Summary of Bat Surveys
Summary
Bat population counts have been regularly conducted since 2021.
The bar graph below shows the summarized result of the bat population for 3 years.
The 2021 bat population resulted to a total average of seven thousand three hundred ninety-two (7,392) individuals. It dropped by 32.64% at the 2022 count, since the total average was four thousand nine hundred seventy-nine (4,979) individuals. Then, it went up to six thousand three hundred sixteen (6,316) individuals on the last count this May 2023 with an increase of 26.85% from 2022. However, if compared with the 2021 result, there is still a decrease of 14.56%.
2023
January
The first bat population count survey for the year 2023 was conducted last January 26, 2023. It was done with CENRO-Guimbal staff.
This year, there are only thirty-seven (37) individual trees left being roosted by the island flying foxes, with still fifteen (15) species.
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).
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.
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.
May
The second bat population count survey for the current year 2023 was conducted last May 19, 2023.
This second trimester, there are forty-four (44) individual trees roosted on by the island flying foxes, with still fifteen (15) species. There was an 18.92% increase in the number of their roosting sites and there was no change in the number of species recorded, compared to last January’s data.
The fifteen (15) species of trees are Agoho (Casuarina equisetifolia), Bubog (Sterculia foetida), Caimito (Chrysophyllum cainito), Coconut (Cocos nucifera), Gmelina (Gmelina arborea), Lanete (Wrightia pubescens), Mahogany (Swietenia macrophylla), Mango (Mangifera indica), Narra (Pterocarpus indicus), Neem Tree (Azidirachta indica), Palawan Cherry (Cassia nodosa), Sambag (Tamarindus indica), Santol (Sandoricum koetjape), Talisay (Terminalia catappa), and Tipolo (Artocarpus blancoi). There are additional seven (7) additional roosting trees.
This May, the total count was six thousand one hundred one (6,101) individuals with eight hundred fifty-seven (857) as the highest count on a mango tree and the least count was two (2) on a talisay tree.
Nine (9) out of the forty-four (44) roosting trees are gmelina, followed by seven (7) mahogany trees, five (5) caimito, four (4) narra trees, three (3) mango trees, two (2) each of agoho, bubog, coconut, lanete, santol and tipolo and one (1) each of the remaining trees.
The highest total average count per tree species is of the mango tree with four hundred ninety-one (491) count, followed by narra tree with two hundred seventy-three (273) count, gmelina tree with one hundred forty-one (141) bats, sambag tree with one hundred thirty (130) bats, mahogany trees and tipolo tree with one hundred twenty-six (126) bats, caimito trees with one hundred seventeen (117) bats, agoho trees with fifty-six (56) bats, palawan cherry tree with fifty-one (51) bats, bubog trees with forty-eight (48) bats, lanete trees with thirty-three (33) bats, santol trees with twenty-five (25) bats, neem tree with twenty-three (23) bats, coconut trees with eleven (11) bats, and talisay tree with two (2) bats.
The bat count population decreased by 6.58% compared with the last January count.
The first bat population count survey for the current year 2022 was conducted last January 16-18, 2022.
there were forty-six (46) individual trees recorded, with fourteen (14) species. This year, there are only twenty-seven (27) individual trees left being roosted by the island flying foxes, with only eleven (11) species left.
The eleven (11) species of trees are Mahogany (Swietenia macrophylla), Acacia (Samanea saman), Caimito (Chrysophyllum cainito), Coconut (Cocos nucifera), Gmelina (Gmelina arborea), Santol (Sandoricum koetjape), Lanete (Wrightia pubescens), Narra (Pterocarpus indicus), Sambag (Tamarindus indica), Kamansi (Artocarpus camansi), and Duldol (Ceiba pentandra).
The total bat population went down to three thousand five hundred ninety-three (3,593) individuals with four hundred eighty-six (486) counts on an Acacia tree as the highest count per tree and the least count was two (2) in a Mahogany tree.
Ten (10) out of the twenty-seven (27) roosting trees are Mahogany trees, followed by three (3) Acacia trees, two (2) Caimito and Coconut trees, one (1) of each remaining tree species recorded.
The highest total average count per tree species is of the Mahogany trees with nine-hundred thirteen (913) total count, followed by Mahogany trees with seven hundred thirty-one (731) total count, Sambag tree with four hundred seventy-one (471) bats, Caimito trees with one hundred seventy-one (171) bats, Narra tree with one hundred sixty-six (166) bats, Santol tree with one hundred fifty (150) bats, Gmelina tree with one hundred fourteen (114) bats, Coconut trees with sixty-six (66), Kamansi tree with sixty-four (64) bats, Duldol tree with fifty-five (55) bats and Lanete tree with only six (6) bats.
For the 2nd trimester of 2022, the count was conducted last May 19, 2022.
