College: Graduate Center
Awards: Fulbright-Hays Group Projects Abroad Program, 2012
Relying on the Wings of Bats
The flying fox - cute by some measures, deadly by others.
With its foxlike head and large eyes, this animal has charisma not usually associated with a bat. But with bodies the length of a human forearm and wingspans of up to five or six feet, it can fly between islands in Southeast Asia and the Pacific, making it a perfect carrier of infectious diseases.
Working with the Center for Biodiversity Strategies at the University of Indonesia, Susan Tsang (CUNY Graduate Center, PhD in biology expected in 2014) is traveling into the jungle as a 2012-13 Fulbright Scholar to study the phylogeography of these animals - that is, how flying foxes are distributed in space and time in a given region.
"If we understand how populations are interconnected, we can improve global health," she says. "These bats are integral parts of the island ecosystem in Southeast Asia and the Pacific; they act as seed dispersers, which are necessary for the continued health of the forest. We also need to understand the ecology and evolution of a host as much as a pathogen in order to take preventive measures in case of an epidemic."
The risk of a bat-derived epidemic - like the fictitious one dramatized in the 2011 Steven Soderberg film "Contagion" - is a legitimate concern. Without getting sick, flying foxes have carried diseases like Lyssavirus and Hendra virus, which have killed livestock and people. They live in vast colonies of up to 50,000, where they easily can transmit viruses among themselves. And because flying foxes are fruit-eaters (unlike their insect-eating American bat cousins), they can transmit disease by dripping saliva onto fruit or defecating into sap-collection containers.
What's more, humans hunt them for food. "Their populations have dropped by 50 percent since people started taking bat counts for them," Tsang says.
Yet, she says, scientists have paid scant attention to flying foxes as disease vectors, focusing much more on birds and swine.
There are 65 recognized species of flying foxes (genus Pteropus) that traverse the Pacific and Indian Oceans from New Guinea and Australia, through tropical and subtropical Asia to the islands off eastern Africa.
Tsang became interested in bats as an undergraduate at Skidmore College (BA in biology, magna cum laude, 2009), for bats are not nearly as well studied as birds - and uncharted islands of knowledge lure researchers.
What really caught her attention is that, unlike most bats, flying foxes do not use sonar to navigate but rely upon their eyes and keen sense of smell. And with their large and flat teeth (as opposed to the American bat's little sharp teeth), they eat only plants. How and why they are so different from most other bats is a question that has caught the attention of many researchers, but the answer still remains unknown.
DNA that Tsang will collect could shed light on how the flying fox evolved away from sonar and got so big as well as to map flying fox populations. And with those maps, disease-prevention experts can plan containment strategies. "I have a collaborator in Singapore who determines what viruses bats have," she says, "but there hasn't been that much effort put into virus-discovery yet."
To learn how to handle flying foxes and see whether she could collect DNA noninvasively from fecal samples at roosting sites, Tsang last year used a National Science Foundation East Asia-Pacific Summer Institute Graduate Fellowship out of Singapore to spend time with captive bats. "It's a good, noninvasive method that could stimulate research in this notoriously elusive bat," she says.
In June, she will head out into the wild with her advisor and collaborators, assisted by local guides. Besides collecting bat guano, she will capture live individuals, take a biopsy punch (a small sample of the skin of the wing that does not hurt them) and swab the insides of their mouth, looking for diseases. "They might have herpes in the mouth but an entirely different set of viruses in their feces," she says.
During her Fulbright year, she hopes to broaden her DNA-gathering by going through flying fox specimens in various Indonesian collections - "skins that they've collected over hundreds of years. That would increase my sampling." In addition, she intends to visit more sites in Indonesia where roosts have been found.
Tsang, who was born in Hong Kong and came to the United States with her family when she was 5, says she chose to do her doctoral research at CUNY because of its partnership with the American Museum of Natural History. She works with CUNY Assistant Professor David Lohman, a butterfly expert who has worked extensively in Southeast Asia, and Nancy Simmons, the museum's curator of vertebrate zoology.
"Your goal at the end of your graduate studies is to become the expert in that thing," she says. "My advisors are experts, and synthesizing what I have learned from them is part of the fun of doing independent research."
And then there's the joy of fieldwork. "These are impressive animals," she says, "and when 15,000 of them go foraging for food at dusk, it darkens the sky."