Amphibian Monitoring at Catoctin Mountain Park, 2023

Catoctin Mountain Park is home to at least 14 amphibian species. The Park Service monitors amphibians in its wetlands and streams: field teams visit wetland pools and record which species they find at which sites. Across all the sites, that gives each species' occupancy — the share of sites where it is present. Streams were surveyed for amphibians for the first time in 2023.

The question is simple: is occupancy changing over time?

Some amphibians live away from the wetlands and streams 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

Crews visited 18 wetland sites once, in April 2023; usually there are two visits a year, which is why the 2023 numbers are lower. They found four wetland species, and also a stream species, the northern spring salamander. Since monitoring began in 2015, 11 wetland species have been seen in all.

Northern green frogs were the most plentiful wetland amphibian in 2023, with one adult and 22 tadpoles counted. Northern green frogs and American bullfrogs were found at the most sites, two 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.

A spotted salamander (Ambystoma maculatum). NPS / C. Shafer.

Streams

Crews surveyed one stream for the first time, in May 2023, and found one stream species, the northern two-lined salamander, as well as a land-dwelling red-backed salamander. Graphs of stream occupancy will follow once there are a few more years of data.

These data were preliminary or provisional as of March 1, 2024, and subject to revision; they had not received final approval from the U.S. Geological Survey.

Sources

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