Surveys of Fruit Bats in Miag-ao

2022

September 2022

The Sulu Garden Foundation’s (SGF) Senior Science Officer, Ms. Norielle Diamante with Unit Head Wildlife Regulatory and Permitting Unit (WRPU)/Protected Area Management Biodiversity and Conservation Unit (PAMBCU)/Forester I, Ms. Jojie P. Gereza and Park Ranger, James Edward Villanueva of the Community Environment and Natural Resources Office (CENRO-Guimbal); and EMS II/Designated MENR Officer, Mr. Isidro Mosura, Jr., MENRO-Miag-ao staff, Ms. Cindy Cabudlay, and Wildlife Enforcement Officers (WEO), Mr. John Paul Nonato of the Municipal Environment and Natural Resources Office (MENRO-Miag-ao) conducted the bat count last September 29, 2022.

Bat count conducted by SGF, CENRO-Guimbal and MENRO-Miag-ao.

Fruit bats roosting at an acacia tree.

We followed the same and pattern of counting from the monitoring from September 2021. For every year, the bat count is conducted every trimester. This September was the last survey for this year.

The number of roosting trees last May was forty-eight (48). This month, it decreased to forty-one (41) trees. That is a 14.58% decrease compared to three months ago. The number of tree species lowered from eighteen (18) to fifteen (15) for this trimester.

The fifteen species of trees are Acacia (Samanea saman), Agoho (Casuarina equisetifolia), Bubog (Sterculia foetida),

Common island flying foxes resting probably after a night of tiresome hunting.

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), Rain Tree, Sambag (Tamarindus indica), Santol (Sandoricum koetjape), and Tipolo (Artocarpus blancoi).

Last May, the total bat population count was five thousand nine hundred eighty-nine (5,989) individuals with one thousand three hundred fifty-three (1,353) counts on an acacia tree as the highest count per tree and the least count was eight (8) in both neem tree and bamboo. This September, the total count was five thousand three hundred fifty-five (5,355) individuals with eight hundred thirty-two (832) as the highest count on a narra tree and the least count was only two (2) on an agoho tree.

Table 1. Distribution of the Bat Population among different trees around Miag-ao town plaza (as of September 2022).

Tree #

Count

Tree Species

Condition (1 lowest and 5 highest)

1

218

Narra (Pterocarpus indicus)

5

2

40

Mahogany (Swietenia macrophylla)

5

3

102

Agoho (Casuarina equisetifolia)

5

4

2

Agoho (Casuarina equisetifolia)

5

5

128

Agoho (Casuarina equisetifolia)

4

6

110

Indian Mango (Mangifera indica)

5

7

718

Acacia (Samanea saman)

1

8

10

Mahogany (Swietenia macrophylla)

4

9

135

Indian Mango (Mangifera indica)

4

10

6

Neem (Azidirachta indica)

5

11

84

Mahogany (Swietenia macrophylla)

4

12

449

Mahogany (Swietenia macrophylla)

3

13

832

Narra (Pterocarpus indicus)

1

14

33

Caimito (Chrysophyllum cainito)

2

15

514

Sambag (Tamarindus indica)

3

16

68

Acacia (Samanea saman)

2

17

6

Duldol (Ceiba pentandra)

4

18

267

Mahogany (Swietenia macrophylla)

5

19

57

Gmelina (Gmelina arborea)

5

20

91

Gmelina (Gmelina arborea)

4

21

36

Caimito (Chrysophyllum cainito)

4

22

205

Mahogany (Swietenia macrophylla)

4

23

35

Mahogany (Swietenia macrophylla)

4

24

30

Mahogany (Swietenia macrophylla)

4

25

44

Caimito (Chrysophyllum cainito)

4

26

81

Santol (Sandoricum koetjape)

3

27

22

Caimito (Chrysophyllum cainito)

3

28

77

Mahogany (Swietenia macrophylla)

2

29

17

Coconut (Cocos nucifera)

3

30

27

Coconut (Cocos nucifera)

3

31

49

Mahogany (Swietenia macrophylla)

5

32

229

Mahogany (Swietenia macrophylla)

5

33

30

Coconut (Cocos nucifera)

5

34

80

Indian Mango (Mangifera indica)

5

35

94

Tipolo (Artocarpus blancoi)

5

36

85

Bubog (Sterculia foetida)

3

37

27

Gmelina (Gmelina arborea)

5

38

317

Gmelina (Gmelina arborea)

5

39

157

Gmelina (Gmelina arborea)

5

40

80

Rain Tree

5

41

69

Tipolo (Artocarpus blancoi)

5

*Rating of the damage to the trees:

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

Eleven (11) out of the forty-one (41) roosting trees are mahogany, followed by five (5) gmelina trees, four (4) caimito, three (3) each of agoho and coconut trees, two (2) trees each of acacia and indian mango, and one (1) each of the remaining trees.

The highest total average count per tree species is of the mahogany tree with one thousand four hundred seventy-five (1,475) count, followed by narra tree with one thousand fifty (1,050) count, acacia trees with seven hundred eighty-six (786) bats, gmelina trees with six hundred forty-nine (649) bats, sambag tree with five hundred fourteen (514) bats, agoho trees with two hundred thirty-two (232) bats, indian mango trees with two hundred fifteen (215) bats, caimito trees with one hundred thirty-five(135) bats, bubog tree with eighty-five (85) bats, santol tree with eighty-one (81) bats, rain tree with eighty (80) bats, coconut trees with seventy-four (74) bats, tipolo tree with sixty-nine(69) bats, and both neem and duldol tree with six (6) bats.

Photos of island flying fox roosting.

The bat count population decreased only by 1.06%. More study is being done to understand better these bats’ activities and habits.

Comparing the results

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

The count last August to September 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).

The decrease in the total bat population compared to last year was 3,799, which makes it a 51.39% decline. It might be because of Typhoon Odette that struck the Philippines last December or the lightings at the Municipal Plaza for Christmas. The decrease with the count for September from May, may not mean that their population actually decreased. It might be that some of them are travelling from one tree to another during the count, given that the decrease is only 1.06% and the method of counting used was visual count. Their movements, tree cover, foliage and line of sight could affect the result of the count.

The next bat count will be on January 2023.

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