Investigation of Headstarted Blanding’s Turtles (Emydoidea blandingii) in Shiawassee National Wildlife Refuge, Saginaw, MI
Szymanski, Melissa
2016-05
Abstract
When implementing management decisions managers should utilize the most cost-effective strategies that also provide the most benefit for the managed species. There are many different management options to consider when the objective is conservation of long lived reptiles (e.g., turtles) with one of them being headstarting. Headstarting is when reptile eggs are collected by managers, hatched in captivity, and hatchlings are raised for a certain time before being released into their native habitat. Blanding’s Turtles (Emydoidea blandingii) are a state species of special concern in Michigan, where this study takes place. Headstarted Blanding’s Turtles were raised for one and a half years and should benefit from being released in a suitable microhabitat within a wetland. This study’s aim was to investigate the success of varying release locations and the headstart program by measuring thermoregulation patterns, survival, and movements of juvenile headstarted Blanding’s Turtles. During June 2014, twenty-four Blanding’s Turtles were released and tracked for eighteen months using radio telemetry to measure survival and to look at the movements among microhabitats; water and carapace temperature data were used to measure thermoregulation patterns. The headstarted juvenile Blanding’s Turtles had an average carapace temperature lower than adults from previous studies and used basking as a thermoregulatory behavior. To evaluate factors that may potentially affect survival of Blanding’s Turtles microhabitat factors at turtle relocation points within Shiawassee National Wildlife Refuge, Saginaw, MI, USA were recorded, including water depth, vegetation type and dominance, substrate depth, and air and water temperature. GIS and ground truth data were used to investigate microhabitat factors and map turtle locations. All of the headstarted Blanding’s Turtles survived overwintering through spring 2015. Turtles were released in four different locations with different microhabitats. Minimum convex polygon home ranges and movement patterns were analyzed to see if differences occurred across release groups and age classes. Significant differences were found between turtle home range size per release group. Comparisons to studies on wild-hatched Blanding’s Turtles were made and showed that these headstarted Blanding’s Turtles behaved similar to their wild-hatched counterparts when comparing behaviors at relocations and home range sizes. Use versus availability showed that the juvenile headstarted Blanding’s Turtles avoided open water, willows, and lowland forest while preferring muskrat dens and cattails. Geographically weighted regression modeling predicted that these turtles would move towards preferred habitats and away from release sites with avoided non-preferred habitats. This research identified an estimated survival of between 63 and 96% over the eighteen month study period with all Blanding’s Turtles surviving their first winter in the refuge. This research suggests that headstarting programs for Blanding’s Turtles should release the species in preferred habitats of dense cattails with plenty of muskrat dens for basking and refuge, if available.Subjects
Blanding's turtle geographic information system (GIS) habitat space use headstarting home range thermoregulation
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