There were forty-eight (48) trees with eighteen (18) species recorded. This May, the total population went up to 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 (2) in both neem tree and bamboo.
Twelve (12) out of the forty-eight (48) roosting trees are mahogany trees, followed by six (6) caimito trees, five (5) coconut trees, four (4) gmelina, three (3) agoho, mango and acacia, two (2) narra, and one (1) of each remaining trees recorded and a bamboo grass.
The highest total average count per tree species is of the acacia trees with one thousand eight hundred forty-three (1,843) total count, followed by mahogany trees with nine hundred eighty-six (986) total count, mango trees with six hundred twenty-two (622) bats, narra trees with six hundred thirteen (613) bats, caimitos trees with five hundred five (505) bats, gmelina trees with two hundred ninety-two (292) bats, agoho trees with one hundred ninety-five (195) bats, tipolo tree with one hundred nine (109), coconut trees with ninety-six (96) bats, balete tree with ninety (90) bats, bubog tree with eighty-nine (89) bats, santol tree with eighty-one (81) bats, payhod tree with seventy (70) bats, talisay tree with sixty-two (62) bats, lanete tree with forty-three (43) bats and neem tree and bamboo grass both with only eight (8) bats.
The number of roosting trees is fifteen (15) this last trimester.
The fifteen 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), 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).
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.
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.
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, Rain Tree, 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.
Tree Number | Count | Tree Species | Condition |
1 | 326 | Narra (Pterocarpus indicus) | 5 |
2 | 24 | Mahogany (Swietenia macrophylla) | 5 |
3 | 106 | Agoho (Casuarina equisetifolia) | 5 |
4 | 55 | Agoho (Casuarina equisetifolia) | 5 |
5 | 94 | Agoho (Casuarina equisetifolia) | 4 |
6 | 223 | Mango (Mangifera indica) | 5 |
7 | 852 | Acacia (Samanea saman) | 1 |
8 | 49 | Mahogany (Swietenia macrophylla) | 4 |
9 | 192 | Mango (Mangifera indica) | 4 |
10 | 7 | Neem (Azidirachta indica) | 5 |
11 | 51 | Mahogany (Swietenia macrophylla) | 4 |
12 | 189 | Mahogany (Swietenia macrophylla) | 3 |
13 | 392 | Narra (Pterocarpus indicus) | 1 |
14 | 116 | Caimito (Chrysophyllum cainito) | 2 |
15 | 393 | Sambag (Tamarindus indica) | 3 |
16 | 246 | Acacia (Samanea saman) | 2 |
17 | 330 | Lunok (Ficus sp.) | 4 |
18 | 48 | Duldol (Ceiba pentandra) | 4 |
19 | 157 | Mahogany (Swietenia macrophylla) | 5 |
20 | 94 | Gmelina (Gmelina arborea) | 5 |
21 | 75 | Gmelina (Gmelina arborea) | 4 |
22 | 40 | Caimito (Chrysophyllum cainito) | 4 |
23 | 194 | Mahogany (Swietenia macrophylla) | 4 |
24 | 65 | Mahogany (Swietenia macrophylla) | 4 |
25 | 98 | Mahogany (Swietenia macrophylla) | 4 |
26 | 25 | Lanete (Wrightia pubescens) | 5 |
27 | 142 | Caimito (Chrysophyllum cainito) | 5 |
28 | 104 | Santol (Sandoricum koetjape) | 3 |
29 | 24 | Caimito (Chrysophyllum cainito) | 3 |
30 | 116 | Caimito (Chrysophyllum cainito) | 4 |
31 | 102 | Mahogany (Swietenia macrophylla) | 2 |
32 | 37 | Mahogany (Swietenia macrophylla) | 2 |
33 | 130 | Mahogany (Swietenia macrophylla) | 5 |
34 | 27 | Coconut (Cocos nucifera) | 4 |
35 | 21 | Coconut (Cocos nucifera) | 5 |
36 | 21 | Coconut (Cocos nucifera) | 5 |
37 | 102 | Tipolo (Artocarpus blancoi) | 5 |
38 | 54 | Agoho (Casuarina equisetifolia) | 4 |
39 | 107 | Agoho (Casuarina equisetifolia) | 4 |
40 | 64 | Kamansi (Artocarpus camansi) | 5 |
41 | 55 | Duldol (Ceiba pentandra) | 3 |
42 | 124 | Acacia (Samanea saman) | 3 |
43 | 59 | Mango (Mangifera indica) | 5 |
44 | 62 | Talisay | 5 |
45 | 125 | Caimito (Chrysophyllum cainito) | 5 |
46 | 70 | Payhod | 5 |
47 | 87 | Bubog (Sterculia foetida) | 5 |
48 | 21 | Gmelina (Gmelina arborea) | 5 |
49 | 173 | Gmelina (Gmelina arborea) | 5 |
50 | 37 | Coconut (Cocos nucifera) | 5 |
51 | 8 | Bamboo | 4 |
52 | 14 | Coconut (Cocos nucifera) | 5 |
53 | 157 | Gmelina (Gmelina arborea) | 5 |
54 | 80 | Rain Tree | 5 |
55 | 69 | Tipolo (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
Thirteen (13) out of the forty-six (46) roosting trees are mahogany, followed by six (6) caimito, five (5) coconut and gmelina, three (3) each of acacia, agoho and mango trees, two (2) narra and one (1) each of the remaining trees.
