The U.S. Fish and Wildlife Service listed the eastern massasauga rattlesnake (Sistrurus catenatus catenatus) as threatened in 2016 under the 1973 Endangered Species Act. We tested a visualencounter survey method during 2016 to aid researchers and managers in successfully detecting massasaugas in occupied habitat in southern Michigan, USA. We conducted 54 surveys (paired, independent searchers) in 2-ha areas occupied by telemetered massasaugas. Our detection process parameters included environmental conditions (air temperature, humidity, solar radiation, surface temperature, precipitation) and searcher characteristics (e.g., experience, time spent searching). We detected massasaugas on 11 of 54 surveys. Detection probability from the null model was 0.31; however, we found that time spent searching and minimum air temperature improved detection probability. Detection probability approached 1.00 as time searched by an individual exceeded 90 minutes and approached 0.80 on cooler mornings (12.8°C).Our findings provide survey protocol guidance to increase massasauga detections during visual encounter surveys, which offer useful information to help guide habitat management decisions.
Freshwater turtle populations are declining worldwide, yet managers have little information about the effects of commercial turtle harvests. In Missouri, the snapping turtle (Chelydra serpentina), smooth softshell (Apalone mutica), and spiny softshell (Apalone spinifera) are harvested commercially in the Missouri River. In 2011 and 2012, we conducted markrecapture of these species to estimate abundance on the Missouri River and two unharvested tributaries, the Osage and Gasconade Rivers. We conducted mock harvests, applying capture methods of the state's primary commercial harvester, to estimate plausible expected harvest proportions. Snapping turtle abundance per 2 km was lower at harvested units (X = 15; SE = 7.1; unharvested: X = 90; SE = 40.3). Smooth softshell abundance was greater at harvested units (X = 59; SE = 7.9; unharvested: X = 14; SE = 28.1), although the difference was not significant. Mean unique spiny softshell captures were similar at harvested (X = 18; SE = 4.3) and unharvested (X = 17; SE = 9.7) units. Expected harvest proportions averaged 23% across species (SE = 5%; range = 6%-79%), exceeding sustainable rates reported for turtles. Our results suggest that on a small scale, using these methods, harvesters can remove a substantial portion of river turtle populations.
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