Blanding’s turtle (Emydoidea blandingii) population and movement ecology in central Iowa to aid conservation management

Abstract

Blanding’s turtles (Emydoidea blandingii) are a species of greatest conservation need (SGCN) in Iowa and face numerous threats throughout their range. These include habitat fragmentation, road mortality, nest depredation, and climate change. The turtles have high adult and juvenile survival and varying hatchling survival and fecundity rates. In central Iowa, there is concern that a lack of recruitment in this population is occurring, due to small numbers of females and little evidence of younger juveniles. The Iowa Department of Natural Resources wants to address these concerns, by collaborating with other organizations and private landowners to plan and implement conservation efforts for the turtles on both public and private lands. However, there is little knowledge about current demographics, vital rates, or movement patterns among this population and land managers do not know which management actions will be most effective to bolster the population. To address these knowledge gaps, we tracked 25 turtles from May 2023 to August 2024 at five wetland complexes. My objectives were to 1) assess population demographics and vital rates at these sites, 2) determine patterns of individual movement and space use, and 3) use the findings to evaluate how management actions may influence population growth. Overall, in central Iowa wetlands, we observed a small population of Blanding’s turtles that was skewed towards older, male individuals. Most of the reproductive aged females we found were gravid at least once, but we did not find any individuals younger than six years old. I determined weekly survival using known-fate models, and found that survival of individuals was high, as only one juvenile male was presumed to have died. I identified patterns in individual movement and site-wide space use, composition, and connectivity using various spatial analyses including minimum convex polygons, 95% kernel density estimates, and land cover assessment. Movement patterns varied seasonally and yearly among sexes and sites. Sites with higher proportions of wetland and grassland area had higher levels of connectivity to other wetlands and supported turtles with larger home ranges. Finally, using the vital rates I identified, and others derived from literature, I developed a population viability analysis to assess how an Iowa population of Blanding’s turtles may respond to different management actions aimed at decreasing probability of extinction. Short-term solutions, like nest protection and head starting, resulted in initial population growth, but did not decrease extinction probability long term. Long-term solutions like habitat improvement resulted in increased population growth and decreased probability of extinction long term. This research can aid land managers by providing information about how turtles may respond to changes in their environment and how a population may respond to management activities, which can aid in planning effective conservation strategies for them in Iowa.