Population and Conservation Status of the Flying Fox Pteropus dasymallus in Taiwan

© 2022 Academia Sinica, Taiwan Open Access Population and Conservation Status of the Flying Fox Pteropus dasymallus in Taiwan Hui-Wen Wu1, Dau-Jye Lu1, Ching-Lung Lin2, Hsi-Chi Cheng3, Chung-Hao Juan4, Tsung-Jen Shen5, Hua-Ching Lin6, and Shiang-Fan Chen4,* 1School of Forestry and Resource Conservation, National Taiwan University, Taipei 10617, Taiwan. E-mail: [email protected] (Wu); [email protected] (Lu) 2Bat Association of Taiwan, Chiayi 606002, Taiwan. E-mail: [email protected] (Lin) 3Division of Zoology, Endemic Species Research Institute, Nantou 552005, Taiwan. E-mail: [email protected].tw (Cheng) 4Center for General Education, National Taipei University, New Taipei City 237303, Taiwan. *Correspondence: E-mail: [email protected] (Chen). E-mail: [email protected] (Juan) 5Institute of Statistics and Department of Applied Mathematics, National Chung Hsing University, Taichung 402002, Taiwan. E-mail: [email protected] (Shen) 6Forestry Bureau, Council of Agriculture, Taipei 100024, Taiwan. E-mail: [email protected].tw (Lin) Received 14 January 2022 / Accepted 4 May 2022 / Published 20 September 2022 Communicated by Teng-Chiu Lin Pteropus dasymallus is widely distributed on islands throughout the western edge of the Pacific Ocean. The Formosan flying fox, P. d. formosus, is an endemic subspecies in Taiwan found mainly on Lyudao; it was previously thought to have been extirpated. Since 2005, intensive surveys have been conducted to investigate the residency, population size and plant resource utilization of P. dasymallus in Taiwan. Interviews were carried out to investigate its former abundance and the causes of population decline. In Taiwan, P. dasymallus is in a state of ongoing oceanic dispersal and colonization and has considerably expanded its geographic range. In addition to remaining in its historic habitat on Lyudao, P. dasymallus has also established colonies on Gueishan Island and in Hualien on Taiwan’s main island in the past few decades. The total population size is estimated to be 240 individuals, and this number is on the rise. Approximately three-quarters of the entire population (73.64%) was found on Gueishan Island. The sex ratio was strongly skewed toward males. A total of 40 plant species were recorded as being used by the flying fox for food, roosts or perches. More agricultural and horticultural plant species were used by the flying fox in urban Hualien. According to the interviews, flying foxes were abundant on Lyudao, but their number dramatically declined from the 1970s to the mid-1980s, mainly due to commercial hunting. Maintaining a sufficient population size and genetic variability is fundamental to the long-term survival of the flying fox. Enforcing conservation laws, restoring habitats, controlling invasive species and improving public awareness are the main steps in the recovery and sustainability of the flying fox population. Key words: Insular ecosystem, Interoceanic dispersal, Local extirpation, Pteropodidae, Ryukyu flying fox. BACKGROUND Pteropus species (Chiroptera: Pteropodidae), known as flying foxes, are keystone species that play important roles in pollination and seed dispersal in Old World tropical and subtropical ecosystems (Aziz et al. 2021; Cox et al. 1991). They are ecologically distinct in their contribution to maintaining forest structure and diversity, particularly on islands with relatively depauperate assemblages of large frugivores and pollinators (Cox et al. 1992). Under the threats of habitat loss, forest degradation, and intentional human use, many flying fox populations have rapidly declined over the past few decades. These threats are intensified on islands and increase the risk of extinction (Frick et al. 2020; Kingston et al. 2021; Mickleburgh et al. 2002). Citation: Wu HW, Lu DJ, Lin CL, Cheng HC, Juan CH, Shen TJ, Lin HC, Chen SF. 2022. Population and conservation status of the flying fox