Scholarly article on topic 'Greater Sage-Grouse and Range Management: Insights from a 25-Year Case Study in Utah and Wyoming'

Greater Sage-Grouse and Range Management: Insights from a 25-Year Case Study in Utah and Wyoming Academic research paper on "Biological sciences"

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Abstract of research paper on Biological sciences, author of scientific article — David K. Dahlgren, Randy T. Larsen, Rick Danvir, George Wilson, Eric T. Thacker, et al.

Abstract Conservation of sagebrush (Artemisia spp.) systems is one of the most difficult and pressing concerns in western North America. Sagebrush obligates, such as greater sage-grouse (Centrocercus urophasianus; hereafter sage-grouse), have experienced population declines as sagebrush systems have degraded. Science-based management is crucial to improve certainty in range management practices. Although large-scale implementation of management regimens within an experimental design is difficult, long-term case studies provide opportunities to improve learning and develop and refine hypotheses. We used 25 years of data across three large landscapes in northern Utah and southwestern Wyoming to assess sage-grouse population change and corresponding land management differences in a case study design. Sage-grouse lek counts at our Deseret Land and Livestock (DLL) study site increased relative to surrounding populations in correspondence with the implementation of small-acreage sagebrush treatments designed to reduce shrub cover and increase herbaceous understory within a prescriptive grazing management framework. The higher lek counts were sustained for nearly 15 years. However, with continued sagebrush treatments and the onset of adverse winter conditions, DLL lek counts declined to levels consistent with surrounding areas. During summer, DLL sage-grouse broods used plots of small, treated sagebrush mosaics more than untreated reference sites. We hypothesize that sagebrush treatments on DLL increased availability of grasses and forbs to sage-grouse, similar to other studies, but that cumulative annual reductions in sagebrush may have reduced availability of sagebrush cover for sage-grouse seasonal needs at DLL, especially when extreme winter weather occurred.

Academic research paper on topic "Greater Sage-Grouse and Range Management: Insights from a 25-Year Case Study in Utah and Wyoming"


RAMA-00047; No of Pages 8

Rangeland Ecology & Management xxx (2015) xxx-xxx

Contents lists available at ScienceDirect

Rangeland Ecology & Management

journal homepage:


Ecology & Management

2 Greater Sage-Grouse and Range Management: Insights from a 25-Year

3 Case Study in Utah and Wyoming^

qi David K. Dahlgren a'*'1, Randy T. Larsen b, Rick Danvirc, George Wilson d, Eric T. Thacker e, Todd A. Blackf,

5 David E. Naugle g, John W. Connelly h, Terry A. Messmer1

6 a Extension Associate, Wildland Resources Department, Utah State University, Logan, UT 84322, USA

7 b Associate Professor, Department of Plant and Wildlife Sciences and the Monte L. Bean Life Sciences Museum, Brigham Young University, Provo, UT 84602, USA

8 c Basin Wildlife Consulting, Casper, WY 82609, USA

9 d Biologist, Utah Division of Wildlife Resources (retired), Council, ID 83612, USA

10 e Range Extension Specialist and Assistant Professor, Wildland Resources Department, Utah State University, Logan, UT 84322, USA

11 f Wildlife Program Manager, Deseret Land and Livestock, Woodruff, UT 84086, USA

12 g Professor, College of Forestry and Conservation, University of Montana, Missoula, MT 59812, USA

13 h Research Scientist, Idaho Department of Fish and Game (retired), Blackfoot, ID 83221, USA

14 i Wildlife Extension Specialist and Professor, Wildland Resources Department, Utah State University, Logan, UT 84322, USA


Conservation of sagebrush (Artemisia spp.) systems is one of the most difficult and pressing concerns in western 27 North America. Sagebrush obligates, such as greater sage-grouse (Centrocercus urophasianus; hereafter sage- 28 grouse), have experienced population declines as sagebrush systems have degraded. Science-based management 29 is crucial to improve certainty in range management practices. Although large-scale implementation of manage- 30 ment regimens within an experimental design is difficult, long-term case studies provide opportunities to improve 31 learning and develop and refine hypotheses. We used 25 years of data across three large landscapes in northern 32 Utah and southwestern Wyoming to assess sage-grouse population change and corresponding land management 33 differences in a case study design. Sage-grouse lek counts at our Deseret Land and Livestock (DLL) study site in- 34 creased relative to surrounding populations in correspondence with the implementation of small-acreage sagebrush 35 treatments designed to reduce shrub cover and increase herbaceous understory within a prescriptive grazing 36 management framework. The higher lek counts were sustained for nearly 15 years. However, with continued sagebrush 37 treatments and the onset of adverse winter conditions, DLL lek counts declined to levels consistent with surrounding 38 areas. During summer, DLL sage-grouse broods used plots of small, treated sagebrush mosaics more than untreated 39 reference sites. We hypothesize that sagebrush treatments on DLL increased availability of grasses and forbs to sage- 40 grouse, similar to other studies, but that cumulative annual reductions in sagebrush may have reduced availability of 41 sagebrush cover for sage-grouse seasonal needs at DLL, especially when extreme winter weather occurred. 42

