Keeping Amphibians Connected in Bucks County

While wildlife face threats, amphibians such as frogs, toads and salamanders are particularly vulnerable. When compared with birds, fish, reptiles or mammals, amphibians have the highest percentage of species on the decline globally: over 40%[1]. The dual threat of habitat loss and climate change are particularly potent for these animals which, due to their permeable skin and soft, fish-like eggs, often require humid environments to reproduce and thrive. A warming climate with more frequent droughts is concerning enough on its own, but as their habitats are fragmented and interior forest is disrupted, frogs and salamanders are cut off from accessing remaining water sources. Fragmentation also alters their previously swampy forest habitat. Intact forest provides a buffer from dry weather while fragmentated habitat leaves swampy, wetland areas vulnerable to the drying effects of more sunlight and wind[2].

In this increasingly inhospitable climate, conservationists in Bucks County are working to link together remaining forested swamps and wetlands to protect one of the most critical refuges of reptile and amphibian diversity in Pennsylvania, the ecosystem known as the Quakertown Swamp. The several hundred acre complex of swamp, forest, creek and wetland habitat is home to 11 of 23 species of amphibians currently found in Bucks County, and 13 of 27 reptile species found in the county. This means that the Quakertown Swamp serves as critical habitat for several species declining across the commonwealth[3].

Keeping amphibians connected

The Quakertown Swamp’s network of streams, swampy forest and vernal pools (temporary ponds that form from rainwater and snowmelt every spring) represent the sort of habitat that was once common in the region. As the land was cleared, first for agriculture and then for suburban development, this critical ecosystem was reduced to only remnant patches[4].

For these remaining wetland pockets to be able to properly support robust amphibian populations, they need to have a minimum size and they must be connected to one another for amphibian populations to remain healthy and disperse between habitats. For example, species like wood frogs (which breed in the ponds) need woodlands around a pond in order to thrive. While they stay close to the water in the spring, they then disperse into the surrounding woodlands during the summer, and remain there to hibernate. And while adult wood frogs will return to a single pond throughout their life, juveniles often disperse to a nearby pond as they reach maturity, highlighting the importance of having intact forest between these ponds[5].

Similar movement patterns are true for other amphibians
at Quakertown Swamp, such as spring peepers and
yellow-spotted salamanders, who also breed in ponds. It
is also critical for species like the four-toed salamander,
which moves through the landscape looking for moist
moss at the waters edge on which to lay their eggs[6].

Knitting a patchwork of preserved land

Starting in 2002, The Heritage Conservancy began to preserve tracts of land southwest of Quakertown along and near Bog Run, which flows into the Tohickon Creek. The Pennsylvania Game Commission already managed 265 acres in this region, comprising State Game Land 139. The Heritage Conservancy’s current total protected footprint is 518 acres, of which 116 are owned by the Conservancy outright and the rest are in conservation easements on private land.

Conservation efforts have prioritized the preservation of 1) contiguous parcels of swampland and 2) land abutting Bog Run, due to the importance of the riparian zone it creates. This is essential for a healthy ecosystem and for supporting the diversity of species that depend on the habitat created where the land meets the water along the streambank. The easements are required to give the highest level of protection to the land in the riparian zone, limiting use of pesticides, herbicides and how agricultural waste is managed[7].

Conserved land in and around the Quakertown Swamp. Credit: The Heritage Conservancy, January 2025.Photo by The Heritage Conservancy, January 2025 | Used by permission

By preserving contiguous swamps, streams, ponds and vernal pools, the Quakertown Swamp has also remained a critical haven for other wildlife as well. The swamp is home to the largest great blue heron rookery in eastern Pennsylvania. It is also home to beavers, whose damming of Bog Run creates additional pond habitat for amphibians, turtles, and wetland bird species[8].

As our climate warms, this moist habitat is particularly precious. 2024’s historic drought saw small streams dry up around the region, and streams that have been disconnected from their larger watershed are particularly vulnerable[9]. As part of a largely intact watershed, Bog Run continued to flow through the 2024 drought, providing a critical refuge for aquatic and semi-aquatic species that make Quakertown Swamp their home.

Helping amphibians cross the road

Despite working to establish a continuous riparian corridor, barriers remain for many amphibians dispersing throughout the Quakertown Swamp. Roads bisect the habitat, and when frogs and salamanders migrate through the area to breed, many are killed by cars, often hundreds a night during peak migration[10]. To address this threat, the Heritage Conservancy began working with volunteers and local governments in 2012 to establish the Quakertown Swamp Amphibian Rescue Partnership[11].

On nights when conditions are particularly favorable for breeding – humid, rainy spring nights after the last winter frosts[12] – partial roadblocks are set overnight up at locations where large numbers of frogs and salamanders cross. In collaboration with Richland and East Rockhill Townships, traffic is slowed, with many volunteers manually crossing individual amphibians by hand. In the 13 years since this program started, the Heritage Conservancy estimates it’s rescued over 4,000 amphibians, helping maintain breeding populations in the face of encroaching fragmentation[13]. The success of these crossing programs highlights the need for more long-term and far-reaching solutions. This should include developing permanent infrastructure – small underpasses beneath these roads at the high-migration areas – to facilitate the movement of salamanders, frogs and other species threatened by traffic as they attempt to cross their disconnected habitat.

A yellow spotted salamander crossing the road at night at Quakertown Swamp.Photo by Sebastian Harris | Used by permission

References

1. Luedtke, J.A., Chanson, J., Neam, K. et al., “Ongoing
declines for the world’s amphibians in the face of emerging
threats,” Nature, 622: 308–314, doi: 10.1038/s41586-023-06578-4, 4 October 2023.

2. Laure Schneider-Maunoury et al., “Abundance signals
of amphibians and reptiles indicate strong edge effects in
Neotropical fragmented forest landscapes,” Biol. Conserv. 200:207-215, doi:.10.1016/j.biocon.2016.06.011, August 2016.

3. Sebastian Harris, Conservation Easement Steward, The Heritage Conservancy, personal communication, 14 January 2025.

4. Ibid.

5. Berven, Keith A., and Thaddeus A. Grudzien. “Dispersal in the wood frog (Rana sylvatica): implications for
genetic population structure,” Evolution 44(8): 2047-2056, doi:10.1111/j.1558-5646.1990.tb04310.x, December 1990.

6. Pennsylvania Natural Heritage Program, Vernal Pool
Salamanders, 2019, accessed at: https://www.naturalheritage.state.pa.us/VernalPool_Salamanders.aspx, 19 February 2025.

7. Sebastian Harris, Conservation Easement Steward, Heritage Conservancy, personal communication, 14 January 2025.

8. Heritage Conservancy, Quakertown Swamp and the Great
Blue Heron (fact sheet), February 2012.

9. The Academy of Natural Sciences of Drexel University, Even After Rain and Snow: What a Drought Watch Means for the Northeastern Region’s Ecosystem (blog post), 22 November 2024.

10. Heritage Conservancy, Amphibians Need Your Help (blog
post), 18 December 2012.

11. Heritage Conservancy, Quakertown Swamp Preserve,
accessed at: https://heritageconservancy.org/resources/expl
ore/ambassador-properties/quakertown-swamp-preserve/ 20 February 2025.

12. Pennsylvania Amphibian & Reptile Survey, Pennsylvania
Seasonal Pond Species and Egg Identification (fact sheet), accessed 20 Feb 2025.

13. Sebastian Harris, Conservation Easement Steward, Heritage Conservancy, personal communication, 14 January 2025.