Pteropus dasymallus in Taiwan. Zool Stud 61:34. doi:10.6620/ZS.2022.61-34. Zoological Studies 61:34 (2022) doi:10.6620/ZS.2022.61-34 1 © 2022 Academia Sinica, Taiwan According to the IUCN Red List of Threatened Species, over half of Pteropus species are considered threatened (IUCN 2021). These threats could also impact flying foxes’ ecological, evolutionary and economic contributions to ecosystem services (Cox and Elmqvist 2000; Florens et al. 2017; McConkey and Drake 2006). Given the high vulnerability and endemism of insular ecosystems, monitoring the status of flying foxes on islands is important for developing corresponding protection and management strategies. Pteropus dasymallus (the Ryukyu flying fox) is widely distributed on islands throughout the western margin of the Pacific Ocean, extending 1,800 km from the Ryukyu Archipelago of southwestern Japan through Taiwan to the northern islands of the Philippines (Kinjo and Nakamoto 2015). Five subspecies, namely, P. d. daitoensis, P. d. dasymallus, P. d. inopinatus, P. d. yayeyamae and P. d. formosus, have been recognized based on their respective island groups (Yoshiyuki 1989). In addition, a Philippine population was discovered in the 1990s on the Batanes and Babuyan Islands. It has not yet been officially designated as a subspecies (Heaney et al. 1998). Although the subspecies are morphologically similar, significant genetic differentiation has been detected among most of them, except between P. d. yayeyamae and P. d. formosus, reflecting historical vicariance events and restricted gene flow across deep, broad oceanic barriers (Chen et al. 2021). Pteropus d. formosus (the Formosan flying fox) historically mainly inhabited Lyudao, with sporadic records of occurrences on the eastern part of Taiwan’s main island and Lanyu (Mickleburgh et al. 1992). The flying fox was distributed island-wide on Lyudao, where the population was estimated to be over 2,000 individuals (Lin and Pei 1999). However, the population size rapidly decreased, likely due to intensive hunting since the 1970s. Subsequently, the flying fox was rarely observed and considered to have been extirpated or in the process of becoming extirpated. Therefore, it has been listed as an “Endangered Species” under the Wildlife Conservation Act (Taiwan) since 1989. Little was known about its status on Lyudao until 2005, when it was formally announced that the flying fox had been rediscovered (Chen et al. 2009). Also, flying fox individuals have occasionally been found on offshore islands or on the eastern part of Taiwan’s main island in recent years. An updated review of its status is necessary. To determine whether P. dasymallus currently resides in Taiwan, we surveyed its historical range, newly recorded locations, and potential habitat. We interviewed residents to gain a better understanding of the former abundance and population decline of the flying fox. In addition, we reviewed sighting records from the last 40 years to determine whether the flying fox was observed frequently. The aim of our study was to assess the status of P. dasymallus in Taiwan, including its presence, current population size, and utilization of plant resources, as well as to investigate residents’ perceptions of the flying fox and identify potential critical threats to the flying fox. MATERIALS AND METHODS Study area We conducted surveys of P. dasymallus on three islands, namely, Lyudao (Green Island, the main historical range), Gueishan Island (Turtle Island, a newly recorded location) and Lanyu (Orchid Island, a potential habitat with a few sighting records), and in Hualien (a newly recorded location) (Fig. 1, Table 1). Lyudao (area: 15.1 km2) is a volcanic island located 30.9 km off the southeastern coast of Taiwan. It is a popular tourist site during summer. Gueishan Island (2.8 km2) is a small volcanic island located 9.7 km off the northeastern coast of Taiwan. There are five trails on the island (see Chen et al. 2017). Residents were required to