Archival data reveals human impacts on Blanding’s turtle population persistence

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Adult survival and nest success figure prominently in turtle population dynamics but human impacts on these life stages can be difficult to quantify. We integrated pooled sets of monitoring data to identify causes of mortality and traumatic injury for the imperiled Blanding’s turtle, Emydoidea blandingii . We also extracted information on Blanding’s turtle nest sites, characterizing the use of natural vs. human-modified habitats. We used survival analysis of telemetry data to quantify human impacts on adult survival and employed the resulting survival estimates in population viability analyses to test the sensitivity of extinction risk in scenarios differing in the degree of human impacts and initial adult population size. Motor vehicles, machinery, and railways accounted for the largest number of human-caused deaths and traumatic injuries. More than half of the nest locations we compiled occurred in rail rights-of-way, landscaped areas, and agricultural fields, habitats that expose nesting females, nests, and hatchlings to elevated risk of injury and death. Survival analysis of 1,541 turtle-years of telemetry data indicated that human-caused deaths have raised annual adult mortality by a factor of 1.21, from 4.3 % to 5.2 %, over mortality from other causes. This increase was sufficient to trigger population decline and made populations smaller than about 30 adults vulnerable to extinction in as little as 25 yr. In scenarios in which juveniles also suffered human-caused mortality, even larger populations were vulnerable to extinction. Increased preserve size, installation of road and rail barrier and passage systems, and habitat enhancements aimed at reducing the use of ‘at-risk’ nest sites would improve Blanding’s turtle population persistence.