amounts of graminoids (85%) for colonized and recently colonized ( ≤ 2 years) site s (Coppock et al. 1983). Prairie dog colonies in Texas had 3 to 4 times the herbaceous standing crop off colony sites compared to on colony sites (We ltzin 1997). Winter et al. (2002) observed lower visual obstruction on prai rie dog colonies compared to random sites in Kanasas. We observed no difference in visual obstruc tion between treatment and control areas on our western sites. Above ground net primary production of on colony sites was similarly not significantly different than off col ony sites at Wind Cave National Park, South Dakota (Whicker and Detling 1988). Wind Ca ve National Park is located in the southwest corner of South Dakota, and has similar vegetation and precipitation characteristics as our two western sites. Vegetation height was affected by cli pping of vegetation by prairie dogs and cattle grazing. Vegetation height was two tim es higher on treatment sites than on control sites in the east and 1.4 times higher for th e treatment than cont rol in the west. Vegetation height was observed to be lower for prairie dog colonies when compared to random sites in southwest Kansas (Winter et al. 2002). Milne-Laux and Sweitzer (2006) observed greater prairie dog ac tivity and expansion into ar eas with reduced vegetation height following controlled burns and mechanical shrub removal. Studies often indicate a reduc tion in grass cover and an increase in forb cover on prairie dog towns (Coppock et al. 1983, Fahnest ock and Detling 2002). We noted only a slight increase in th e relative percent canopy coverage of grass from control to treatment47 plots, and no significant diffe rences in relative forb ca nopy coverage between treatment and control. This finding is supported by Johnson-Nistler et al . (2004) who observed minimal differences in forb cover between on and off colony sites. However, an increase in forb abundance and decrease in grass abundance was observed following colonization at Badlands National Park (F ahnestock and Detling 2002). Mi nor differences in forb and grass cover between our treatmen t and controls may be the re sult of the shor t duration (2 years) our sites had been esta blished. Prairie dog colonies , especially those that have been established for long periods of time can ta ke considerable time to revert back to precolonization conditions (Osborn and Allen 1949) . Uresk (1985) indicated that it may take ≥ 4 years for plant production to show in creases on rangelands where prairie dogs were established. Evidence suggests that inte nsive grazing by prairi e dogs can lead to a shift toward shorter ecotypes of plants (Whicker and De tling 1988). Forb biomass increased on areas colonized 3-8 years at Wind Cave National Park, South Dakota, and this was the time of maximum species di versity of plants (Coppock et al. 1983). Litter and bare ground also can be affected by prairie dog grazing. Our study site however, showed no significant differences in the amount of litte r observed between treatment and control plots and location (eas t to west). Bare ground was greater on the control as compared to the treatment areas (2.6 times in East, 1.9 times in West). Johnson-Nistler et al. (2004) observed an in creased amount of litter (23% to 27%) from colonized sites to uncolonized rangeland a nd an increase in bare ground from 17% on uncolonized to 27% on colonized prairie. Similar trends were reported by Fahnestock and Detling (2002). Prairie dogs clip and main tain short vegetation as a mechanism for48 predator detection (Hoogland 1995) ; therefore, litter is less li kely to accumulate within the boundaries of prairie dog towns. The shor t duration of treatment establishment and the drought conditions from the previous year may have contributed to the similarities between the control and treatment plots relati ve to litter during our study. Accumulation of dead plant biomass was limited due to dr ought conditions that oc curred prior to and during the first year of the study. We observed no difference in plant speci es richness betwee n the control and treatment plots. This finding is suppor ted by a Texas study that indicated all plant species found on colony sites also were found off colony and were common to the area (Weltzin et al. (1997). Copp ack et al. (1983) also observe d little change seen in the number of plant species areas colonized for 2 years or less. Our results contrast with Fahnestock and Detling (2002) who found that species richness was greater on colony than off colony because of an increased forb community. Prairie dog colonies may act as colonization sites for annual forbs due to th e increase in soil disturbance found in an active prairie dog colony (Fahnestock and Det ling 2002). However, Johnson-Nistler et al. (2004) indicated that plant species richness wa s lower on colonized (13) as compared to uncolonized (17) sites. This finding is likely due to the duration of occupancy of the prairie dog colony. Prairie dogs influence plant communities di fferently in different portions of their range. Differences in vegetative character istics caused by location may be more the result of precipitation changes. Annual pr ecipitation in South Dakota increases from west to east (South Dakota Office of Clim atology 2006). At our study areas, however,49 average annual precipitation was similar for Fall River County and Bad River Road. Winner site had the highest prec ipitation and the Fort Pierre s ite had the lowest. Johnson and Larson (1999) stated that th is precipitation gradient crea tes bands of vegetation types running north and south in South Dakota. This gradient may explain the variation in the increased relative contribution of western wheatgrass to the plant communities in the eastern sites. Johnson and La rson (1999) indicated that s carlet globemallow increases on drier sites, which may explain the higher amount s on western sites. The similarities for Japanese brome between Fall River county and Bad River Road may be due to the similarities in average annual precipitation. Variation in relative canopy coverage may be characteristic of the prai rie biome. Knapp and Smith ( 2001) found that variation in net primary production as a response to intersea sonal fluctuations in precipitation was highest in prairie biomes when compared to forest, arctic, and dese rt biomes. Vegetation responses in both species composition and ne t primary production may affect the amount and type of influence prairie dogs have on their environment.50

