An Assessment of Prescribed Grazing for Lesser Prairie-Chicken Habitat on Beef Herd Health and Productivity

Lesser prairie-chickens (Tympanuchus pallidicintus; hereafter LEPC) have experienced severe widespread range reductions and extreme population declines, both estimated at ~ 97 % below historical levels. This is attributed to direct habitat loss via conversions from native prairie to row crop agriculture, wind energy, and oil/gas developments, decreased carry capacity in existing habitats from continuous livestock grazing, vegetation community change from overuse of herbicides, and alterations in wildfire frequency, intensity, and size that historically acted as natural ecological and plant community drivers. In November 2020, the United States Fish and Wildlife Service (USFWS) listed the Southern Distinct Population Segment (DPS) of LEPC as endangered, which includes populations within the Sand Shinnery Oak Prairie Ecoregion (SSOP). An Area of Critical Environmental Concern (ACEC) managed by the Bureau of Land Management (BLM) exists in eastern Chaves County, New Mexico, where management prioritizes LEPC habitat conservation and management while also providing public use opportunity, like livestock grazing, under a multi-use mandate. Although continuous grazing systems have been linked as a main factor contributing to LEPC declines, livestock production under rotational grazing systems on native rangelands may be linked to maintaining portions of remaining LEPC habitat, and moderate grazing regimes have been shown to be beneficial in creating a mosaic of habitat types required for the annual lifecycles of LEPC. Grazing is a prominent socio-economic driver in the region, therefore incorporating beef production into habitat management for LEPC within the SSOP may be beneficial. The goal of this research is to quantify the use of grazing in the context of the BLM’s prescribed grazing goals and LEPC habitat conservation within the SSOP. My specific objectives included quantifying standing herbaceous biomass (SHB) response to grazing treatments and in relation to water source locations, estimating species diversity response to grazing treatments, estimating plant community composition response to grazing treatments and in relation to water source locations, estimating available herbaceous biomass nutrient composition, quantifying overall beef herd health using fecal samples, supplemental feed rates, body condition scores, pregnancy, calving, and mortality rates, and the average age of first calving, and estimating cattle habitat selection at various spatial scales. Prescribed grazing treatments were performed from 5 May 2020 - 7 December 2020 within two treatment units, Old Savory and Crowley, located within the southern and eastern portion of the ACEC, respectively. Standing herbaceous biomass reduction was estimated at 54 % in Old Savory and 58 % in Crowley, below the BLM’s prescribed goal of 70 % removal. There was no significant difference in SHB between immediate post-grazing treatment and one-year post-grazing treatment temporal survey windows (P = 0.71); a continued decrease in SHB from 307 kg/ha immediately post-grazing treatment to 262 kg/ha one-year post-grazing treatment was detected. Species diversity increased from pre-grazing to one-year post grazing treatment temporal survey windows (0.65 to 0.81). MANOVA results detected a significant difference in plant community composition between pre-grazing treatment and one-year post-grazing treatment temporal survey windows (Pillai’s Trace = 0.38, F5,84 = 10.50, P ≤ 0.0001), and an interaction effect was detected among grazing treatment temporal survey windows and water buffer zones (Pillai’s Trace = 0.15, F5,84 = 3.11, P = 0.012). During the pre-grazing treatment temporal survey window, treatment units were composed of 44 % bare ground/litter overall (40 % bare ground/litter cover within water source buffer zones and 45 % beyond water source buffer zones), and 35 % shrub cover overall (43 % shrub cover within water source buffer zones and 33 % beyond water source buffer zones). One-year post-grazing treatments, bare ground/litter composition within treatment units increased to 56 % overall (P = 0.0005; 64 % within water source buffer zones and 47 % beyond water source buffer zones), and shrub composition decreased to 18 % overall (P ≤ 0.0001; 17 % within water source buffer zones and 8 % beyond water source buffer zones). Herbaceous biomass nutrient composition differed between the two treatment units, Old Savory and Crowley, (Pillai’s Trace = 0.19, F6,210 = 8.44, P ≤ 0.0001) and among grazing treatment survey windows of pre-, during, immediately post-, and one-year post-grazing treatments (Pillai’s Trace = 1.02, F18,636 = 