52.

Indomalayan Lesser Bamboo Bat

Tylonycteris fulvida

French: Vespertilion fauve / German: Indomalayische Bambusfledermaus / Spanish: Tilonicterio indomalayo

Other common names: Amber Bamboo Bat

Taxonomy. Scotophilus fulvidus Blyth, 1859,

“Schwegyin, Sittang River, Southeast Burma.”

Previously included in 7. pachypus as a subspecies or synonym, but molecular evidence suggests it represents a distinct species occurring throughout mainland South-east Asia; it 1s considered sister to 1. pachypus from Sundaland. Distributional limits and morphological distinctions between the two species have not been thoroughly investigated and are considered putative here. Listed subspecies have not recently been compared on morphological or molecular basis; there may be cryptic species in China, based on morphological data. Two subspecies tentatively recognized.

Subspecies and Distribution.

T.f.fulvidaBlyth,1859—E&NEIndia(Sikkim,WestBengal,Assam,ArunachalPradesh,Meghalaya,Manipur,Mizoram,andTripura),Bangladesh,SEChina(Yunnan,Sichuan,Guizhou,Guangxi,Guangdong,andHongKong),andmainlandSEAsia,aswellasAndamanIs(Karmatang,Webi,andtheSouthAndaman);possiblyalsoinBhutan.

T. f. aurex Thomas, 1915 — S India (Kerala and Karnataka).

Descriptive notes. Head-body 34-43 mm, tail 19-8-31-7 mm, ear 610 mm, hindfoot 3:9-6-3 mm, forearm 22-9-27-9 mm; weight 3-1-3.5 g. Head is dorso-ventrally flattened and broadened. Dorsal pelage is thick, short, and shiny golden brown with a variably reddish hue; ventral pelage is slightly lighter and very sparsely furred with pink skin. Juveniles are typically darker and less reddish. Muzzle, ears, and membranes are hairless and dark brown. Ears are subtriangular, relatively long with a broadly rounded tip; tragusis short and blunt. Base of thumbs and soles of hindfeet have well-developed rounded fleshy pads for gripping smooth surfaces; these pads are extremely smooth and are made up of 40% epidermis, a small layer of dermis, and a thicker layer of subcutaneous fat. Wing membrane attaches at base of metatarsus; uropatagium extends to tip oftail, and calcar is over halfway to tail from ankle. Skull is small, very broad, and flattened; nasal emargination is shorter than in any of the greater bamboo bats; rostrum is short; there is no sagittal crest; lambdoid crests are very well developed. I? is narrow and bicuspid; I is unicuspid and subequal to second cusp of I*; P* is small with crown area about a quarter part of M'; there is a well-developed protocone on P*lower incisors are tricuspid; P, and P_ are subequal in size; skull is similar to that of Sunda Lesser Bamboo Bat ( 7. pachypus) overall and specific morphometric comparison is needed to diagnose both species fully, based on skull morphology. Chromosomal complement has 2n = 46 and FN = 56 (Malaysia); and 2n = 30 and FN = 56 (Guangdong, China).

Habitat. Primary tropical deciduous forests with abundant bamboo. Recorded from sea level up to 1262 m in India, and up to 1220 m in Malaysia.

Food and Feeding. Indomalayan Lesser Bamboo Bats appear to forage in areas highly cluttered with vegetation; they catch insects in the mouth and eat them on the wing. In Guangxi, diet consisted largely of Hymenoptera (53-4% by volume), Diptera (29%), and Coleoptera (13:4%) with smaller amounts of Hemiptera (2:1%), Homoptera, Blattodea, and Embioptera. They have been observed feeding on termite swarms in Malaysia. There is seasonal variation in the diet, and in Guangxi they progressively fed more on Hymenoptera and less on Diptera from spring to autumn; percentage volume of Coleoptera in diet decreased to its lowest point in May, and diet seemed to be most varied in March and April, when no food item made up over 50% of the total volume; from May to October, Hymenoptera made up over 50% of diet. In the submandibular glands of this species, a bacteria was reported which may aid in digestion, but further research is needed.

