Impact of the human footprint on anthropogenic mortality of North American reptiles

Human activities frequently result in reptile mortality, but how direct anthropogenic mortality compares to natural morality has not been thoroughly investigated. There has also been a limited examination of how anthropogenic reptile mortality changes as a function of the human footprint. We conducted a synthesis of cause-specific North American reptile mortality studies based on telemetry, documenting 550 mortalities of known cause among 2461 monitored individuals in 57 studies. Overall 78% of mortality was the result of direct natural causes, whereas 22% was directly caused by humans. The single largest source of mortality was predation, accounting for 62% of mortality overall. Anthropogenic mortality did not increase with the human footprint or with species body mass, though predation mortality increased with decreasing human footprint. The relatively low amount of anthropogenic mortality compared to other taxa suggests that reptiles may be more impacted by indirect than direct anthropogenic mortality. As a result, mitigating these indirect impacts, which include habitat loss and introduction of invasive species, is essential for conservation of North American reptiles.