Rare Dragonfly Calls Rondout Reservoir Home

One of our field ecologists recently discovered an extremely rare species of dragonfly living along a small tributary that feeds into Rondout Reservoir. This particular dragonfly is considered critically imperiled in New York, and it is rare enough that many experts fear localized extinction in the few places where it is known to exist.

The dragonfly, known as the Southern pygmy clubtail, can only survive and reproduce in extremely clear and clean waters. Read the Press Release.

The Discovery

Field Ecologist Frank Beres discovered the dragonfly during a short hike to a water-quality sampling site in the forest surrounding Rondout Reservoir. In addition to his work at DEP, Beres is a naturalist who has photographed and documented thousands of macroinvertebrates, insects, birds and other animals.

After Beres spotted the rare creature, it hopped on his finger and took a pose, allowing him to take several photos before flying off.

“One of the most exciting moments for an ecologist or naturalist is the sighting of a rare species,” Beres wrote in a brief report about his encounter with the dragonfly. “This chance encounter with a rare, unique, secretive and delicate organism that requires a specific, pristine habitat emphasizes the ecological intricacies of the Catskills and the importance of all work performed to assess and protect lands and waters in the watershed.”

The Southern Pygmy Clubtail

The Southern pygmy clubtail’s habitat is limited to pristine and rocky streams, groundwater-fed brooks, and seepages in forested areas. Its larvae do not thrive in areas with excessive sedimentation pollution (read about How Sediment Causes Pollution). Their sensitivity to sedimentation pollution makes them an excellent indicator of water quality. They are so secretive and rarely viewed that little is known about the species’ life, habits and population dynamics.

The Southern pygmy clubtail (Lanthus vernalis) originates from an ancient genus, Lanthus, that branched into three species more than 175 million years ago. Its dwindling population in New York and the Northeast have been documented since 2000, and a five-year survey failed to find the dragonfly at half the New York sites where it was known to historically exist. As a result, the New York Natural Heritage Program upgraded the Southern pygmy clubtail to “critically imperiled” in 2012. That ranking describes species that are especially vulnerable to localized extinction due to their rarity, restricted range and habitat, or steep population decline.

Indicators of Water Quality

Our scientists regularly collect macroinvertebrates and insects from streams in the watersheds that feed New York City’s reservoir system. The careful analysis of these stream-dwelling creatures can tell us a lot about water quality, as many of them can only survive in extremely clean and cold water. By tracking their presence over time, we can also understand trends in water quality at different locations throughout the watershed.

The examination of macroinvertebrates and insects compliments a wider program of water quality monitoring we perform every day of the year. In 2018, our scientists collected 53,200 samples of water from the watershed and sampling stations in the five boroughs of New York City. Those samples were analyzed 654,000 times for approximately 240 water quality parameters. A growing network of robotic monitoring instruments on the reservoirs provided another 1.3 million water-quality data points that were analyzed by scientists and engineers throughout the year to help operate our reservoir system.