Literature Cited Cooper, J, and L. Gabriel. 2005. South Da kota black-tailed prairi e dog conservation and management plan. Final Draft-Februa ry 2005. South Dakota Department of Game, Fish and Parks, Pierre, South Dakota. Coppock, D. L., J. K. Detling, J. E. Ellis, and M. I. Dyer. 1983. Plant-herbivore interactions in a North American Mixed-gr ass prairie. I. Effects of black-tailed prairie dogs on interseasonal aboveground plant biomass and nutrient dynamics and plant species divers ity. Oecologia 56:1-9. Daubenmire, R. F. 1959. A canopy-covera ge method of vegetational analysis. Northwest Science 33:43-64. Fahnestock, J. T., and J. K. Detling. 2002. Bison-prairie dog-plant interactions in a North American mixed-grass prairie. Oecologia 132:86-95. Franklin, W. L., and M. G. Garrett. 1989. Nonlethal control of prairie dog colony expansion with visual barriers. Wildlife Society Bulletin 17:426-430. Higgins, K. F., and W. T. Barker. 1982. Changes in vegetation structure in seeded nesting cover in the prairi e pothole region. Special Sc ientific Report-Wildlife 242 U. S. Fish and Wildlife Service, Washington, D. C. 27pp. Hoogland, J. L. 1995. The black-tailed prairie dog: social life of a burrowing mammal. University of Chicago Press. Chicago, Illinois. 557pp.51
Johnson, J. R., and G. E. Larson. 1999. Gr assland plants of South Dakota and the Northern Great Plains. S outh Dakota State University College of Agriculture and Biological Sciences, South Dakota Agricu ltural Experiment Station, Brookings, South Dakota. Johnson, R. R., K. F. Higgins, and D. E. H ubbard. 1995. Using soils to delineate South Dakota physiographic regions. Gr eat Plains Research 5:309-322. Johnson-Nistler, C. M., B. F. Sowell, J. W. Sherwood, and C. L. Wambolt. 2004. Blacktailed prairie dog effects on Montana’s mi xed-grass prairie. Journal of Range Management 57:641-648. Kotliar, N. B., B. W. Baker, and A. D. Whic ker. 1999. A critical review of assumptions about the prairie dog as a keystone sp ecies. Environmental Management 24:177-
192. Miller, B., R. Reading, J. Hoogland, T. Clar k, G. Ceballos, R. List, S. Forrest, L. Hanebury, P. Manzano, J. Pacheco, and D. Uresk. 2000. The role of prairie dogs as a keystone species: response to Stapp. Conservation Biology 14:318-321. Milne-Laux, S., and R. A. Sweitzer. 2006. Experimentally induced colony expansion by black-tailed prairie dogs ( Cynomys ludovicianus ) and implication for conservation. Journal of Mammalogy 87:296-203. Osborn, B., and P. F. Allan. 1949. Vegetation of an abandoned prairie-dog town in tall grass prairie. Ecology 30:322-332.52 Robel, R. J., J. N. Briggs, A. D. Dayton, and L. C. Hulbert. 1970. Relationships between visual obstruction measurements and weight of grassland vegetation. Journal of Range Management 23:295-297. Sidle, J. G., D. H. Johnson, and B. R. Euliss. 2001. Estimated areal extent of colonies of black-tailed prairie dogs in the Northern Great Plains. Journal of Mammalogy
82:928-936. Snell, G. P., and B. D. Hlavachick. 1980. Control of prairie dogs-the easy way. Rangelands 2:239-240. South Dakota Office of Climatology. 2006. Te mperature and Precipitation Archives. South Dakota State University . Brookings, South Dakota. http://climate.sdstate.edu/climate_site /archive_data.htm. Accessed 7 June 2006. Stubbendieck, J. L., M. J. Coffin, and L. M. Landholt. 2003. Weeds of the Great Plains. Nebraska Department of Agricult ure. Lincoln, Nebraska. 605pp. Uresk, D. W. 1985. Effects of controlling black-tailed prairie dogs on plant production. Journal of Range Management 38:466-468. Vermeire, L., T., and R. L. Gillen. 2001. Estimating herbage standing crop with visual obstruction in tallgrass prairie. Journal of Range Management 54:57-60. Weltzin, J. F., S. L. Dowhower, and R. K. Heitschmidt. 1997. Prairie dog effects on plant community structure in southern mi xed-grass prairie. The Southwestern Naturalist 42:251-258. Whicker, A. D., and J. K. Detling. 1988. Ecological consequences of prairie dog disturbances. BioScience 38:778-785.53 Winter, S. L., J. F. Cully, Jr., and J. S. Pon tius. 2002. Vegetation of prairie dog colonies and non-colonized short-grass prairie. Journal of Range Management 55:502-
508.54

