Section VI: Decision Support Tools (2B of 11)

Appendix B: Descriptions of Hopper’s Ranch Models

By Melvin Skold, Rob Davis, and James S. Berry

List of Existing Model Names and Descriptions
Model Names in Hopper

Recent definitions of economic thresholds (ET’s) and economic injury levels (EIL’s) by economists and entomologists have shown that these concepts are dynamic in nature and must be evaluated for each site under consideration for treatment. Key economic parameters to evaluate include ranch type, rangeland productivity, cost of alternative sources of forage for livestock, and nontreatment options available to the rancher. Biological parameters for evaluating an ET or EIL depend on density of grasshopper species, life stage at time of treatment, mix of economic and noneconomic species, and VI.2–30.presence of beneficial insects. Other factors of importance are proximity to waterways and presence of rare or endangered species.

The Grasshopper Integrated Pest Management (GHIPM) Project has provided economic models for eight important range ecosystems in the Western States. Within these range ecosystems, typical ranches are defined which characterize the predominant ranching practices of the area. Between range types, ranches vary considerably with respect to amounts, types, and costs of forages used. Livestock production and management strategies also differ between range types. An evaluation of these typical ranches through Hopper shows how the economic justification for treating rangeland grasshoppers changes between locations and ranching systems.

List of Existing Model Names and Descriptions (Range Types).—The range ecosystems included in Hopper are those identified by APHIS, PPQ personnel as having recurring grasshopper infestations. The selected areas characterize seven range ecosystems and eight typical ranch types. For one area, the Northern Highland Prairie, both beef cow–calf ranches and beef–sheep ranches are common; consequently, two typical ranches were defined to analyze the impacts from grasshoppers infestations more fully.

Generic.—The generic model can be used for any area in the United States or Canada. This model does not use the detailed economic model nor forage production model. Therefore, you will need to use the default value of a replacement AUM ($11.00) or enter a different value (calculated in the other, more detailed models). An AUM (animal unit month) is defined as the amount of forage a cow and calf consume in 1 month (about 800 lb of air-dry forage).

Northern Great Plains.—The rangeland is located within the Northern Great Plains range type, and about 2.2 to 3.3 acres are required to produce 1 AUM. The grazing season is approximately 8 months long; cattle are placed on grazing lands about May 1 and continue to graze until December 31. About half the forage needed on the ranch comes from public land, a quarter from private grazing lands, and the remaining quarter from hay and crop residue.

Located in western North Dakota on the Little Missouri National Grassland, the typical ranch in this model can be used for all of the Little Missouri National Grassland and extrapolated to eastern Montana with changes to rangeland productivity, herd size, leases, weather-generation models, etc. The rangeland is characterized as a northern mixed prairie and is predominantly cool-season grasses, forbs, and shrubs.

Northern Highland Prairie.—About 4 acres are required to produce 1 AUM of forage on this range type. Because elevations in the northern Highland Prairie are somewhat higher than in the northern Great Plains, the grazing season is shorter. Grazing begins about May 1 and continues through early September.

There are two typical ranches defined for this region. The first is a cow–calf ranch that is supplied 23 percent of forage needs by public grazing lands. Hay stocks are produced for winter feeding needs, and private rangeland supplies the balance of forage AUM’s (56 percent) for the livestock. A calf crop of 85 percent is achieved, with the calving season starting in March.

The second ranch has both a cow–calf enterprise and a range sheep enterprise. This ranch receives 41 percent of forage AUM’s from public rangeland, no hay is produced, and private grazing lands supply the balance of forage needs. Lambing begins about May 15; a lambing crop of 122 percent is the norm. The calving season for this ranch starts in March, with a calving percentage of 80 percent.

Located in Johnson County, WY, this typical operation is a large cow–calf ranch; these model parameters can be used for ranches throughout eastern Wyoming, south-central Montana, and possibly northeastern Colorado (assuming the weather, rangeland productivity, herd size, leases, etc., are changed when data are input). This rangeland, is characterized as Northern Mixed Prairie, is predominantly cool-season grasses, forbs, and shrubs.

Central Great Plains.—This region is characterized by highly productive rangelands of predominantly warm-season grass species. The typical ranch of about 2,200 acres of grazing land is a cow—calf operation with a 6- month summer grazing season. Grazing land can support approximately 1 AUM/acre. Hay is fed in the winter to supplement crop-residue grazing and supplies 14 percent of the total AUM’s of forage. Public grazing land is available to only a portion of these ranches. Livestock graze on rangeland owned by the rancher and rangeland leased from other landowners.

