Media & Education
BATS Magazine

Volume 39, Issue 1, 2020

The Stinky Part of Bat Research

Scholarship recipients explore bats’ role in pollinating the world’s most pungent fruit

By Lynn Davis


It’s been called fetid, putrid, disgusting, and gagging. It’s been likened to the smell of wet garbage, old gym socks, rotting melon, turpentine with a hint of onions, and several impolite terms this polite conservation organization will avoid.

If beauty is in the eye of the beholder, surely the smell of durian—long considered the world’s stinkiest fruit—is an acquired smell and a cultivated taste. In Southeast Asia, where durians grow on trees, the fruit is favored by bats and sought after by multitudes of humans.

Yes, despite the pungent smell and the fact that hotels and public transit systems have banned people from carrying durian into public spaces, there are lots of people who consider durian a treat and a delicacy. Durian is a very marketable item, and the economics of the durian market—saving durian trees—may ultimately be the best way to save bats, particularly the flying fox, which is also considered an edible delicacy.

The Research

Dr. Amanda M. Adams, BCI’s conservation research manager, wouldn’t go so far as to add durian to her top food choices. She sampled it, claims it’s “not that bad,” and acknowledges she tasted a mild version of the thorny-on-the-outside, pulpy-on-the-inside fruit. Indeed, it’s safe to say Dr. Adams’ interest in durian is not epicurean or olfactory. Rather, it is directed at the symbiotic relationship bats have with pollinating the notoriously stinky fruit.

For the past year, BCI has supported field research in Sulawesi, a large island east of Borneo and south of the Philippines. Governed by Indonesia, the sprawling island of four extending peninsulas was once lush, nurturing more than 100 endemic plant and animal species found nowhere else on Earth. Today, according to a comprehensive ecological study, 80 percent of Sulawesi’s forests have been decimated or degraded due to unbridled logging and clearing for agriculture projects. The result? Many of Sulawesi’s endemic species—including one bat species—are now considered endangered.

Enter a dauntless researcher named Sheherazade, who goes by Shera. With a single name only, common in her country of birth, Shera grew up in an Indonesian city and spent her childhood holidays at a family farm planting strawberries and tomatoes. She never envisioned that her academic studies and career would take her up dizzying heights with the goal of capturing bats in her leather-gloved hands, or that her research would lay the foundation for preserving three bat species. Shera applied to BCI for a grant to study how bats might be pollinating durian trees, with the hope of documenting how bats are important to the island’s economy.

“What needs to be noted is that island residents were bush hunting bats for their meat and not making the connection that bats are important to the local economy in pollinating the durian and sustaining the durian harvests,” Dr. Adams says. “Shera’s proposal addressed two facets of conservation work: documenting important data and building the case that healthy conservation practices can support local economies.”

The BCI Student Scholarship grant Shera received was from a fund dedicated to assisting bat conservation research in developing countries.

Shera and fellow researchers Holly Ober and Susan Tang went to work climbing durian trees, numbering the flowers on target trees and setting up three different study treatments. In one, the research team “bagged” flowering blooms to prohibit pollination. In another, the team “netted” blooms so only insects could pollinate the blooms. The third treatment numbered “open” blooms and employed camera traps to record all interactions that animals (including bats) made with unobstructed blooms.

The research team published their findings in the journal Biotropica in October 2019. Key findings included:

  • Three bat species were observed pollinating durian flowers: the small Cave nectar bat (Eonycteris spelaea), the larger black flying fox (Pteropus alecto), and the Sulawesi flying fox (Acerodon celebensis).
  • Durian flowers accessible to bats had much higher rates of pollination.
  • The overall presence of bats positively influenced the production of semi-wild durian in the surveyed areas.

Using bio-economic data, the researchers estimated the value of the bat pollinators as $117 per hectare (approximately $47 per acre) during the fruiting season. Some of their additional findings noted that bats made contact with the stigma (where pollen germinates) and the anther (where pollen is produced), often making contact with both, which is crucial to successful pollination. Most notably, all bats drank nectar without harming the flowers, which is not an easy feat. Large species, like the Sulawesi flying fox and black flying fox, were observed hanging down and bending their heads to access the nectar, resulting in minimal bloom damage.

Dr. Adams, who worked with bats at Tolga Bat Hospital in Australia and studied bats in Jamaica, Cuba, Belize, Costa Rica, Canada, Israel, and Mexico before joining BCI, is enthusiastic about BCI’s global research. She is also optimistic about student research.

“Shera’s work illustrates our increasing global presence,” she says. “Last year, we funded nine meaningful grants. We’re getting the word out to up-and-coming conservationists that we have available grants and we’re helping students apply for additional funding. BCI-supported work in Indonesia with durian pollination is just one of many interesting research projects in the world of bat conservation.”

[Sidebar]

What do we know about bats and their sense of smell?

Not enough, says Dr. Amanda M. Adams, BCI’s conservation research manager. We know the ability to smell is very important to some bats, like fruit-eating bats. We also know that some bats use pheromones in their courtship rituals. But more research is needed.

Male Greater sac-winged bats (Saccopteryx bilineata) in the rain forests of Central and South America rely on scent to attract their mates. The male fills the sac-like pouches on his wings with drops of urine and other secretions, and then hovers in front of his female target, flapping his wings to waft his scent.

 

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