Bats of Miagao
SGF conducts annual bat counts for long-term monitoring to provide crucial baseline data for understanding bat populations and developing effective conservation strategies.
Background & History
History of the Bat’s Presence in Miagao
Miagao is a first-class municipality in the Province of Iloilo, composed of 119 barangays and home to 68,115 residents.
Its most iconic landmark is the Santo Tomas de Villanueva Church—built by forced labor between 1787 and 1797. The intricate artistic native motif sculptural relief on its facade earned it UNESCO World Heritage status in 1993. Another spectacular architecture that can be found in Miagao is the Britanico Bridge, formerly Sapa Bridge, near the Sulu Garden Foundation headquarters.
These historic sites draw visitors, but the municipality’s greatest natural spectacle is its thriving fruit bat population. Townspeople report bats coexisting with humans for over 70 years. A 2014 survey estimated 5,000 individuals, swelling to more than 7,000 before they abandoned their former roost in 2018.
The Mystical Bubog
Back then, these bats were roosting on a giant Bubog tree (also called kalumpang/skunk tree) 300 meters from the beach and in the midst of a heavily populated area of town. The locals say the Bubog is considered a centennial tree, but no one seems to know exactly how old they are.
Native to the Middle East, Southeast Asia, and Pacific Islands, Bubog (Sterculia foetida) can reach over 115 feet in height. Coincidentally, the genus Sterculia was named after the Roman god, Sterquilinus—a fitting homage given the bats’ prolific droppings.
This was a drone shot of the Bubog tree back in 2015 and each one of those tiny dots are actually fruit bats. The bats really liked this tree. But where they came from is unknown, why they stayed or chose Miag-ao is even more a mystery.
Bubog trees are considered enchanted in most parts of Panay Island. Perhaps even much more so in Miag-ao. But, the elders would regale at telling stories of enchantment and hauntings that took place in the past. Maybe this is part of the reason why the folks living under and near the Bubog trees leave the bats alone to their own devices, despite the smell and the noise.
One local folklore is that Princess Olayra anchors her golden ship along the creek (perhaps it was a river long ago) beside the Bubog trees before going out to the sea. There were sightings of a white house with bright lights that appeared with Caucasian folks inside inviting out-of-town visitors to come in for dinner. Then later, the white house will vanish into thin air. Or, more recent stories by the people living near the bat trees hearing the sound of an anchor being lifted out of the water in the middle of the night, of abandoned machinery and parts that failed to work beside the Bubog trees and magically lifted in the mist. Folks say that the Bubog trees are home to underworld creatures and one must seek permission first by whispering ‘tabi-tabi po” before coming close or taking anything from the tree. And of course, the classic Manananggal and Aswang lore connected to bats due to their appearance. And there are plenty more of those stories to share.
One certain advantage for the fruit bats—people leave them alone most of the time.
Princess Olayra
Aswang
The Bubog died later on due to structural damage around 2018-2019. No one knows how and why, unsure if it was a typhoon, or what. But parts of the tree collapsed and there is no foliage already. Since then, the bats have moved to other trees but mostly not that far away from the “original” tree.
Annual Bat Count
The annual bat count is the pioneering project of SGF in the community of Miagao prior to its establishment with the aim of establishing baseline estimates of fruit bat abundance and potentially track seasonal and annual fluctuations which would later on provide critical data to prioritize conservation actions. Throughout the years, the SGF collaborates with government agencies such as the Municipal Environment and Natural Resources Office of Miagao and the Community Environment and Natural Resources Office-Guimbal.
Each bat count event involves three key components:
- Direct manual counting of bats in each roost tree, conducted alongside MENRO and CENRO staff.
- Identification and mapping of active roosting trees, using morphological diagnostics.
- Community interviews to capture local knowledge and perceptions about the bats.
Since 2021, SGF has done at least 8 bat counts. The bar graph below shows the summarized result of the fruit bat population for 5 years based on the field work of the Sulu Garden Foundation and its collaborators.
The Flying-Foxes
Locally, bats have been called a lot of names, but some actually say that they would refer to smaller bats as paniki or kabug, whereas the larger fruit bats (flying-foxes) they call ‘kabilaw‘.
Before, it was first thought that the species of fruit bats in Miagao was only the small island flying fox, Pteropus hypomelanus. However, through the PREVENT (Pandemic Response Preparedness for Emerging Bat-Borne Viruses from Rural and Peri-Urban Environments) Program under Dr. Phillip A. Alviola, it was found out that there are different species of fruit bats in Miagao and there are at least three Pteropus species. The previously observed Pteropus hypomelanus, which turned out to be the most abundant hence the assumption, the large flying fox Pteropus vampyrus, and the little golden-mantled flying fox Pteropus pumilus.
