Between the bay and a hard place: Diamondback terrapin nesting movements and stress levels demonstrate the effects of bulkheading upon estuarine wildlife

Background/Question/Methods

The highest rate of shoreline development of any mid-Atlantic estuary in the United States is in Barnegat Bay, New Jersey, where bulkheading has increased 30% over the past 30 years. Bulkheading could affect the behavior of diamondback terrapins (Malaclemys terrapin), a threatened, salt tolerant estuarine turtle that requires access to upland habitat for annual nesting. To quantify the impact of bulkheading on terrapin reproductive behavior, we measured movement and stress levels in terrapins relative to artificial bulkheading at two fidelic nesting sites in Barnegat Bay over two seasons. We utilized acoustic and radio telemetry to assess terrestrial and aquatic movements of reproductive female terrapins at both experimentally bulkheaded and adjacent reference beaches. We quantified terrapin stress response to artificial bulkheading via adrenocortical activity (i.e., stress), comparing corticosterone and testosterone levels between blood samples of barrier-exposed terrapins to those nesting under unmodified conditions. In addition, we exposed 15 individuals to handling stress and collected blood samples at 30 and 60 min following capture to create plasma profiles of acute corticosterone secretion.

Results/Conclusions

At one location, reproductive terrapins encountering bulkheading travelled greater distances, with more tortuous paths than females nesting at an unobstructed beach. At another location, terrapins spent more time in the water adjacent to blocked nesting beaches. There were no increases in corticosterone or testosterone due to bulkheading, indicating that barriers did not elicit a stress response in nesting terrapins. After handling, terrapin profiles of acute corticosterone increased significantly over 60 min to 8 ng/ml, however hormone secretion in terrapins encountering bulkheading did not approach these peak levels. Our results suggest that diamondback terrapins lack physiological responses to anthropogenic stressors at nesting beaches, causing them to travel further with less direct paths, and ultimately spend more time in these dangerous areas. To conserve shorelines for terrapins and other estuarine wildlife, sustainable development and accessible artificial nesting habitats must be implemented. The diamondback terrapin’s habituation to human activity should encourage wildlife managers to implement access ramps to artificial nesting habitat near bulkheading, knowing that terrapins will utilize these structures without becoming stressed. With the increasing rate of bulkheading construction in Barnegat Bay, and along most shorelines, this study acts as a novel approach to guiding management of human-wildlife conflict within America’s estuaries.