Eonycteris spelaea (Dobson, 1871)

Don E. Wilson & Russell A. Mittermeier, 2019, Pteropodidae, Handbook of the Mammals of the World – Volume 9 Bats, Barcelona: Lynx Edicions, pp. 16-162 : 83-84

38.

Lesser Dawn Bat

Eonycteris spelaea

French: Eonyctere des cavernes / German: Kleiner Langzungenflughund / Spanish: Eonicterio pequeno

Other common names: Cave Nectar Bat, Common Dawn Bat, Common Nectar Bat, Dobson's Long-tongued Fruit Bat

Taxonomy. Macroglossus spelaeus Dobson, 1871 ,

“Penang, Moulmein, the Nicobar and Andaman Islands.” Restricted by K. Andersen in 1912 to “Farm Caves, Moulmein [= Mwalamyaing, Myanmar].”

Eonycteris has traditionally been considered closely related to Macroglossus , but genetic studies have determined that it is most closely related to Rousettus and is placed in a distincttribe (Eonycterini) within Rousettinae. Boundaries of subspecies need to be assessed using more complete genetic and morphological studies because specimens from the Greater Sundas seem to form a single clade that does not match current subspecific distributions. Four subspecies recognized.

Subspecies and Distribution. E.s.spelaecaDobson,1871—NW,S&NEIndia(Uttarakhand,AndhraPradesh,Karnata-ka,Kerala,TamilNadu,Sikkim,Assam,Meghalaya,Nagaland,Manipur,andMizoram),WNepal,Myanmar,SChina(YunnanandSWGuangxi),Indochina,MalayPeninsula,Sumatra,andJava;alsoonAndamanIsandTiomanI.

E.s.glandiferaLawrence,1939—LesserSundaIs(Bali,Lombok,Sumba,Timor),Philip-pines(includingPalawanI),SSulawesi(includingMunaI),andSulaIs(Sanana).

E.s.rosenbergiiJentink,1889—NSulawesiandNMoluccas(Halmahera,Ternate,Tidore,andBacanIs).

E. s. winnyae Maharadatunkamsi & Kitchener, 1997 — Borneo.

Descriptive notes. Head—body 79- 5-130 mm, tail 11-25 mm, ear 17-24 mm, hindfoot 15-24 mm, forearm 61-80 mm; weight 40-79- 5 g. The Lesser Dawn Bat is small to medium-sized, with elongated narrow snout and head, a long-pointed tongue with papillae at tip, and no claw on second finger. Males are generally larger (¢.20% larger by weight) than females and have ruff of elongated hairs on side of neck. Size is the primary distinction between subspecies; winnyaeis smallest. Pelage is short and velvety. Dorsal pelage ranges from brownish gray to dark brown and rarely blackish brown,is relatively uniform in color from head to rump, and often tinged with yellow or orange around neck. Ventral pelage is generally lighter and grayer than dorsum and darker around genitals. Ears are bluntly pointed, medium in length, and dark brown; eyes are large, with dark reddish-brown irises. Wings, legs, and uropatagium are dark brown. Arms are lightly covered in brown hairs. Both sexes have unique, well-developed, kidney-shaped anal glands on either side of anus, being smaller in younger individuals and largest in breeding males (with strong and distinct odor). Tail is short, covered sparsely with hairs, and dark brownish; uropatagium attaches at base of tail and short keel at ankles, giving V-shaped gap wheretail is. Second digit of wing lacks a claw, and metacarpals offifth digit are much shorter than metacarpals of third digit; skin over wing bones is pigmented. Skull is elongated, with long rostrum; anterior premaxillae are in contact or slightly divided; and braincaseis heavily deflected downward. Dental formula for all species of Eonycterisis 12/2, C1/1,P 3/3, M 2/3 (x2) = 34. Teeth are sharp and not as reduced as in some nectarfeeding bats, although molars and premolars have considerably reduced cusps and are narrow and elongated. M,is very small, and P, is occasionally missing. Upper incisors are small and triangular, C! is relatively long, and C, is small, simple, and heavily curved outward. Chromosomal complement has 2n = 36 and FN = 68 (Java and Thailand) or 66 ( Malaysia).

Habitat. Primarily forested regions, especially around mangroves and plantations, from sea level up to elevations of ¢. 1000 m. Density of Lesser Dawn Bats tends to decrease at higher elevations. They seem to prefer secondary forests but have been recorded in primary forests. They typically roost in caves but have also been found in small group in attics of village huts in north-eastern India and Myanmar.

