Jeffrey C. Mosley

Elk, Mule Deer, and Cattle Foraging Relationships on Foothill and Mountain Rangeland

Abstract Foraging niche overlap among Rocky Mountain elk (Cervus elaphus nelsoni), Rocky Mountain mule deer (Odocoileus hemionus hemionus), and cattle (Bos taurus) was studied for 2 years on 37 000 ha of nonforested foothill and mountain habitat in northwestern Wyoming. Microhistological analysis was used to quantify botanical composition of ungulate diets from monthly fecal collections. Feeding habitat use was determined through monthly surveys from fixed-wing aircraft to record nonsolitary animals in nonforested habitat. Kulcyznskis similarity index was used to calculate dietary and feeding habitat overlap among the 3 ungulates, and these 2 indices were multiplied together to estimate foraging niche overlap. In all seasons, elk and cattle consumed grass-dominated diets (mean = 61% and 81%, respectively), although elk diets were more diverse. Mule deer consumed more forbs and shrubs than either elk or cattle (P < 0.10). Foraging niche overlap was high (45%) between mule deer and elk in spring. Cattle in summer and fall had ≥60% foraging niche overlap with elk in spring, indicating that, in spring, elk foraged in many of the same places (largely sagebrush grassland) and ate diets similar in botanical composition to what cattle did during summer and fall (principally Festuca idahoensis, Pseudoroegneria spicata, and Achnatherum spp.). Foraging niche overlap also was high (41%–51%) between elk in winter and cattle in summer and fall. Therefore, if competitive or complementary relationships existed between elk and cattle, these interactions most likely occurred on sagebrush grasslands where cattle use in summer–fall was followed by elk use in winter–spring. We recommend that resource managers focus their forage utilization and range trend monitoring in foothill sagebrush grasslands.

Defoliation timing effects on spotted knapweed seed production and viability.

Abstract Spotted knapweed (Centaurea stoebe L.), a perennial invasive forb that reproduces largely by seed, often forms new flowers after prescribed sheep grazing or mowing is applied during the bolting or flowering stage. It is unknown if these new flowers produce viable seeds by the end of the growing season. The purpose of this 2-yr study was to determine the appropriate timing (or timings) or combination (or combinations) of timings of defoliation on spotted knapweed to reduce its viable seed production. Spotted knapweed plants on foothill rangeland in west-central Montana were hand-clipped at seven different timings and frequencies of defoliation: June (bolting stage); July (late-bud–early flowering stage); August (full-flowering stage); June + July; June + August; July + August; or June + July + August. Unclipped plants were controls. Plants clipped in the bolting stage were defoliated at 35–40% relative utilization. Plants clipped at all other timings had 100% of their buds and flowers removed, plus 3 cm of each bud or flower stem. Plant response was evaluated from mid-August through September, whenever the seed heads of each treatments plants reached maturity but while their seed-head bracts remained tightly closed. Clipping at any timing or combination of timings reduced the number of buds and flower heads per plant (P < 0.01), number of seeds per plant (P < 0.01), percentage of viability of seeds (P < 0.01), and number of viable seeds per plant (P < 0.01) compared with no clipping. Clipping during the bolting stage reduced the number of viable seeds by nearly 90% compared with no clipping. Clipping during the late-bud–early-flower or full-flower stage reduced the number of viable seeds by nearly 100% compared with no clipping. Spotted knapweed defoliation via prescribed sheep grazing or mowing in summer should suppress viable seed production of spotted knapweed.

Prescribed Sheep Grazing to Suppress Spotted Knapweed on Foothill Rangeland

Abstract Spotted knapweed (Centaurea biebersteinii DC.) is a perennial, invasive forb that infests millions of hectares of private and public rangelands in western North America. Previous research indicates that domestic sheep (Ovis aries) readily graze spotted knapweed, but landscape-scale prescriptive grazing of spotted knapweed has not been studied. We quantified the diets and forage utilization of a ewe–lamb band (about 800 ewes and 1 120 lambs) that prescriptively grazed spotted knapweed–infested foothill rangeland in western Montana in the summers of 2003 and 2004. In mid-June or mid-July, sheep grazed light and moderate infestations of spotted knapweed (13% and 36% of vegetative composition, respectively). Nutritive quality of sheep diets was similar to sheep grazing uninfested rangeland, and sheep exhibited few forage preferences or avoidances. Sheep diets averaged 64% spotted knapweed in the moderate infestation and 26% in the light infestation. Sheep in the light infestation ate fewer graminoids in June than July (17% vs. 55% of their diet, respectively; P  =  0.04), whereas sheep in the moderate infestation ate fewer graminoids in July (45% in June vs. 20% in July; P  =  0.09). In the moderate infestation, relative utilization of spotted knapweed was greater in July than June (50% vs. 35%, respectively; P  =  0.04), but averaged 46% in the light infestation. Previous research suggests that these levels of relative utilization may make herbicide application uneconomical. Relative utilization of graminoids was light in both infestations (15% in June or 31% in July). Our results indicate that sheep can prescriptively graze light or moderate spotted knapweed infestations in either June or July. Sheep consumption and relative utilization of graminoids will be less if light infestations are grazed in June rather than July. In moderate infestations, sheep will eat fewer graminoids and utilize spotted knapweed more heavily when grazed in July rather than June.

