For many threatened and endangered species, the importance of human‐caused mortality relative to other sources has not been quantified, making it difficult to assess the effectiveness of mortality‐reduction strategies. We used radio telemetry data, pooled across studies at protected sites in the US states of Illinois and Wisconsin, to estimate natural and human‐caused mortality rates for the imperiled ornate box turtle Terrapene ornata and to inform population viability analyses (PVA), comparing a baseline model without human‐caused mortality to scenarios that include it. Survival analysis of 399 turtle‐years of telemetry data collected over 12.5 years indicated that human‐caused deaths increased the annual mortality of adult ornate box turtles from 4.6% to 5.2%, a 12.5% increase. Although the anthropogenic increase appears small, our PVA suggests an increase of this magnitude would be sufficient to trigger declines in otherwise stable populations and make small populations (< ca 30 adults) vulnerable to extinction. PVA scenarios in which human‐caused deaths also increase juvenile ornate box turtle mortality rates result in more rapid population declines and make even moderately‐sized populations (40–70 adults) vulnerable to extinction. Considering our data come from populations in protected areas, these estimates may underestimate human‐caused mortality of ornate box turtles in unprotected landscapes. Ornate box turtles would benefit from measures to reduce human‐caused mortality, including modified habitat management schedules to prevent equipment strikes, barrier and passage systems at road‐kill hotspots to minimize vehicle strikes, and land acquisition or conservation agreements with neighboring landowners to reduce equipment strikes on adjacent agricultural lands.
King et al. (Thu,) studied this question.