From left to right: Pteropus hypomelanus (Photo by: John Paul Nonato, MENRO Miagao, Pteropus vampyrus (Photo by: Daniel Geronimo Panganiban, PREVENT Program), Pteropus pumilus (Photo by: Kim Alunan, SGF).
PREVENT also recorded non-Pteropus species: Jeoffroy’s rousette (Rousettus amplexicaudatus); Common nectar bat (Eonycteris spelaea); Greater musky fruit bat (Ptenochirus jagori); and Peter’s fruit bat (Cynopterus luzoniensis).
Because manual counts cannot reliably distinguish species, SGF focuses on overall abundance. Future plans include refined methodologies—such as acoustic monitoring and genetic barcoding—to parse species-level trends.
Although others remain within town limits, every dusk between 5:30 and 6:30 PM, many bats depart the roost, heading northwest or northeast. The first assumption was the bats are going to Antique more likely to forage and feed.
Yet anecdotal reports note bats emerging near residences up to 750 meters from known roosts. From these areas, fruit trees such as caimito (Chrysophyllum cainito), mango (Mangifera indica), and chico (Manilkara zapota) were confirmed to be some of the feeding trees that these bats visit every night.
In the future, SGF aims to deploy GPS and remote tagging to chart their nightly routes and assess the status of key feeding trees.
Acoustic Monitoring of the Fruit Bat Colony in Miag-ao, Iloilo
Every evening at dusk (between 5:30 and 6:30 PM), large colonies of fruit bats emerge from their communal daytime roosts in Miagao, signalling the start of their nightly foraging activity. Individuals disperse across the surrounding landscape, some even believed to reach the far areas of Antique, in search of food and resources before returning to the same communal roosts prior to sunrise, completing a consistent activity cycle of emergence, nocturnal foraging, and roost re-entry.
Fruit bat vocal communication has received increasing scientific attention over the past several decades. Studies of Grey-headed Flying Foxes (Pteropus poliocephalus) have demonstrated that these bats possess multiple distinct call types associated with specific social behaviors, including aggression, courtship, maternal care, alarm, and feeding. Juvenile flying foxes also produce individually distinctive isolation calls that may enable mothers to recognize their offspring. More recent work has shown that Grey-headed Flying Fox vocalizations remain largely unaffected by typical urban noise levels, although extremely loud anthropogenic sounds, such as low-flying aircraft, can temporarily suppress colony vocal activity through what has been termed the “silentium effect.” Advances in machine learning have further demonstrated that several flying fox vocalizations can be automatically recognized and classified in real time.
Research on Egyptian fruit bats (Rousettus aegyptiacus) has expanded understanding of social communication even further. Long-term continuous recordings collected over more than a year have produced one of the world’s largest annotated fruit bat vocalization datasets, documenting hundreds of thousands of social calls together with behavioral observations and vocal development from birth to adulthood. These studies have shown that fruit bat vocalizations contain information about the identity of the caller, the intended recipient, the social context, and the behavioral response, highlighting the complexity of fruit bat communication.
Despite these advances internationally, comparable research has not yet been documented for Philippine fruit bats. Existing bat bioacoustic studies in the Philippines have largely focused on the echolocation calls of insectivorous bats, while long-term investigations of the social vocalizations, and acoustic activity patterns and behavior of Philippine fruit bats remain absent from the published literature. To address this, the Sulu Garden Foundation has started their acoustic monitoring project of the fruit bat population in Miag-ao, a long-term initiative for documenting and analyzing the vocalizations and acoustic activity of the municipality’s fruit bat population. Consequently, this project is poised to become one of the first long-term passive acoustic monitoring programs for fruit bat colonies in the Philippines.
How We Record
The project uses passive acoustic monitoring through a dedicated wildlife sound recorder deployed near the colony’s communal roosting site. The monitored colony consists of more than 105 fruit bats (counted as of June 2026) roosting in a rain tree behind Sulu Garden, Miag-ao, Iloilo. Previous observations have confirmed the presence of the island flying fox (Pteropus hypomelanus), the large flying fox (Pteropus vampyrus), and the little golden-mantled flying fox (Pteropus pumilus). Because these species roost together and their vocalizations have not yet been identified to species level, the recorded calls cannot currently be attributed with certainty to any particular species. Consequently, the acoustic recordings represent the collective vocal activity of the mixed-species colony rather than that of a single fruit bat species.
