The Echo
Putting a Price Tag on Cambodian Bats’ Worth

The Echo

Putting a Price Tag on Cambodian Bats’ Worth

Published on October 25, 2017
Written by Michelle Z. Donahue


Rising green and sudden from the low plains along Cambodia’s southwestern coast, the limestone karst hills in the country’s Kep Province are wild punctuation marks in a sea of surrounding rice paddies. At night, bats emerge from caves and crevices whittled into the cliffs, raiding the rice fields and forests for insect prey.

Reilly worked alongside Cambodian forestry officials and other
bat researchers to identify the habits of the karst-dwelling bat species.  
Courtesy of Reilly Jackson

Here and in other places like it throughout the country, fields are the financial lifeblood for a majority of Cambodia’s population. After tourism and textiles, agriculture is the third largest sector of the economy. But construction is booming, and increasingly, locals and corporations are targeting the karsts as a source of limestone.

And as go the karst, so do the bats. But what will happen to the fields if the pest control the bats currently provide diminishes?

To begin to answer that question, University of Tennessee grad student Reilly Jackson spent most of July and August in Kep, working on a project that seeks to define the economic impacts of the region’s cave-roosting bats. Supported by a grant from BCI, Jackson worked alongside Cambodian forestry officials and several other bat researchers to capture and identify which bats live in the karst, where they are foraging, and which insect species they are consuming in the fields surrounding their roosts.

The team hopes to be able to put a price tag on the economic
value of karst-dwelling bats.
Courtesy of Reilly Jackson

This was her first visit to Cambodia for bat science, though she came equipped with plenty of experience from previous cave work in Tennessee and Belize. Despite fieldwork coinciding with the start of the monsoon season, Jackson timed the trip to take advantage of peak bloom in the rice fields. Insects and bats alike would be present in large numbers, giving her a better chance of catching and identifying as many species as possible.

Via Skype, Jackson described her first three weeks in the field as productive.

“We’re catching between 20 and 30 bats in a night,” she said. “That’s higher than anything we work with in the United States.”

Along with University of Tennessee colleagues Emma Willcox, Riley Bernard, and David Ader, who spends roughly half of each year in Cambodia, Jackson worked in five caves and their surrounding fields and villages. Neil Furey, a biologist with Fauna and Flora International, and a specialist in Southeast Asian bats, also assisted the team with site selection.

Jackson’s Cambodia work builds on earlier work conducted in Thailand, where researchers from Stanford and Germany looked at how populations of wrinkle-lipped bats (Tadarida plicata) were connected to pest control in local crops. They found that the bats’ consumption of white-backed planthoppers in rice prevents a loss of 2,900 tons of rice annually, enough to feed 26,200 people every year.

Black-bearded tomb bats (Taphozous melanopogon)
were one of the species observed during
Reilly's fieldwork
Courtesy of Ch'ien Lee / Minden Pictures

While that study was looking at the impact of a bat species that can gather by the millions in its roosting sites, Jackson’s work in Cambodia focused on smaller, mixed-species congregations with several hundred to thousands of bats.

“By looking at the bats’ dietary components, and cross-referencing that with what’s in the local agricultural fields, we hope to put a price tag on the economic value these bats are providing for agriculture,” Jackson said. “Though that’s far down the line though, this is a pilot study where we’re hoping to collect the data we need to start this footwork.”

In the first several weeks of netting, Jackson caught a number of primarily insectivorous bats, including greater roundleaf bats (Hipposideros armiger), least horseshoe bats (Rhinolophus pusillus) and black-bearded tomb bats (Taphozous melanopogon). False vampire bats (Megaderma lyra) also turned up; though they do eat larger-sized insects, these carnivorous predators primarily eat birds, other bats, reptiles and fish.

Using mist nets to capture bats for physical identification, Jackson also collected fecal samples from each bat, which will be analyzed in her home lab for insect remains and DNA. With that information, Jackson and her colleagues will be able to begin making early assessments of the bats’ economic value to the farmers, in terms of damage avoided through bat-based pest control.

The 2017 work was focused primarily on gathering basic data, including setting up echolocation stations to create a library of calls from bats present in the region. Jackson plans to gather more insect information on a return trip set for the summer of 2018.

False vampire bats (Megaderma lyra) hunt rodents
and other agricultural pests.
Courtesy of Stephen Dalton / Minden Pictures

Though the caves are currently of high interest for mining, excavations is only the latest threat to Kep’s bats. Humans have long used the bats’ roosting sites for religious ceremonies and observations; Jackson said that locals frequent four of the five caves her team visited for surveys because they contain shrines.

Combined with disappearing habitat and long-term, prolonged disturbance by humans visiting the caves, the pressures may be too much for the bats to overcome.

In December, Jackson said the team hopes to start a pilot project in the region to survey residents of the villages around the caves and get a sense of locals’ opinions on bats, as well as talk with them about the benefits of keeping healthy bat populations nearby. That will help lay the groundwork for encouraging conservation at the community level.

“Most of the people we’ve been talking to are super open and supportive of what we’re doing,” Jackson said. “The communities there are pretty tight knit, so when one is interested, others will be interested as well. We hope this opens up positive communication about bats, and why the areas where they live are so freaking cool. We’re just hoping to give them the tools and information on what’s going on around them, and help them make the best-informed decisions possible.”

 

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