Two tiny out-of-state vacationers have given wildlife biologists a "Eureka!" moment.
A couple of endangered bats - chestnut brown with a Garbo-esque shyness and a Chuck Yeager need for speed - have relocated from the deep recesses of a limestone cave to leafy hickory trees in Carroll County.
They're called Indiana bats, although these two winter in Pennsylvania's Canoe Creek State Park. And fewer than 400,000 of them are left in the United States.
Biologists have long suspected that Indiana bats make the trek to Maryland each summer to fatten up on bugs and have their young.
This is the first year, however, that they have been able to prove it. That could help them save the species.
The joint research project by the Pennsylvania Game Commission and the Maryland Department of Natural Resources might begin to answer a question similar to one posed by human parents this time of the year.
"We want to know who are they spending the summer with and what are they doing," says Glenn Therres, the DNR associate director for endangered species.
Because of their size - 3 inches long and weighing about a quarter-ounce - the bats aren't candidates for traditional radio collars used on other migratory animals.
A Canadian company built a transmitting backpack with a 21-day battery life that weighs less than a paperclip.
That, it seems, was the easy part. Snaring six female bats to wear them was another matter.
In April, Pennsylvania biologists set a trap at the entrance to Hartman Mine, near Altoona, and waited for an exodus of 25,000 migrating bats, most of them other species.
As the critters hit fishing line strung across the opening and dropped into a catch bag, biologists plucked six Indiana bats large enough to carry the transmitters without difficulty.
No sooner were their little backpacks glued in place than one bat zoomed off to the east, a small state airplane and ground trackers in pursuit.
"You're basically chasing a Tic-Tac in the dark for 92 miles," says Cal Butchkoski, the biologist who sat beside the pilot, giving directions. "Time was important because of the battery life. We picked one and gave chase."
Like a moth, the bat took a dizzying 60-mile, post-midnight tour of southern Pennsylvania - including a stop at the Gettysburg battlefield - before heading south and settling several days later in a hickory tree in Wentz, just south of the Pennsylvania line.
Teams of ground trackers, working in shifts, followed another bat to its Taneytown roost. Trackers lost a third bat along the lower Susquehanna River near the state line.
Researchers are overjoyed with their newfound ability to shadow the pocket rockets. In 1967, Myotis sodalis was one of the first bat species to be placed on the federal endangered species list.
The population declined because of vandalism of caves, the increase in spelunking and possible pesticide poisoning.
"We've long concentrated on the hibernation sites, but summer habitat and migration routes are just as important and just as critical," says Butchkoski, who has been studying Indiana bats for nearly 20 years. "Other states with Indiana populations can use our techniques to study migrating bats to identify, manage and protect summer roosts."
The bats' range includes the eastern United States and part of the Midwest.
The project is shifting below the Mason-Dixon Line, where Maryland biologists will try to determine whether there is something special about the roost sites, where each bat will raise a single offspring.
The Taneytown bat is in a maternity colony of 64 animals; the Wentz bat is residing with 30 others. Pennsylvania has lent three backpacks to Maryland for additional tracking.
"We didn't envision them crossing the Pennsylvania line," says Therres. "We're at the beginning of the answer. We're at the beginning of the puzzle."