Continuous audio recordings are collected throughout the week every night to capture the full range of bat acoustic activity, including periods before emergence, during mass departure, throughout nocturnal activity, and prior to the colony’s return at dawn. These recordings are analyzed to identify distinct vocalizations, characterize temporal patterns in acoustic activity, quantify changes in calling intensity, and determine peak periods of colony movement. Long-term datasets will be generated and will enable comparisons across seasons and years, supporting the detection of changes in colony activity, and providing a foundation for future studies on fruit bat behavior, communication, and population monitoring. The resulting archive will then help in the development of better methods for recognizing bat vocalizations and distinguishing biologically relevant calls from environmental sounds.
Equipment used:
– Song Meter Mini 2 (Wildlife Acoustics) and 64GB Micro SD card
Take a Closer Look at the Bats
Aerial view of roosting bats near Sulu Garden taken on July 28, 2026, 5:30 PM.
Listen to the Colony
Vocalizations while bats remain in the roost before departure (July 27, 4:21 PM – 4:22 PM)
Peak colony activity during dusk (July 27, 5:37 PM – 5:38 PM)
Acoustic activity recorded during bats return (July 27, 4:24 – 4:25 AM)
The project also documents the bats through synchronized photography, videography, and direct field observations. Integrating these will allow researchers to correlate vocal activity with observable behaviors, validate acoustic interpretations, and improve understanding of colony dynamics during different stages of the nightly activity cycle.
Bat roosting site on rain tree behind Sulu Garden
As the project expands, the growing collection of recordings, annotated vocalizations, photographs, and behavioral observations will serve as a valuable scientific resource for researchers, students, conservation practitioners, and the wider community.
Beyond improving our understanding of Philippine fruit bat acoustic ecology, the project is intended to contribute to the long-term study of fruit bat biology and to provide baseline information that supports the conservation and management of this ecologically important, Near Threatened species. The resulting long-term acoustic dataset will provide valuable information for monitoring changes in colony activity, detecting potential shifts in population behavior over time, and informing future conservation and management efforts.
References
Christesen, T., & Nelson, J. (2000). Vocal communication in the Grey-headed Flying-fox (Pteropus poliocephalus).
Nelson, J. (1964). Vocal Communication in Australian Flying Foxes (Pteropodidae; Megachiroptera).
Pearson, T., & Clarke, J. A. (2019). Urban noise and grey-headed flying-fox vocalisations: Evidence of the silentium effect. Urban Ecosystems, 22(2), 271–280. https://doi.org/10.1007/s11252-018-0814-2
Grey-Headed Flying Fox Vocalisation Machine Listening. More-than-Human Futures.
Prat, Y., et al. (2017). An annotated dataset of Egyptian fruit bat vocalizations across varying contexts and during vocal ontogeny. Scientific Data.
Prat, Y., et al. (2016). Everyday bat vocalizations contain information about emitter, addressee, context, and behavior. Scientific Reports.
Van Parijs, S. M., & Corkeron, P. J. (2002). Ontogeny of Vocalisations in Infant Black Flying Foxes, Pteropus alecto. Behaviour, 139(9), 1111–1124. http://www.jstor.org/stable/4535976
Results
March
June
November
January
May
January
May
September
The dates of the survey for 2022 were January 16-18, May 19 and September 29. The SGF staff conducted it together with MENRO-Miag-ao and CENRO-Guimbal.
There were a total of 46 individual trees recorded as the bats’ roosting sites and it consists of twenty (20) species.
The 20 species of trees are: Acacia (Samanea saman), Agoho (Casuarina equisetifolia), Bubog (Sterculia foetida), Caimito (Chrysophyllum cainito), Coconut (Cocos nucifera), Duldol (Ceiba pentandra), Gmelina (Gmelina arborea), Mango (Mangifera indica), Kamansi (Artocarpus camansi), Lanete (Wrightia pubescens), Lunok (Ficus sp.), Mahogany (Swietenia macrophylla), Narra (Pterocarpus indicus), Neem (Azidirachta indica), Payhod, Sambag (Tamarindus indica), Santol (Sandoricum koetjape), Talisay and Tipolo (Artocarpus blancoi). And there was also one Bamboo grass.
The Common Island Flying Foxes’ average total population in the town of Miag-ao for 2022 is four thousand nine hundred seventy-nine (4,979) individuals. The highest average count in a tree was from the Acacia tree with eight hundred fifty-two (852) individuals and the least was from a Neem tree with only seven (7) counts.
Figure 1. the total number of bats per trimester that the count was conducted.
September
News & Blogs
Here are some blogs from our partner organization, Sulu Garden:
- Living in the shadow of the enchanted bubog trees and 7,000+ fruit bats (2015). Read more.
- Bats of Miagao (2015). Read more.
