Environmental Science and Management

Second Major

Wildlife and Conservation Biology


Meyerson, Laura

Advisor Department

Natural Resources Science




habitat suitability index; terrapins; northeast; soil grain size analysis; HSI

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.


Northern diamondback terrapins (Malaclemys terrapin terrapin) are a state-endangered species in Rhode Island and is the only species of northeastern turtle that lives in brackish water. Although their conservation status varies by state, terrapins are primarily negatively impacted by anthropogenic factors such as hunting and habitat loss. To improve conservation, management, and restoration efforts for this species, we developed a new habitat suitability index (HSI) for diamondback terrapins, but with a modern twist.

Habitat suitability indices were first developed by the US Fish and Wildlife Service in 1974 as part of their habitat evaluation procedures (HEP) to predict species survival in particular environments using life history and habitat requirements. However, the 1988 HSI published for diamondback terrapins is outdated and includes only three variables to assess nesting site suitability (% shrub cover, % grass cover, and slope).

This project focused on updating the HSI by using more site variables to assess habitat suitability and modernizing data collection and analysis. Specifically, we included: soil grain size, soil organic matter, land cover, slope, aspect, mean higher-high water (MHHW), and human influence. This new HSI can be used to evaluate known nesting habitat, to identify potential nesting sites, and to guide nesting habitat restoration. We collected nesting habitat data from 25 terrapin nesting sites in the northeastern USA using survey responses, field collected soil samples, Landsat8 satellite imagery, and data from the US Census Bureau, NRCS web soil survey, and NOAA. We then ranked the importance of nesting habitat variables according to expert opinion, performed soil grain size analysis for all sites, used Google Earth Engine to analyze landcover data, and ArcGIS to map and analyze data for the new HSI.

Our data showed that soil type and land cover are the most important site factors. While sandy soils are important for nesting, soil sand fraction size is less important, and terrapins tend to nest in soils low in organic matter. In terms of nest position, we found that the highest terrapin nesting occurs at sites with south, southwest or west facing aspects. In general, we also found that sites with more shallow slopes and lower mean higher-high water had more terrapins. For human influences, we found that while terrapin abundance tended to be lower at sites with higher human population density, the site with most terrapins also had the highest human density. There was no consistent relationship between terrapin abundance and distance to roads.

This modernized HSI can be used to assess existing terrapin nesting habitat and to guide consistent data collection and monitoring efforts across sites and regions to better assess nesting habitat quality for this unique species, and improve their chances of survival.

HannahDallas_PosterNarrative.docx (11 kB)
Poster narrative