Young Explorer Cara Brook is in Madagascar studying the spread of infections diseases to humans through bats consumed as bushmeat.
Pteropus rufus, the Madagascan Flying Fox, is the largest of the three species of Malagasy fruit bat, and the lone tree-rooster of the three. We’ve never netted P. rufus before, and our week of field sampling is an adventure in experimentation and learning—made possible only via the help of our twenty-three-year old Malagasy bat hunter and new friend, Ando.
How to Catch a Bat
Habitat-pressured P. rufus has resorted to suboptimal roosting in nonnative trees, especially in the more deforested boundaries of the Malagasy highlands, like the Mangoro River Valley in the District of Moramanga, where this week finds our work. And so, it is a Eucalypt which Ando scales to rig a pulley system from the tree-top.
We string rope and fishing line and specially-made artisanal nets in the canopy, then haul them from the ground to watch them flutter in the wind like a kite. At dusk, our nets are perceptible—though barely—and hundreds of flying foxes soar backwards and forwards, halting just shy of the line and performing impressive acrobatics to swirl backwards and evade capture.
As the sky darkens, our luck lifts. We catch bats on their way out of the roost for a night of fruit feeding—it is mango season, after all—and laboriously untangle them from our lines, hanging them nestled in pillowcases for the night.
Then, we, too, settle down on our windy ridgeline to shiver through the lonely hours, though it is soon—near 3am—when we rouse our stiff bodies from half-slumber to monitor the net again. And then the bats come back, and we catch them again until dawn breaks over the forest to the east.
And then we process—we take measurements of weight and length, we band the bats’ thumbs with numbered golden rings, and we take swabs of fecal, oral, and urogenital excretions to deposit into a stabilizing buffer and then into liquid nitrogen to await eventual export for PCR or viral isolation. We take hair snips to examine the bats’ diet based on the chemical isotope composition—you really are what you eat—and we draw blood from the pulsing brachial vein for serological antibody testing for our pathogens of interest.
It is November and breeding season for Pteropus rufus, and some of our bats carry a pup—usually one but occasionally two—and we measure and weigh and photograph these precious little creatures. It is thought that viral shedding rates are highest during periods of reproduction and lactation, and I wonder what results our slimy samples might yield in the coming months.
I wonder, too, what the population pressure is like for these bats, threatened by hunting and habitat loss. In ecology, density-dependent populations knocked below carrying capacity will try to regain some optimal population size by heightening per capita reproductive rates. Could our bats be doing the same? And could viral shedding be elevated in consequence? No one knows, but we are trying to find out…
Between netting and processing, there are hours at camp where I live in a half-dream state and marvel that a mere week ago I was bidding goodbye to my cohort, labmates, and housemates back at Princeton University. Already, the western world seems a lifetime away. I’ve never been much good at napping, so instead, I drink sugary Malagasy coffee around-the-clock and read and write and study my language flashcards while I watch the rice bubble and the etona—steam—hiss from the beans in our pressure cooker.
I find that word learning is a bit of a voyage down memory lane—I can see the place and moment and person who taught me every phrase, most over this past summer, but occasionally, too, from that first soujourn to southeastern Madagascar, back in 2010.
At night, there is fire on the mountain, for occidental fall is the season of tavy and doro-tanetry—the slash-and-burn agricultural practices used, respectively, for rice cultivation and cattle grazing in Madagascar—and this, too, is reminiscent of my first autumn on the Eighth Continent. I ask Christian why the farmers burn at night, and he tells me it is more discrete. “Not really,” I argue. “You can see the fire clear as day against the black sky.”
“You can see the fire, yes,” he laughs, “but not the man who makes it.”
And then—just like that—our week is up, and we head back to Tana, via bumpy kibota (tractor) and crowded taxi-brousse, clutching our vat of frozen liquid with its precious samples inside. At the laboratories of Institut Pasteur-Madagascar, the French and Malagasy scientists stare at our filthy hair and tattered clothing, as we unpack our échantillons into the freezer. We’ve managed to land Christian an official internship with Virology Unit at Institut Pasteur, but he laughs that most of their staff do work very different than his. “That’s because you’re the only one also working with a crazy American,” I grin, and he nods.
“Angamba adaladala antsika,” he says. Maybe we are crazy. “But if so, I am glad.”
Iaho koa, Christian. Me too.