Harpers Ferry Amphibian Monitoring, 2023

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

Harpers Ferry National Historical Park is home to at least 10 amphibian species. The Park Service monitors its wetlands.

What is measured

Crews visit the park's monitoring sites and record which species they find where. Across all sites, that gives occupancy: the share of sites where a species is present. The question: is occupancy changing over time?

Some species live away from the habitats monitored — red-backed salamanders on land, eastern spadefoot toads underground. They may be in the park, but the survey isn't designed to find them; chance sightings are noted but left out of the analysis.

Wetlands in 2023

• Species seen: one — of 10 wetland species recorded since monitoring began in 2015.
• Visits: 8 wetlands, each visited once, between April and May 2023. There are usually two visits a year, which is why the numbers are lower.
• Most abundant: toads (17 egg masses), also found at the most sites.

Figure 1: occupancy of each species in Harpers Ferry's wetland pools. NPS.

Reading the charts

• Dark gray bars: occupancy from raw sightings.
• Black dots and lines: estimated occupancy. Amphibians hide well, so there are usually more present than crews can count; the estimate fills those gaps.
• Light gray bands: 95% credible intervals.
• "Gray treefrog complex" and "Toad complex": closely related species grouped together.
• "Trend" box, atop each graph: a number and a color for the direction of the estimated trend — blue rising, white neutral, yellow slightly falling, red falling. The numbers in parentheses are the 95% credible interval.
• Species run alphabetically by common name.

The data are preliminary and may be revised; they have not had the U.S. Geological Survey's final approval.

Sources

Based on "Harpers Ferry Amphibian Monitoring 2023," part of the series Amphibian Monitoring in the National Capital Region, National Park Service; a work of the United States government in the public domain.