© 2015 The Authors. Published by Elsevier B.V. on behalf of Society for Range Management. This is an open access 43 article under the CC BY-NC-ND license (

16 Article history:

17 Received 5 May 2014

18 Accepted 23 June 2015

19 Available online xxxx

20 Keywords:

21 case study

22 greater sage-grouse

23 livestock grazing

24 sagebrush management

25 Utah

26 Wyoming

45 Introduction

46 Increasing losses in biodiversity across the globe demand an unprec-

47 edented scale and certainty in application of conservation actions to slow

48 declines (Waldron et al., 2013). Most imperiled are species with high

49 vulnerability and low adaptive capacity that can only be maintained

50 through species-specific management actions (Goble et al., 2012).

51 Science-based management underpins conservation effectiveness, and

☆ Research was funded in part by U.S. Department of Agriculture Sage-Grouse Initiative, Jack H. Berryman Institute, Deseret Land and Livestock Quinney Professorship for Wildlife Conflict Management, and Open Range Consulting.

* Correspondence: David Dahlgren, Wildland Resources Dept, Utah State University, Logan, UT 84322, USA. Tel.:+1 435 881 1910.

E-mail address: (D.K. Dahlgren). 1 Current address: David Dahlgren, Wildland Resources Dept, Utah State University, 5230 Old Main Hill, Logan, UT 84322-5230, USA.

without it, well-intentioned practitioners may implement actions that 52 are ineffective or even detrimental to species recovery. Effectiveness of 53 management actions can take decades to assess given inherent variabil- 54 ity in climate and lag times that can span years to decades, particularly 55 for species with low reproductive rates and longer life spans. Moreover, 56 although experimental design and replication are trademarks of science- 57 based management, replicated experiments can be difficult or even im- 58 possible to conduct on large scales. In these scenarios, case studies can 59 offer an approach that provides reliable information and serves as a valu- 60 able precursor to hypothesis testing (Hebblewhite, 2011). 61

Conservation of sagebrush (Artemisia spp.) ecosystems is one of the 62 most pressing issues in western North America (Knick and Connelly, 63 2011). Sagebrush occurs across a large portion of western North 64 America where sagebrush communities and their associated fauna are 65 threatened by energy development, urbanization, conversion to crop- 66 land, invasion of exotic plants and subsequent catastrophic wildfire, 67 016/j.rama.2015.07.003

1550-7424/© 2015 The Authors. Published by Elsevier B.V. on behalf of Society for Range Management. This is an open access article under the CC BY-NC-ND license (


2 D.K. Dahlgren et al. / Rangeland Ecology & Management xxx (2015) xxx-xxx

conifer encroachment, and sagebrush eradication (Naugle, 2011; Knick et al., 2013; Murphy et al., 2013). Loss and degradation of sagebrush communities have led to conservation challenges for a variety of species (Baker et al., 1976; Miller and Eddleman, 2000; Bradley, 2010). At greatest risk are obligate species found only in this ecotype (Oyler-McCance et al., 2001; Ingelfinger and Anderson, 2004; Holloran, 2005).

Greater sage-grouse (Centrocercus urophasianus; hereafter sage-grouse) are sagebrush obligates that use this ecosystem throughout all phases of their life cycle. As with other sagebrush obligates, sage-grouse populations have declined in response to habitat loss and degradation (Garton et al., 2011). New outcome-based science is quantifying the efficacy of proactive conservation measures to stem population losses (e.g., conifer removal [Baruch-Mordo et al., 2013] and conservation easements [Copeland et al., 2013]), but examples of increasing populations as a direct result of management intervention are rare, leaving practitioners unsure of management actions that could be implemented proactively to further conservation of sage-grouse.

The detrimental impacts of sagebrush canopy removal or reduction on sagebrush obligate species across large areas are widely known (Beck et al., 2012). The efficacy of small-scale (e.g., < 200-ha mosaics) shrub removal in sage-grouse management, however, remains fiercely debated. On one hand, removal or thinning of sagebrush in small areas in mosaic patterns within sagebrush landscapes may promote growth of grasses and forbs, which could improve brood-rearing habitat and sage-grouse recruitment (e.g., Dahlgren et al., 2006). Conversely, removal of shrubs may reduce availability of sagebrush during winter, reduce nesting habitat, facilitate invasion of exotic plants, and further fragment existing sagebrush systems. Because sage-grouse are currently being considered for federal Endangered Species Act listing (Stiver, 2011), a better understanding of the response of sage-grouse to small-scale sagebrush canopy reduction with applications of mechanical, chemical, or prescribed fire is needed. Long-term case studies have been suggested as alternative options to assess the efficacy of these practices and provide important learning opportunities for practitioners (Krausman et al., 2009). To date, however, no such long-term studies exist.