leave by 1977 when Gueishan Island was designated a military control area. Since then, except for the Coast Guard, no residents have inhabited the island. The island is open to the public from March to November during the day. Lanyu (46.8 km2), another volcanic island, is located 60.8 km off the southeastern coast of Lyudao and 104.8 km north of the Batanes Islands, Philippines. Lanyu is part of the island chain where P. dasymallus is distributed; however, only one occurrence was formally recorded and was traced back to 1933 (Kuroda 1938). The residents of the island are indigenous Tao people. Hualien is on the east coast of Taiwan’s main island, located between the Pacific Ocean and the Central Mountain Range. Hualien’s natural habitats are relatively well preserved, except in the city center (29.4 km2). Field survey To assess whether the flying fox was resident and to monitor population changes, we conducted field surveys on Lyudao (August 2005–April 2008 and September 2018–October 2021) and Gueishan Island (March 2009–March 2013 and July 2018–October 2021) and in Hualien City (September 2018–November 2021). Surveys were performed monthly, seasonally or semiannually, depending on the objectives in different page 2 of 15Zoological Studies 61:34 (2022) © 2022 Academia Sinica, Taiwan stages, with a higher survey intensity during 2005–2013 to verify the presence and foraging habitat of the flying fox. Each survey session lasted for 3–6 consecutive days. Surveys were performed along 12–18 500-m transects of potential habitats across Lyudao, along the five trails on Gueishan Island, and in 21 potential localities in Hualien City. Night surveys were conducted from 6–10 PM to record the numbers, localities and behavior of the flying fox using direct observations (sight and sound). During the day, we also investigated feces and masticated pellets as indirect signs of the presence of the flying fox. All identified feces and pellets were removed to prevent duplicate records. A one-time 10-day survey was performed on Lanyu in Fig. 1. A map of Taiwan showing the occurrence records of Pteropus dasymallus. Full circles, empty circles and empty triangles represent resident populations and sporadic and dubious records, respectively. Approximate locations are presented for numbers 1–6, 9 and 21, where precise coordinates are unavailable (please refer to Table 1 for the details of localities). N page 3 of 15Zoological Studies 61:34 (2022) © 2022 Academia Sinica, Taiwan April 2009 to detect the occurrence of the flying fox. We applied the capture-mark-recapture method to estimate population size. Individual information was obtained via direct capture, observation and noninvasive genetic sampling of feces, pellets and food remains. Capture was carried out on Gueishan Island. Mist nets were placed in the flight paths of the animals before dusk and until midnight during March 2009– September 2012 and October 2019–October 2021. For each individual, wing membrane samples were collected using 3-mm biopsy punches and stored in 99.5% ethanol or silica beads for genetic analysis. Each individual was injected with a subcutaneous passive integrated transponder (PIT) tag between the scapulae or fitted with a uniquely numbered metal band around its thumb for individual identification. After being measured, sexed, sampled and marked, all flying foxes were released. Identification via direct observation was only applied on Lyudao during August 2005–April 2008, where the flying fox’s occurrence was relatively regular. Individuals were identified by color pattern, body size and sex. Fresh feces, pellets and food remains were collected on Lyudao and Gueishan Island and in Hualien City from May 2019 to October 2021. DNA extraction and amplification, sex determination and individual identification were performed following the methods described in Chen (2020) and Chen et al. (2021). Population size was estimated using the Chao 2 estimator for replicated incidence data (Chao 1987; Table 1. Records of Pteropus dasymallus in Taiwan since 1873. The year of discovery, location, number of individuals, sex and reference are provided. Resident populations are displayed in bold No. Year (month) Location Number and sexaReference 11873 Kaohsiungb1 M, 1 F (Sclater 1873) 2 1920 Lyudaoc? N (Kuroda 1920) 3 1932 Hualien (Sinchen) 1 N (Horikawa 1932) 4 1933 Lanyuc1 N (Kuroda 1938) 5 1934 Taitung (Chenggong) ? N (Kuroda 1938) 6 1969 Hualien (Yuli) 1 F NMNHd 71985 Taitung (City) 1 N (C.