Implications of Linear Infrastructure in the Owens Valley: A Case Study on the Movement and Dispersal Patterns of the Federally-Threatened Desert Tortoise (Gopherus agassizii)
Wildlife & Ecosystems
The scope of this project would be aimed toward gathering data on Desert Tortoise populations in the southern portion of the Owens Valley in California. As the Owens Valley represents the northern extent of the desert tortoise range in California, there is little known about these northerly populations. As climate change effects are projected to shift desert tortoise range further north, there is potential for desert tortoise populations in the Owens Valley to increase. Being a Federally and State-listed species, it is critical that local and state agencies have the data needed to make well-informed planning and management decisions. In relation to transportation projects, the Olancha/Cartago 4-Lane Project must comply with permit conditions from CDFW and USFWS related to Desert tortoise. For this project Caltrans is required to install 26 miles of permanent desert tortoise exclusion fencing, along with 13 desert tortoise-specific undercrossings. As there is currently no data on desert tortoise populations in this project area, this is a unique opportunity to gather/analyze data post-construction relating to: desert tortoise movement, desert tortoise undercrossing use rates, desert tortoise distribution with respect to hard movement barriers (i.e., Los Angeles aqueduct, roads, etc.), and potentially a rough estimate of desert tortoise density in the southern portion of the Owens Valley. This project would require GPS and/or VHF devices to be attached to desert tortoise individuals throughout the southern portion of the Owens Valley. This would likely be achieved through extensive field surveys during the desert tortoise active season. GPS data could then be analyzed to determine individual home range sizes, movement patterns, and other behavioral responses related to noise, roads, and barriers. Ideally, this project would be carried out as a partnership between Caltrans Environmental staff and pertinent regulatory agencies in the area.
As it stands now, the lack of data on Desert Tortoise populations in the Owens Valley has resulted in permitting conflicts between state agencies and the expenditure of millions of taxpayer dollars towards mitigation efforts that lack scientific basis. Further, these mitigation efforts (required by state permitting agencies) are potentially detrimental to desert tortoise populations in this area. The results and data obtained from the project would provide insight to movement and distribution patterns of desert tortoise as it relates to linear infrastructure project. This information would aid the planning, design, and permitting processes of future projects in the Owens Valley.
June 2, 2020
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