Emballonura semicaudata, Peale, 1848

Bonaccorso, Frank, 2019, Emballonuridae, Handbook of the Mammals of the World – Volume 9 Bats, Barcelona: Lynx Edicions, pp. 350-373 : 361

26 . Pacific Sheath-tailed Bat

Emballonura semicaudata

French: Emballonure du Pacifique / German: Pazifik-Freischwanzfledermaus / Spanish: Embalonuro del Pacifico

Other common names: Caroline Sheath-tailed Bat, Mariana Sheath-tailed Bat, Polynesian Sheath-tailed Bat

Taxonomy. Vespertilio semicaudatus Peale, 1848 ,

Samoa .

S. J. Oyler-McCance and colleagues in 2013 reviewed taxonomy of E. semicaudata and found genetic distances in the cytochrome-b gene among subspecies to be larger than typically reported for mammalian subspecies. They also found that rotensis was more closely related to palauensis than semicaudata . No genetic information is available for sulcata.

According to K. M. Helgen and T. F. Flannery in 2002, records from Vanuatu are believed to be in error. Four subspecies recognized.

Subspecies and Distribution.

E. s. semicaudata Peale, 1848 - Samoa (Savai’i and Upolu Is), American Samoa (Ta’u Is), Fiji (Rotuma, Kuata in Yusawa Group, Taveuni, Ovalau, and Lakeba Is), and Tonga (Niuafo’ou and ‘Eua Is, and likely occurs on other islands in the group). Not recorded in Tutuila (American Samoa) since 1976 despite dedicated searches for cave roosts and use of echolocation detectors and also likely extinct on Vitu Levu (Fiji) where the last specimens were collected in 1979.

E. s. palauensis Yamashima, 1932 - Palau Is (including Babeldaob, Koror, Peleliu, and Angaur).

E. s. rotensis Yamashima, 1943 - Northern Mariana Is and Guam I, last surviving population is currently restricted to tiny Aguigan I; it appears to be extirpated on Anatahan, Tonowas, Rota, Saipan, and Tinian Is, and on Guam I.

E. s. sulcataG. S. Miller, 1911 — Caroline Is (Chuuk and Pohnpei Is).

Descriptive notes. Head-body 41-49 mm, ear 10-13-6 mm, forearm 44-48 mm; weight 5-5—8 g. No data available for tail length. The Pacific Sheath-tailed Bat is sexually dimorphic, with females being larger than males. It is medium-sized and brown. Dorsal fur is dark brown; venter is paler brown or yellow-brown. Flight membranes, ears, and bare regions on face are black. Eyes are large, with dark brown irises.

Habitat. Understories of moist, closed-canopy forests on Aguigan and Pohnpei and also towns, over roads and lawns with scattered coconut palms, in Palau, Chuuk, and Pohnpei, from sea level to elevations of c.300 m.

Food and Feeding. Pacific Sheath-tailed Bats feed by aerial-hawking of small insects and hunt above or below canopies of native forests. Hymenopterans, coleopterans, and lepidopterans are the most important prey items on Aguigan. Among Hymenoptera , parasitic wasps (Ichneumonoidea) and alate (winged) ants ( Formicidae and Ponerinae ) were important in diets. Body lengths of prey items are 1-7-6-4 mm.

Breeding. Reproduction of Pacific Sheath-tailed Bats on Aguigan is timed so that late gestation, lactation, and maturation ofyoung coincides with lateJune-early November rainy season. A single period of parturition resulting in one young occurs from late June to earlyjuly. It is suspected that mating on Aguigan occurs early in the year in dry season because no males have been observed with descended testes or spermatozoa in epididymis in June-July.

Activity patterns. Pacific Sheath-tailed Bats are crepuscular and roost in limestone caves, including sea caves, and under rock overhangs. They prefer to roost in larger caves and display significant fidelity to roosting caves. On Aguigan, they began to emerge in twilight conditions around sunset and had fully emerged 15 minutes after sunset. Emerging bats immediately moved to shaded understories in evergreen forests where they forage early in the evening, and they often moved above forest canopies after dark. Flight is slow and fluttery.