-Y. Lu pers. comm.) 81992 Hualien (City) 1 N (M.-J. Liao pers. comm.) 9 1995 (or 1996) Yilan (Luodong) 2 F, 4 N (W.-L. Chi pers. comm.) 10 1995 (Mar.) Hualien (City) 3 N (T.-L. Yu pers. comm.) 11 1998 Taitung (Changbin) 1 N (H.-D. Gu pers. comm.) 12 2004 (Sep.) Gueishan Islandc2 N (C.-C. Tsai pers. comm.) 13 2006 (Sep.) Yilan (Su’ao)e1 M (C.-W. Lin pers. comm.) 14 2006 (Oct.) Hualien (Fenglin) 1 M (K.-C. Yeh pers. comm.) 15 2008 (Mar.) Taitung (Changbin) 1 M (J.-N. Hu pers. comm.) 16 2008 (Sep.) Taitung (City) 1 N (G.-D. Zhong pers. comm.) 17 2008 (Sep.) Taitung (Chenggong) 1 N (G.-D. Zhong pers. comm.) 18 2009 (Apr. or May) Hualien (Xiulin) 1 N (T.-P. Lan pers. comm.) 19 2009 (Nov.) Hualien (City) 2 M (C.-H. Wu pers. comm.) 20 2010 (Apr. or May) Hualien (Xiulin) 1 N (T.-P. Lan pers. comm.) 21 2015 (Sep.) Taipei (Gongliao) 1 M, 1 F (J.-Y. Lin pers. comm.) 22 2015 (Oct.) Pengjia Isletc1 N (I.-F. Fu pers. comm.) 23 2015 (Oct.) Taipei (Yehliu) 1 N (P.-W. Chang pers. comm.) 24 2017 (Apr.) Lanyuc1 N (Y.-R. Zhang pers. comm.) 25 2018 (Sep.) Hualien (Fenglin) 1 N (G.-Y. Lin pers. comm.) 26 2018 (Sep. and Oct.) Taipei (Yehliu) pellets This study 27 2018 (Sep. and Oct.) Taitung (Chenggong) pellets This study 28 2018 (Oct.) Taitung (Changbin) pellets (H.-D. Gu pers. comm.) 29 2018 (Oct.) Taitung (City) pellets This study 30 2019 (Jun.) Hualien (Ji’an) 2 N (W.-H. Li pers. comm.) 31 2020 (Aug.) Hualien (Guangfu) 1 N (K.-C. Yeh pers. comm.) 32 2020 (Oct.) Hualien (Shoufeng) 1 N (X.-C. Zhong pers. comm.) 33 2021 (Oct.) Yilan (Toucheng) 2 N (X. Li pers. comm.) a: “M” denotes males, “F” denotes females, “N” denotes unknown sex, “?” denotes an unknown number, and “pellets” indicate observation of masticated pellets only. b: A dubious record (please refer to text for the details). c: Outlying islets. d: National Museum of Natural History, USA. Accession no: USNM358143. e: This is a record of an individual found in the open ocean. page 4 of 15Zoological Studies 61:34 (2022) © 2022 Academia Sinica, Taiwan Chao and Chiu 2016), based on the following formulas: ŜChao2 = Sobs + ( m-1 m) q1 2 2q2 for q2 > 0 and ŜChao2 = Sobs + (m-1 m) q1(q1-1) 2 for q2 = 0, where Sobs is the total number of distinct individuals observed in a study area, q1 and q2 are the numbers of individuals observed once and twice, respectively, and m is the number of surveys. The logtransformed 95% confidence intervals of population size are [Sobs + ŜChao2 - Sobs C, Sobs + (ŜChao2 - Sobs) C], where C = exp { 1.96 [ ln (1 + vâr (ŜChao2) (ŜChao2 - Sobs)2) ] 1 2 } , where vâr (ŜChao2) = q2 [ 1 2 ( m-1 m) ( q1 q2 )2 + ( m-1 m)2 ( q1 q2 )3 + 1 4 ( m-1 m)2 (q1 q2 )4 ] for q2 > 0 and vâr (ŜChao2) = ( m-1 m) q1(q1-1) 2 + (m-1 m)2 q1(2q1-1)2 4 - ( m-1 m)2 q1 4 4ŜChao2 for q2 = 0. We also estimated the intrinsic rate of natural increase (rm) based on the female population on Gueishan Island, where more capture-mark-recapture data were available. We assumed that the small population experienced exponential growth on the recently successfully colonized island with abundant resources and few predators. The rate was calculated with the formula rm = [ ln (Nt N0 ) ] 1 t, where N0 is the number of animals at time 0 and Nt is the number of animals at time t (McIlwee and Martin 2002). To examine the utilization of plant resources, we identified the plant species in the feces, pellets and food remains of flying foxes according to seed size and shape, content texture and color, and the surrounding flora according