18.14, P ≤ 0.0001). Herbaceous nutrient composition overall averaged 5.77 % crude protein (CP), 33.80 % total digestible nutrients (TDN), 0.33 % calcium (Ca), and 0.02 % phosphorus (P), with digestible organic matter to crude protein (DOM: CP) ratios averaging 6.43, and Ca: P averaging 7.14. Fecal nutrient deposition levels of calcium (P ≤ 0.0001) and phosphorus (P = 0.01) differed between treatment units, but CP (P = 0.49), TDN (P = 0.87), DOM: CP (P = 0.81), Ca: P (P = 0.43) did not. Fecal nutrient deposition overall averaged 8.33 % CP, 42.7 % TDN, 1.26 % Ca, 0.15 % P, 5.2 DOM: CP, and 9.55 Ca: P. Supplemental feed rates were ~ 28 % protein, ~ 6 % fat, and most likely improved nutrient intake. During grazing treatments, the cattle herd exhibited overall reproductively efficient metrics with an average body condition score of 5, average age of first calving at ~ 2 years, calving intervals of ~ 365 days, ~ 94 % conception rate, ~ 92 % calving rate, and < 1 % death rate. Overall, mean cow home range size was 1026 ha (± 758 SE) and mean core area size was 132 ha (± 100 SE). In Old Savory, mean home range size was 652 ha (± 310 SE), and mean core area size was 83 ha (± 39 SE). In Crowley, mean home range size was 1442 ha (± 401 SE), and mean core area size was 189 ha (± 51 SE). Results from ANOVA indicated no significant differences in home range size among individuals (F4,2 = 6.16, P = 0.14) or between treatment units (F1,2 = 2.43, P = 0.25). Similarly, there was no significant difference detected in core area sizes among individuals (F4,2 = 6.46, P = 0.13) or between treatment units (F1,2 = 2.67, P = 0.24). At the 2nd Order of habitat selection, cows selected for one water source and land cover type, avoided the other two water sources, and neither selected nor avoided sand dunes within Old Savory treatment unit, and within Crowley treatment unit, cows selected for one water source and land cover type and avoided the two other water sources and sand dunes. At the 3rd Order, cows selected for one water source, avoided the other two water sources, and neither selected nor avoided land cover types or sand dunes within Old Savory, and within Crowley treatment unit, cows selected for land cover types, avoided two water sources, and neither selected nor avoided one water source or sand dunes. At the 4th Order of selection, individuals varied in what land cover types they selected for. In Old Savory treatment unit, all cows used Apacherian-Chihuahuan Mesquite Upland Scrub more than expected, and either showed no difference in expected versus observed locations or no observed points within North American Warm Desert Active and Stabilized Dune, Chihuahuan Stabilized Coppice Dune and Sand Flat Scrub, and Inter-Mountain Basins Semi-Desert Shrub Steppe land cover types. In Crowley treatment unit, all cows used Western Great Plains Shortgrass Prairie more than expected, and all cows showed no observed used points or no difference in observed versus expected use within North American Warm Desert Active and Stabilized Dune, North American Warm Desert Wash, and Chihuahuan Cresosotebush, Mixed Desert and Thorn Scrub land cover types. Our results elucidate the increased importance of carefully considering potential or on-going drought conditions that managers need to take when considering the use of grazing as a management tool in the SSOP, especially in relation to lesser prairie-chicken management. When using grazing to manage LEPC habitat in the SSOP, land managers and cattle producers should implement a ≤ 50 % herbaceous biomass reduction cutoff threshold to reduce the potential of compounded affects from grazing and extreme, prolonged, and unpredictable drought conditions, which may be further exasperated by climate change affects. Cattle producers also need to prepare for variations in annual and seasonal precipitation patterns, and understand how it affects the quality and quantity of forage so that they may provide supplemental feed accordingly in order to maintain reproductively efficient cow-calf operations. Considering the impact of water sources, managers can use water to lure cattle to different areas, however the size and terrain of the pasture, as well as seasonal precipitation patterns, may influence how well multiple water sources can distribute grazing patterns. Each chapter is formatted as an independent manuscript, and meant to facilitate future publication of results. Chapters contain redundancies in introduction, study area, and methods because they are meant to be complete, stand-alone documents. These chapters are formatted to meet the guidelines of the Journal of Wildlife Management. All methods were approved under the Texas Tech University Animal Care and Use Protocol # 19051-06.