Movements, Home range and Social organization. Roosting distances are maintained between Pacific Sheath-tailed Bats, and they cling to vertical cave walls. Roosting populations on Aguigan in 2008 ranged from one to 332 individuals, based on emergence counts. One cave consistentiy held the largest colony of c.300-332 individuals, and six other roost caves had one to 64 individuals.

Status and Conservation. Classified as Endangered on The IUCN Red List. Extent of occurrence of the Pacific Sheath-tailed Bat is less than 5000 km2, its distribution is severely fragmented on small islands, and there are continuing declines in quality and extent of its habitat, number of locations where it is occurs, and number of mature individuals in various populations. Population on Aguigan was estimated at 400-600 individuals during surveys in 2008 and 2011. Feral goats {Capra hircus) on Aguigan are a threat to native forest regeneration that the Pacific Sheath-tailed Bats heavily rely on as foraging habitat, placing them in peril. Eradication of these goats combined with reforestation could increase and enhance foraging habitat. The Pacific Sheath-tailed Bat might have been extirpated in American Samoa, Guam, Vitu Levu in Fiji, and all of its former distribution in the Commonwealth of the Northern Marianas, except tiny Aguigan Island that is only 7 km2. World War II negatively impacted caves and probably had severe impact on the decline of the Pacific Sheath-tailed Bat in the Marianas. Use of pesticides and disturbance of roost caves also are attributing to declines.

Bibliography. Bonaccorso & Allison (2008), Bruner & Pratt (1979), Esselstyn, Wiles & Amar (2004), Flannery (1995b), Gorresen eta /. (2009), Helgen & Flannery (2002), Koopman (1997), Lemke (1986), Oyler-McCance et al. (2013), Palmeirim, Champion, Naikatini, Niukula, Tuiwawa, Fisher, Yabaki-Gounder, Qalovaki & Dunn (2005), Palmeirim, Champion, Naikatini, Niukula, Tuiwawa, Fisher, Yabaki-Gounder, Thorsteinsdóttir et al. (2007), Tarburton (2002), Wiles, Aguon et al. (1995), Wiles, Engbring & Otobed (1997), Wiles, Worthington et al. (2009).

Figures

On following pages: 22. New Guinea Sheath-tailed Bat (Emballonura furati); 23. Beccari's Sheath-tailed Bat (Emballonura beccarti); 24. Large-eared Sheath-tailed Bat (Emballonura dianae); 25. Seri'sSheath-tailed Bat (Emballonura sertii); 26. Pacific Sheath-tailed Bat (Emballonura semicaudata); 27. Western Sheath-tailed Bat (Paremballonura tiavato); 28. Peters's Sheath-tailed Bat (Paremballonura atrata); 29. African Sheath-tailed Bat (Coleura afra); 30. Seychelles Sheath-tailed Bat (Coleura seychellensis); 31. Madagascar Sheath-tailed Bat (Coleura kibomalandy); 32. Dark Sheath-tailed Bat (Mosia nigrescens); 33. Chestnut Sac-winged Bat (Cormura brevirostris); 34. Gray Sac-winged Bat (Balantiopteryx plicata); 35. Thomas's Sac-winged Bat (Balantiopteryx io); 36. Ecuadorian Sac-winged Bat (Balantiopteryx infusca).

Subspecies and Distribution. E. s. semicaudata Peale, 1848 - Samoa (Savai’i and Upolu Is), American Samoa (Ta’u Is), Fiji (Rotuma, Kuata in Yusawa Group, Taveuni, Ovalau, and Lakeba Is), and Tonga (Niuafo’ou and ‘Eua Is, and likely occurs on other islands in the group). Not recorded in Tutuila (American Samoa) since 1976 despite dedicated searches for cave roosts and use of echolocation detectors and also likely extinct on Vitu Levu (Fiji) where the last specimens were collected in 1979. E. s. palauensis Yamashima, 1932 - Palau Is (including Babeldaob, Koror, Peleliu, and Angaur). E. s. rotensis Yamashima, 1943 - Northern Mariana Is and Guam I, last surviving population is currently restricted to tiny Aguigan I; it appears to be extirpated on Anatahan, Tonowas, Rota, Saipan, and Tinian Is, and on Guam I. E. s. sulcataG. S. Miller, 1911 — Caroline Is (Chuuk and Pohnpei Is).