The highest total average count per tree species is of the acacia tree with four hundred seven (407), followed by sambag tree with three hundred ninety-three (393) count, narra trees with three hundred fifty-nine (359) bats, lunok tree with three hundred thirty (330) bats, mango trees with one hundred fifty-eight (158) bats, santol tree with one hundred four (104) bats, mahogany trees with ninety-seven (97) bats, caimito trees with ninety-four (94) bats, gmelina trees with ninety-one (91) bats, bubog tree with eighty-seven (87) bats, agoho and tipolo tree with eighty-five (85) bats, rain tree with eighty (80) bats, payhod tree with seventy (70) bats, kamansi tree sixty-four (64), talisay tree with sixty-two (62), duldol with fifty-two (52) bats, lanete with twenty-five (25) bats, coconut with twenty-four (24) and neem tree seven (7) bats.
Figure 1 below shows the total number of bats per trimester that the count was conducted.
From the period of August 26 to September 3, 2021, the staff from Sulu Garden Foundation surveyed the Municipality of Miag-ao to list, identify and plot the roosting sites of Common Island Foxes on a map and count their population.
There are forty-six (46) individual trees recorded as the bats’ roosting sites and it consists of fourteen (14) species.
The 14 species of trees are: Agoho (Casuarina
equisetifolia), Narra (Pterocarpus indicus), Mango (Mangifera indica), Mahogany (Swietenia macrophylla), Coconut (Cocos nucifera), Caimito (Chrysophyllum cainito), Santol (Sandoricum koetjape), Lanete (Wrightia pubescens), Sambag (Tamarindus indica), Acacia (Samanea saman), Lunok (Ficus), Gmelina (Gmelina arborea), Kamansi (Artocarpus camansi), and Duldol (Ceiba pentandra).
The Common Island Flying Foxes’ average total population in the town of Miag-ao is seven thousand three hundred ninety-two (7,392) individuals as of September 3, 2021. The highest count in a tree was from the Acacia tree with one thousand forty-four (1,044±4) individuals and the least was from the two (2) Agoho trees beside Miag-ao Church with only three (3) counts each.
Table 1. Distribution of the Bat Population among different trees around Miag-ao town plaza.
| TREE # | TREE SPECIES | TREE CONDITION RATING* | COUNT | NUMBER OF BATS (MEAN ± SEM) | ||
| 1st COUNT | 2nd COUNT | 3rd COUNT | ||||
| 1 | Agoho (Casuarina equisetifolia) | 5 | 28 | 25 | 25 | 26 ± 1 |
| 2 | Agoho (Casuarina equisetifolia) | 5 | 3 | 3 | 3 | 3 |
| 3 | Agoho (Casuarina equisetifolia) | 5 | 3 | 3 | 3 | 3 |
| 4 | Agoho (Casuarina equisetifolia) | 5 | 65 | 90 | 74 | 76 ± 7 |
| 5 | Agoho (Casuarina equisetifolia) | 5 | 75 | 65 | 69 | 69 ± 3 |
| 6 | Agoho (Casuarina equisetifolia) | 5 | 153 | 155 | 155 | 154 ± 1 |
| 7 | Agoho (Casuarina equisetifolia) | 5 | 130 | 132 | 130 | 131 ± 1 |
| 8 | Agoho (Casuarina equisetifolia) | 5 | 120 | 132 | 136 | 129 ± 5 |
| 9 | Agoho (Casuarina equisetifolia) | 5 | 149 | 152 | 150 | 150 ± 1 |
| 10 | Agoho (Casuarina equisetifolia) | 5 | 124 | 129 | 129 | 127 ± 2 |
| 11 | Agoho (Casuarina equisetifolia) | 5 | 117 | 115 | 117 | 116 ± 1 |
| 12 | Narra (Pterocarpus indicus) | 5 | 250 | 250 | 251 | 250 |
| 13 | Agoho (Casuarina equisetifolia) | 4 | 154 | 160 | 158 | 157 ± 2 |
| 14 | Agoho (Casuarina equisetifolia) | 4 | 197 | 208 | 202 | 202 ± 3 |
