Amphibian Monitoring at Manassas National Battlefield Park, 2023

Manassas National Battlefield Park is home to at least 13 amphibian species, and its wetland pools are monitored for them.

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 27 wetland sites twice between March and May 2023 — all except Blue House Pool, visited once — and found 10 wetland species. Since monitoring at Manassas began in 2008, 13 wetland species have been seen in all.

Wood frogs were by far the most plentiful, with 4,067 tadpoles and 211 egg masses, and were found at the most sites, 9 of the 27. Northern green frogs and spotted salamanders came next for the number of sites.

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.

A spotted salamander (Ambystoma maculatum). 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, "Manassas Amphibian Monitoring 2023," in the series Amphibian Monitoring in the National Capital Region. https://www.nps.gov/articles/000/manassas-amphibian-monitoring-2023.htm