In northern Utah, the 76 700-ha private Deseret Land and Livestock (DLL) ranch reported a dramatic increase in average males counted per lek between the late 1980s and early 2000s (Danvir, 2002). However, in 2010, lek counts on DLL declined to levels approximating surrounding populations. DLL employed range management practices during this period that were distinctly different from the surrounding areas in northern Utah and western Wyoming. These practices included a prescriptive grazing strategy where cattle were managed in three or four large herds and rotated through pastures for short periods of time (Danvir et al., 2005). Combined with prescriptive grazing, sagebrush treatments were conducted at small (generally < 200-ha) scales in mid- and high-elevation sagebrush communities. The surrounding areas largely consisted of U.S.D.I. Bureau of Land Management (BLM) allotments with limited inclusions of nonfederal land. These areas were managed using different grazing regimens and few sagebrush management projects. The DLL ranch provided habitat for a sage-grouse population adjacent to populations in north Rich County (RICH) and southwestern Wyoming (WWY). All three populations have been monitored using spring lek counts of male sage-grouse as an index of abundance for multiple decades.

The purpose of this case study was to document changes in sage-grouse populations over the past 25 years and begin to assess response of sage-grouse to differences in long-term, landscape-level (e.g., across multiple allotments or an entire 75 000 ha ranch) management actions. We first compared counts of breeding males (i.e., number of males per lek) between our three study areas. Next, we considered available data on brood counts and sage-grouse use of treatment areas on DLL. Although our approach lacks a true experimental design, it is a long-term retrospective case study that considers the preponderance of evidence accumulated over a 25-year period. Our intention was to use these data to provide information that begins to fill knowledge gaps and

develop hypotheses that could be tested in replicated experimental designs in the future.

Study Areas

We identified three study areas for retrospective analysis that included 1) Deseret Land and Livestock (DLL) located in Morgan, Rich, and Weber Counties, Utah; 2) north Rich (RICH) located in Rich County, Utah; and 3) western Wyoming (WWY) located in Uinta and Lincoln Counties, Wyoming (Fig. 1). Sage-grouse habitats in each study area shared similar soils, elevations, vegetation types, and weather patterns. The study areas contained two Major Land Resource Regions (MLRAs) (USDA Agriculture Handbook 296, 2006). Sage-grouse occurred on the study areas throughout MLRA 34A (Cool Central Desertic Basins and Plateaus) and in the lower elevations of MLRA 47 (Wasatch and Uinta Mountains). Occupied habitat throughout the study areas ranged in elevation from 1 950 to 2 600 m on substrate composed of shale- and sandstone-derived Aridisols and Entisols.

Sage-grouse habitat in our study areas included at least three community types based on elevation: 1) low elevations (<2000 m) were dominated by Wyoming big sagebrush (A. tridentata wyomingensis) or low sagebrush (A. arbuscula) and Douglas rabbitbrush (Chrysothamnus viscidiflorus); 2) midelevation (between 2000 m and 2100 m) habitats were dominated by basin big sagebrush (A t. tridentata) with inclusions of low sagebrush, often intermixed with rabbitbrush; and 3) high elevation (>2100 m) sagebrush communities were dominated by mountain big sagebrush (A. t. vaseyana), with intermixed bitterbrush (Purshia tridentata), serviceberry (Amalanchier alnifolia) or snowberry (Symphoricarpos albus), and inclusions of aspen (Populus tremuloides) and Douglas fir (Pseudotsuga meniziesii) at the highest elevations. Mean annual precipitation was 25 cm at lower elevations and 55 cm at higher elevations. Irrigated, native riparian, and meadow habitats (< 5% of study area) occurred along the Bear and Green River drainages.

Anthropogenic influences in each study area included livestock grazing by domestic cattle as the primary land use. During our study period we estimated active well density at 4.54 wells per 100 km2,1.96 wells per 100 km2, and 2.86 wells per 100 km2 for DLL, RICH, and WWY, respectively in 6.4-km buffers (see Walker et al., 2007) around known leks. Well spudding rates during the study period were 2.22 per 100 km2, 0.44 per 100 km2, and 0.76 per 100 km2, for DLL, RICH, and WWY, respectively (Utah data from oilgasmining; Wyoming data from Well pad densities in all three areas were extremely low compared with density thresholds (e.g., 150 wells per 100 km2) showing negative impacts to sage-grouse populations in other areas (Harju et al., 2010). Therefore we did not consider differences in oil and gas well densities between study areas as likely to influence sage-grouse populations.

The three study areas differed in land ownership, grazing management strategies, and frequency of sagebrush removal. The RICH study area was 158 100 ha in size, including ~ 53% publicly owned and 47% privately owned lands. The WWY study area was 407 000 ha in size, including ~64% publicly and 36% privately owned lands. The RICH and WWY study areas were primarily federally owned lands, principally controlled by the U.S. Department of Interior, Bureau of Land Management (BLM); U.S. Department of Agriculture; and U.S. Forest Service (USFS). Most of the private rangelands "checker-boarded" within the RICH and WWY areas were managed as part of BLM allotments. Allotments in the northern and southern portion of the WWY area were generally single pastures grazed May-September. The central portion of the area consisted of the Uinta-Cumberland allotment, which used a four-pasture deferred-rotation grazing plan in which pastures were grazed for 1-2 months per pasture May-October. Allotments in RICH included single pastures grazed May-September. Few pastures in RICH or WWY received growing-season rest, and cattle were generally stocked at a rate of 2.5-5 AUM • ha-1. Conversely, DLL consisted of 76 700 ha, 93% of which was privately owned with the remaining 7% BLM inholdings.