to the plant checklists from the Red List of Taiwan Plants (Editorial Committee of the Red List of Taiwan Plants 2017), Plants of Taiwan (Institute of Ecology and Evolutionary Biology, National Taiwan University 2022), and World Flora Online (WFO 2022). Unidentified samples were taken back to the laboratory for detailed examination following the methods described by Chen et al. (2017). Resident interviews Interviews were conducted with elderly residents of Lyudao, Gueishan Island and Lanyu to determine the role of the flying fox in local communities. Interviewees from Lyudao and Lanyu, aged over 50 and 70 years, respectively, have lived on the islands since they were young; in contrast, interviewees from Gueishan Island, aged over 50 years, lived on the island until 1977. A semistructured in-depth interview was conducted to capture their knowledge of the flying fox, including past experiences with and memories of this species. For Lyudao residents, the questions included the flying fox’s occurrence, ecological habits, and local customary uses, as well as possible reasons for its disappearance. For residents from Gueishan Island and Lanyu, the questions focused on their life and industry on the islands and whether they had ever heard or seen the flying fox. The interviews were conducted in 2009–2010. We repeated the interview survey of Lyudao residents aged over 60 years in 2021 to assess changes in public perception. Historical records Sighting records of flying foxes during the last 40 years and relevant literature were collected and reviewed. We interviewed or corresponded with some observers regarding their encounters with flying foxes and determined whether the events occurred frequently or rarely. Distances to the nearest coast were measured using Google Earth for locations that had precise coordinates. All interviews were conducted sporadically during 2009–2021. In this study, we excluded subspecies names in data regarding newly discovered individuals/ populations in Taiwan since P. d. yayeyamae and P. d. formosus are still indistinguishable by morphology and genetics. RESULTS Field surveys Our surveys revealed that the flying fox is present on Lyudao and Gueishan Island and in Hualien yearround. On Lyudao, flying foxes were most frequently detected in a forest valley by the main road and on steep mountainsides by an open area during night surveys. All these areas were away from villages. Flying foxes often stayed in those areas to feed or rest, sometimes even throughout the night. A female carrying dependent young was observed in mid-April. On Gueishan Island, flying foxes were mainly observed on ridge crests beside Lake Gueiwei. Flying foxes sometimes aggregated and interacted on a specific Taiwan date palm (Phoenix hanceana Naudin.) found in grasslands, with up to eleven individuals recorded. Copulation was observed in November. Females carrying young pups were recorded beginning in midMay. Flying foxes have been regularly observed in Hualien City, Ji’an and Shoufeng since 2009, 2019 page 5 of 15Zoological Studies 61:34 (2022) © 2022 Academia Sinica, Taiwan and 2020, respectively. They were recorded roosting or foraging at schools, parks, and along trails and riversides, in greater numbers and in an increasing number of locations (Table 1, Appendix 1). Females carrying young were observed beginning in mid-April. During 2009–2012, 22 individuals were captured on Gueishan Island. Two bats were recaptured in different surveys. The population size was approximately 114 individuals, according to the Chao 2 estimator. In the recent period (2019–2021), 60 individuals were captured or detected with fecal and pellet genetic analyses. Twelve individuals were recaptured or rediscovered. The estimated population was 176 individuals. The overall observed sex ratio was 1.96:1 (males: females), which was significantly different from parity (binomial test: P < 0.01). The estimated intrinsic rate of natural increase was 0.058 based on