Food and Feeding. Lesser Dawn Bats feed on nectar and pollen of various flowering plants, including many agriculturally important species. They are known to forage in canopies of primary and secondary forests, mangroves, gardens, orchards, and other agricultural settings. They do well in agricultural areas where they feed on nectar in flowers of many agricultural and orchard crops (especially durian, Durio , Malvaceae ; Parkia , Fabaceae ; and banana plantations) and serve as important pollinators. They forage by landing on a flower or hovering near it and lapping up nectar with their tongue. Their face is often covered with pollen. In Borneo, fecal samples indicated that the most regular supply of nectar for individuals in the Batu Caves came from Duabanga grandiflora (Lythraceae) and Artocarpus (Moraceae) fruit trees but also included jambu ( Syzygium , Myrtaceae ) and durian flowers. In the same area, individuals traveled more than 38 km to feed on nectar of coastal mangrove flowers ( Sonneratia , Lythraceae ) and were recorded feeding on 31 species of plants. Throughout South-east Asia, they feed on a variety of fruiting plants, such as Parkia, Duro , Musa (Musaceae) , and various mangrove trees, serving as important pollinators. Data from 1155 diet records in Thailand indicated that they feed mainly on pollen and nectar of economically important food plants, such as Parkia (34% of diet), Musa (28%), and less on Eugenia (Myrtaceae) , Oroxylum indicum ( Bignoniaceae ), Durio zibethinus and Ceiba pentandra ( Malvaceae ), Sonneratia , and Cocos nucifera ( Arecaceae ). Throughout the year, the main dietary components were Parkia and Musa , but Durio became more important in March-April, making up 39-42% of diets. In the same study, individuals fed from flowers of up to six plants each night. In another recent study in Thailand, Lesser Dawn Bats traveled 1-17- 9 km from their roosts to find food sources and moved 0-25- 8 km between each food source, foraging at 1-3 foraging areas each night. A similar spread of food sources was also found in southern Cambodia, in which a variety of cultivated plants ( Sonneratia ; Bombax anceps , Malvaceae ; Durio zibethinus, Musa ; Parkia ; Ceiba pentandra; and Oroxylum indicum) made up most of the diet throughout the year, although eucalypt species were also reported in diets. As food availability changes throughout the year, Lesser Dawn Bats alter their feeding habits relative to what plants are flowering.

Breeding. Lesser Dawn Bats seem to breed throughout the year, asynchronously and without any seasonal trends at least in India and Peninsular Malaysia. There might be peaks in pregnancies associated with rainfall that results in flowering and fruiting. They might have harems in roosts as a resource defense polygynous mating system, although this has not been proven. Anal glands on both sexes might have a role in reproductive behavior because glandular size appears to be synchronized with adult male testicular cycle. Females might also signal sexual receptivity with these glands. Females give birth to one young and have two pregnancies a year. Females become sexually mature at ¢.6 months old, and males take c.1 or more years to mature. Gestation is estimated at c.120 days.

Activity patterns. Lesser Dawn Bats are primarily nocturnal. They leave roosts soon after sunset and return around dawn, visiting multiple trees throughout the night to collect nectar and pollen. In Thailand, mature males seem to return early in the night (as soon as midnight); most females generally returned at dawn. Time spent outside a cave ranged from two hours and 46 minutes to nine hours and 35 minutes (average six hours and 17 minutes) in southern Thailand; mature males spent the shortest time (average five hours and 17 minutes) outside roosts, followed by immature females (six hours and 33 minutes), immature males (seven hours and 52 minutes), and mature females (eight hours and 29 minutes). Mature females might be out later to fulfill nutritional requirements during reproduction, and mature males might return earlier to defend a roosting site in a cave, which is attractive to females. These patterns have been recorded in harem-forming fruit bats (e.g. Cynopterus spp. and Bornean Spottedwinged Fruit Bats, Balionycteris maculata ) and suggest Lesser Dawn Bat form harems. Males that spend less time out of the cave were also heavier than males that spend more time out of the cave, similar to other harem-forming species in which males that formed harems were heavier. In the same study, Lesser Dawn Bats spent more time out of the roost in January-April (dry season) and less time in May-July (rainy season) in southern Thailand. Seasonal differences in foraging time might be associated with food availability because during dry season, its main food source ( Parkia speciosa ) is no longer flowering.

Movements, Home range and Social organization. Lesser Dawn Bats are highly gregarious, sedentary, and commonly found roosting in very large colonies of up to several thousand individuals (often ¢.2000 individuals), with one roost on Palawan Island estimated to exceed 50,000 individuals. These colonies are very noisy and generally occur in completely dark parts of caves. Lesser Dawn Bats make loud clapping noises with their wings while flying. They form tight roosting clusters of males and females yearround. In Thailand, mean home ranges were 460-8 ha, 518-4 ha, and 562-5 ha, depending on the sampling method. Males and females have continuous oily secretions from their anal glands that serve to mark roosting sites, define territories, or announce sexual receptiveness in females. Although generally sedentary, Lesser Dawn Bats seem to move across the Andaman Islands and breed nearly panmictically across the population, as suggested by lack of population structure; majority of genetic variation occurs within island populations rather than among them. Lesser Dawn Bats often roost with Geoffroy’s Rousettes ( Rousettus amplexicaudatus ).

