Do wetland buffers protect overwintering and breeding of wood frogs (Lithobates sylvaticus) in the New Jersey Pine Barrens?

Background/Question/Methods

The wood frog (Lithobates sylvaticus (LeConte, 1825)) utilizes both temporary pools and upland forest habitats for its lifecycle. In the New Jersey Pine Barrens, wetlands are protected from development by specific buffers, but upland forest beyond such buffers is treated as inherently developable. Students in Stockton University’s undergraduate ecology lab began long-term ecological studies on anurans on the campus in Atlantic County, New Jersey, in 2007. This report covers a two-year study by students in the ecology lab and in independent studies after completing the class. We captured wood frogs moving towards a breeding pond to determine whether a reduced 175 ft. or the standard 300 ft. wetland buffer zone protects the frogs’ winter habitat. Concentric rows of drift fence and pitfall traps were constructed in February, 2014: the first 25 ft. from the edge of the breeding pond, the second, 175 ft. away and the third, 300 ft. away. Students and faculty checked the traps and sexed, counted and released the frogs daily from February to April, except during harsh weather, when the traps were kept closed. We also studied the breeding pond to see how it differed in chemistry, hydrology and biota from ponds unoccupied by L. sylvaticus.

Results/Conclusions

In 2014, 44% and in 2015, 63% of captures occurred at the outer two fences. The totals for 2015 by fence were inner 159 males, 35 females; middle 161, 56; outer 92, 23. We conclude that even a 300-foot buffer does not protect the wood frogs’ entire overwinter habitat. Protecting the habitat surrounding ponds that support wood frogs’ explosive breeding is important to ensure that this species continues to thrive. Our preliminary results and review of the literature suggest that moderately deep ponds that warm up in early spring and that support a large population of benthic macroinvertebrates such as chironomids and copepods may be most likely to permit rapid development before drying in early- to mid-summer. Smaller and shallower ponds, although chemically similar, either dry up too quickly for larvae to metamorphose or do not contain the resources to support rapid growth. We plan to continue the study to gain a better understanding of the wood frog population.