the change in the female population over a period of 9 years (2012–2021). In Hualien City, 12 individuals were identified from genetic analyses of feces, pellets, food remains and carcasses. The estimated population was 60 individuals. The observed sex ratio was 3.5:1, which was not statistically significant (binomial test: P = 0.180). Only four and two individuals were identified on Lyudao in 2005–2008 and 2019–2021, respectively. The estimated populations were five and three individuals, respectively (Table 2). In total, 40 species of plants were used as food, day roosts or night perches by the flying fox (Table 3). Eleven were nonnative plants (27.50%), including an invasive species, Indonesian cinnamon Cinnamomum burmannii (Nees) Blume, which was recorded in Hualien Ji’an; the other species were agricultural or Table 2. Estimated population size with log-transformed 95% confidence intervals of Pteropus dasymallus on Lyudao and Gueishan Island and in Hualien City. The number of identified individuals by sex (M: male, F: female, N: unknown) is also displayeda Location Lyudao Gueishan Island Hualien City Sex M F N M F N M F N Years 2005–2013 Number of identified individuals 1 1 2 14 80 - - - Estimated population size 5 (4–17) 114 (44–407) - Years 2019–2021 Number of identified individuals 0 0 2 39 19 2 7 2 3 Estimated population size 3 (2–12) 176 (110–330) 60 (27–162) a: Individuals were identified by multiple methods, including direct observations, capture and genetic analyses of feces, pellets and food remains, as described in the text. Table 3. The plant resources used by Pteropus dasymallus for food (F), day roosts (R) or night perches (P) on Lyudao and Gueishan Island and in Hualien City Species LyudaoaGueishan Island Hualien Dicotyledons Anacardiaceae Mangifera indica L.bF, P F, P Asteraceae Wedelia biflora (L.) DC. F, P Bignoniaceae Spathodea campanulata Beauv.bP Caricaceae Carica papaya L.bF, P F, P Casuarinaceae Casuarina equisetifolia L.bF, P P Combretaceae Terminalia catappa L. F, P F, P, R Terminalia mantaly H. Perrier.bP page 6 of 15Zoological Studies 61:34 (2022) © 2022 Academia Sinica, Taiwan Species LyudaoaGueishan Island Hualien Ebenaceae Diospyros blancoi A. DC. F, P, R F, P P Diospyros maritima Blume F, P F, P Diospyros morrisiana Hance F, P Euphorbiaceae Macaranga tanarius (L.) Müll. Arg. P Calophyllaceae Calophyllum inophyllum L. F, P Clusiaceae Garcinia subelliptica Merr. F, P F, P Lauraceae Cinnamomum burmannii (Nees) BlumebF, P Cinnamomum camphora (L.) J. Presl. var. camphora F, P Malvaceae Bombax ceiba L. F, P Moraceae Broussonetia papyrifera (L.) L’Hér. ex Vent. F, P Ficus ampelas Burm. f. F, P Ficus benjamina L. R Ficus cumingii Miq. var. terminalifolia (Elmer) Sata F, P Ficus fistulosa Reinw. ex Blume F, P F, P F, P Ficus microcarpa L.f. var. microcarpa P F, P, R Ficus septica Burm.f. F, P F, P F, P Ficus sp. P Ficus superba (Miq.) Miq. var. japonica Miq. P F, P Ficus virgata Reinw. ex Blume F, P Morus australis Poir. F, P Primulaceae Ardisia sieboldii Miq. F, P Myrtaceae Psidium guajava L.bF, P Syzygium samarangense (Blume) Merr. & L.M. PerrybF, P Rosaceae Rubus sp. F, P Sapotaceae Palaquium formosanum Hayata F, P, R F, P Staphyleaceae Turpinia ternata Nakai F, P Pentaphylacaceae Eurya japonica Thunb. F, P Monocotyledons Arecaceae Livistona chinensis R. Br. var. subglobosa (Mart.) Becc. F, P Phoenix hanceana Naudin. F, P F, P Roystonea regia (Kunth) O.F. CookbP F, P, R Musaceae Musa sp.bF, P F, P Strelitziaceae Ravenala madagascariensis Sonn.bP Pandanaceae Pandanus odoratissimus L.f. F, P Total number of species: 40 15 18 25 Number and percentage of nonnative species: 11 (27.50%) 5 (33.33%) 1 (5.56%) 10 (40.00%) a: Some of the Lyudao records were obtained from interviews with elderly residents. b: Nonnative species. Table 3. (Continued) page 7 of 15Zoological Studies 61:34 (2022) © 2022 Academia Sinica, Taiwan horticultural plants found on school campuses or in parks, secondary forests or beside