D.K. Dahlgren etal. / Rangeland Ecology & Management xxx (2015) xxx-xxx

Fig. 1. Location of greater sage-grouse (Centrocercus urophasianus ) leks across our three study areas used to assess population response of sage-grouse to differences in range management, 1989-2013. Study areas were Deseret Land and Livestock (DLL; dark squares), north Rich (RICH; filled circles), and western Wyoming (WWY; open triangles).

198 DLL practiced a prescriptive grazing strategy that emphasized growing-

199 season rest. Contrasted with the RICH and WWY areas, cattle occurred

200 in a few large herds and pastures experienced higher stock densities,

201 shorter grazing periods (1-2 weeks per pasture during May-

202 September), and longer periods of rest and recovery (generally > 12

203 months) before regrazing (Danvir et al., 2005). Up to 30% of pastures

204 on DLL received a full year's rest annually and were not grazed during

205 the same growing-season during subsequent use. DLL pastures were

206 stocked at a rate of 1.2-1.6 AUM • ha-1 during April-November.

207 During our study period, sagebrush canopy control applications of

208 Lawson aerator, disking, chain harrow, Tebuthiuron, and prescribed

209 fire were used, primarily at DLL. The Lawson aerator is a large drum

210 (usually filled with water for added weight) pulled behind a tractor

211 that crushes sagebrush and impacts the soil surface. A disk is pulled be-

212 hind a tractor to rip sagebrush plants out of the ground and disturb the

213 soil surface. A chain harrow is also pulled by tractors and is a large

214 swiveled chain with welded harrows, which rotate to rip and crush

215 sagebrush. Tebuthiuron (i.e., Spike) is a chemical herbicide application

216 usually applied aerially in the fall in pellet form. Seeding of forbs and

217 grasses (both native and non-native) followed most treatments by

218 broadcasting behind a tractor or aerially. These management actions

219 were designed to achieve one or more of the following objectives: 1) in-

220 crease herbaceous production and plant species richness by reducing

221 plant competition with sagebrush, 2) create interspersion (complexity)

222 of vegetative conditions, and 3) reduce fuel loads or create "green-

stripping" to decrease catastrophic wild-fire risks while maintaining ad- 223

equate sagebrush cover for sage-grouse and other sagebrush obligates 224

(Aoude, 2002; Summers, 2005; Danvir et al., 2005). Treatment sizes var- 225

ied (Fig. 2) but were generally < 200-ha mosaics, situated in elevations 226

above 2 000 m in mid- (i.e., basin big sagebrush) and high-elevation 227

(i.e., mountain big sagebrush) communities in breeding (nesting 228

and early brooding) and late brood-rearing habitats. Treatments charac- 229

teristically had meandering edges with interspersed "islands" of 230

0-100 101-200 201-300 301-400 401-500 501-600 >600 Size of treated area (ha)

Fig. 2. Frequency of sagebrush treatments by size (ha) on Deseret Land and Livestock (DLL) ranch in northern Utah, 1989-2013.


D.K. Dahlgren et al. / Rangeland Ecology & Management xxx (2015) xxx-xxx

untreated sagebrush within treated areas (on average, 30% of treatment polygons were left untreated). In addition, several relatively small (< 1 610 ha) wildfires occurred at DLL in largely mid- or high-elevation sagebrush habitats during the study period (Table 1).

Between 1995 and 2008 ~ 8% of the WWY area experienced 29 500 ha of wild or prescribed fires and 1 600 ha of Tebuthiuron sagebrush treatments. Shrub cover was removed from 60-70% of impacted areas (Slater, 2003). Between 1993 and 2009 < 2% of the RICH study area experienced sagebrush removal (1 550 ha of wildfires, 1 300 ha of primarily Lawson aerator treatment). Conversely, approximately 1.5% of DLL sagebrush habitat received wildfire or a prescribed sagebrush treatment annually from 1992-2009 (Table 1) resulting in nearly 15% of total sagebrush habitat affected (Table 1).


Lek Analysis

We analyzed 25 years (1989-2013) of lek count data at DLL and compared it with adjacent areas RICH and WWY to determine if the observed trend in counts of males per lek at DLL was different from adjacent populations exposed to similar environmental conditions. We secured available lek data for these analyses from the Utah Division of Wildlife Resources (UDWR) and Wyoming Game and Fish Department (WGFD). Lek surveys were conducted each spring by UDWR, WGFD, and DLL personnel. In all study areas, each lek was counted at least three separate mornings (usually 7-10 days apart) between a half-hour before 1.5 hours post sunrise from the first of April to early May. Generally, weather conditions were required to consist of low wind speeds and low percent cloud cover. The maximum count of the > 3 samples was used as that year's lek count for a given lek. We included leks in our analysis that occurred on DLL and limited our analysis to those within ~50 km of the DLL ranch border for RICH and WWY in an effort to minimize the influence of spatial variation in climatic conditions on lek counts. Some interchange of sage-grouse between our study areas likely occurred, especially during late fall and winter periods. However, telemetry-based research on DLL suggested that most sage-grouse that attended leks on the ranch spent their entire life cycle on the property or within a couple km of the ranch boundary. Therefore, these 3 areas generally corresponded to Connelly et al.'s (2000) definition of distinct breeding populations.

