Applying circuit theory and landscape linkage maps to reintroduction planning for California Condors

Abstract

Conservation practitioners are increasingly looking to species translocations as a tool to recover imperiled taxa. Quantitative predictions of where animals are likely to move when released into new areas would allow managers to better address the social, institutional, and ecological dimensions of conservation translocations. Using >5 million California condor (Gymnogyps californianus) occurrence locations from 75 individuals, we developed and tested circuit-based models to predict condor movement away from release sites. We found that circuit-based models of electrical current were well calibrated to the distribution of condor movement data in southern and central California (continuous Boyce Index = 0.86 and 0.98, respectively). Model calibration was improved in southern California when additional nodes were added to the circuit to account for nesting and feeding areas, where condor movement densities were higher (continuous Boyce Index = 0.95). Circuit-based projections of electrical current around a proposed release site in northern California comported with the condor’s historical distribution and revealed that, initially, condor movements would likely be most concentrated in northwestern California and southwest Oregon. Landscape linkage maps, which incorporate information on landscape resistance, complement circuit-based models and aid in the identification of specific avenues for population connectivity or areas where movement between populations may be constrained. We found landscape linkages in the Coast Range and the Sierra Nevada provided the most connectivity to a proposed reintroduction site in northern California. Our methods are applicable to conservation translocations for other species and are flexible, allowing researchers to develop multiple competing hypotheses when there are uncertainties about landscape or social attractants, or uncertainties in the landscape conductance surface.

Evaluation of landscape connectivity between protected areas using pinch points

“…The methods used in determining landscape connectivity corridors are least-cost-path (LCP) and Euclidean distance (ED) (McRae and Kavanagh, 2011). Using circuit theory (Cushman and Landguth, 2010;Cushman et al, 2006;D'Elia et al, 2020;Dyer et al, 2010;Hanks and Hooten, 2013;Lookingbill et al, 2010;McRae, 2006;McRae and Beier, 2007;McRae et al, 2008;Owen-Smith et al, 2010;Rayfield et al, 2011;Saura and Rubio, 2010;Urban et al, 2009) the severity of the connection was measured to keep the overall network between the corridors connected. In this study, Circuitscape v4.0.5 programme was used for the easy application of circuit theory (McRae et al, 2014).…”

“…When the studies conducted using graph theory and circuit theory methods, which are the most up-to-date methods for determining connectivity corridors in the landscape, are examined (D'Elia et al, 2020;Dickson et al, 2019;McRae, 2006;McRae and Beier, 2007;McRae et al, 2008;McRae and Kavanagh, 2011), it is seen that a target species is determined and regional corridor connections are created based on landscape resistance maps for this species. The regional landscape connectivity corridor study, which was carried out by preparing a landscape resistance map of a specific species in our country, was carried out by Özcan and Aytaş (2020) in the example of Cankiri, but no landscape resistance maps for a specific species were produced for other provinces.…”

Condors in space: an individual-based population model for California condor reintroduction planning

“…In addition to captive breeding operations spread across multiple zoos, ongoing CACO releases are occurring in Mexico and across six US. release sites, with an additional planned release site in Redwood National Park (D'Elia and Haig 2013;D'Elia et al 2019;NPS et al 2021). In the wild, the locations of virtually all CACOs are tracked via some form of telemetry, and many individuals are outfitted with GPS-Global System for Mobile Communications (GSM) transmitters where location, altitude, and accuracy information are recorded at 2-30 min intervals.…”

Yaban Hayatı Ekolojisini Korumak Amacıyla Merkezlik Metriklerinin Kullanılması ve Habitat Bağlantılılık Analizi

“…Current flow centrality is a measure of the importance of a connection keeping the public network connected. This is circuit theory (Cushman & Landguth, 2010;Cushman et al, 2006;D'Elia et al, 2020;Dyer et al, 2010;Hanks & Hooten, 2013;Lookingbill et al, 2010;McRae, 2006;McRae & Beier, 2007;McRae et al, 2008;Owen-Smith et al, 2010;Rayfield et al, 2011;Saura & Rubio, 2010;Urban et al, 2009) In this study, the Circuitscape v4.0.5 software was used for easy application of circuit theory.…”

“…In this study, a connectivity analysis was conducted using graph theory, which describes the relationship between movements of species in the landscape and its habitats and provides complementary information for both corridor design and regional conservation planning (D'Elia et al, 2020;McRae, 2012;McRae et al, 2008;McRae & Kavanagh, 2011). In this theory, a graph is a set of nodes where node pairs can be connected by edges representing functional connections between nodes (Urban et al, 2009).…”