Long-term Butterfly Monitoring

There are five butterfly transects monitored in the Metroparks, currently: three occur in Oak Openings Preserve, one at Wildwood Preserve and one at Swan Creek Preserve. While large tracts of the Oak Openings Region have historically been the state strongholds for species like Karner Blue, Persius Duskywing, and other rare species, the small pieces of savanna remnants at Wildwood Preserve Metropark are of special interest because they still support species of concern and high biodiversity when almost entirely surrounded by suburban sprawl. Swan Creek has also shown that even an urban park can have much butterfly diversity. Metroparks staff and volunteers have been participating in gathering data for the Long-term Ohio Butterfly Monitoring Project since 1999 in Oak Openings Preserve Metropark, since 2008 in Wildwood Preserve Metropark, and since 2014 at Swan Creek Preserve Metropark.

The statewide, “Long-term Butterfly Monitoring Project” that Metroparks contributes to, is sponsored by the Ohio Department of Natural Resources, Division of Wildlife, Ohio Lepidopterists, and the Cleveland Museum of Natural History. Long-term butterfly monitoring is important because it can reveal long- term trends. Long-term data that track regional and local trends in abundance are essential to revealing population declines before their final stages (declines are hidden when they occur slowly and/or lag years behind their causes). The rationale for this project includes obtaining baseline data throughout the state of Ohio in order to identify butterfly flight periods, seasonal variations of abundance,  and fluctuations in numbers due to migrations, colonization’s, extinctions, and immigrations of non-native species as  habitats undergo progression and land management resulting in short-term and long-term effects.

Because many butterflies are specialist species with restricted and obligate larval food sources, their biodiversity helps to measure the overall biodiversity of the natural area, making them indicators of healthy ecosystems and barometers for successful land management. It is widely believed that there are butterflies in danger of disappearing from Ohio. In the Oak Openings Region, the Karner Blue is Federally endangered, the Persius Dusky-wing and Frosted Elfin are state endangered, the Silver-bordered Fritillary is a state threatened species, and the Dusted Skipper is a state species of concern.  Long-term monitoring of these rare species is a necessary part of responsible land stewardship.

The transects are set up through assigning sections reflective of the local habitats. Volunteers follow the Pollard/Yates method as protocol. Transects are walked at an even pace and only the butterflies which come within 15 feet of the recorder are counted. Monitors walk in a virtual “box,” 15 feet wide, 15 feet tall and extending 15 feet ahead.  As monitors walk, butterflies located within these parameters are noted on the monitoring form. Although, species on actual, adjacent nectar sources (not necessarily inside of the “box”) also can be noted.

Transect routes are restricted to paths. Each route was divided into sections which represent different habitat types or a subdivision of the same habitat, which is being managed differently.

Recording time is restricted to a period around the middle of the day, starting after 11:00 and ending before 5:00. Transects are not walked when the temperature is less than 60 degrees F. Between 60-65 degrees, a transect may be walked providing it is sunny for at least 75% of the sections. Between 65-70 degrees F, a transect may be walked provided it is sunny for at least 50% of the sections. Above 70 degrees F, a transect may be walked in any conditions, providing it is not actually raining.

Wind speed is estimated using the Beaufort scale at the beginning and end of the monitoring time. Monitoring does not occur if winds are in excess of 19-24 mph. Wind direction, as well as the percentage of cloud cover and temperature are also noted.  The percent cloudiness is estimated by examining the sky from horizon to horizon.

If larvae are observed, then they are noted on the form. Energy sources that the butterflies are currently using, as well as the flowers/trees currently in bloom are also listed.

Transects are walked once a week starting April 1 through October 31, unless there is rain.

Each season, the information gathered through this project is submitted to the Cleveland Museum of Natural History for the statewide database. This information is also entered onto a Metroparks spreadsheet for input onto an accompanying GIS map that illustrates the particular butterfly species and butterfly counts found on each section of each transect. Finally, data is presented annually at the Oak Openings Research Forum and at Ohio Lepidopterist conferences.