Our analysis followed several steps. First, to evaluate changes in lek counts over time at DLL only, we used a Bayesian Change Point (BCP) analysis (Erdman and Emerson, 2007) in program R (RDevelopmentCoreTeam, 2008). This method partitions sequential information (in our case summed number of males at DLL for each year) into contiguous blocks such that means were assumed constant within each block but allowed to vary or change between blocks. This process is then iterated across the sequence to estimate posterior probabilities ofchange for each year in the time sequence. Because BCP requires consecutive numbers and in the current implementation does not allow for missing values, we were limited to data from 9 leks on DLL counted continuously since 1989 for this initial analysis. Second, to evaluate differences in mean number of males counted per lek across the three study areas we plotted mean males counted per lek across all active leks for each study area and used a generalized additive model (GAM) smoother

to create a confidence band surrounding mean males per lek for study area comparison. This approach allowed for incorporation of missing values, and thus we were able to use all of the available information associated with counted leks within the study areas. We evaluated the potential use of information from 21, 29, and 91 leks at DLL, RICH, and WWY, respectively, for this analysis and used available data within our study period (1989-2013), as well as data up to 5 years previous (i.e., beginning in 1984 using Utah and Wyoming lek data referenced above) to define active leks. Third, we calculated lek persistence rates and 95% confidence intervals for each area. For lek persistence, we considered leks as active if they had two or more males counted in two or more of the 5 years surrounding our initial start date (1989) and within 5 years of our end date (2013). We considered leks inactive if they did not meet this criteria (Connelly et al., 2004) and calculated persistence rates as the proportion of leks active at the beginning of our study period that were still active at the end.

Brood Surveys

Annual estimates (1985-2009) of the number of chicks per brood on DLL were obtained by driving through multiple brooding areas across the ranch or walking through brooding areas not adjacent to a road (rare). Once established, areas searched were kept consistent year to year. We only used observations collected July 1 to August 30. Chicks per brood were compared between years before rangeland treatments (1985-1993) and in years following the initiation of rangeland treatments (1994-2009) using mean, standard error, and 95% confidence intervals.

Sage-Grouse Use of Treated Areas on DLL

From 1996-1998, we monitored sage-grouse use of five plots treated by disking or prescribed fire within the previous 4 years. In 2005, we monitored three plots treated with a Lawson aerator within the previous 5 years. All treated sagebrush areas on DLL, whether by Lawson aerator, disking, chain-harrow, or prescribed fire, were designed in a mosaic pattern creating increased edge and attempting to only remove a portion of the sagebrush cover from large contiguous areas. Plots averaged ~140 ha (range 100-200 ha). For all sampling, we paired each treatment site with a nearby (< 1 km) reference site. Intact sagebrush reference sites were of similar size and delineated by field personnel based on proximity and similarity of site characteristics to treatment plots. We monitored sage-grouse use of the treatments by sampling each study plot with two to three pointing dogs followed by two to three observers mounted on horseback (1996-1998) or foot (2005). Pointing dogs searched in a quartering pattern in front of observers, sampling up to 250 m on each side of the edge of the treatment (Dahlgren et al., 2006). Surveys required approximately an hour to complete, and we did so in a circular course for each study plot. We counted and categorized grouse as adults without young, brood members (hens and chicks), and total sage-grouse. To sample the plots during the best scenting conditions for pointing dogs (Gutzwiller, 1990; Dahlgren et al., 2010, 2012), we sampled each plot two to four times during late June to mid-August (1996-1998) or late June to early July (2005) between 0700 and 1000 or 1800 and 2100 hours. When sage-grouse flushed, we marked the location with a GPS and calculated the distance to nearest treatment boundary (intact sagebrush or treatment edge).

Area (ha) of sagebrush canopy manipulated by treatment type on Deseret Land and Livestock in northern Utah, USA, 1993-2009.

Elevation Type of treatment

Wild fire Prescribed fire Disked planting Mechanical (Aerator, chain) Tebuthiuron (spike) Total

< 2 000 m 163 0 489 554 0 1 206

2 001-2100 m 507 538 3 192 1 684 47 5 968

>2100 m 1 603 853 352 413 991 4 212

Total 11 386


D.K. Dahlgren etal. / Rangeland Ecology & Management xxx (2015) xxx-xxx

Fig. 3. Posterior means (upper frame; summed number of male sage-grouse lek (Centrocercus urophasianus) and probability of change (lower frame) for nine leks on Deseret Land and Livestock Ranch, northern Utah, USA 1989-2013.