Table 3.1. Mean (SE) of vegetation characte ristics measured at five study sites in western South Dakota during August 2004 and 2005 a . Visual obstruction (VOR) and vegetation height (Veg. Height ) presented in cm. Graminoid cover, forb cover, bare ground, and litter cover are rela tive percent canopy cover.
East West Treatment Control Treatment Control VOR 8.583 (1.888) 2.317 (0.254) 2.950 (0.967) 1.850 (0.741) Veg. Height 29.65 (4.934) 14.383 (0.655) 13.00 (2.169) 9.175 (2.030) Graminoid Cover 65.850 (7.241) 46.183 (8.238) 49.875 (16.444) 29.20 (11.072) Forb Cover 15.633 (5.484) 11.733 (5.575) 5.6 (2.308) 10.40 (5.024) Bare Ground 10.117 (1.789) 26.317 (2.319) 19.150 (6.814) 36.575 (9.574) Litter Cover 8.383 (2.625) 15.750 (2.608) 25.375 (14.888) 23.725 (9.700) No. of Species 24.3 (6.7) 24.3 (1.3) 16.3 (2.6) 16.3 (5.0)

a East Treatment n=6, East Control n=6, West Treatment n=4, West Control n=4.55 Table 3.2. Relative percent canopy cover for top three most abundant species on five study sites in western South Dakota in August 2004 and 2005.
Site 2004 2005 Pascopyrum smithii 24.7 Pascopyrum smithii 31.9 Fort Pierre a Bromus japonicus 10.8 Bromus japonicus 16.2 Kochia scoparia 10.8 Kochia scoparia 9.4 Total 46.3 57.5 Buchloe dactyloides 51.7 Buchloe dactyloides 41.0 Bad River Road a Pascopyrum smithii 7.0 Pascopyrum smithii 21.4 Vulpia octoflora 7.1 Carex spp. 8.6 Total 65.8 71.0 Pascopyrum smithii 42.0 Pascopyrum smithii 46.4 Winner a Bromus inermis 2.6 Bromus japonicus 4.6 Bromus japonicus 2.6 Agropyron cristatum 3.1 Total 47.2 54.1 Buchloe dactyloides 25.6 Agropyron cristatum 39.2 Custer Cty. b Carex durius 10.4 Sphaeralcea coccinea 9.1 Aristida purpurea 10.8 Pascopyrum smithii 3.4 Total 46.8 1.756 (Table 3.2 Continued) Site 2004 2005 Buchloe dactyloides 1.8 Bromus japonicus 39.4 Fall River Cty. b Carex durius 1.8 Pascopyrum smithii 9.3 Sphaeralcea coccinea 0.5 Buchloe dactyloides 8.1 Total 4.1 56.8