streets. Resident interviews We interviewed 25 elderly residents on Lyudao during 2009–2010. Each of them reported having seen flying foxes in the past. Locals referred to flying foxes as “panichi” but could not explain the term’s exact meaning. A few interviewees also referred to flying foxes as “tò-tiàu tsiáu” in Taiwanese (literally “upsidedown bird”). Most interviewees reported that flying foxes used to be very common (84.00%) and could be seen year-round (64.00%, Table 4). The height at which the flying foxes roosted during the daytime varied among seasons and was higher in summer than in winter. A few interviewees claimed that they had seen flying foxes flying over the open ocean, heading to Lyudao at night. Nearly half of the Lyudao interviewees (48.00%) reported capturing flying foxes for consumption in the past. Captures often occurred during the winter slack farming season when residents could not go fishing. Long bamboo sticks with ends sharpened or mounted with iron wires, nails or darts were used to stab or strike bats off trees. Fallen bats could not take off from the ground. Some residents used homemade dip nets (mesh nets with long bamboo handles) to scoop up bats on trees. From the 1970s to the mid-1980s, flying foxes were harvested commercially with bird netting installed on crest lines between valleys in the major flight paths, which was a more efficient approach for capture. The price for each bat at that time was NT$ 500–700 (US$ c. 14–20; the per capita income of Taiwan was US$ 2,139 in 1980). Flying foxes captured for commercial purposes were transported to Taiwan’s main island and traded in markets. No regulations were imposed on the capture and trading of flying foxes prior to the implementation of the Wildlife Conservation Act in 1989. More than half of the interviewees had eaten flying foxes in the past (56.00%). They cooked flying foxes in several ways: mostly simmering them with local peanut crops, stir-frying chunks of flying fox meat with soy sauce and sesame sauce seasonings, or sometimes stewing them with dried vegetables. The capture and consumption of flying foxes tended to be more prevalent in villages close to mountain areas. Nearly half of the interviewees believed no individuals remained on Lyudao (48.00%). A total of 36.00% of the interviewees claimed that the flying fox was still present or likely present, and 16.00% were uncertain about its presence. However, only a few Table 4. Interviewee responses regarding experience with Pteropus dasymallus on Lyudao in 2009–2010 and 2021 Questions Interviewee responses Percentage reported (%) 2009–2010 (n = 25) 2021 (n = 16) Population abundance in the past Often seen 84.00% Occasionally 16.00% Seasonal variation Year-round 64.00% Mainly in summer 8.00% Mainly in winter 8.00% Not sure 20.00% Hunting experience Yes 48.00% No 52.00% Consumption experience Yes 56.00% No 44.00% Causes for population declines Overhunting 56.00% Plantation 16.00% Typhoons 12.00% Not sure 20.00% Last observation > 30 years ago 32.00% 37.50% 21-30 years ago 24.00% 12.50% 11-20 years ago 12.00% 0.00% ≤ 10 years 12.00% 25.00% Not sure/no response 20.00% 25.00% Population status Rare 36.00% 37.50% Extirpated 48.00% 25.00% Not sure 16.00% 37.50% page 8 of 15Zoological Studies 61:34 (2022) © 2022 Academia Sinica, Taiwan (12.00%) witnessed flying foxes in the last ten years (1999–2009). Most of them had not seen flying foxes for more than 20 years (i.e., flying foxes were last seen before 1989; 56.00%). Overhunting was considered the main cause of population decline (56.00%), followed by habitat degradation due to extensive plantations of the alien Australian pine (Casuarina equisetifolia L.) and damage from typhoons (Tables 4, 5). A more recent interview of 16 Lyudao residents in 2021 showed that more interviewees recently encountered flying foxes (2011–2021, 25.00%). Fewer (25.00%) reported that the flying fox was extirpated. Of the interviewees, 37.50% claimed that the flying fox was