Status and Conservation. Classified as Least Concern on The IUCN Red List. Lesser Dawn Bats have a wide distribution and are generally common. They seem to do well in some disturbed habitats and agricultural settings, especially in fruiting orchards and (to a lesser extent) palm oil plantations. Nevertheless, they are locally threatened by deforestation from logging and land conversion to agricultural use in some regions of South Asia. Because they roost in caves, they are also probably threatened by cave tourism and lighting as some caves, such as the Borra Caves in Andhra Pradesh, India, have become tourism hotspots. They are unfortunately listed as vermin under Schedule V of the Indian Wildlife (Protection) Act, similar to most other fruit bats in India. They are apparently under heavy hunting pressure for bushmeat in some regions of China, Cambodia, Borneo (where it has been hunted to extinction in Niah), and the Philippines.

Bibliography. Acharya, Racey, McNeil et al. (2015), Acharya, Racey, Sotthibandhu & Bumrungsri (2015), Achondo et al. (2014), Andersen (1912b), Ando et al. (1980a), Aul et al. (2014), Beck & Lim (1973), Bhat et al. (1980), Bhattacharyya (1975), Bumrungsri, Harbit et al. (2008), Bumrungsri, Lang et al. (2013), Chakravarty et al. (2018), Esselstyn, Widmann & Heaney (2004), Flannery (1995a), Francis (2008a), Giannini & Simmons (2007a), Gould (1988), Heaney, Balete, Dolar et al. (1998), Heaney, Balete & Rickart (2016), Hisheh et al. (1998), Hood et al. (1988), Khan et al. (2007), Kingston & Rossiter (2004), Kruskop (2013a), Krutzsch (2005), Maharadatunkamsi & Kitchener (1997), Maharadatunkamsi et al. (2003), Mickleburgh et al. (2009), Nameeret al. (2016), Phillipps & Phillipps (2016), Singaravelan et al. (2009), Smith & Xie Yan (2008), Start & Marshall (1976), Struebig et al. (2005), Thavry etal. (2017), Winkelmann et al. (2000), Yong & Dhaliwal (1976).

Figures

32. Zenker’s Fruit Bat (Scotonycteris zenkeri), 33. Hayman’s Fruit Bat (Scotonycteris occidentalis), 34. Bergmans’s Fruit Bat (Scotonycteris bergmansi), 35. Short-palated Fruit Bat (Casinycteris argynnas), 36. Pohle’s Fruit Bat (Casinycteris ophiodon), 37. Campo-Ma’an Fruit Bat (Casinycteris campomaanensis), 38. Lesser Dawn Bat (Eonycteris spelaea), 39. Greater Dawn Bat (Eonycteris major), 40. Philippine Dawn Bat (Eonycteris robusta), 41. Geoffroy’s Rousette (Rousettus amplexicaudatus), 42. Bare-backed Rousette (Rousettus spinalatus), 43. Leschenault’s Rousette (Rousettus leschenaultin), 44. Linduan Rousette (Rousettus linduensis), 45. Sulawesi Rousette (Rousettus celebensis), 46. Egyptian Rousette (Rousettus aegyptiacus), 47. Malagasy Rousette (Rousettus madagascariensis), 48. Comoro Rousette (Rousettus obliviosus), 49. Long-haired Fruit Bat (Stenonycteris lanosus)

Subspecies and Distribution. E.s.spelaecaDobson,1871—NW,S&NEIndia(Uttarakhand,AndhraPradesh,Karnata-ka,Kerala,TamilNadu,Sikkim,Assam,Meghalaya,Nagaland,Manipur,andMizoram),WNepal,Myanmar,SChina(YunnanandSWGuangxi),Indochina,MalayPeninsula,Sumatra,andJava;alsoonAndamanIsandTiomanI. E.s.glandiferaLawrence,1939—LesserSundaIs(Bali,Lombok,Sumba,Timor),Philip-pines(includingPalawanI),SSulawesi(includingMunaI),andSulaIs(Sanana). E.s.rosenbergiiJentink,1889—NSulawesiandNMoluccas(Halmahera,Ternate,Tidore,andBacanIs). E. s. winnyae Maharadatunkamsi & Kitchener, 1997 — Borneo.