a Eastern sites. b Western Sites.57 Table 3.3. Precipitation as regi stered by the nearest weathe r station within 25 km of study sites for 2004 and 2005. Growing season includes rainfall from 1 April to 31 August. Rainfall Total (cm) Site Average Annual Growing Season Ave. Growing Season 2004 Growing Season 2005 Bad River Rd 48.82 30.15 22.04 28.6 Fort Pierre 37.95 26.95 23.34 22.05 Winner 60.25 38.94 32.99 41.43 Custer Cty 42.14 30.12 24.31 26.57 Fall River Cty 48.82 29.69 11.48 42.2958

Figure 3.1. Location of study ar eas used in vegetative ba rrier study in western South Dakota in 2004 and 2005. 0 75 150 225 300 37.5 Kilometers Fall River

Custer Stanley

Tripp59
Chapter 4

Management Implications and Conclusions

Prairie dog control has historically cons isted of lethal methods to maintain, reduce, or eliminate populations in South Da kota and throughout the range of the species (Schenbeck 1982, Boddicker 1983, Ures k et al. 1987, Hanson 1988, Knowles 1988, Hanson 1993). Non-lethal methods of control are needed to meet changing management objectives for the black-tailed prairie dog. These objectives include long-term, selfsustaining populations of prairie dogs wh ile reducing landowner conflicts (Cooper and Gabriel 2005). Development of non-lethal met hods of control is necessary for areas such as preserves, parks, and private lands wher e lethal methods are not allowed or use is limited. Negative binomial models were constructe d to describe the relationship between black-tailed prairie dog town expansion and char acteristics associated with vegetation of buffer strips as well as the mean density of active burrows next to the buffer strips. Vegetation height and visual obstruction were important variables in the models. Vegetation height and vi sual obstruction alone had a mean corrected r 2 of 0.61 and 0.71, respectively. Models indicated that breakth roughs (presence of ne w active burrows) were minimized at 40-cm of vegetation height a nd 10-cm visual obstruction. The addition of buffer width into models increased the mean corrected R 2 to 0.85 for vegetation height and 0.86 for visual obstruction i ndicating that buffer width pl ays a significant role in60 limiting prairie dog town expansi on. Prairie dogs utilize shor t vegetation as a means of predator avoidance (King 1955, Hoogland 1995). Having a barri er that includes a depth component may utilize this behavior to create a zone where prairie dogs are uncomfortable and therefore will avoid. Add ition of vegetation char acteristics such as relative percent graminoid cover, forb c over, bare ground, and litter did not improve models. Mean number of active burrow densiti es adjacent to buffer strips also did not improve models. Vegetation characteristics of the property can play an important role in the success of natural vegetative buffers as a barr ier to the expansion of black-tailed prairie dogs. Vegetation communities need to be comp osed of species that have potential to increase in height and density with increased prec ipitation, consequently, this method of control of expansion of prairi e dog towns may be more effec tive in the eastern edge of black-tailed prairie dog distribut ion where taller, more robus t species are present, and precipitation is greater. In areas that ha ve vegetation capable of meeting the minimum requirements of our models (40-cm vegetati on height, and 10-cm visual obstruction) a 40-m wide buffer strip may be e ffective at limiting prairie dog town expansion. In areas that are not able to meet the minimum vege tation height (40-cm) and visual obstruction (10-cm), our modeling indicated that a buffer of about ≈ 100-m in width would be required to minimize breakthroughs. However, predictions from models that are outside of the range of the data used to generate them need to be evaluated and we would recommend further study of increased buffer widths in areas with lower vegetation and visual obstruction measurements. We woul d also recommend evaluating prairie dog61 populations based on visual count s rather than an index ba sed on active burrow counts to determine the effect of prairie dog popul ation size on expansion through barriers. Vegetation characteristics were recorded for treatment and control areas at each study site during 2004 and 2005. Vegetation charact eristics were compared for treatment and control areas as well as in eastern and western study si tes. Visual obstruction was greater on treatment areas compared to cont rol areas in eastern sites while vegetation height increased from treatment to controls and from east to west. Bare ground also was greater on controls than on trea tment areas. Grass cover, fo rb cover, and litter cover showed only minor changes be tween treatment and controls , and eastern and western sites. Plant species richness was not differe nt between study sites, but increased species richness was observed on eastern compared to western sites. Buffer strips that are established longer than 2 years may show gr eater changes in vegetation from control areas. Effectiveness of buffer strips may incr ease as the age of the buffer strip increases. Increases in taller ecotypes of graminoid species over ti me may increase the mean vegetation height and visual obstruction of the buffer strip. Prairie dog control efforts take a subs tantial amount of time and money from state, federal, and private landowners. Buff er strips offer economical alternatives to traditional lethal controls. Collins et al. ( 1984) found that initial investments in lethal control were not justified give n the rate of recolonization in one area of western South Dakota. Buffer strips that reduced or el iminated the expansio n of prairie dog towns would make lethal controls more effective.62

