By CVC’s Adrienne Ockenden, Specialist, Watershed Monitoring

One of the greatest things about stepping out into the natural world is experiencing the vast array of sounds: the buzzing of insects, the calls of frogs, the songs of birds. Sounds provide important clues about the health of our local environment.

Through our Integrated Watershed Monitoring Program (IWMP), we study living and non-living features of groundwater, stream, forest and wetland ecosystems. Monitoring our watershed’s ecosystems requires a lot of time observing, not just what we see but also what we hear. Sound is the most effective way to monitor frog communities. Each species has its own set of unique calls making it easier to find creatures hidden by leaves and in the water.

New tools improve frog monitoring
Last year we made an exciting change in the way we collect frog data. We started using acoustic recording units (ARUs) at each of our wetland monitoring sites. These devices automatically record sound every day during the frog breeding season from April through early July, from late evening to early morning. Last year, this gave us a total of 2,368 recording hours across all sites. In comparison to the previous year, we had just under three hours hours of human survey time.

Monitoring staff install ARUs to record frog calls

Using our ARUs, we detected a total of eight out of the ten frog species known to live in the Credit River Watershed. We’re learning that some species are more common in our wetland monitoring sites than our old survey methods suggested. For example, we found Northern Leopard Frog at eight sites where they weren’t found the previous year. Listen to the Northern Leopard Frog call. Also, we found Mink Frog at two sites. Previously, we only had a single record of the species in our 15 years of monitoring.

Leopard Frog

Fortunately, we don’t have to listen to all those hours of data. We have specialized software that groups similar sounds together. Compared to the traditional method for surveying frogs (listening to calls in person), with ARUs we can collect data over a longer time period, both within a breeding season and within a day. This means we have a better chance of detecting species with infrequent calls or species that call at different times over a season or night.

Frogs are indicators of healthy wetlands
We use frogs as indicators of wetland health. Frogs are sensitive to changes in their environment. A healthy wetland typically has a good diversity of species. We find frogs living in our urban wetlands, resident species like American Toad are more tolerant of changes in their environment. Overall, wetlands in urbanized areas are not as healthy as those in the rest of the watershed.

American Toad

The many benefits of wetlands
Wetlands, even urban ones, provide important ecological benefits like flood protection, water purification and wildlife habitat for plants and animals, including species at risk.

Since European settlement, we’ve lost about a third of our wetlands in the watershed as a result of land use changes such as agriculture and urbanization. We’ve set a target to return wetland cover close to its estimated pre-European settlement levels, at just over 10 per cent of the watershed’s land cover. Protecting and restoring our wetlands is critical to achieving this target to build a heathy and resilient Natural Heritage System.

Test your monitoring skills with #CreatureCalls
You can practice your identification skills with us. Starting next week, we’ll be asking you to guess what animal the call belongs to. Follow us on Twitter and Facebook to get involved.

Learn more about how we’re monitoring the wetlands and other ecosystems in the Credit River Watershed, visit:

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