Bluebunch Wheatgrass Response to Spring Defoliation on Foothill Rangeland

Abstract Spring elk grazing may reduce forage availability for wildlife or livestock in summer and may harm forage resources on foothill rangeland. We quantified bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Love) response to spring defoliation on foothill rangeland in southwestern Montana. Two experiments were conducted simultaneously on a foothill grassland site and a foothill sagebrush steppe site. Bluebunch wheatgrass plants (n  =  800) were selected and excluded from wild and domestic ungulates. Clipping treatments were applied in either early spring (mid- to late April) or late spring (mid- to late May), and plants were clipped to 1 of 3 residual heights (3, 6, or 9 cm) for 1, 2, or 3 successive years. Unclipped plants served as controls. Plant response was measured in late June and late July on both sites. April clipping for 3 successive years did not adversely affect bluebunch wheatgrass in June or July (P > 0.05) at either site. On foothill grassland, May defoliation to 3 cm for 2 consecutive years reduced leaf height (P  =  0.04) in July. May defoliation for 3 successive years to 3 or 6 cm reduced plant yield (P < 0.05) and leaf height (P < 0.05) in June, and May defoliation for 3 successive years to 3 cm reduced leaf height (P  =  0.02) in July. On foothill sagebrush steppe, 3 successive years of May defoliation to ≤ 9-cm stubble heights decreased leaf height in June (P < 0.05). We conclude that foothill rangelands where bluebunch wheatgrass receives moderate or light defoliation (6–9-cm residual stubble heights) in mid- to late May should be limited to no more than 2 successive years of mid- to late May grazing, whereas sites that receive heavy to severe defoliation (≤ 3-cm residual stubble heights) in mid- to late May should not be grazed for 2 successive years during mid- to late May.

Spotted knapweed utilization by sequential cattle and sheep grazing.

Abstract Prescribed (or targeted) sheep grazing can effectively suppress the invasive perennial forb spotted knapweed (Centaurea stoebe L. ssp. micranthos [Gugler] Hayek). Some ranchers and other natural resource managers, however, resist using this weed management tool over concerns that sheep may consume too much of the graminoid standing crop, thereby decreasing its availability to cattle and wildlife and possibly harming graminoids with excessive defoliation. One potential approach to address these concerns is to graze spotted knapweed infestations first with cattle, immediately followed by sheep. We evaluated this sequential grazing strategy on foothill rangeland in western Montana, comparing sequential grazing at a moderate stocking rate in mid June (spotted knapweed in bolting stage) vs. mid July (spotted knapweed in late-bud/early flowering stage). Pastures (0.81 ha) were grazed with three yearling cattle for 7 d, immediately followed with 7 d of grazing by seven yearling sheep. Combined relative (i.e., utilization) of graminoids by cattle and sheep averaged 40% in June and July, safely within sustainable grazing use levels recommended for the site. Combined relative use of spotted knapweed by cattle and sheep also did not differ between June and July, averaging 62%. Previous research indicates that this degree of use is sufficient to suppress spotted knapweed. Our results indicate that prescribed sheep grazing can be applied immediately following cattle grazing in either June or July to suppress spotted knapweed without overusing desirable graminoids. Cattle and sheep will eat less graminoids and more spotted knapweed if cattle and sheep graze sequentially when spotted knapweed is in its late-bud/early flowering stage (mid July) rather than its bolting stage (mid June).

Sulfur Cinquefoil (Potentilla recta) Response to Defoliation on Foothill Rangeland