Literature Cited Boddicker, M. L. 1983. Prairie dogs. Pa ges B-75-84 in Prevention and Control of Wildlife Damage. Cooperative Extension Service, Institute of Agriculture and Natural Resources, University of Ne braska-Lincoln, Lincoln, Nebraska. Collins, A. R., J. P. Workman, and D. W. Uresk. 1984. An economic analysis of blacktailed prairie dog ( Cynomys ludovicianus ) control. Journal of Range Management
37:358-361. Cooper, J, and L. Gabriel. 2005. South Da kota black-tailed prairi e dog conservation and management plan. Final Draft-Februa ry 2005. South Dakota Department of Game, Fish and Parks, Pierre, South Dakota. Hanson, R. 1988. A chronology of prairi e dog control operations and related developments in South Dakota. Pages 121- 122 in D. W. Uresk, G. L. Schenbeck, and R. Cefkin, Technical Coordinators. Eighth Great Plains Wildlife Damage Control Workshop Proceedings, 28-30 Ap ril 1987, Rapid City, South Dakota. USDA Forest Service Genera l Technical Report RM-154. Hanson, R. 1993. Control of prairie dogs and related developments in South Dakota. Pages 5-7 in J. L. Oldemeyer, D. E. Biggi ngs, B. J. Miller, and R. Crete, Editors. Proceedings of the Symposium on the Mana gement of Prairie Dog Complexes for the Reintroduction of the Black-footed Fe rret. U.S. Fish and Wildlife Service, Biological Report 13. Hoogland, J. L. 1995. The black-tailed prairie dog: social life of a burrowing mammal. University of Chicago Press. Chicago, Illinois. 557pp.63 King, J. A. 1955. Social behavior, social organization, and population dynamics in a black-tailed prairie dog town in the Black Hills of South Dakota. Contributions from the Laboratory of Vertebrate Biol ogy Number 67. University of Michigan, Ann Arbor, Michigan. Knowles, C. J. 1988. An evaluation of s hooting and habitat alteration for control of black-tailed prairie dogs. Pa ges 53-56 in D. W. Uresk, G. L. Schenbeck, and R. Cefkin, Technical Coordinators. Eighth Great Plains Wildlife Damage Control Workshop Proceedings, 28-30 April 1987, Rapid City, South Dakota. USDA Forest Service General Technical Report RM-154. Schenbeck, G. L. 1982. Management of black-tailed prairie dogs on the national grasslands. Pages 207-213 in R. M. Timm and R. J. Johnson, Editors. Proceedings Fifth Great Plains Wild life Damage Control Workshop, 13-15 October 1981, Lincoln Nebraska. Institute of Agriculture and Natural Resources, Lincoln, Nebraska. Uresk, D. W., R. M. King, A. D. Apa, and R. L. Linder. 1987. Efficacy of zinc phosphide and strychnine for black-tailed prairie dog control. Journal of Range Management 39:298-299.64 Appendix A. Plant species identified on the Bad River Road study site, 2004 and 2005.