| 15 | Indian Mango (Mangifera indica) | 5 | 237 | 259 | 247 | 248 ± 6 |
| 16 | Mahogany (Swietenia macrophylla) | 5 | 41 | 52 | 49 | 47 ± 3 |
| 17 | Coconut (Cocos nucifera) | 4 | 32 | 35 | 35 | 34 ± 1 |
| 18 | Coconut (Cocos nucifera) | 4 | 5 | 5 | 5 | 5 |
| 19 | Mahogany (Swietenia macrophylla) | 3 | 228 | 233 | 221 | 227 ± 3 |
| 20 | Caimito (Chrysophyllum cainito) | 2 | 35 | 33 | 34 | 34 ± 1 |
| 21 | Santol (Sandoricum koetjape) | 3 | 132 | 135 | 129 | 132 ± 2 |
| 22 | Caimito (Chrysophyllum cainito) | 5 | 17 | 26 | 24 | 22 ± 3 |
| 23 | Lanete (Wrightia pubescens) | 5 | 15 | 16 | 15 | 15 |
| 24 | Mahogany (Swietenia macrophylla) | 4 | 291 | 296 | 287 | 291 ± 3 |
| 25 | Mahogany (Swietenia macrophylla) | 3 | 235 | 250 | 238 | 241 ± 5 |
| 26 | Mahogany (Swietenia macrophylla) | 5 | 125 | 130 | 132 | 129 ± 2 |
| 27 | Coconut (Cocos nucifera) | 4 | 10 | 10 | 10 | 10 |
| 28 | Caimito (Chrysophyllum cainito) | 5 | 81 | 79 | 87 | 82 ± 2 |
| 29 | Indian Mango (Mangifera indica) | 3 | 480 | 495 | 489 | 488 ± 4 |
| 30 | Mahogany (Swietenia macrophylla) | 5 | 156 | 159 | 160 | 158 ± 1 |
| 31 | Mahogany (Swietenia macrophylla) | 3 | 113 | 130 | 118 | 120 ± 5 |
| 32 | Mahogany (Swietenia macrophylla) | 5 | 8 | 8 | 8 | 8 |
| 33 | Narra (Pterocarpus indicus) | 2 | 291 | 314 | 302 | 304 ± 7 |
| 34 | Caimito (Chrysophyllum cainito) | 1 | 146 | 149 | 152 | 149 ± 2 |
| 35 | Sambag (Tamarindus indica) | 3 | 205 | 213 | 209 | 209 ± 2 |
| 36 | Acacia (Samanea saman) | 1 | 977 | 983 | 985 | 982 ± 2 |
| 37 | Lunok (Ficus sp.) | 4 | 19 | 19 | 19 | 19 |
| 38 | Acacia (Samanea saman) | 2 | 1050 | 1045 | 1036 | 1044 ± 4 |
| 39 | Mahogany (Swietenia macrophylla) | 4 | 17 | 17 | 17 | 17 |
| 40 | Gmelina (Gmelina arborea) | 5 | 57 | 63 | 67 | 62 ± 3 |
| 41 | Gmelina (Gmelina arborea) | 4 | 27 | 30 | 30 | 29 ± 1 |
| 42 | Mahogany (Swietenia macrophylla) | 3 | 309 | 311 | 300 | 307 ± 3 |
| 43 | Indian Mango (Mangifera odorata) | 3 | 118 | 128 | 125 | 124 ± 3 |
| 44 | Kamansi (Artocarpus camansi) | 4 | 73 | 77 | 68 | 73 ± 3 |
| 45 | Duldol (Ceiba pentandra) | 4 | 44 | 48 | 39 | 44 ± 3 |
| 46 | Acacia (Samanea saman) | 3 | 145 | 132 | 151 | 153 ± 6 |
*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
Thirteen (13) out of the forty-six (46) roosting trees of the Common Island Flying Fox are Agoho; followed by ten (10) Mahogany; four (4) Caimito; three (3) Mango and Coconut; two (2) Acacia, Narra and Gmelina; and one (1) for the remaining six (6) species of trees.
The highest total average count per tree species is of Agoho tree with one thousand three hundred forty-six (1,346) individuals, followed by the Acacia tree with one thousand one hundred eighty-six (1,186) bats, Mahogany tree with nine hundred thirty-six (936) bats, Mango tree with eight hundred fifty-nine (859) bats, Narra tree with five hundred fifty-three (553) bats, Caimito tree with two hundred eighty-eight (288) bats, Sambag tree with two hundred nine (209) bats, Santol tree with one hundred thirty-two (132) bats, Gmelina with ninety-one (91) bats, Kamansi with seventy-three (73) bats, Coconut with forty-nine (49), Duldol with forty-four (44), Lunok with nineteen (19), and Lanete with fifteen (15) bats.
Figure 1. Bar chart showing the total average population of the Common Island Flying Fox per tree species (survey date, September 2021)
