Amphibian Monitoring at Prince William Forest Park, 2023

Prince William Forest Park is home to at least 17 amphibian species. Its wetlands and streams are both monitored.

The Park Service monitors amphibians in the National Capital Region by visiting sites and recording which species are found where. Across all sites, that gives each species' occupancy — the share of sites where it is present — and the question is whether occupancy is changing over time.

Some amphibians live away from the places being monitored — land-dwelling red-backed salamanders, for instance, or burrowing eastern spadefoot toads. They may live in the park, but the monitoring is not designed to find them, and chance sightings are noted but left out of the analysis.

A wood frog (Rana sylvatica). NPS / C. Shafer.

Wetlands in 2023

Crews visited 28 wetlands once, in March 2023; usually there are two visits a year, which is why the 2023 numbers are lower. They found eight wetland species. Since wetland monitoring began at Prince William in 2017, 14 wetland species have been seen in all.

Wood frogs were the most plentiful, with roughly 1,255 tadpoles and 12 egg masses. Spotted salamanders, eastern newts and spring peepers were found at the most sites, four wetlands each.

Occupancy by species in the park's wetland pools. NPS.

Reading the graphs

• Dark grey bars are occupancy based on the raw sightings.
• Black dots, joined by lines, are estimated occupancy. Estimates help fill gaps, because amphibians hide easily and there are usually more present than monitoring teams can count.
• Light grey shading marks the 95 percent credible interval.
• "Gray treefrog complex" and "toad complex" group closely related treefrog and toad species together.
• The "Trend" box at the top of each graph gives a trend value, with its 95 percent credible interval in brackets, and a colour for its direction: blue positive, white neutral, yellow slightly negative, red negative.
• Species are in alphabetical order of their common names.

Streams

Three salamanders have been recorded in the park's streams: the northern two-lined, northern dusky and northern red salamander. Crews last surveyed five streams, twice each, in June and July 2021; no streams were surveyed in 2022 or 2023.

Occupancy by salamander species in the park's streams: EBIS, northern two-lined; DFUS, northern dusky; PRUB, northern red. Black dots are estimated occupancy, grey lines 95 percent confidence intervals. NPS / C. Shafer.

The data were preliminary or provisional and subject to revision, and had not received final approval from the U.S. Geological Survey.

Sources

• National Park Service, National Capital Region, "Prince William Amphibian Monitoring 2023," in the series Amphibian Monitoring in the National Capital Region. https://www.nps.gov/articles/000/prince-william-amphibian-monitoring-2023.htm