Scientific Name Common Name Class Astragalus lotiflorus Low milkvetch Forb Astragalus vexilliflexus Bentflower milkvetch Forb Atriplex argentea Silverscale saltbush Forb Bouteloua gracilis Blue grama Grass Bromus japonicus Japanese brome Grass Buchloe dactyloides Buffalo grass Grass Camelina microcarpa Smallseed falseflax Forb Carex sp. Sedge Grass Coryphantha sp. Pincushion Forb Euphorbia glyptosperma Ridgeseed spurge Forb Euphorbia marginata Snow-on-the-Mountain Forb Euphorbia serpens Matted sandmat Forb Grindelia squarrosa Curlycup gumweed Forb Helianthus annuus Annual sunflower Forb Lepidium densiflorum Greenflower pepperweed Forb Linum rigidum Stiffstem flax Forb Medicago sativa Alfalfa Forb Melilotus officinalis Yellow sweetclover Forb Mirabilis linearis Narrowleaf four-o'-clock Forb Monolepis nuttalliana Nuttall povertyweed Forb Opuntia macrorhiza Bigroot pricklypear Forb Panicum capillare Witchgrass Grass Pascopyrum smithii Western wheatgrass Grass Plantago patagonica Indianwheat Forb Polygonum ramosissimum Bushy knotweed Forb Sphaeralcea coccinea Scarlet globemallow Forb Stipa viridula Green needlegrass Grass Taraxacum officinale Common dandelion Forb Verbena bipinnatifida Dakota mock vervain Forb Vicia americana American vetch Forb Vulpia octoflora Sixweeks fescue Grass65 Appendix B. Plant species identified on the Custer county site, 2004.

Scientific name Common Name Class Agropyron cristatum Crested wheatgrass Grass Aristida purpurea Red threeawn Grass Artemisia ludoviciana Cudweed sagewort Forb Asclepias pumila Plains milkweed Forb Bouteloua gracilis Blue grama Grass Bromus japonicus Japanese brome Grass Buchloe dactyloides Buffalo grass Grass Carex duriuscula Needleleaf sedge Grass Carex filifolia Threadleaf sedge Grass Convolvulus arvensis Field bindweed Forb Coryphantha sp. Pincushion Forb Dalea purpurea Purple prairie clover Forb Echinacea angustifolia Purple coneflower Forb Erysimum asperum Western wallflower Forb Euphorbia glyptosperma Ridgeseed spurge Forb Euphorbia strictospora Slimseed sandmat Forb Gaura coccinea Scarlet gaura Forb Grindelia squarrosa Curlycup gumweed Forb Haplopapus spinulosus Cutleaf goldenweed Forb Hedeoma hispida Rough falsepennyroyal Forb Hymenoxys acaulis Stemless hymenoxys Forb Ipomoea leptophylla Bush morningglory Forb Lappula occidentalis Western sticktight Forb Lepidium densiflorum Greenflower pepperweed Forb Liatris puncata Dotted gayfeather Forb Lygodesmia juncea Rush skeletonplant Forb Opuntia macrorhiza Bigroot prickly pear Forb Pascopyrum smithii Western wheatgrass Grass Plantago elongata Prairie plaintain Forb Plantago patagonica Indianwheat Forb Potentilla pensylvanica Pennsylvania cinquefoil Forb Psoralea tenuiflora Slimflower scurfpea Forb Salsola collina Slender Russian thistle Forb Schedonnardus paniculatus Tumblegrass Grass Schizachyrium scoparium Little bluestem Grass Sisymbrium altissimum Tumble mustard Forb Solanum triflorum Cutleaf nightshade Forb Solidago missouriensis Missouri goldenrod Forb Solidago mollis Soft goldenrod Forb Solidago rigida Stiff goldenrod Forb Sphaeralcea coccinea Scarlet globemallow Forb Stipa viridula Green needlegrass Grass Tradescantia bracteata Bracted spiderwort Forb66 Appendix C. Plant species identified on the Custer county site, 2005.

Scientific Name Common Name Class Agropyron cristatum Crested wheatgrass Grass Amaranthus albus Tumble pigweed Forb Buchloe dactyloides Buffalo grass Grass Chenopodium sp. Goosefoot Forb Dyssodia papposa Fetid marigold Forb Euphorbia glyptosperma Ridgeseed spurge Forb Grindelia squarrosa Curlycup gumweed Forb Helianthus annuus Annual sunflower Forb Lepidium densiflorum Greenflower pepperweed Forb Melilotus officinalis Yellow sweetclover Forb Opuntia microrhiza Bigroot prickly pear Forb Pascopyrum smithii Western wheatgrass Grass Solanum rostratum Buffalobur Forb Solanum triflorum Cutleaf nightshade Forb Sphaeralcea coccinea Scarlet globemallow Forb Verbena bracteata Prostrate vervain Forb67 Appendix D. Plants identified on Fall River county site, 2004 and 2005.

