Gopher tortoise burrow surveys: External characteristics, burrow cameras, and truth

The gopher tortoise (Gopherus polyphemus) occupies the southeastern Coastal Plain of the United States where it digs burrows in upland habitats. Two burrow survey techniques commonly used to estimate tortoise population size (classification of burrows based on external characteristics and surveying burrow contents with a burrow camera) were tested to determine accuracy and subjectivity among researchers. Accuracy of both methods was verified by excavating the burrows to determine if tortoises were present. Classification of burrows based on external characteristics was found to be highly subjective, related to the researchers' prior gopher tortoise experience, and unrelated to familiarity with the landscape. Burrow camera surveys were accurate, but should be used with caution as mistakes can be costly. Inadequacies in the currently accepted burrow survey methods are discussed and suggestions for improvements are made. Abstract. The gopher tortoise (Gopherus polyphemus) occupies the southeastern Coastal Plain of the United States where it digs burrows in upland habitats. Two burrow survey techniques commonly used to estimate tortoise population size (classification of burrows based on external characteristics and surveying burrow contents with a burrow camera) were tested to determine accuracy and subjectivity among researchers. Accuracy of both methods was verified by excavating the burrows to determine if tortoises were present. Classification of burrows based on external characteristics was found to be highly subjective, related to the researchers' prior gopher tortoise experience, and unrelated to familiarity with the landscape. Burrow camera surveys were accurate, but should be used with caution as mistakes can be costly. Inadequacies in the currently accepted burrow survey methods are discussed and suggestions for improvements are made.