Amphibian Monitoring at Chesapeake and Ohio Canal National Historical Park, 2023

Chesapeake and Ohio Canal National Historical Park is home to at least 19 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 30 wetlands once, in March 2023; usually there are two visits a year, which is why the 2023 numbers are lower. They found seven wetland species, and also a burrowing species, the eastern spadefoot toad. Since monitoring began in 2005, 14 wetland species have been seen in all.

Wood frogs were the most plentiful, with 2,151 tadpoles and 11 egg masses. Spotted salamanders were found at the most wetlands, 8 of the 30, followed by wood frogs and marbled salamanders.

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.

Field technicians survey for amphibians near a wetland. NPS / C. Shafer.

Streams

Crews visited 7 streams once, in May 2023. Three stream salamanders have been recorded so far: the northern dusky, northern two-lined and northern red salamander. An eastern red-backed salamander, a land species, turned up on a stream bank and is left out of the stream analysis. Northern two-lined salamanders were the most plentiful in 2023 (5 adults, 1 juvenile and 19 larvae) and were found in the most streams.

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, "C&O Canal Amphibian Monitoring 2023," in the series Amphibian Monitoring in the National Capital Region. https://www.nps.gov/articles/000/c-o-canal-amphibian-monitoring-2023.htm