Scientific Name Common Name Class Bromis japonicus Japanese brome Grass Buchloe dactyloides Buffalo grass Grass Carex duriuscula Needleleaf sedge Grass Kochia scoparia Kochia Forb Lepidium densiflorum Greenflower pepperweed Forb Medicago sativa Alfalfa Forb Melilotus officinalis Yellow sweetclover Forb Opuntia macrorhiza Bigroot prickly pear Forb Pacopyrum smithii Western wheatgrass Grass Rumex stenophyllus Narrowleaf dock Forb Solanum rostratum Buffalobur nightshade Forb Sphaeralcea coccinea Scarlet globemallow Forb Stipa viridual Green needlegrass Grass Taraxacum officinale Common dandelion Forb68 Appendix E. Plant species identifie d on Fort Pierre study site, 2004 and 2005.

Scientific Name Common Name Class Agropyron cristatum Crested wheatgrass Grass Artemisia frigida Fringed sagebrush Forb Astragalus lotiflorus Low milkvetch Forb Atriplex argentea Silverscale saltbush Forb Bouteloua gracilis Blue grama Grass Bromis japonicus Japanese brome Grass Buchloe dactyloides Buffalo grass Grass Camelina microcarpa Smallseed falseflax Forb Chenopodium sp. Goosefoot Forb Collomia lenearis Slenderleaf collomia Forb Convolvulus arvensis Field bindweed Forb Corispermum netidum Shiny bugseed Forb Euphorbia glyptosperma Ridgeseed spurge Forb Grindelia squarrosa Curlycup gumweed Forb Gutierrezia sarothrae Broom snakeweed Forb Helianthus annuus Annual sunflower Forb Hordeum jubatum Foxtail barley Grass Kochia scoparia Kochia Forb Lactuca serriola Prickly lettuce Forb Lepidium densiflorum Greenflower pepperweed Forb Lotus purshianus American deervetch Forb Melilotus officinalis Yellow sweetclover Forb Monolepis nuttalliana Nuttall povertyweed Forb Pascopyrum smithii Western wheatgrass Grass Plantago elongata Prairie plaintain Forb Poa pratensis Kentucky bluegrass Grass Polygonum ramosissimum Bushy knotweed Forb Portulaca oleracea Common purslane Forb Rumex stenophyllus Narrowleaf dock Forb Schedonnardus paniculatus Tumblegrass Grass Sphaeralcea coccinea Scarlet globemallow Forb Taraxacum officinale Common dandelion Forb69 Appendix F. Plant species id entified on Winner site, 2004 and 2005.