present on the island; another 37.50% of the interviewees were uncertain that it was present. We interviewed 15 elderly residents who inhabited Gueishan Island until 1977. All claimed that they had never encountered, or heard about, flying foxes when living there. We interviewed 16 indigenous Tao elders on Lanyu. None of them had ever seen a flying fox. Locals called bats “peypeynget.” Five interviewees (31.25%) learned the term “panichi” from earlier generations to refer to bats. However, they interpreted the meaning differently as follows: (1) The two terms are indistinguishable, both referring to bats. In Tao, objects are commonly identified by more than one term. (2) The two terms denote different species inhabiting different habitats. Some interviewees mentioned that panichi was larger than peypeynget and was caught for food by earlier generations. Some described panichi as present on Lanyu in the past but currently absent. Historical records All occurrences of P. dasymallus were in eastern, northeastern or northern Taiwan based on the literature and interviews of observers (Fig. 1, Table 1). The only exception was the record of Kaohsiung in southwestern Taiwan, which was likely the locality of the donor rather than where the animals were collected (Kuroda 1920; Sclater 1873). This record was therefore excluded from the analysis of sporadic records. Islands with records of sightings included Lyudao, Lanyu, Gueishan Island, Pengjia Islet and Taiwan’s main island. Lyudao was the only locality with resident P. dasymallus until 2004, when a new resident population was found on Gueishan Island. No resident population was recorded on Taiwan’s main island until 2009, when one was reported in Hualien. Most of the recorded sporadic sightings on Taiwan’s main island occurred in the east (Hualien and Taitung). Few were in the northeast (Yilan) or north (Taipei). There was one historical record from Lanyu in 1933 (Kuroda 1938) and a recent record in 2017. To date, there was only a single record on Pengjia Islet in 2015. No flying fox fossils have been found. The number of sporadic individuals found ranged Table 5. Examples of interviewee responses regarding the occurrence and ecology of Pteropus dasymallus on Lyudao Previous sightings “I saw it every day when going to the mountains to collect firewood.” (G13) “Everywhere in the mountains.” (G14) Ecology of the flying fox “Normally one or two bats [hanging on trees].” (W15) “As many as 30–40 bats hanging on a fig tree in the Big Valley.” (N02) “They hung on trees and hid within vines.” (G09) “Particularly more bats in cool shaded valleys.” (DW42) “A group of five or six bats, sometimes three or four, were on a screw pine, biting each other and scrambling for the fruits.” (DW40) “While fishing on the coast, we saw a group of panichi flying over the open ocean, heading over to Lyudao.” (DW42) Capturing the flying fox for local consumption “We could not go fishing during winter so no harvest at all. We went to the mountains to find some food.” (DW06) “Use a long bamboo stick with a sharp-pointed metal hook to stab bats. Then, pull the bats off the trees.” (G6) “We needed to hide downwind. Bats could escape if we approached from an upwind direction.” (G05) Capturing the flying fox for the commercial market “Purchasers from Taiwan’s main island come to buy bats. Since then, hunters used nets to catch bats, which drove the bats extinct.” (N02) “He [the hunter] caught bats every day for years.” (C03) Consumption of the flying fox “Boil it in hot water to remove the hair. Then, chop into small pieces. Simmer with peanuts or fry with sesame oil and shredded ginger.” (DW49) Remaining population “Few, less than five or six.” (A12) “It is gone. Most likely, will not see it again.” (DW11) Conservation of the flying fox “The Formosan flying fox is so unique, only on Lyudao. We did not know that until now. We want to preserve it, but the population has gone.” (C04) page 9 of 15Zoological Studies 61:34 (2022)