The Costs of Bat Decline
June 5, 2025
Can we afford to lose bats? A recent study by Eyal Frank of the University of Chicago reveals that the dramatic decline in U.S. bat
For me, our trip highlight was the visit to the Khao Chong Pran Cave in Ratchaburi Province. Nearly 40 years ago Buddhist monks who owned the cave had asked my advice. Their monastery relied on bat guano fertilizer sales for support. But in 1981 production was plummeting. Of course, and the monks wanted to know why.
Before dawn the next morning, my then young field assistant and interpreter, Surapon Duangkhae, and I discovered poachers using large fish nets to capture bats at the cave entrance. They were selling them to local restaurants. We hired two of the poachers to help us document the extent of the problem, then advised the monks to hire a game warden to protect their bats.
Having returned in 1989, 2012 and 2015, I was aware of a massive success, best documented by growth in guano sales from less than 13,000 U.S. dollars in 1981 to 135,000 by 2002, not to mention emergences visible for more than a mile. Also, thousands of tourists had begun visiting to enjoy the spectacular event.
Nevertheless, during my 2015 visit, I was informed that, despite careful protection, the cave’s Asian wrinkle-lipped bats (Chaerephon plicatus) were again in decline. At a glance, the cause was apparent. Trees, vines, and other vegetation had grown too near the main entrance. Jet-like-flying wrinkle-lipped bats simply couldn’t avoid them, undoubtedly giving predators a feast.
With Pongsanat’s interpretation I quickly explained to a monk and wardens that trees and other vegetation needed to be removed from within 20 meters of the cave entrance, especially in the bats’ primary flight path.
On this year’s return I was anxious to evaluate the impact of my 2015 advice. Again, the guano harvest removed any doubt. The average weekend harvest had risen from roughly 300 to nearly 600 buckets, now selling for more than 200,000 U.S. dollars annually!
Additionally, research published in 2013 had documented that these bats were already saving rice growers 300,000 dollars per season in avoided planthopper damage.
Despite the huge progress seen, we also discovered new problems. Fast growing vegetation was already beginning to renew its encroachment. Additionally, two smaller entrances had been covered with wire mesh. As a result, thousands of emerging bats were colliding and falling to the ground.
We were fortunate to have Surapon join our group. Inspired by his 1981 field work with me, he had become one of Southeast Asia’s leading conservationists. And he was an outstanding help in explaining these bat management needs to Wisuthanathkun. We pointed out that if the mesh was removed and replaced by protective fencing, that didn’t interfere with bat emergence, the cave could shelter even more bats.
Wisuthanathkun has become an enthusiastic bat conservationist. He proudly recalls Surapon and my first visit when he was just a young novitiate in training. He is now the head monk, supervising 84 temples as a powerful friend of bats. Thanks to him, commercial hunting is now illegal in the region.
He also was exceptionally gracious and took time from his busy schedule to meet with our group, explaining how much bats had benefitted a whole region of communities who share in the proceeds from guano sales and tourism. He was especially proud of how bat funds enabled him to support the local school, including scholarships for worthy students to attend college.
We were mesmerized by the spectacular evening emergence. And the next morning we were allowed to enter Khao Chong Pran Cave to observe the weekly guano collection among the millions of returning bats who roost high overhead. The long-protected bats ignored us. But there were some in-cave surprises, such as Clara’s discovery of a rat perched on her shoulder!
The next morning, we climbed to the cave’s main entrance to inspect for potential problems.
Obviously, our trip accomplished much more than entertainment. It enabled us to provide crucial conservation advice and inspiration wherever we went, expand our photo gallery, and train participants with hands-on field experience in bat surveys and photography.
Best of all Surapon, who is now officially retired, has volunteered his invaluable expertise and connections. He will serve as MTBC’s Thailand Representative for Bat Conservation. Our initial goals include production of educational programs and exhibits for the locations we visited, especially students at the Khao Chong Pran school, and support for the temple monks in their enthusiastic efforts to educate visitors regarding the many values of bats. We’re also preparing a long-term management plan for Khao Cong Pran’s bats and hoping to obtain grant support to underwrite the cost of editing Teresa’s outstanding video material documenting the Khao Chong Pran story.
Following our groups’ return home, Surapon spent two days aiding in key introductions and interviews, including the head forester responsible for protecting area bats, the Khao Chong Pran monks, the local school principal, teachers, and students.
He also organized a meeting with Dr. Boripat Siriaroonrat, Director of Thailand’s National Science Museum, followed by a lecture for his staff. They have a very impressive museum but hadn’t yet featured the extraordinary values of Thai bats, something we hope to help them with.
Though our group reluctantly headed for Bangkok and flights home on November 25, Surapon, Teresa Nichta and I remained at Khao Chong Pran for two final days of interviews with Wisuthanathkun and other monks, the local school principal and community members. Teresa, assisted by her videographer fiancé, Hugo Zesati, was able to shoot outstanding documentation, including spectacular slow-motion video of the wrinkle-lipped bat emergence.
During the two-day extension, we were particularly pleased to film teachers and students who one-day-per-week wear colorful bat shirts in recognition of the bats’ support.
A comprehensive study of the full economic impact of restoring this one bat cave is urgently needed. Caves and their bat populations are being lost at alarming rates throughout much of Southeast Asia without anyone even noticing! Little is likely to change till more humans and their governments recognize bat caves as potentially key resources.
This trip would not have been possible without the invaluably volunteered leadership planning and daily guidance of Daniel Hargreaves, expertly assisted in the field by Daniel Witbey. Also, local guides, Pongsanant P’Kwang, and Kop, were superb. We are deeply appreciative.
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Madelline Mathis has a degree in environmental studies from Rollins College and a passion for wildlife conservation. She is an outstanding nature photographer who has worked extensively with Merlin and other MTBC staff studying and photographing bats in Mozambique, Cuba, Costa Rica, and Texas. Following college graduation, she was employed as an environmental specialist for the Florida Department of Environmental Protection. She subsequently founded the Florida chapter of the International DarkSky Association and currently serves on the board of DarkSky Texas. She also serves on the board of Houston Wilderness and was appointed to the Austin Water Resource Community Planning Task Force.
Michael Lazari Karapetian has over twenty years of investment management experience. He has a degree in business management, is a certified NBA agent, and gained early experience as a money manager for the Bank of America where he established model portfolios for high-net-worth clients. In 2003 he founded Lazari Capital Management, Inc. and Lazari Asset Management, Inc. He is President and CIO of both and manages over a half a billion in assets. In his personal time he champions philanthropic causes. He serves on the board of Moravian College and has a strong affinity for wildlife, both funding and volunteering on behalf of endangered species.