Turtle Monitoring Program

In spring of 2010, River Action received partial funding from an Iowa DNR Wildlife Diversity small grant for the initiation of a turtle-monitoring program at Nahant Marsh in Davenport, Iowa. Mik Holgersson, former Program Director of Natural Resources at River Action, applied for the grant in anticipation of employing his nearly three years of turtle research experience to outfit Nahant Marsh with a set of equipment and to standardize methods for comprehensively inventorying and monitoring the resident turtle community. A total of nine turtle traps plus measuring equipment were purchased through the grant. The remaining grant funds, with a match from River Action, supported ten bi-weekly trapping sets between May 6th and September 30th.

At the onset of this project, several species of turtles were known to inhabit Nahant Marsh, including painted turtles (Chrysemys picta), snapping turtles (Chelydra serpentina), spiny softshell turtles (Apalone spinifera), red-eared sliders (Trachemys scripta elegans), and the state threatened Blanding's turtle (Emydoidea blandingii). These turtles had generally been identified and documented through direct observation, photographic evidence, and chance captures. The first formal study of Nahant's turtles was conducted in 2003 when Sheri Pennock, then a St. Ambrose University student, conducted a standalone trapping study in the main open water marsh. Her efforts resulted in the capture and documentation of 241 turtles, including 210 painted turtles, 25 snapping turtles, 5 red-eared sliders, and a single Blanding's turtle.

The Nahant Marsh turtle-monitoring program was conceived in the spirit of Pennock's work, though with the lofty goal of establishing a multi-year project that makes every feasible effort to capture and document the entire turtle community residing in and traversing through Nahant's diverse wetland habitats. The program will be used to quantify demographics for each species and to discern population health and trends. As applicable, this information will guide resource management at Nahant Marsh to better conserve each turtle species. The state threatened Blanding's turtle is of special concern and the condition of Nahant's population is unknown save for the occasional sighting. Locating and capturing this species is a top priority for the Nahant Marsh turtle-monitoring program: both because of its regional rarity and because it is in need of informed resource management.

From May 6th to August 12th of 2010, seven trapping sessions were conducted that resulted in the capture, marking, measuring, and release of 160 individual turtles. These were predominately painted turtles and snapping turtles (similar to Pennock's results), plus two spiny softshell turtles, and one adult red-eared slider. No Blanding's turtles had been captured or spotted during this period, though this was not particularly surprising. The choicest Blanding's turtle habitat was inaccessible for trapping due to excessive rain and flooding. Blanding's turtles prefer cool, shallow ponds, with dense submergent vegetation and basking areas; trapping during this period was confined to canoe-accessible open waters often bordered by cattail thickets, which are both avoided by these turtles.

By September, a break in the rain pattern finally permitted access to suitable Blanding's turtle habitat located in the more remote reaches of the marsh. The eighth trapping session was set on September 1st in a pair of relatively small, constructed Conservation Reserve Program (CRP) marshes with the characteristic cool, shallow water and dense submerged vegetation that Blanding's turtles typically prefer. When retrieved on September 3rd, these traps resulted in the capture of six adult Blanding's turtles (four males, two females) plus seven painted turtles and one small snapping turtle. The ninth and tenth trapping sessions were sampled on September 17th and September 30th, respectively. Both sessions' traps were set in the CRP marshes as well as a neighboring natural marsh complex created by a network of beaver dams. Together, these trapping sessions yielded five additional Blanding's turtles, for a total of 11 individuals comprised of eight males and three females.

The capture of Blanding's turtles was a welcomed capstone to the highly successful first season of the turtle-monitoring program. After ten trapping sessions, the program resulted in the capture and documentation of 196 individual turtles at Nahant Marsh. In summary, the 11 Blanding's turtles accompanied 146 painted turtles, 35 snapping turtles, two spiny softshell turtles, and two red-eared sliders that were marked and measured through this study. Ten of the painted turtles displayed marks that had been applied by Pennock in 2003. In response to this successful first season, funding has been ensured through 2012. Mik will continue to focus trapping on areas most likely to hold Blanding's turtles. While data from all species captured will be collected to estimate population sizes and to assess the sex ratio and age structure of each population, it is especially important to document as many of the regionally imperiled Blanding's turtles as possible. Obtaining this information will be a first step towards answering several questions important to the conservation of Blanding's turtles at Nahant Marsh, including: Is Nahant Marsh's Blanding's turtle population growing or in decline? What are the key features of the habitat being used by these turtles and how and where should restoration efforts be employed to improve and increase such habitat? Are suitable nesting sites available, are they being used, and, if so, are nests producing hatchlings?

For more information or if you would like to provide financial support for the turtle-monitoring program, please contact Mik Holgersson via email at mholgersson@vildmarkconsulting.com or River Action's office at 563-322-2969.

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