Jillena Yeager to Study Wood Frogs on Stockton’s Campus This Winter

Most students flock to the Library with umbrellas in hand or stay in their dorm rooms on wet winter afternoons, but this semester, Jillena Yeager will head outdoors after each rainfall and twice daily to conduct her research.

The junior Environmental Science major is studying the campus’s wood frog population during the species’ breeding season in mid to late February. “The wood frog is one of the many amphibians that breed in temporary ponds where fish are absent. At Stockton, there are at least 22 of these temporary ponds, called vernal ponds,” she explained. A pond called ‘S’ is where she will focus her study.


Yeager, of Hillsborough, will work with her advisor, Dr. Jamie Cromartie, associate professor of Entomology. “I knew Jillena was someone out of the ordinary during our nighttime frog hunt last March, when she brought me a big water beetle she had caught barehanded,” said Cromartie about the aspiring herpetologist.

Yeager explained that her project seeks “to determine how close to vernal pond ‘S’ wood frogs spend the winter.  This information will then be used to assess whether the current buffer regulation for this vernal pond protects the wood frogs’ winter habitat.”

“A buffer zone is the vegetated area around a wetland which plays a crucial role in maintaining the health of the wetland and its associated species. The New Jersey Department of Environmental Protection and the New Jersey Pinelands Commission mandates that 300 feet of land be preserved around any wetland; however, Stockton is approved to have a reduced 175-foot buffer around wetlands located in ‘core’ or main areas of campus,” she said.

Silt fencing, which is often seen at construction sites, will be installed at varying distances from vernal pond S on campus to create zones. The first fence will be located along the edge of the pond and two more will be located at 175 feet and 300 feet from the pond.

Water-bound frogs will be captured in each of the zones when they hop into buckets buried flush to the ground at locations within each zone. Damp sponges line the interior of the buckets to mimic a terrarium habitat to protect the frogs and other trapped critters from desiccation.

“The captives will be immediately released inside the last fence toward the vernal pond,” she said.

When Yeager checks the buckets each day, she will record the gender, time and location of her captures. The fencing allows her to document the differing densities of frogs in the various zones.

Yeager’s fieldwork starts when the frogs begin unearthing themselves from the leaf litter, especially after rainfall, to move to vernal ponds.  The frogs’ distinct call, deep quaking sounds, signal the start of the breeding season. Collectively the females will lay thousands of eggs in the vernal pond.

“They breed explosively for a few days to one week,” she said.

“I came up with the idea for this project after realizing not much is known about the winter distribution of the wood frogs here on campus. Stockton is home to such a diversity of wildlife, and it is awesome to have the opportunity to learn and conduct meaningful research right in our own backyard,” said Yeager, adding that her study can contribute information to regional wood frog studies.

In her spare time, Yeager likes to be outdoors hiking, camping or running. At Stockton, she serves as the vice president of the Geology Club. Her long-term goal is to study “the distribution and habitat ranges of herptofauna in order to better understand their land use for best management and conservation practices.”

Follow Yeager’s wood frog research on her blog.

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