336 We used PROC GLIMMIX (SAS 9.2) to test for differences in mean num-

337 ber of total grouse, adults, and brood members. We treated location/site

338 of paired plots as a blocking factor to account for inherent variability

339 among sites and more directly assess treatment effect (SAS Institute

340 Inc. 2002-2003).

341 Results

342 Lek Data

343 The summed males per lek for nine leks on DLL initially decreased

344 from > 200 (1989-1992) to < 150 during 1993 and 1995 (Fig. 3). Subse-

345 quent summed males per lek for the same nine leks increased dramati-

346 cally in the late 1990s to more than 400 in 2000 and 2001. Following

347 2001, counts fluctuated but remained nearly double those observed dur-

348 ing the first 10 years of the study period until 2010, when they decreased

349 to summed males per lek (~150 males) similar to those observed during

350 the first part of the study period. The increase in males per lek during the

351 late 1990s and decrease in 2010 were both assigned high (~90%) poste-

352 rior probabilities of change (Fig. 3). Posterior probabilities of change for

353 all other years were < 30% (Fig. 3). Average males per lek at DLL reflected

354 similar changes decreasing slightly to less than 25 males per lek in the

355 early 1990s, increasing to nearly 50 between 2000 and 2009, and then

356 decreasing drastically in 2010 (Fig. 4). The increase in counts during

357 the middle part of our study period was not observed at the RICH or

358 WWY study areas, and confidence bands surrounding estimated mean

359 counts did not overlap during most of this period (Fig. 4). Conversely,

360 substantial overlap in confidence intervals occurred during the initial

361 and ending years of our study period (Fig. 4).

362 The lek persistence probability at DLL was 1.00 (95% CI: 0.92-1.0)

363 where all (n = 9) of the active leks counted in 1989 were still active in

364 2013. During the same period, persistence probabilities were 0.80 (95%

365 CI: 0.62-0.98; n = 20 leks) and 0.47 (95% CI: 0.23-0.71; n =17 leks)

366 for WWY and RICH, respectively. Confidence intervals around persistence

367 probabilities showed DLL with a significantly higher persistence probabil-

368 ity than the other two study areas, which overlapped considerably.

369 Brood Surveys

We counted 182 brood groups during pretreatment years




' \ / V

/ r ... mfc

. / * / - H

2000 Year

Fig. 4. Mean counts of greater sage-grouse (Centrocercus urophasianus) males at leks on Deseret Land and Livestock (DLL) ranch in northern Utah, Rich County (RICH), and western Wyoming (WWY), USA 1989-2013.

0.24, 95% CI = 3.21-4.16) compared with 365 brood groups detected 372 in post-treatment years (1994-2009; n = 411 hens, n = 1717 chicks, 373

Xpost-treatment = 4.06, SE = 0.26, 95% CI = 3.55-4.57). 374

Sage-Grouse Use of Burned and Disked Plots 375

Treatment plots from 1996-1998 and 2005 combined averaged more 376 adult grouse (Xtreated = 2.79, SE = 0.62; xcontroi = 0.73, SE = 0.14; F = 377 10.57, P < 0.01), brood members (Xtreated = 5.80, SE = 0.83; Xcontroi = 378 0.71, SE = 0.62; F = 24.17, P < 0.01), and total grouse (xreated = 8.42, 379

SE = 1.16; xœnml = 1.19, SE = 0.58; F = 31.12, P < 0.01) counted in all treatments compared with control comparisons. Flush location data suggested that most sage-grouse (80% of both adults and broods) used areas within 60 m of a habitat edge (Table 2).

Discussion 384

The number of male sage-grouse counted on leks at DLL was not dif- 385 ferent from surrounding areas in the late 1980s and early 1990s. Then 386 the DLL sage-grouse population experienced an increase and sustained 387 higher lek count trends for nearly 15 years compared with RICH and 388 WWY populations. By 2013, however, numbers of males on leks at 389 DLL had returned to levels similar to the beginning of our study period 390 and comparable with those of adjacent areas. The increase in the DLL 391

brush removal continued and adverse weather conditions occurred in 394

population during the middle portion of our study period corresponded with the initiation of small-scale sagebrush treatments, but as sage-

(1985-1993; n = 223 hens, n = 857 chicks, xpre-


= 3.68, SE =

winter and early spring of 2010 and 2011, the number of males on leks at DLL declined precipitously to levels similar to RICH and WWY areas.

Depending on the period evaluated, inference about the influence of 398 DLL's management actions on sage-grouse changed from neutral (first 399 decade) to positive (middle period) back to neutral or negative (end 400 of study period). These changes spanned periods of increased spring 401 precipitation (early 1990s), drought (much of the 2000s), and two ex- 402 treme winters (1992-1993 and 2010-2011) providing a range of condi- 403 tions for sage-grouse to respond to DLL's management actions. This 404 suite of conditions also provided a basis from which to generate hypoth- 405 eses concerning sage-grouse population response to range manage- 406 ment actions. 407


D.K. Dahlgren et al. / Rangeland Ecology & Management xxx (2015) xxx-xxx

Table 2

Distance to habitat edge for sage-grouse flushed during pointing dog surveys of treatment and reference plots on Deseret Land and Livestock (DLL) ranch in northern Utah, USA, 1996.

