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Article

Visual Head Counts: A Promising Method for Efficient Monitoring of Diamondback Terrapins

1
Department of Environmental Conservation, University of Massachusetts–Amherst, Amherst, MA 01003, USA
2
Department of Biology, Monmouth University, West Long Branch, NJ 07764, USA
*
Authors to whom correspondence should be addressed.
Diversity 2019, 11(7), 101; https://doi.org/10.3390/d11070101
Received: 3 April 2019 / Revised: 22 June 2019 / Accepted: 24 June 2019 / Published: 27 June 2019
(This article belongs to the Special Issue Advances in the Biology and Conservation of Turtles)
Determining the population status of the diamondback terrapin (Malaclemys terrapin spp.) is challenging due to their ecology and limitations associated with traditional sampling methods. Visual counting of emergent heads offers a promising, efficient, and non-invasive method for generating abundance estimates of terrapin populations across broader spatial scales than has been achieved using capture–recapture, and can be used to quantify determinants of spatial variation in abundance. We conducted repeated visual head count surveys along the shoreline of Wellfleet Bay in Wellfleet, Massachusetts, and analyzed the count data using a hierarchical modeling framework designed specifically for repeated count data: the N-mixture model. This approach allows for simultaneous modeling of imperfect detection to generate estimates of true terrapin abundance. Detection probability was lowest when temperatures were coldest and when wind speed was highest. Local abundance was on average higher in sheltered sites compared to exposed sites and declined over the course of the sampling season. 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. View Full-Text
Keywords: abundance; detection; diamondback terrapin; Malaclemys terrapin; monitoring; N-mixture; salt marsh; visual-head count abundance; detection; diamondback terrapin; Malaclemys terrapin; monitoring; N-mixture; salt marsh; visual-head count
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MDPI and ACS Style

Levasseur, P.; Sterrett, S.; Sutherland, C. Visual Head Counts: A Promising Method for Efficient Monitoring of Diamondback Terrapins. Diversity 2019, 11, 101. https://doi.org/10.3390/d11070101

AMA Style

Levasseur P, Sterrett S, Sutherland C. Visual Head Counts: A Promising Method for Efficient Monitoring of Diamondback Terrapins. Diversity. 2019; 11(7):101. https://doi.org/10.3390/d11070101

Chicago/Turabian Style

Levasseur, Patricia, Sean Sterrett, and Chris Sutherland. 2019. "Visual Head Counts: A Promising Method for Efficient Monitoring of Diamondback Terrapins" Diversity 11, no. 7: 101. https://doi.org/10.3390/d11070101

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