Endangered Butterflies as a Model System for Managing Source Sink Dynamics on Department of Defense Lands
[Technical Report, Final Report]
TUFTS UNIV BOSTON MAInstitute for Wildlife StudiesMICHIGAN STATE UNIV HICKORY CORNERSDUKE UNIV DURHAM NCWASHINGTON STATE UNIV VANCOUVER
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Background and Objective Background Department of Defense DoD lands provide the best available habitat for numerous threatened, endangered and at-risk species TER-S, and many of these species are currently managed on military lands by controlled disturbances e.g. fires or by de novo restoration of habitat. However, these management strategies run the risk of converting sources where births exceed deaths into sinks where deaths exceed births or of creating ecological traps - low-quality but attractive restored habitat that bleeds animals from nearby sources, threatening metapopulation viability. In addition, disturbance during and successional changes in habitat quality following management or restoration may lead local habitat patches to cycle from sink to source status and back.Objective Through a combination of field studies and state-of-the-art quantitative models, we used three species of endangered butterflies as a model system to rigorously investigate the source-sink dynamics of species being managed on military lands. Butterflies have numerous advantages as models for source-sink dynamics, including rapid generation times and relatively limited dispersal, but they are subject to the same processes that determine source-sink dynamics of longer-lived, more vagile taxa.1.2 Technical Approach For two of our focal species, we used previous restorations and ongoing management to study temporal source-sink dynamics. For the third, initiated new restoration, allowing us to examine management effects in a controlled experiment. We measured demography and movement at all phases of the disturbance cycle following management or restoration. We used these data to parameterize detailed spatially explicit individual-based simulation models SEIBMs linked to real landscapes with dynamic changes in habitat quality due to management. We also validated our general approach by comparing patterns in our focal species to general, cross-taxa, patterns.