Habitat Restoration for Spiny Softshell Turtles on Lake Champlain Shores

The shores of Lake Champlain historically provided prime habitat for five different species of turtles. Currently, of the 441 miles of Lake Champlain shoreline in Vermont, only 38 percent remains undeveloped leaving less habitat for these species. Lack of high-quality shoreline nesting habitat is a potential factor limiting Lake Champlain turtle populations and may be especially important for the state threatened spiny softshell turtle.

Lake Champlain Sea Grant funded University of Vermont (UVM) researchers Dr. Brittany Mosher and Dr. Jed Murdoch and Master of Science graduate student Destini Acosta to investigate turtle habitat restoration on Lake Champlain. The three researchers, all in the UVM Rubenstein School of Environment and Natural Resources, partnered with the Vermont Fish and Wildlife Department, Lake Champlain Land Trust, and the Winooski Valley Park District on the study.

The researchers will identify differences between ten sites that are theoretically good habitat for spiny softshell turtle nesting and four currently known turtle nesting sites. They will compare soil type, tree canopy cover, soil temperature, soil moisture, human use, predator activity, and surrounding vegetation at the different sites. These observations will help researchers better understand factors that influence nesting habitat requirements and will inform Vermont Fish and Wildlife’s management of habitat.

“Spiny softshell turtles are a state threatened species that only nest in very few places around Lake Champlain,” explains Mosher. “Having very few locations of nests makes this species prone to further population declines from stressors like development, human activity, and predation. We know there are other locations that could theoretically be good nesting habitat for softshells that are not used. Our research focuses on understanding characteristics that make for high quality softshell nesting habitat and understanding whether there is the potential to restore habitat in other places to help bolster populations.”

At Delta Park, right at the mouth of the Winooski River and a historical nesting site for spiny softshell turtles, there has been no sign of softshell nesting in the past century. The research team partnered with the Winooski Valley Park District and the City of Colchester to create an experiment that manipulates the habitat on the beach by splitting it up into plots with different conditions. Some of the plots were kept as they were found and act as a control. In some plots, the vegetation was removed, in others the woody debris was removed, and in the remaining plots, both woody debris and vegetation were removed. Researchers hypothesize that restoring beach habitat will provide more high-quality nesting habitat for turtles.

In these experimental plots, the researchers are observing which habitat is the most appealing for other species of turtles to use for nesting. They will observe painted turtle and map turtle nesting preferences which they predict will mirror those of spiny softshell turtle habits.

The researchers visit Delta Park every week to look for signs of successful nests or signs of predation on the nests. To find successful nests, the researchers look for quarter-sized holes in the sand where turtle hatchlings tunnel out of the nest and head toward the water. This process usually begins in mid-August. Throughout the summer, the researchers have already observed many nests that failed due to predation and have taken note of any animal tracks and other signs of predation.

“It’s exciting finding successful nests after starting the field season with finding only predated nests,” says Acosta. “Being able to evaluate nesting habitat preference and predator density will help ensure future successful nests.”

Based on their observations throughout Lake Champlain and at Delta Park, the researchers will develop a habitat scorecard for spiny softshells to assess the restoration of potential nesting sites. If they can pinpoint the characteristics of a good nesting site, the researchers can work with local and regional government bodies to inform guidelines, or best management practices, to support these potential habitats and increase turtle nesting grounds on and around Lake Champlain.

Outreach partner Lake Champlain Land Trust will use information generated by the study in future land acquisition decisions. The land trust will also get the information to lakeshore landowners who are interested in restoring their own properties to provide better habitat for turtles.