Abstract Sulfur cinquefoil is an invasive, perennial forb on rangelands of western Canada and the United States. Sulfur cinquefoil reproduces solely by seed and it is a prolific seed producer. Our 2-yr study (2006, 2007) investigated the optimal timing and intensity of defoliation to decrease aboveground productivity and seed production of sulfur cinquefoil plants on foothill rangeland in southwestern Montana. Each year, 150 sulfur cinquefoil plants within a 430-m2 enclosure were tagged for identification and randomly assigned to one of 15 clipping treatments with 10 plants per treatment. Clipping treatments were conducted at three timings: (preflower [early June], flowering [late June], and seedset [mid-July]) and all possible combinations of timings for a total of seven timing treatments clipped to two stubble heights (7.5 cm or 15 cm), comprising 14 unique treatments. The final (15th) treatment consisted of an unclipped control. Response variables collected at senescence (late July) included aboveground biomass; number of buds, flowers and fruits on each plant; and number and viability of seeds produced. Results indicated that defoliation of sulfur cinquefoil can effectively reduce its yield and seed production. All clipping treatments reduced aboveground biomass of sulfur cinquefoil compared with control plants (P ≤ 0.05), except clipping to 15 cm during preflowering in the wetter year of 2006. Clipping to either 7.5 cm or 15 cm at all times or combinations of timings reduced the number of buds, flowers, fruits, and seeds produced by sulfur cinquefoil (P ≤ 0.05). Viable seed production was reduced 99 to 100% when plants were clipped once to either 7.5 or 15 cm during flowering or seedset. Results suggest that targeted livestock grazing or mowing applied one time per season during flowering or seedset could effectively suppress the biomass production and viable seed production of sulfur cinquefoil. Nomenclature: Sulfur cinquefoil, Potentilla recta L. PTLRC Management Implications: Sulfur cinquefoil is a nonnative, perennial, invasive weed that currently infests thousands of acres of rangeland and abandoned cropland in the western United States and Canada. This plant is a concern because it produces thousands of seeds and is capable of invading undisturbed rangeland. There are no approved biological controls, and herbicide treatment is expensive; therefore, we evaluated the potential for defoliation to reduce yield and seed production of sulfur cinquefoil. Hand-clipping treatments were applied at 14 different timing and intensity combinations to determine those most appropriate to suppress sulfur cinquefoil. Overall, clipped plants produced ∼ 80% less aboveground forage and > 90% fewer viable seeds than control plants. Clipping applied when sulfur cinquefoil plants were flowering or in early seedset had the greatest impact on forage and seed production. Plants clipped one time to either a 15- or 7.5-cm stubble height at flower or later were unable to produce any viable seed during the current growing season. Multiple defoliations were not necessary to decrease seed production if the first defoliation occurred at the flower stage or later. The intensity of the defoliation did not matter so long as the fruits were removed from the plant. Because of the longevity and abundant seed production of the plant, areas infested with sulfur cinquefoil likely have a large soil seed bank, and multiple years of uniform defoliation will be necessary before any noticeable change in the existing population can be determined. However, defoliation holds potential to reduce the competitive ability of sulfur cinquefoil as well as the ability of the plant to add to the seed bank. Targeted livestock grazing or mowing are two potential ways to defoliate sulfur cinquefoil at the appropriate timing and intensity to suppress the plant on rangeland or pasture.

Elk Foraging Site Selection on Foothill and Mountain Rangeland in Spring

ABSTRACT Previous research suggests facilitative grazing by cattle during the preceding summer-fall can enhance spring foraging habitat of Rocky Mountain elk (Cervus elaphus nelsoni). However, previous studies were limited to 1 year or conducted within relatively small experimental pastures. We evaluated elk foraging site selection during spring across 4 years and 59 040 ha of foothill and mountain rangeland in northwestern Wyoming and west-central Montana. Elk in spring avoided foraging in nonforested portions of cattle-grazed pastures where cattle had not grazed during the previous summer — early fall. In contrast, elk selected foraging sites where cattle had grazed lightly (11 – 30% forage use) or moderately (31 –60% forage use), and selection by elk was stronger for moderately grazed sites. Neither moderate nor light cattle grazing intensity were correlated with any other elk habitat attribute that we sampled, and both moderate and light cattle grazing intensity exerted more influence on elk foraging site selection than any other variables, including distance to security cover, distance to primitive roads, distance to improved roads, aspect, or slope. We developed and validated a resource selection model that correctly classified 80 – 89% of elk foraging observations across five study sites and 4 years. Resource managers can use our model to map predicted changes in elk grazing distribution when considering potential habitat adjustments in security cover, roads, or cattle grazing intensities and distribution. Our results indicate that resource managers can use targeted cattle grazing in summer — early fall to purposely modify elk forage conditions to 1) increase elk foraging efficiency in spring, 2) lure elk away from places needing rest or deferment from spring elk grazing, or 3) lure elk away from places where elk in spring are experiencing conflicts with humans, predators, or other wildlife.

