Levasseur, P.; Sterrett, S.; Sutherland, C. Visual Head Counts: A Promising Method for Efficient Monitoring of Diamondback Terrapins. Diversity2019, 11, 101.
Levasseur, P.; Sterrett, S.; Sutherland, C. Visual Head Counts: A Promising Method for Efficient Monitoring of Diamondback Terrapins. Diversity 2019, 11, 101.
Levasseur, P.; Sterrett, S.; Sutherland, C. Visual Head Counts: A Promising Method for Efficient Monitoring of Diamondback Terrapins. Diversity2019, 11, 101.
Levasseur, P.; Sterrett, S.; Sutherland, C. Visual Head Counts: A Promising Method for Efficient Monitoring of Diamondback Terrapins. Diversity 2019, 11, 101.
Abstract
Generating a range-wide population status of the diamondback terrapin (Malaclemys terrapin spp.) is challenging due to a combination of species ecology and behavior, and limitations associated with traditional sampling methods. Visual counting of emergent heads offers an efficient, non-invasive and promising method for generating abundance estimates of terrapin populations across broader spatial scales and can be used to explain spatial variation in population size. We conducted repeated visual head count surveys at 38 predetermined sites along the shoreline of Wellfleet Bay in Wellfleet, Massachusetts. We analyzed the count data using a hierarchical modeling framework designed specifically to analyze repeated count data: the so-called N-mixture model. This approach allows for simultaneous modeling of imperfect detection to generate estimates of true terrapin abundance. We found detection probability was lowest when skies were overcast and when wind speed was highest. Site specific abundance varied but we found that abundance estimates were, on average, higher in unexposed sites compared to exposed sites. We demonstrate the utility of pairing visual head counts and N-mixture models as an efficient method for estimating terrapin abundance and show how the approach can be used to identifying environmental factors that influence detectability and distribution.
Keywords
abundance; detection; diamondback terrapin; Malaclemys terrapin; monitoring; N-mixture; salt marsh; visual head count
Subject
Biology and Life Sciences, Ecology, Evolution, Behavior and Systematics
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
