Diamondback Terrapins (Malaclemys terrapin) are listed as a “near threatened” species in Virginia. Diamondback Terrapins face a variety of threats such as habitat loss, nest predation (by ravens, foxes, raccoons, etc.), boat strikes, and drowning in crab pots. Understanding Diamondback Terrapin nesting behavior is important to better understand the threats to terrapin populations. During their nesting season in June of 2017, we performed a mark-recapture study and observed how the timing of nesting behavior correlated with tidal patterns. We hypothesized that Diamondback Terrapins would prefer to nest during high tide to reduce risk of dehydration, reduce exposure to predation, and reduce energy expenditure by walking a shorter distance to nesting sites. We surveyed the causeway on the Wallops Island Flight Facility from approximately 8:30 to 17:30 every day during the nesting season and collected nesting turtles. The tide and time of capture was noted for each terrapin. Each terrapin was brought back to the lab and weighed, measured, and given a unique number via scute notching.
Results/Conclusions
We found that nesting during low tide was significantly preferred to nesting during high tide (χ2 = 35.96, p < 0.05). This result contradicts findings from previously published studies which suggest a strong preference for nesting at high tides; however those studies were conducted in other geographic areas within the range of Diamondback Terrapins. Our findings suggest that terrapins have a strong preference to nest during the morning, regardless of tide. We observed greatest amount of nesting activity during daytime between 9:00 AM and 10:45 AM, which is supported by other published studies. While some studies have suggested that terrapins occasionally nest at night, the majority occur during the day. This could be linked to predation pressure from nocturnal predators (e.g. foxes and raccoons). Nesting during daylight hours might reduce the risk of nest and adult predation, which could outweigh other risks like energy expenditure and desiccation that may occur when nesting during daylight hours.