Scientific Name Common Name Class Agropyron cristatum Crested wheatgrass Grass Amaranthus albus Tumble pigweed Forb Astragalus vexilliflexis Bentflower milkvetch Forb Atriplex argentea Silverscale saltbush Forb Bouteloua gracilis Blue grama Grass Bromus inermis Smooth brome Grass Bromus japonicus Japanese brome Grass Buchloe dactyloides Buffalo grass Grass Carex filifolia Threadleaf sedge Grass Carex inops Sun sedge Grass Carex sp. Sedge Grass Chenopodium sp. Goosefoot Forb Cirsium arvense Canada thistle Forb Convolvulus arvensis Field bindweed Forb Ellisia nyctelea Waterpod Forb Euphorbia glyptosperma Ridgeseed spurge Forb Euphorbia strictospora Slimseed sandmat Forb Grindelia squarrosa Curlycup gumweed Forb Hedeoma hispida Rough falsepennyroyal Forb Helianthus annuus Annual sunflower Forb Kochia scoparia Kochia Forb Lactuca serriola Prickly lettuce Forb Lepidium densiflorum Greenflower pepperweed Forb Lotus purshianus American deervetch Forb Malva rotundifolia Roundleaf mallow Forb Melilotus officinalis Yellow sweetclover Forb Monolepis nuttaliana Muttal povertyweed Forb Panicum capillare Witchgrass Grass Pascopyrum smithii Western wheatgrass Grass Plantago patagonica Indianwheat Forb Polygonum ramosissimum Bushy knotweed Forb Portulaca oleracea Common purslane Forb Salsola collina Slender Russian thistle Forb Schedonnardus paniculatus Tumblegrass Grass Solanum rostratum Buffalobur Forb Sphaeralcea coccinea Scarlet globemallow Forb Taraxacum officinale Common dandelion Forb Tradescantia bracteata Bracted spiderwort Forb Verbascum thapus Common mullein Forb Verbena bracteata Prostrate vervain ForbAppendix G. Breakthroughs of new, active burrows, and vegetationcharacteristics associated withfive study sites in westernSouth Dakota, August 2004 and 2005.Bad River RoadControl 10m 25m 40m2004 2005 2004 2005 2004 2005 2004 2005Break through9 0 7 8 7 5 5 0VOR (cm)1.9 2.0 2.7 2.8 2.6 2.7 2.6 9.7Vegetation Height (cm)14.6 11.3 17.4 16.4 12.8 20.5 14.2 36.7Graminoid cover (%)62.4 69.7 72.5 81.4 84.4 88.8 85.3 88.1Forb cover (%)2.6 3.6 3.9 4.6 3.6 3.5 3.4 3.1Liter cover (%)8.9 7.1 6.3 6.3 3.9 4.7 2.9 3.6Bare ground (%)26.0 19.6 17.3 7.6 7.8 3.0 8.4 5.3 70(Appendix G Continued)Fort PierreControl 10m 25m 40m2004 2005 2004 2005 2004 2005 2004 2005Break through10 11 3 9 9 5 5 4VOR (cm)1.9 2.1 9.9 7.2 7.6 9.4 11.3 11.6Vegetation Height (cm)14.5 15.1 28.0 28.5 23.0 26.1 30.6 36.2Graminoid cover (%)17.6 27.3 59.2 73.8 37.6 57.4 42.9 56.4Forb cover (%)28.8 29.9 14.5 14.8 32.2 24.6 34.6 29.8Liter cover (%)17.8 16.8 11.2 8.0 11.4 10.7 6.3 4.4Bare ground (%)35.8 26.0 15.0 3.5 19.0 7.3 16.1 9.4 71(Appendix G Continued)Custer CountyControl 10m 25m 40m2004 2005 2004 2005 2004 2005 2004 2005Break through40 20 23 17 22 16 36 13VOR (cm)2.6 3.4 1.7 3.0 2.8 3.4 3.1 3.2Vegetation Height (cm)14.3 8.6 15.5 9.5 15.1 10.2 17.2 11.3Graminoid cover (%)54.5 33.4 62.6 52.2 73.5 38.1 69.8 51.7Forb cover (%)23.8 11.9 9.4 7.4 5.9 19.4 10.0 9.1Liter cover (%)11.0 4.5 21.1 6.0 13.4 6.5 14.7 4.9Bare ground (%)10.7 50.1 7.0 34.4 7.2 36.0 5.4 34.4 72(Appendix G Continued)Fall River CountyControl 10m 25m 40m2004 2005 2004 2005 2004 2005 2004 2005Break through69 40 72 27 67 28 44 16VOR (cm)0.0 1.4 0.5 1.9 0.4 2.3 0.4 5.1Vegetation Height (cm)4.4 9.4 9.3 10.6 7.0 12.5 7.7 15.8Graminoid cover (%)0.7 28.2 9.2 74.1 2.3 68.9 2.9 75.1Forb cover (%)0.7 5.2 0.6 1.5 0.7 3.1 0.9 2.4Liter cover (%)46.3 33.1 76.1 17.8 75.7 13.4 69.6 12.3Bare ground (%)52.2 33.5 14.2 6.6 21.4 14.5 26.6 10.2 73(Appendix G Continued)WinnerControl 10m 25m 40m2004 2005 2004 2005 2004 2005 2004 2005Break through15 10 12 8 20 6 18 0VOR (cm)2.5 3.5 2.3 4.9 2.1 8.3 3.0 13.3Vegetation Height (cm)16.0 14.8 16.6 25.4 15.0 31.6 16.0 44.2Graminoid cover (%)47.2 52.9 53.2 55.2 47.8 61.7 56.7 65.7Forb cover (%)2.4 3.1 4.7 6.7 6.8 7.4 11.7 11.2Liter cover (%)21.7 22.2 16.8 15.8 15.7 17.8 16.8 16.3Bare ground (%)28.7 21.8 25.3 22.4 29.8 13.2 14.8 6.7 74