by Christine Healy
At quick glance, Pine Barrens tree frogs (PBTF), with their vivid green backs, deep purple sides, and vibrant yellow thighs, might put folks in mind of Central and South American rainforests. Based on their visage, they could, theoretically, be at home beside red-eyed tree frogs and poison arrow frogs – the poster children of amphibian diversity. They have occupied that spotlight themselves. In fact, in his 1983 Endangered Species series, American pop artist Andy Warhol chose to immortalize the PBTF in silkscreen as the lone representative of herptiles. But these tiny beauties do not favor the tropics. Occurring in three disjunct populations across the eastern United States including the Florida/Alabama panhandle, the Carolinas and, naturally, New Jersey, PBTF are habitat specialists. They reside in seepage bogs where the water is relatively acidic, due to the presiding vegetation. Sadly, as is the case with many animals reliant on very specific landscape features, habitat loss and fragmentation pose a concern for the persistence of this species, which is listed as threatened in New Jersey.
CWF is very excited to be partnering with NJDEP, Division of Watershed Protection and Restoration on a long-term study aimed at better understanding the effect of development on vulnerable species. We will measure abundance, adult health and survival, and larval growth of Pine Barrens tree frogs within a population impacted by encroaching construction to evaluate whether current wetland regulations, including buffer size, are sufficient for species conservation.
Work began back in June with evening call monitoring surveys to locate breeding males. Once spotted, we carefully captured them by hand (often necessitating a swim through highbush blueberry and greenbrier) and temporarily housed them within individual containers labeled with their GPS coordinates. After all adults were collected, they were measured, inspected for unique markings, weighed, and photographed by an assembly line of researchers, in an effort to minimize processing time. Frogs were subsequently returned to their origin point. To enable captures outside of the breeding period, we installed a series of PVC pipes on trees surrounding each pool within our study site that are checked during each visitation. These tubes act as refugia for adults while increasing the likelihood of late-season encounters.
By mid-July the PBTF’s distinctive call disappeared from the nightly chorus, marking the end of the breeding period and a transition, for us, to diurnal field work. At this point, eggs deposited early on had hatched, so we shifted our focus from adults to tadpoles. Using a combination of minnow traps and dipnetting, we intensively surveyed the site. We were able to collect individuals of a diversity of species before low water levels, associated with the abnormally dry conditions we’ve experienced this summer, precluded further sampling.
With the completion of data collection for our pilot season, we move on to our analysis. We’ll spend the next few weeks identifying tadpoles within our photo library and processing call data that was collected by recording devices affixed around each pool. Our results from this effort will establish a baseline against which we’ll compare data from future years, as the footprint of the construction moves closer to the wetland buffer. We hope that lessons learned from this study will strengthen our ability to protect wetland species from adverse anthropogenic impacts.
Tags: Amphibians, frogs, NJDEP, Pine Barrens Tree Frog, Survey