366.

Disk-footed Bat

Eudiscopus denticulus

French: Murin a disques / German: DiskusfliBige Fledermaus / Spanish: Ratonero de ventosas

Taxonomy. Discopus denticulus Osgood, 1932,

“Phong Saly, Laos. Altitude 4,400 feet [= 1341 m].”

Eudiscopus has been placed in the tribe Vespertilionini, mainly because of adhesive organs on thumb and foot that it shares with the genera Glischropus and Tylonycterus. In 2003, it was placed in Myotinae because it shares external and dental features with Myotis and was found to be basal to different species of Myotis . In 2018, a large-scale phylogenetic study supported inclusion of Eudiscopus in Myotinae with Myotis and Submyotodon, but other analyses placed it outside of Myotinae . In 2019, Eudiscopus was found to be sister to Hesperoptenus tickelli . More research is needed to establish the real phylogenetic relationships of Fudiscopus. A Miocene fossil bat from Slovakia, Paleptesicus priscus, reportedly has similarities with Fudiscopus. Monotypic.

Distribution. Recorded from several localities in Myanmar (Bago Region), Thailand (Kamphaeng Phet, Loei, Ratchaburi, and Surat Thani provinces), N Laos (Phongsaly Province), and Vietnam (Son La, Nghe An, Kon Tum, Binh Phuoc, and Dong Nai provinces).

Descriptive notes. Head—body 41- 5—49 mm, tail 36- 5-45 mm, ear 12-14- 7 mm, hindfoot 4-4-5- 7 mm, forearm 34- 6-38 mm; weight 4.6- 7-8 g. Specimens from Myanmar tend to be smaller and more brightly colored than those from Laos. The Disk-footed Bat resembles a small Myotis, with well-developed disk-like adhesive pads on feet like those in genera Tylonycteris and Glischropus but more pronounced. Fur is dense and soft. Upperparts are cinnamon-brown to reddish brown, and underparts are paler bufty brown. Ears are moderately long (one-half the ear length), with narrow tragus that has bluntly rounded tip and bends forward in the middle. Foot has large, pinkish plantar pad (3- 3 mm wide and 4-5 mm long), like a suction pad, that is disk-shaped ventrally and rectangular. Toes are short. Pads at bases of thumb are poorly developed and thickened at base and probably function as friction pads, not adhesive pads. Foot and thumb pads are probably adaptations for roosting in small cavities with smooth surfaces such as internodes of bamboo culms or narrow crevices in trees and rocks. Wing membranes are dark and insert at base of outer toe; calcar has well-developed keel. Ears and muzzle are not as dark as membranes. Membranes, ears, and muzzle are dark. Baculum is c. 0-6 mm long, more or less triangular in upper view because of well-developed basal projections, and pointed sideward, backward, and somewhat downward, with deep and wide basal notch. Main bone body in its distal point is slightly widened and blunt; its basal one-third forms rounded inflation. Underside is somewhat concaved, with definite urethral groove. Skull is relatively broad and strikingly flattened; rostrum is elongated and relatively long and upturned anteriorly relative to flattened braincase. Braincase is 3-5- 3-9 mm high. Interorbital region has pronounced depression. Condylo-canine lengths are 12:8-13- 4 mm; maxillary tooth row lengths are 5-1-5- 5 mm. C' is Myotislike, with blunt posterior blade and without any supplementary cusps or cingulum; I’ is larger that I* as in Myotis; P, is much reduced, displaced to innerside of tooth row, notvisible from outside, and compressed between P, and P; and lower molars are myotodont. Dental formula is I 2/3, C 1/1, P2/3,M3/3 (x2) = 36.

Habitat. Hilly forests (Myanmar), lowland bamboo forests (Vietham), and mixed deciduous forests and moist evergreen forests, both with bamboo stands (Thailand), at elevations of ¢. 30-1300 m.

Food and Feeding. Acoustic study of the Disk-footed Bat in Vietnam suggested that it is an edge and open-space aerial forager. One individual from peninsular Thailand was caught in a mist net while hunting swarming insects at edge of secondary forest.

Breeding. Births probably occur in late-April in Vietnam.

Activity patterns. Disk-footed Bats are nocturnal. Their flattened skull is adapted to crawl through narrow crevices. In Khlong Lan National Park in Thailand, seven Disk-footed Bats were discovered closely together in an upper part of an internode of giant bamboo ( Gigantochloa sp., Poaceae), ¢. 5 m aboveground, 57 cm long, and 9- 2 cm in diameter. In Cat Tien National Park (Vietnam), flight was slow and highly maneuverable; hovering alternated with short gliding phases during which wings remained still in slightly lifted position similar to nightjars ( Caprimulgidae). Disk-footed Bats seem to use FM-CF calls (broadband FM signal with narrowband nearly CF end). Length of CF part was always quite short, but this might have been because individuals were partly or mostly recorded in a restricted range; calls started at c.110-135 kHz and ended at ¢.52 kHz.

Movements, Home range and Social organization. Disk-footed Bats roost in small groups of 67 individuals.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Diskfooted Bat is widespread but not abundant across South-east Asia. It apparently faces no major threats and is not declining at a rate that would qualify for a threatened category.

Bibliography. Amadoret al. (2018), Boitani et al. (2006), Borisenko & Kruskop (2003), Borisenko, Kruskop & Ivanova (2008), Conisbee (1953), Corbet & Hill (1992), Dang Ngoc Can et al. (2008), Francis (2008a), Gorfol et al. (2019), Hughes et al. (2011), Kock & Kovac (2000), Koopman (1970, 1994), Kruskop (2010a, 2013a, 2013b, 2017), Kruskop et al. (2003), Kunz & Lumsden (2003), Osgood (1932), Rossina et al. (2006), Ruedi, Csorba et al. (2015), Ruedi, Stadelmann et al. (2013), Schliemann & Hoeber (1978), Schliemann & Kock (2000), Shi & Rabosky (2015), Simmons (2005), Soisook, Csorba et al. (2016), Tate (1941d), Thewissen & Etnier (1995), Zsebok et al. (2014).