He wants their blood

It was around midnight in a dark, quiet Sherborn barn when Chris Richardson put his foot on the top of the stepladder and reached back to his assistant, T.J. Porter, for the big net.

Paying no heed to the safety sticker on the ladder warning him not to climb so high, Richardson directed his attention -- and the light of his headlamp -- to a cluster of fuzzy brown creatures clinging to the peak of the ceiling overhead.

``I hope they don't pee on me," he said. Then he began cooing reassuringly as he reached for one of them, using long forceps.

Those creatures, bats, are Richardson's life, or at least they have been for the decade he's been studying them in the Boston University lab of bat expert Thomas Kunz, director of BU's Center for Ecology and Conservation Biology, under a National Science Foundation grant.

This summer, the Newton resident has frequented the barns of Sherborn, catching the flying mammals and testing the level of the stress hormone cortisol in their blood. He's interested in how their environment affects their stress levels and how stress may affect their immune system, specifically their resistance to rabies.

Richardson, who recently received his doctorate for work on bats, has been focusing on the big brown bat, which is common to the area. The bats have a wingspan of about a foot, but their bodies are about the size of an adult's thumb. Fully grown, they weigh around 15 grams, about half an ounce.

Bat hunting can be a tricky proposition. Sometimes Richardson and his two assistants arrive in the middle of the night to find that there are no bats hanging around. Once they are caught, bats try to bite anything nearby with their tiny, V-shaped jaws as they screech and chatter like cicadas on speed. Richardson and his bat-catching crew had rabies shots as a precaution before beginning this year's work.

Richardson's team found this barn, well off the street near Farm Pond, after canvassing the suburbs early in the summer, hanging posters seeking tips about likely bat hangouts.

The team is also studying bats at several other barns in town, as well as at Town Hall. Sherborn selectmen recently approved Richardson's access to the building amid jokes about the town having bats in its belfry.

Arriving at the barn on a recent Thursday night after a drive along pitch-black roads, Richardson and his two assistants worked with stealth as they hauled nets, a tank of liquid nitrogen, and other equipment from the trunk of Richardson's aged Nissan Sentra.

Richardson was glad to see the bats were home because when the weather turns cold, the colony, which numbers about 40, huddles out of reach behind an attic wall in an adjacent house.

His assistants, Porter, 22, a Lexington resident and recent graduate of the College of Wooster in Ohio, and Maria Tosa, 17, an Arlington resident and high school senior at Boston University Academy, patiently worked to string one bat-catching contraption, called a ``harp trap" for its resemblance to the musical instrument, in a barn window. A net, as thin as a spider's web, was also hung from a rafter. The creatures snoozed, seemingly unaware of the team's presence.

With the nets in place, the crew set up a makeshift lab near the doorway of the barn, opening a fishing tackle box of supplies that include tiny glass vials for collecting blood samples, drawstring cloth bags for storing bats after testing, and the all-important notebook where data was to be recorded.

Richardson has previously studied the cortisol levels of bats clustered around the expansion joints of a bridge in Alabama. Oddly, those bats appeared less stressed than those in the quiet Sherborn barns. Richardson's figures supported research by a scientist in Indiana who is looking at the stress level of bats near a military base.

There's a lot to learn from the bat, Richardson said.

``Every time we have more understanding of how hormones are affected by different influences, it gives us a better understanding of the whole basic system of physiology," he said.

Bat researchers are also interested, Richardson said, in how the animals' hormonal signals change, allowing them to overeat to store energy before they hibernate, which could be important information for the study of obesity in humans. And they're interested in the bats' torpor, a deep state of rest in which their metabolism slows.

With all the equipment in place, Richardson plucked a bat from the eaves, dropped it into a net, then handed the net off to Tosa. The cool evening helped, Richardson said, because the resting bats were torpid, which made the cluster much less likely to scatter when he disturbed one or two.

Tosa took the bat out of the net, letting it bite her gloved hands. The night was so cool she removed her headlamp and held the squealing bat against it to warm it so the blood would be easier to collect. Richardson sat across from her on a camp chair as she spread the bat's wing to expose a tiny vein that runs behind its leg. The light from the headlamp easily shone through the brownish, paper-thin wing.

``Awesome," Richardson whispered. ``Now we'll get some blood." Asked whether he finds it ironic that he's acting out the reverse of the Dracula myth, he grunted but offered no response.

Soon, he held one of the needle-thin vials against a measuring stick to determine whether enough blood was collected -- a minuscule amount, he said, that is about equivalent to a couple of drops from a human. He went out to the portable centrifuge, which disturbed the quiet barnyard briefly with a whirring sound while separating plasma from red blood cells. The vial was labeled and frozen in the nitrogen.

Then Richardson headed back to grab another one. Other bats flew into the harp trap or the net and were collected there.

``I've done this hundreds, thousands of times," he said.

Along with the blood samples, he takes four or five bats from each trip back to his BU laboratory for further study. After a day there, the bats are driven back to Sherborn and released.

Optimal conditions for collecting specimens exist only a few weeks in summer. That's when Richardson's team is most active.

The work is embraced by some residents. Gail Cronin welcomed Richardson back to her 120-year-old barn on Washington Street this summer for the 10th year. Cronin and her family feel a part of his work, which has included showing bats, close-up, to local kids. ``They're wonderful people," she said.

Sherborn turns out to be a treasure trove of bats. Bats like the town because it's not too developed, compared with areas closer to Boston, Richardson said. ``And for some reason, a lot of people haven't torn down their old barns. This is the closest thing to their optimal habitat, which are old growth hollowed-out trees."

In addition to the barns and Town Hall in Sherborn, Richardson collected bats this summer from a huge colony of about 700 in an old Milford, N.H., barn, and a colony at an 18th-century farm in Petersham in Western Massachusetts.

Before bats, Richardson, 38, a Milwaukee native and graduate of the University of Wisconsin at Madison, studied rodents. Then he learned about Kunz's program at BU. ``I came to realize this species was ideal for my PhD," he said. ``I wanted to study evolutionary physiology and the interplay of ecology and physiology."

Tosa will use the summer's work for a senior thesis, relying on Richardson and Porter's later lab work to fill out the data she'll need. Bats are a means to an end for her. She's really more interested in animals other than bats, she said.

Porter studied biology at college. Whether he'll contract Richardson's nearly rabid enthusiasm for bats isn't clear. ``I know I'll be doing this at least for the next year," he said.

It's been a long summer for Richardson, who jokes that his nighttime schedule has caused him to become more bat-like -- nocturnal and stressed by his environment. He acknowledges having some frustrations. Despite catching dozens of specimens, he has only been able to officially record results of less than a dozen tested thus far due to laboratory glitches. He had hoped for 40 by now.

Richardson, whose official title is postdoctoral research associate, can reel off reams of information about bats at the drop of a hat. He said some people react strangely when they learn how he spends his time.

``Most people are pretty freaked out by bats and they think I'm kind of a novelty," he said.

The cold weather will soon end his field work and he'll be back in the lab for the winter, with time to work on his speech for next month's North American Symposium on Bat Research in North Carolina. By next May, he hopes to be back in the suburbs, catching bats again.

Alison O'Leary Murray may be reached at amurray@globe.com.