Breeding. Indomalayan Lesser Bamboo Bats are polygynous and breed once a year, probably copulating between September and November when the males’ testes are enlarged. Females will generally mate with a number of males throughout a season and throughout their life-span. Spermatogenesis occurs in late October and seems to near termination by late November and early December. Preparation for ovulation seems to occur in late May to June, and follicular growth may begin prior to weaning in juvenile females. Ovulation generally occurs in early January and appears to be triggered by higher afternoon temperatures associated with the dry season. Females appear to store sperm until prey abundance increases between December and June, which is relatively uncommon in tropical bats. Sperm has been recorded in the females’ reproductive track clumped together with heads in the epithelium and tails outwards in November, December, and January. In Malaysia, pregnant females have been recorded in February, March, and April. Gestation lasts ¢.12-13 weeks and twins are born in April and May. Although twins are most common, there have been reports of single and triplet litters; twins are usually dizygotic, but a monozygotic set was recently reported in China. Young are hairless and blind at birth, with body mass ¢.0-6 g. They cling to their mothers’ body while she flies, but as they get older they are eventually left in the roost while she forages. Lactating females have been recorded in May in Malaysia with the emergence of volant, weaned juveniles by the end of May. Young become volant at ¢.22-25 days of age. Males and females become sexually mature by their first breeding season.

Activity patterns. The Indomalayan Lesser Bamboo Bat is nocturnal and leaves the roost around dusk to forage. Day roosts are inside hollow bamboo internodes. Chosen roosts have entrances that are small vertical slits (mean vertical length of 33 mm and mean horizontal width of 4-9 mm in Malaysia), which are only accessible because of the flattened skull and body shape. Cracks used by these bats to enter the bamboo are created by the emergence of beetle larvae (particularly Lasiochila gory: in Malaysia). In Malaysia, they primarily used the bamboo Gigantochloa scortechinii (Poaceae) for roosting. Although they usually roost in bamboo shafts, they have also been observed roosting in small rock crevices and may use the abandoned holes of the Indomalayan Pencil-tailed Tree Mouse ( Chiropodomys gliroides). Unlike many other vespertilionids, the species does not enter torpor, but it may become more lethargic at higher temperatures. Call shape is a steep FM/QCF sweep. In Thailand, average peak frequency was recorded at 50-5 kHz, maximum frequency 134-4 kHz, minimum frequency 39-4 kHz, duration 1-6 milliseconds, and pulse interval 26-8 milliseconds.

Movements, Home range and Social organization. Females are more gregarious, with average group sizes of 4-9 individuals (maximum 20) in Malaysia, whereas males typically roost solitarily or with a group of females. An average roostsize of 12-6 individuals was recorded in Guangxi, with maximum of 38 in a single roost, and roosts with several males (2-6) were reported in the same region. Both sexes switch roosts almost daily, and group size within roosts changes often. When females are in estrus, one male in a group of females may prevent other males from roosting with them.

Status and Conservation. Not assessed on The IUCN Red List as a separate species from the Sunda Lesser Bamboo Bat, which is classified as Least Concern. The Indomalayan Lesser Bamboo Batis generally common throughout its distribution, but was considered locally extinct in Singapore until a single specimen was collected in 1997.

Bibliography. Aul (2014), Aul et al. (2014), Bates, Francis, Rosell-Ambal, Heaney, Molur & Srinivasulu (2008), Eguren & McBee (2014), Hua Panyu et al. (2011), Huang Chujing et al. (2014), Hughes et al. (2011), Kruskop (2013a), Medway & Marshall (1970), Pottie et al. (2005), Smith & Xie Yan (2008), Srinivasulu et al. (2017), Tandler et al. (1995), Thewissen & Etnier (1995), Tu Vuong Tan, Csorba et al. (2017), Yong et al. (1971), Zhang Libiao, Jones, Parsons et al. (2005), Zhang Libiao, Jones, Rossiter et al. (2005), Zhang Libiao, Liang Bing, Parsons et al. (2007), Zhang Libiao, Liang Bing, Zhou Shanyi et al. (2004a).