ATM blogger Megan Gambino is spending this week in Panama reporting on research taking place at two locations—Barro Colorado Island and Bocas del Toro—of the Smithsonian Tropical Research Institute (STRI). Read on in this dispatch and in future installments to follow her day-to-day adventures.
Day 1, Part 2: A Visit to Bat Cove
Elisabeth Kalko, one of the foremost experts on bats, spends two months a year, usually March and sometime between July and October, conducting research at Barro Colorado Island. Luckily, I managed to catch her there just before she planned to head back to Germany, where she is the head of the experimental ecology department at the University of Ulm. And I couldn’t pass up her offer to take me out to "Bat Cove," just a five-minute boat ride from BCI.
We left just before sunset and anchored in the cove. On the edge of the forest, Elisabeth explained, there is a 65-foot-tall hollow tree where Noctilio leporinus, the only bat on the island with fish as its primary diet, has a roost. Also known as the greater bulldog bat, Noctilio swoops down over the water, snatching fish in its talons. Apparently, it curls its head down to grab the fish to eat, chews it and fills its cheek pouches like a hamster. Elisabeth and a grad student working with her set up their echolocation recording equipment in the boat as we waited for dark to set in and the first bats to start foraging.
To put things in perspective, there are 1,100 species of bats in the world. Around 120 (over a tenth of those worldwide) live in Panama, and of those, 73, ranging in size from three grams to the notorious vampire bat that’s the size of a small puppy, can be found on BCI. Elisabeth has worked closely on understanding the behaviors of a quarter of the 73 and probably observed 60 of them. Her interest is the various foraging strategies and other behaviors that have allowed so many species to coexist. In her research, she has found bats that live in termite nests; bats off the coast of Baja, Mexico, that forage miles into the ocean; and bats that use echolocation to find stationary prey, like dragonflies perched on leaves.
Elizabeth had a bat detector with her on the boat that could pick up the high frequency echolocation calls of nearby bats and make them audible. Slowed down, the calls sounded like the chirps of birds, and Elizabeth can recognize the species from the frequency and pattern of the calls. The chirps would come in loud on the detector, and her research assistant would cast his headlamp across the surface of the water. "Wah!" Elisabeth would exclaim as one flitted by the boat.
In the beginning, several circled the area. But as the night wore on, the activity calmed down, mostly because it was just a day or two after the full moon, and bats don’t like that much moonlight; most insects don’t come out then. It was certainly a surreal experience. I think Elisabeth put it best when, perched on the bow of the boat, looking up at the moon, she said, "So many billions of people in the world are doing the same thing, day in and day out. But we three are the only people out here, looking for fishing bats."