Surveys of Fruit Bats in Miag-ao


January 2023

The first bat population count survey for the current year 2023 was conducted last January 26, 2023. It was done with the technical support of Unit head Wildlife Regulatory and Permitting Unit (WRPU)/Protected Area Management Biodiversity and Conservation Unit (PAMBCU)/Forester I, Ms. Jojie P. Gereza and Forest Technician (FT) II, Ms. Lore Calapardo, both from the Community Environment and Natural Resources Office (CENRO) – Guimbal.

With CENRO-Guimbal technical staff.

The same visual method was used and based on the count last September 2022 (click here to learn the September 2022 survey results), there were forty-one (41) individual trees recorded, with fifteen (15) species. This year, there are only thirty-seven (37) individual trees left being roosted by the island flying foxes, with still fifteen (15) species. There was a 9.76% decline in the number of their roosting sites and there was no change in the number of species recorded, compared to last year’s data.

The fifteen (15) species of trees are Acacia (Samanea saman), Bubog (Sterculia foetida), Caimito (Chrysophyllum cainito), Coconut (Cocos nucifera), Duldol (Ceiba pentandra), Gmelina (Gmelina arborea), Indian Mango (Mangifera indica), Mahogany (Swietenia macrophylla), Narra (Pterocarpus indicus), Neem (Azidirachta indica), Palawan Cherry (Cassia nodosa), Rain Tree, Sambag (Tamarindus indica), Santol (Sandoricum koetjape), Tipolo (Artocarpus blancoi). The Agoho species from last September was deserted by the fruit bats and an additional species of Palawan Cherry was added to the roosting sites. Four (4) out of the forty-one (41) roosting trees last year were abandoned by the island flying foxes.

Last September, the total bat population count was five thousand three hundred fifty-five (5,355) individuals with eight hundred thirty-two (832) counts on a narra tree as the highest count per tree and the least count was two (2) in an agoho tree. This January, the total count was six thousand five hundred thirty-one (6,531) individuals with seven hundred twenty-one (721) as the highest count on a acacia tree and the least count was fourteen (14) on a coconut tree.

Table 1. Distribution of the Bat Population among different trees around Miag-ao town plaza (as of January 2023).

Tree #CountTree SpeciesCondition (1 lowest and 5 highest)
1721Acacia (Samanea saman)1
226Mahogany (Swietenia macrophylla)4
3206Indian Mango (Mangifera indica)4
4150Neem (Azidirachta indica)5
541Mahogany (Swietenia macrophylla)4
657Mahogany (Swietenia macrophylla)3
788Palawan Cherry (Cassia nodosa)4
8453Narra (Pterocarpus indicus)1
9131Caimito (Chrysophyllum cainito)2
10293Sambag (Tamarindus indica)3
11986Acacia (Samanea saman)2
12158Duldol (Ceiba pentandra)4
1356Mahogany (Swietenia macrophylla)5
14223Gmelina (Gmelina arborea)5
15140Gmelina (Gmelina arborea)4
1697Gmelina (Gmelina arborea)5
17138Caimito (Chrysophyllum cainito)4
18529Mahogany (Swietenia macrophylla)4
19193Mahogany (Swietenia macrophylla)4
20270Mahogany (Swietenia macrophylla)4
21145Caimito (Chrysophyllum cainito)4
22105Santol (Sandoricum koetjape)3
2345Caimito (Chrysophyllum cainito)3
24136Mahogany (Swietenia macrophylla)2
2523Coconut (Cocos nucifera)3
2614Coconut (Cocos nucifera)3
27261Mahogany (Swietenia macrophylla)5
28120Mahogany (Swietenia macrophylla)5
2919Coconut (Cocos nucifera)5
3054Indian Mango (Mangifera indica)5
31135Tipolo (Artocarpus blancoi)5
3223Bubog (Sterculia foetida)3
33178Gmelina (Gmelina arborea)5
34165Gmelina (Gmelina arborea)5
3598Gmelina (Gmelina arborea)5
3638Rain Tree5
3716Tipolo (Artocarpus blancoi)5

*Rating of the damage to the trees:

1 = 81% – 100% damage   2 = 61% – 80% damage   3 = 41% – 60% damage    4 = 21% – 40% damage   5 = 0% – 20% damage

Ten (10) out of the thirty-seven (37) roosting trees are mahogany, followed by six (6) gmelina trees, four (4) caimito, three (3) coconut trees, two (2) trees each of acacia, indian mango, and tipolo and one (1) each of the remaining trees.

The highest total average count per tree species is of the acacia tree with eight hundred fifty-four (854) count, followed by narra tree with four hundred ffity-three (453) count, sambag tree with two hundred ninety-three (293) bats, mahogany trees with one hundred sixty-nine (169) bats, duldol tree with one hundred fifty-eight (158) bats, gmelina and neem trees with one hundred fifty (150) bats, indian mango trees with one hundred thirty (130) bats, caimito trees with one hundred fifteen (115) bats, santol tree with one hundred five (105) bats, palawan cherry tree with eighty-eight (88) bats, tipolo tree with seventy-six (76) bats, rain tree with thirty-eight (38) bats, bubog tree with twenty-three (23) bats, and coconut trees with nineteen (19) bats.

The bat count population increased by 21.96% compared with the last September 2022 count.

Comparing the results

Figure 1 below shows the total number of bats per trimester that the count was conducted.

The count last August 2021 was seven thousand three hundred ninety-two (7,392). Last January 2022 totaled to three thousand five hundred ninety-three (3,593), then last May, it went up to five thousand nine hundred eighty-nine (5,989) and this September, it just went down a bit to five thousand three hundred fifty-five (5,355). This January 2023 count, the bat population increased to six thousand five hundred thirty-one(6,531).

Throughout the survey, we noticed that they keep changing their roosting sites aside from those trees with maximum damage. The difference in the count might be that some of them are travelling from one tree to another during the count and the method of counting used was visual counting. Their movements, tree cover, foliage and line of sight could affect the result of the count.

The next bat count will be on May 2023.

Written by: Senior Science Officer, Norielle Diamante (See profile)

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