Grouse and habitat type Distance from flush site to habitat edge

0-30 m 30-60 m 60-90 m > 90 m

Broods in intact sagebrush n= 15 1 0 3

'P(x) 0.79 0.05 - 0.16

Broods in treatment areas n= 34 13 5 6

'P(x) 0.59 0.22 0.09 0.10

Adults in intact sagebrush n= 8 3 1 0

'P(x) 0.67 0.25 0.08 0.00

Adults in treatment areas n= 11 8 3 4

'P(x) 0.42 0.31 0.12 0.15

'P(x) = proportion of broods or adult grouse.

Because sagebrush treatments on DLL increased herbaceous cover and production (Aoude, 2002; Summers, 2005) and were implemented in a mosaic pattern consisting of small annual acreage treated primarily in mid- to high-elevation sagebrush habitats (Connelly et al., 2000), we hypothesize that treatments increased availability of grasses and forbs for sage-grouse, similar to other studies (Slater, 2003; Dahlgren et al., 2006; Stringham, 2010). Treatments on DLL were applied against a backdrop of a large intact sagebrush landscape with relatively few threats from invasive plants or urban development and with prescriptive grazing during all years evaluated. We propose these herbaceous plants were able to establish and persist because the prescriptive grazing strategy employed at DLL provided periods of growing-season recovery between bouts of livestock grazing (Davies et al., 2011). Without growing-season rest, herbaceous cover may quickly disappear from treatments resulting in short-lived benefits (Davies et al., 2011).

During surveys observers and pointing dogs detected more sage-grouse, particularly broods, using treated areas (primarily edges) compared with adjacent untreated reference areas consistent with other studies (Slater, 2003; Dahlgren etal., 2006; Stringham, 2010; Thacker, 2010). We hypothesize that sage-grouse responded to increased availability of forbs and grasses by using treated areas and potentially increasing production and recruitment, particularly during favorable weather conditions during the 1990s (Guttery et al., 2013; Robinson and Messmer, 2013). Although there remains uncertainty concerning the influence of sagebrush treatments on adult and chick survival, herbaceous plants, especially forbs and associated arthropods, are linked to sage-grouse nutrition (Gregg et al., 2008) and survival (Connelly et al., 2000; Dunbar et al., 2005). Increased recruitment is important for sage-grouse population growth (Johnson and Braun, 1999; Dahlgren, 2009; Taylor et al., 2012) and low chick survival has been implicated as limiting for some populations (Connelly and Braun, 1997; Taylor et al.,

2012). Additionally, increased forb availability on DLL could have facilitated increased nutrients for prelaying hens, resulting in better production through higher nest success and chick survival (Dunbar et al., 2005; Gregg et al., 2008). However, similar to Connelly et al. (2000), we emphasize that manipulating sagebrush in nesting habitat within 5 km of leks to benefit sage-grouse could be counterproductive (Coates et al.,

2013). More research concerning the relationship of treatments, associated forb response, and prelaying hen use and nutrition is needed.

We further hypothesize that cumulative annual reductions in sagebrush may have reduced availability of sagebrush cover for sage-grouse seasonal needs at DLL, especially when extreme weather occurred. However, on the basis of our available data we cannot distinguish which factor, sagebrush removal or severe weather, was most influential or if an interaction of both affected the decrease in DLL's sage-grouse population. The extreme winter and spring weather of 2010 and 2011, where cold wet conditions continued through the nesting period, may have resulted in decreased nest success and survival of adult sage-grouse with corresponding decreases in number of males counted at leks over subsequent years. Sage-grouse typically use high canopy

cover sagebrush to conceal nests and early broods (Connelly et al., 2000). It has been well documented that nesting habitat may be compromised if large areas of sagebrush-dominated landscapes have reduced shrub cover (Wallestad and Pyrah, 1974; Braun et al., 1977; Gregg et al., 1994; Sveum et al., 1998; Connelly et al., 2000). Lek counts in RICH and WWY, as well as other populations in Utah, showed declining trends similar to DLL from 2008-2013, although DLL's declining trend was steeper than surrounding populations (Bernales et al., 2012).

Stable populations of sage-grouse occur within large landscapes of intact sagebrush (Aldridge et al., 2008; Knick et al., 2013). We emphasize that sagebrush treatments at DLL were small (vast majority < 200 ha in size) and did not accumulate to more than 20% of the landscape over our study period. We also note with caution that large-scale treatments have not maintained or improved populations (Connelly et al., 2000) and are associated with significant population declines (Wallestad, 1975; Braun et al., 1977; Swenson et al., 1987; Beck et al., 2003). Where sage-grouse habitat is a concern, sagebrush treatment is not recommended for Wyoming big sagebrush dominated landscapes at lower elevations (Beck etal., 2009,2012; Hess and Beck, 2012; Davies et al., 2011), especially where the potential for invasive plants occur (e.g., cheatgrass; Bromus tectorum; Davies et al., 2011; Knick et al., 2011; Miller et al., 2011). Treatments during our study period predominantly occurred in mid to high elevations in breeding (nest and early brooding) and summer (late brooding) habitats, not in wintering habitat at lower elevations.