This typical ranch is located in western Nebraska, and its parameters can be extrapolated to ranches located in southeastern Wyoming, north-central Colorado, and the Nebraska panhandle.

Southern Great Plains.—The typical southern Great Plains ranch has both cow–calf and sheep enterprises. There is an 8-month grazing season, with 34 percent of the total AUM’s of forage coming from public rangelands. The typical ranch includes about 15,600 acres. Privately owned rangelands supply 26 percent of total needed AUM’s, and raised hay stocks supply the remaining 40 percent of forage needs.

Almost 53 acres are required to produce 1 AUM of forage. The grass and forb species in this area are predominantly warm season, and most vegetative growth occurs in July, when the monsoon rains come.

The typical ranch in this model is located in eastern New Mexico.

Mexican Highland Scrub.—The typical ranch for this region is a cow–calf operation. Total forage comes from public grazing land (34 percent), from privately owned grazing land (13 percent), private rangeland (10 percent), and from raised hay stocks (43 percent). The elevation is low, and summers are very hot. Most vegetative growth occurs in late summer, when monsoon rains occur. Almost all plant species present are warm season. The grazing season is 9 months long, and hay is fed to supplement the grazing.

Located in southeastern Arizona, this typical operation is a smaller cow–calf ranch operating in the “hot desert” environment. About 64 acres are required to produce 1 AUM of forage. Results from the Mexican Highland Scrub typical ranch profile can be extrapolated to ranches in southwestern New Mexico.

Gila Mountains.—Grazing needs are satisfied for this cow–calf ranch with a year-round grazing season. About 6.5 acres are required to produce 1 AUM of forage. There are no hay stocks produced. The split between public and private grazing lands is about 50–50. The grass species in this region have high percentages of both warm- and cool-season grasses. Most vegetative growth occurs in late July with the onset of summer monsoon rains.

Located in central Arizona in the Chino Valley near Prescott, this typical ranch is a very large cow–calf operation in a transition zone next to a hot desert zone.

Eastern Intermountain Basin.—The typical ranch for the southeastern Great Basin region is a cow–calf ranch that receives about 7 percent of its total forage supplies from public rangelands, 32 percent from leased private rangelands, 41 percent from owned rangeland, and 20 percent from hay produced on the ranch. About 12 acres are required to produce 1 AUM of forage. The grazing season is year-round, with hay stocks supplementing the rangeland forage supplies during the winter. Public rangelands are used during the spring months.

This typical ranch is located in western Utah, and results from this ranch profile can be extrapolated to ranches in southern Idaho and eastern Nevada.

Northern Intermountain Basin.—A cow–calf ranch was defined for this region. The grazing season starts in mid-April and runs until early November. About 9 to 10 acres are required to produce 1 AUM of forage. Public rangelands supply 44 percent of the total forage needs of the cow herd. Raised hay stocks supply 22 percent of the forage and are used in the winter months. Privately owned rangelands and leased private rangelands supply the remainder of forage needs (34 percent).

Located in Harney County, OR, this typical ranch is a cow–calf operation in the Great Basin Desert, which is dominated by big sagebrush. Results from this ranch profile can be extrapolated to operations in southern Idaho and northern Nevada.

Back to Top of Page

Model Names in Hopper

(CC = cow–calf, CS = cow–sheep enterprise)

NGP = Northern Great Plains (western North Dakota)

NHP = Northern Highland Prairie (north-central Wyoming)

CGP = Central Great Plains (southeastern Wyoming, north-central Colorado, Nebraska panhandle)

SGP = Southern Great Plains (eastern New Mexico)

MHS = Mexican Highland Scrub (southeastern Arizona, southwestern New Mexico)

GM = Gila Mountain (central Arizona)

EIB = Eastern Intermountain Basin (western Utah, southern Idaho, eastern Nevada)

NIB = Northern Intermountain Basin (eastern Oregon, western Idaho)

Generic = Any area in the United States or Canada. This model does not use the detailed economic model nor forage model. Therefore, you will need to enter the value of replacement AUM’s (calculated in the other, more detailed models). These files will have the extension *.gn3 (e.g., generic.gn3).

Back to Top of Page

Back to Hopper 4.0 User’s Guide