June 15, 2007
Researchers Track Butterfly Populations
MIAMI -- The volunteers tote a butterfly net, binoculars and field guides around the Miami Metrozoo grounds, scanning the plants and flowers for fluttering wings. But they aren't searching for a rare species or collecting specimens for display - they're counting butterflies for the Florida Butterfly Monitoring Network, then leaving the insects to continue their zigzagging flights through the humid air.
As the summer butterfly watching season warms up, researchers hope similar counts organized by the North American Butterfly Association and a few separate state monitoring networks will contribute new data to help track butterfly populations and develop land management strategies.
Basic counting gives researchers a picture of where butterflies currently thrive, and alerts them to population and habitat changes, said Jaret Daniels, a researcher at the University of Florida's McGuire Center for Lepidoptera and Biodiversity who modeled the Florida network in 2003 after similar networks in Illinois and Ohio.
The counts may help scientists prevent any more butterflies from becoming as rare as the Miami blue, a quarter-sized species now found only on one island in the Florida Keys, Daniels said. The Miami blue was abundant throughout South Florida a generation ago, and scientists were slow to recognize the extent of its decline.
"Once we have multiple years of data, we can start looking at trends of these species, and identify declining species before they become so rare that they need to be listed" as endangered species, Daniels said.
All the counts follow roughly the same protocol: Volunteers walk at a steady pace along a fixed route through a predetermined location, counting the butterflies within view. Butterflies can be briefly caught for identification, but volunteers can't chase butterflies too far from the designated path. All individual butterflies seen during the count, along with the weather, are noted on a data sheet later submitted to NABA or one of the state networks.
At Miami Metrozoo, a monthly count is split between the natural pine rockland and a cultivated butterfly garden in the children's zoo. Volunteers have been trained to identify dozens of species drawn to the wild and manmade habitats.
On a recent morning just after a rainfall, a handful of tiny butterflies are spotted from a gravel path through the rockland. A pale blur no bigger than a quarter is easily identified mid-air as a common Florida butterfly, the Cassius blue.
"The low-level flying, the erratic path, then you can see the tinge of blue," said volunteer Yvonne Leung, 55, of Miami.
A darker dot fluttering above the gravel is harder to identify by flight pattern alone. Adam Stern, the zoo's invertebrates expert, traps it in a butterfly net and gingerly transfers it to a clear plastic container so the volunteers can compare its tawny-orange wings with pictures in their field guides. After a minute, they conclude it's a Baracoa skipper and release it; Stern would have photographed it for identification later if the group had not been able to name the minuscule, fast-flying butterfly common to South Florida lawns.
More butterflies are counted in the walk through the gardens in the children's zoo: Striped zebra longwings, including one laying eggs, and bright orange Julias float in the sunbeams breaking through the clouds.
The diversity of butterflies flying across the zoo's property has surprised Stern since he began leading the Metrozoo counts four years ago, with some species differentiated only by subtle markings.
"So what you thought was one type of butterfly, once you stopped to look at it, actually became four different butterflies that you'd been counting as one," he said.
About 3,000 people participated in 483 NABA counts across the continent last year, according to the New Jersey-based organization. While the participants are mostly amateurs, they collect information individual scientists cannot easily access, such as large-scale surveys of migratory species across multiple states, said Leslie Ries, a postdoctoral researcher at the University of Maryland who is analyzing three decades of NABA counts. She has found the data matches results independently compiled by the Illinois and Ohio butterfly monitoring networks from about 100 sites across each state.
Through the data, the seemingly inconsequential butterfly shows how people have altered the environment, said Joe Keiper, curator of invertebrate zoology at the Cleveland Museum of Natural History, which organizes the data collected by the Ohio monitoring network.
According to the counts, the most common butterfly now in Ohio is the cabbage white butterfly - a species native to European lawns and meadows, Keiper said. The absence of a species from a site count is also revealing - such as in the case of the West Virginia white, whose forest habitat has been decimated by development and exploding deer populations.
The national and statewide counts have encouraged some butterfly watching groups to keep statistics that might help local conservation efforts. The Miami Blue Chapter of NABA, for example, has adopted the nationwide count protocol into all their field trips through southern Florida and the Keys.
"We think if we keep track a little bit better, use these walks as censusing devices, who knows when we're going to want to have an argument with Everglades National Park over burning or mowing or herbicides?" said Elaine Neuhring, the chapter's program chair. "If we could pull out three years of censusing, wouldn't that be interesting?"
On the Net:
Florida Butterfly Monitoring Network: http://www.flbutterflies.net
North American Butterfly Association: http://www.naba.org
Ohio Lepidopterists Long-Term Monitoring of Butterflies: http://www.ohiolepidopterists.org/bflymonitoring/
Illinois Butterfly Monitoring Network: http://www.bfly.org