Nonetheless, DLL personnel have noticed when snow levels are high, covering Wyoming big sagebrush, sage-grouse move upslope into areas of tall basin big sagebrush still available above the snow and treatments may have reduced access to food and cover during these conditions. Recent evidence from other studies suggests that extreme winter weather may also negatively influence survival rates of adult sage-grouse (Anthony and Willis, 2010; Moynahan et al., 2006). During the winter, sage-grouse use sagebrush for both food (~99 % of the diet) and cover, with specific-use areas selected on the basis of sagebrush type, nutrition, and availability of sagebrush above the snow (Remington and Braun, 1985; Schroeder et al., 1999; Thacker et al., 2012; Frye et al., 2013). Our results highlight the importance of maintaining sagebrush habitats with adequate amounts of tall sagebrush for sage-grouse to use as nesting and winter habitat. If adult survival on DLL declined during our study due to limited winter habitat, sagebrush treatments and grass plantings at lower elevations decades before (1960s) our study period might also be implicated (see Ripplinger et al., 2015).

Elements of the prescribed grazing practices at DLL may also have provided benefits to sage-grouse independent of or in concert with sagebrush treatments. In combination, these practices tend to create heterogeneity, which can be beneficial to grouse (Boyd et al., 2011). Our annual brood surveys on DLL showed higher point estimates but significant overlap in confidence intervals for chicks per brood from pre-treatment to post-treatment years. The relatively high counts of chicks per brood in pretreatment years may have been an artifact of changes made in grazing practices a decade or more before the implementation of small-scale sagebrush treatments.

Regardless, we caution that our results are based on a case study relying on the preponderance of evidence from management actions implemented outside of an experimental design. More research concerning the demographic responses we have proposed herein is warranted and may be conducted where relatively stable sage-grouse populations exist. However, we can state with some certainty that the range management principles and practices used on DLL were associated with high lek persistence rates and lek counts that for nearly 15 years were higher than adjacent areas with different management practices. We believe this case study provides an initial step to quantify the influence of landscape-level management actions and relate it to population responses. Though our data do not identify mechanisms that lead to population change, they provide evidence of a correlation between management actions and indices of sage-grouse abundance. At a


D.K. Dahlgren etal. / Rangeland Ecology & Management xxx (2015) xxx-xxx

524 minimum, our data provide a starting point for future research. Given

525 the range-wide reports of declining sage-grouse populations during

526 our study period and the nearly ubiquitous nature of livestock grazing

527 across sage-grouse range, it is imperative that the conservation commu-

528 nity increase our understanding of the influence of rangeland manage-

529 ment practices on sage-grouse populations (Connelly and Braun,

530 1 997; Davies et al., 2011; Garton et al., 2011). Although fully designed

531 and replicated experiments remain the standard in science, case studies

532 such as this one can provide valuable information leading to hypothesis

533 development and testing.

534 Implications

535 Sagebrush type, elevation, precipitation regimens, vegetative resil-

536 iency (recovery time/period), and other environmental factors must

537 be considered when planning sagebrush treatments (Davies et al.,

538 2011). The range management strategy employed at DLL is likely not

539 suitable in areas where grasslands predominate (e.g., much of the east-

540 ern fringe of sage-grouse habitat) because big sagebrush cover is gener-

541 ally < 20% and not the primary vegetative type. If sagebrush treatments

542 are planned, we recommend use of information on sage-grouse

543 seasonal-use patterns for specific populations whenever possible to

544 help in delineation of treatments in large, intact, mid- or high-

545 elevation sagebrush communities (Dahlgren et al., 2006). To maintain

546 sage-grouse populations, the average annual treatment rate should

547 not exceed the sagebrush recovery rate. Furthermore, treatment pat-

548 terns should be highly mosaic creating as much edge as possible. We

549 recommend treatment widths of 120 m or less to maximize benefits

550 to sage-grouse and suggest chemical treatment occur at low active in-

551 gredient rates where small isolated treatment patches can be created

552 (Dahlgren et al., 2006). Prescribed fire, most appropriate in high eleva-

553 tion systems, can create mosaics favorable to sage-grouse use if con-

554 ducted under conditions resulting in low-intensity fire (Thacker,

555 201 0). We also encourage using grazing practices that provide adequate

556 growing-season rest. Benefits to herbaceous cover from treatments may

557 not persist if pastures do not receive periodic growing-season rest

558 (Aoude, 2002; Davies et al., 2011). We strongly recommend further re-

559 search be conducted to fill knowledge gaps hypothesized herein.


561 We thank the late J. Clark for investigating sage-grouse use of the

562 Lawson aerator treatments on DLL. We also thank B. Hopkin, S. Kearl,

563 A. Aoude, T. Cornia, and G. Simonds, who assisted with data collection

564 and developing treatments and grazing practices. We thank our associ-

565 ate editor and reviewers D. Johnson and one anonymous for their efforts

566 to improve this manuscript.

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