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Protecting Bighorn Sheep with Repeatable GIS Analysis

Posted by Bo Wilmer on Apr 24, 2013

Protecting Bighorn SheepBighorn sheep are timeless symbols of the Wild West, but their numbers have plummeted to just 8% of their peak population. Surprisingly, a significant cause of this decline is disease transmitted from domestic sheep. To mitigate disease spread, US federal land management agencies and state wildlife managers have discouraged shared use of ranges by bighorn and domestic sheep.

In 2012, The US Forest Service Intermountain Region (R4) and the Payette National Forest (a Forest with significant shared range) developed a range modeling methodology to assess risk of contact and disease transmission. Critigen’s integration of different modeling tools into a single GIS interface marks the first time that disease risk amongst Bighorn Sheep can be assessed quickly and consistently across the federal landscape.

Bighorn Sheep Range GISThis risk assessment tool, developed as an Esri ArcGIS Desktop v 10.1 extension, allows Forest managers to determine the expected range of wild sheep based on tracking devices and statistical analysis in a scientific, repeatable and automated way and to provide a statistically valid assessment of the risk of disease transmission given various range usage scenarios or proposals. Both of these features supply them with the ability to work collaboratively with ranchers, private land owners, state wildlife managers and others with factual, scientific and visual information. The success of the tool is leading to its use by other regions and other Federal agencies where Bighorn sheep are present.

Bighorn Sheep Range GIS Analysis ToolThe workflow-based solution integrates multiple technologies, workflows and data sources into one easy-to-use interface, replacing time consuming and error-prone manual processes. The risk of disease contact model consists of two distinct analyses. The first, a Core Herd Home Range (CHHR) analysis is used to delineate areas where most animals in each herd spend most of their time. The second, a foray analysis, examines the characteristics of bighorn sheep movements, or “forays”, outside of the home range (CHHR). This foray analysis examines how frequently and at what season forays occur, as well as how far beyond the CHHR animals are likely to travel. The CHHR and foray analyses are used along with a habitat selection model to estimate the probability that a bighorn sheep will reach any of the open domestic sheep allotments in a given year. Integrating these separate workflows and tools into a single tool, built on ArcGIS 10.x with intuitive interface streamlined and standardized the analysis process to make it accessible to a wider audience of range management agencies.

Consistent with Critigen’s mission of bringing location to bear on land management challenges, this tool renders a series of complex scientific models into the ArcGIS Platform, enabling a much wider audience to run the models and understand the results. The GIS results generated by this innovative tool are facilitating a thoughtful, data-driven discussion about how to best manage wild herds of Bighorn sheep across the West.

Learn more about Critigen GIS Consulting and geospatial services and solutions for natural resources, and follow us on Twitter or Facebook to be notified when the whitepaper comes out.


Author Info

Bo Wilmer, US Forest Service GIS Solutions, Federal Civil Sales
Bo Wilmer
Federal Civil Sales

Mr. Wilmer has more than 20 years experience developing innovative geospatial solutions to assess ecosystem conditions, identify threats, and design land management strategies.