Dyacopterus spadiceus (Thomas, 1890)

Don E. Wilson & Russell A. Mittermeier, 2019, Pteropodidae, Handbook of the Mammals of the World – Volume 9 Bats, Barcelona: Lynx Edicions, pp. 16-162 : 71

16.

Common Dayak Fruit Bat

Dyacopterus spadiceus

French: Cynoptére dayak / German: Gewohnlicher Dayak-Flughund / Spanish: Dyacoptero dayak

Other common names: Dayak Fruit Bat

Taxonomy. Cynopterus spadiceus Thomas, 1890 ,

“Baram [ Sarawak], N.W. Borneo,” Malaysia.

This species is monotypic.

Distribution. Malay Peninsula, Sumatra, and W, N & E Borneo.

Descriptive notes. Head-body 106— 130 mm, tail 16-26 mm, ear 18-21 mm, hindfoot 15 mm, forearm 74-81- 5 mm; weight 70-100 g. Muzzle is wide, almost hairless with brown skin; nostrils are shortly tubular and divergent, with thickened rims; philtrum is obvious, reaching upper lip and lined with small papillae; and lower lip has paired pads and other small papillae. Eyes are large; iris is dark brown. Ears are short, grayish brown, and pointed at tips. Head is very wide, with marked temporal muscles. Head pelage is very short and dark grayish brown, nape is sparsely haired, and dorsum is brown. Tail is long, surpassing wide uropatagium, and calcar is short. Throat and chest are sparsely haired, and light brown, becoming darker on flanks; belly is pale brown to cream. Tuft of orange-brown hairs occurs on sides of neck. Wing membranes are dark gray from sides of body and attach to second toe, index claw is present, and all claws are unpigmented and whitish. Skull has no basicranial deflection and is generally very robust. Laterally, rostrum is moderately short and deep, premaxillae are fused, narial opening is deeply concave, forehead is flat, orbit is large, uropatagium is unusually large, zygomatic root is above upper alveolar line, zygoma is strong and arched, and braincase is moderately rounded. Dorsally, rostrum widens posteriorly, paranasal recesses are inflated, zygoma is very wide, postorbital foramen is minute or obliterated, postorbital constriction is moderately obvious, postorbital processes are oriented posterolaterally, temporal lines are joined in sharp sagittal crest, braincase is oval and elongated, and nuchal crest is well marked. Ventrally, palate is flat; tooth rows diverge slightly; post-dental is moderately short and converging, without palatine spine; sphenoidal crest is inconspicuous; and ectotympanic is very wide, especially anteriorly. Mandible has sloping symphysis; ventral border is convex; coronoid slopes steeply, with rounded tip; condyle is above lower alveolar line; and angle has strongly marked rim. There are 21 palatine ridges, and central onehalf is divided by median ridge. Upper dentition has small and crowded incisors, with I* slightly larger; C' is relatively short, straight, and proclivous, has well-developed vertical groove on its anteromedial surface and a posterior basal cusp; P' is absent; next premolar (P°) is massive, stout, high-crowned, very wide, and square in outline, with anteromedial cingular ledge; and M' is more elongated and low crowned. Lower dentition has very small incisors, spaced apart; 1, is slightly larger; C, is relatively small, short, and strongly decurved; P, is relatively large and wide; posterior cheekteeth are massive and squarish in outline, changing from high- to low-crowned; and M,is peg-like.

Habitat. Primary lowland to lower montane evergreen rainforest from sea level up to elevations of at least 1190 m. The Common Dayak Fruit Bat uses forest subcanopies and canopies.

Food and Feeding. The Common Dayak Fruit Bat is primarily frugivorous and forages in groups searching for subcanopy and emergent fruiting trees with large crops that ripen synchronously. Diets include fruits of Elaeocarpus (Elaeocarpaceae) , Ficus (Moraceae) , and Prunus (Rosaceae) . Strong dentition suggests it also eats hard fruits. It forages alongside other species (e.g. Horsfield’s Short-nosed Fruit Bat, Cynopterus horsfieldii ).

Breeding. Pregnant and lactating Common Dayak Fruit Bats were recorded in June in Brunei and September in Kalimantan; in Peninsular Malaysia, pregnant females were found in January, March, October, and December, suggesting seasonal bimodal polyestrous breeding. Pregnant females carried one fetus per pregnancy. A controversy exists regarding lactation in male Common Dayak Fruit Bats; milk secretion in small quantities has been recorded in males and is considered either a unique feature ofits natural breeding cycle or a consequence of ingestion of phytoestrogens concentrated in some fruit.

Activity patterns. The Common Dayak Fruit Bat apparently flies in open spaces and above the canopy to reach feeding areas. Day roosts are found in ferns and tree cavities in understory and crowns of canopytrees.

Movements, Home range and Social organization. Common Dayak Fruit Bats roost alone or in small groups of up to three individuals. It is transient as it searches for fruits.

Status and Conservation. Classified as Near Threatened on The IUCN Red List. Widespread habitat loss throughout much of the distribution of the Common Dayak Fruit Bat suggests that populations are in decline. Nevertheless, the species is less uncommon that previously thought, and it has accounted for up to 45% offruit bats sampled in appropriate habitat and with adequate devices (e.g. subcanopy mist nets). Present in some protected areas (e.g. Krau Wildlife Reserve, Peninsular Malaysia).

Bibliography. Csorba, Bumrungsri, Francis, Bates, Gumal & Kingston (2008c), Francis (1994), Francis et al. (1994), Helgen et al. (2007), Hodgkison (2001), Hodgkison et al. (2003, 2004a, 2004b), Hodgkison etal. (2004a), Kingston et al. (2006), Racey, D.N. et al. (2009), Rahman et al. (2010).

Figures

15. Brooks's Dayak Fruit Bat (Dyacopterus brooksi), 16. Common Dayak Fruit Bat (Dyacopterus spadiceus), 17. Philippine Large-headed Fruit Bat (Dyacopterus rickarti), 18. Blanford’s Fruit Bat (Sphaerias blanfordi), 19. Bornean Spotted-winged Fruit Bat (Balionycteris maculata), 20. Malayan Spotted-winged Fruit Bat (Balionycteris seemundi), 21. Bornean Pygmy Fruit Bat (Aethalops aequalis), 22. Common Pygmy Fruit Bat (Aethalops alecto), 23. Common Swift Fruit Bat (Thoopterus nigrescens), 24. Suhaniah’s Swift Fruit Bat (Thoopterus suhaniahae), 25. Mindanao Pygmy Fruit Bat (Alionycteris paucidentata), 26. Fischer’s Pygmy Fruit Bat (Haplonycteris fischeri), 27. Luzon Pygmy Fruit Bat (Otopteropus cartilagonodus), 28. Salim Ali’s Fruit Bat (Latidens salimaliz), 29. Sundaic Black-capped Fruit Bat (Chironax melanocephalus), 30. Sulawesi Black-capped Fruit Bat (Chironax tumulus), 31. Lucas’s Short-nosed Fruit Bat (Penthetor lucasu)

Distribution. Malay Peninsula, Sumatra, and W, N & E Borneo.