Recovery and Viability of Sulfur Cinquefoil Seeds From the Feces of Sheep and Goats

Abstract Targeted grazing by sheep or goats is a potentially useful tool for suppressing the noxious weed sulfur cinquefoil (Potentilla recta L.). However, possible transmission of weed seeds by grazing livestock is a serious ecological concern that must be addressed in any targeted grazing prescription. We investigated the effect of sheep and goat digestion on the viability of sulfur cinquefoil seeds collected from live plants growing on a foothill rangeland site in southwestern Montana. Eight sheep and eight goats (all wethers) were each gavaged with 5 000 sulfur cinquefoil seeds. Four animals of each species received immature seeds, and four animals received mature seeds. All animals were fed ground grass hay in excess daily, and intake averaged 2.0% body weight · d−1. Total fecal collection began immediately after gavaging and continued for 7 consecutive days. Once each day, all identifiable sulfur cinquefoil seeds were recovered and counted from fecal subsamples. Seed viability before gavaging averaged 36% for immature seeds and 76% for mature seeds. Sheep and goats excreted similar numbers of viable seeds. Almost all (98%) of the viable seeds recovered from sheep and goats were excreted during Day 1 and Day 2 after gavaging. No viable seeds were recovered from either sheep or goats after Day 3. Our estimates of sulfur cinquefoil seed excretion and viability in sheep and goat feces are likely inflated compared with targeted grazing animals because gavaging with seeds bypassed mastication. Grazing livestock that consume sulfur cinquefoil seeds should be kept in a corral for at least 3 d to prevent transferring viable seeds to uninfested areas.

Impacts from winter–early spring elk grazing in foothills rough fescue grassland

Abstract. Foothills rough fescue (Festuca campestris) grasslands provide important foraging habitat for wildlife and livestock in the northwestern United States and southwestern Canada. Foothills rough fescue is sensitive to grazing during late spring —early summer but is believed to be more tolerant of grazing during winter—early spring. We evaluated vegetation and soil impacts from long-term winter—early spring grazing at 2 intensities (HG = heavy grazing, LG = light grazing). We studied a foothills rough fescue grassland in west central Montana, USA, that had been grazed almost exclusively by Rocky Mountain elk (Cervus elaphus nelsoni ) during winter—early spring for 58 years. Foothills rough fescue tolerated LG but not HG, whereas bluebunch wheatgrass (Pseudoroegneria spicata) and Idaho fescue (Festuca idahoensis) did not tolerate either LG or HG. Decreased productivity of foothills rough fescue in HG was accompanied by decreased herbaceous ground cover and increased abundance of the invasive dense clubmoss (Selaginella densa). Soil nutrient status (OM, C, N, C:N ratio) did not differ between HG and LG; however, soil bulk density was 18% greater in HG, and the Ah horizon was 20% thinner in HG. Overall, our results indicate that long-term elk grazing during winter—early spring degraded this terrestrial ecosystem, and we conclude that periodic rest from ungulate grazing during winter— early spring is necessary to sustain foothills rough fescue grasslands.

Targeted Sheep Grazing to Suppress Sulfur Cinquefoil (Potentilla recta) on Northwestern Montana Rangeland

ABSTRACT Sulfur cinquefoil (Potentilla recta L.), a perennial forb native to the eastern Mediterranean region of Eurasia, is a major noxious weed on rangelands of the northwestern United States and southwestern Canada. We assessed targeted sheep grazing to suppress sulfur cinquefoil in a 2-yr rangeland field experiment in northwestern Montana. We evaluated targeted sheep grazing with and without protein-energy supplementation (37 g crude protein [CP] sheep-1 d-1 and 0.17 kg total digestible nutrients [TDN] sheep-1 d-1) during late June (sulfur cinquefoil in early flowering stage) and mid-July (sulfur cinquefoil in late flowering—early seedset stage). Sheep readily consumed sulfur cinquefoil stems, leaves, flowers, and developing seed heads, with or without supplementation. Sulfur cinquefoil comprised the largest proportion of sheep diets during both late June and mid-July, averaging 46%, but more sulfur cinquefoil dry matter (DM) was consumed by sheep during mid-July (0.6 vs. 1.0 kg DM sheep-1 d-1 in June vs. July, respectively). Supplementation did not increase DM intake (DMI) of sulfur cinquefoil, nor did supplementation improve the nutritive quality of sheep diets. We also documented that 1) targeted sheep grazing achieved heavy utilization of sulfur cinquefoil (67%) while keeping perennial graminoid use light to moderate (18–41%); 2) targeted sheep grazing reduced viable seed production of sulfur cinquefoil by 97% in June-grazed paddocks and 95% in July-grazed paddocks; and 3) targeted sheep grazing reduced sulfur cinquefoil yield the next summer by 41% in June-grazed paddocks and 47% in July-grazed paddocks without decreasing yield or plant community composition of perennial graminoids. We conclude that supplemented or nonsupplemented targeted sheep grazing applied in either late June or mid-July can effectively suppress sulfur cinquefoil. Sheep nutrition and sulfur cinquefoil DMI will be optimized by targeted sheep grazing applied during mid-July.