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School of Environment and Natural Resources


TWEL Evan Amber Thesis

Evaluating AHDriFT Camera Traps and Traditional Survey Methods for Eastern Massasauga Rattlesnake (Sistrurus catenatus) Presence-Absence

Evan Douglas Amber, MS

Advisor: William E. Peterman, PhD


The Eastern Massasauga Rattlesnake (Sistrurus catenatus) is Federally threatened and Ohio endangered. Accepted Ohio survey protocols includes visual encounter surveys (VES) and artificial cover (corrugated tin sheets) surveys. Although effective, these traditional methods require intensive field effort (~25 weekly visits). The Adapted-Hunt Drift Fence Technique (AHDriFT) is a new low-effort camera trap and drift method for ectotherms and small mammals. However, the method has not been applied for Massasauga or in their habitats, or even evaluated beyond proof-of-concept.


The objectives of this study were to: (1) assess AHDriFT as a wildlife survey tool; (2) compare AHDriFT efficacy for Massasauga presence-absence surveys to VES and tin surveys in terms of detection rates, detection probability, and cost-efficiency; (3) determine optimal AHDriFT deployment for Massasauga in terms of camera trap timing and length, array spatial placement, and weather influence; and (4) provide preliminary recommendations for a Massasauga survey protocol using AHDriFT.


I deployed 15 Y-shaped AHDriFT arrays in fields with known Massasauga populations from March – October 2019 and 2020. In 2019, I compared arrays to prior VES and tin surveys, and assessed between-field detection covariates. In 2020, I evaluated concurrent surveys and assessed within-field detection covariates.


Equipment for each array cost approximately US$1,570. Construction and deployment of each array took about three hours, with field servicing requiring 15 minutes per array. Arrays proved durable under wind, ice, snow, flooding, and heat. Processing two-weeks of images of 45 cameras averaged 13 person-hours. In 2019, arrays obtained 9,018 detections of 41 vertebrate species comprised of 5 amphibians, 13 reptiles (11 snakes), 16 mammals, and 7 birds. Arrays cumulatively detected all amphibians and 92% of expected snakes and small mammals.


Arrays obtained a total of 206 Massasauga detections, 2 – 4 times that of traditional methods. In 2019, arrays detected 0.48 snakes/person-hour, surpassing prior VES (0.11) and tin surveys (0.28). In 2020, arrays exceeded tin catch-per-person-hour by at least 2.6 – 6 times. Weekly array detection probability equated to maximum tin detection probability per survey (0.5) using only 1 array/~15 ha. Additional arrays increased weekly detection probability to 0.6 – 0.9. However, arrays have lower weekly detection probability (0.1 – 0.4) in small population sites. Such sites therefore required longer camera trapping timeframes and higher array densities to achieve low error rates.


Arrays were most effective from June – October, requiring as few as five field visits for 16 weeks of camera trapping. Optimal array placement is in dense vegetation away from predator perch trees. After equipment purchases, AHDriFT was more cost- effective than tin. Overall, AHDriFT was an effective snake and small mammal survey and inventory tool. The method also demonstrates high promise as a more effective Massasauga survey tool than traditional surveys. Still, AHDriFT needs to be tested in Massasauga sites more representative of their typically small population sizes in Ohio.