Case Study: Ecological corridors in ecological networks
This case study is part of the IUCN Guidelines for conserving connectivity through ecological networks and corridors illustrating initiatives around the world that are working toward maintaining, enhancing, and restoring ecological connectivity. See all case studies here.
Conserving long-distance migration: The Red Desert to Hoback Mule Deer Corridor, Wyoming, USA
By Matthew J. Kauffman, Wyoming Cooperative Fish and Wildlife Research Unit; Holly Copeland, Wyoming Cooperative Fish and Wildlife Research Unit; and Hall Sawyer, Western EcoSystems Technology, Inc.
Key lesson
This work demonstrates how scientific studies documented migratory corridors for wildlife, resulting in the purchase of private lands that otherwise would have been developed.
Context and challenge
Effective protection of landscapes for migratory species is recognised as a global conservation challenge in the face of ever-increasing anthropogenic land-use changes. Ungulates that migrate long distances must move across a variety of jurisdictional boundaries, altered or degraded habitats, and human obstacles such as roads, fences, housing and energy development. Globally, long-distance terrestrial migrants continue to decline as a result of these challenges, and ungulates in the American West are no exception. Mule deer (Odocoileus hemionus) are an iconic migratory species of the western US, and Wyoming has some of the longest, most intact mule deer migrations in the lower 48 states. In western Wyoming, the Upper Green River Basin is a region known to contain some of the largest mule deer populations in North America. Dozens of long-distance migration routes traveled by mule deer, elk (Cervus canadensis) and pronghorn (Antilocapra americana) have now been mapped across Wyoming’s mountains and plains. As anthropogenic influences increase and migratory ungulates continue to decline worldwide, a focus on landscape connectivity is needed to broaden conservation efforts beyond winter and summer ranges to include migration routes as critical habitat.
Figure 1. The Red Desert to Hoback mule deer migration corridor spans 240 km in southwest Wyoming, USA, crossing a multiple-use landscape. The top ten potential obstacles to the continuity of the corridor are noted. Map from Wild Migrations: Atlas of Wyoming’s Ungulates, Oregon State University Press. © 2018 University of Wyoming and University of Oregon. Image courtesy of Wyoming Migration Initiative (migrationinitiative.org).
Approach
Detailed mapping of migration routes has emerged as a first step towards identifying threats and implementing long-term conservation, aided by new data on ungulate movements from global positioning system (GPS) telemetry studies. The new maps allow assessments of land-use patterns and threats along the routes, which can directly inform conservation action.
Examples of ecological corridors
In 2014, scientists discovered a 240-km-long mule deer migration route, stretching from the desert basins in southwest Wyoming to surrounding mountain ranges. It is known as the Red Desert to Hoback corridor (Figure 1). An estimated 1,000 mule deer travel a one-way distance of 240 km from the Red Desert to the Hoback Basin and surrounding mountain ranges, where they merge with 4,000 to 5,000 other deer that winter in the foothills of the Wind River Range. They all then travel a narrow corridor along the base of the mountains for 96 km before crossing the upper Green River Basin.
Researchers mapped the ecological corridor in detail and then published an assessment analysing land-use patterns and threats for each section (Sawyer et al., 2014). This assessment identified the top ten threats along the length of the corridor and provided conservation organisations with information needed to direct scarce funds to sites where they are most needed, such as specific bottlenecks, road crossings or unprotected segments of private land. At the top of the threats list was the Fremont Lake ‘bottleneck’, a 400-m-wide constriction created by the lake and the expanding town of Pinedale, where 4,000 to 5,000 deer squeezed through twice a year. The deer were required to either swim (or, when frozen, walk across) the lake, or ford its outlet, which put them on the wrong side of a 2.5-m-high woven wire fence.
Results
The Fremont Lake bottleneck consisted largely of a 145-ha parcel of private lands that was slated for subdivision and conversion to lakeside cottages which, if developed, would have blocked deer migration. Guided by information within the assessment, The Conservation Fund, a national non- profit conservation organisation, identified and purchased the parcel. The land was given to the Wyoming Game and Fish Department, which subsequently protected it through designation as the Luke Lynch Wildlife Habitat Management Area, thereby maintaining in perpetuity the connectivity of the ecological corridor at this key pinch point (Figure 2).
Figure 2. Location of the Fremont Lake bottleneck, now conserved as the Luke Lynch Wildlife Habitat Management Area. Map from Wild Migrations: Atlas of Wyoming’s Ungulates, Oregon State University Press. © 2018 University of Wyoming and University of Oregon. Image courtesy of Wyoming Migration Initiative (migrationinitiative.org)
References
Sawyer, H., Hayes, M., Rudd, B., and Kauffman, M. (2014). The Red Desert to Hoback Mule Deer Migration – A Migration Assessment. Laramie: University of Wyoming.https://migrationinitiative.org/content/red-desert-hoback-migration- assessment (Accessed: 20 February 2020).