Balantiopteryx io, Thomas, 1904

Bonaccorso, Frank, 2019, Emballonuridae, Handbook of the Mammals of the World – Volume 9 Bats, Barcelona: Lynx Edicions, pp. 350-373 : 365

35 . Thomas’s Sac-winged Bat

Balantiopteryx io

French: Emballonure de Thomas I German: Thomas-Sackflügelfledermaus / Spanish: Embalonuro de sacos de Thomas

Other common names: Least Sac-winged Bat

Taxonomy. Balantiopteryx io Thomas, 1904 ,

“ R[ioJ. Dolores, near Coban [Alta Verapaz], Guatemala.”

This species is monotypic.

Distribution. Atlantic slope of Mexico and Central America from S Veracruz and Oaxaca to E Guatemala and Belize.

Descriptive notes. Head—body 38-44 mm, tail 8—18 mm, ear 10—13 mm, hindfoot 7-8 mm, forearm 36-41-4 mm; weight 3-4 g. Dorsal fur of Thomas’s Sac-winged Bat is dark brown to black; venter is paler gray-brown. Flight membranes are black. Wings attach to ankles.

Habitat. Semideciduous or evergreen forests from sea level to elevations of c.500 m. In the Maya Mountains of Belize, Thomas’s Sac-winged Bat occurs in semideciduous forest.

Food and Feeding. Thomas’s Sac-winged Bats forage on small, aerial insects. Although direct visual observations are difficult due to their late emergence from roost, echolocation call characteristics suggest that they hunt in clutter close to vegetation of forest habitats or over water.

Breeding. Pregnant Thomas’s Sac-winged Bats have been recorded in March, May, and July, suggesting polyestry.

Activity patterns. Thomas’s Sac-winged Bats are nocturnal. They roost widely and evenly spaced, often occupying dark recesses of large, limestone caves on ceilings of high chambers. Activity starts well after sunset, later than related species. Echolocation calls include long narrowband component and maximum amplitude on second harmonic. Thomas’s Sac-winged Bats show slightly downward narrowband component that initially starts at 50-2 kHz and drops to 45-9 kHz, on average, and does not turn upward as in other genera of forest emballonurids. Average call duration is 7-8 milliseconds. During approach and terminal phases, call changes to obtain accurate target information after potential prey has been detected.

Movements, Home range and Social organization. Groups of Thomas’s Sac-winged Bats commonly number 50 or more individuals and occasionally 1000—2000 individuals in large caves.

Status and Conservation. Classified as Vulnerable on The IUCN Red List. Thomas’s Sacwinged Bat because depends on highly fragile forested habitat, and it is estimated to have declined by more than 30% due to habitat loss and degradation in the last ten years, with remaining subpopulations fragmented. Adventure tourism leading to vandalism in caves has been and is a significant threat, particularly in Belize, Yucatan, and Guatemala. Needed conservation actions include management and protection of roost caves and additional protection of rapidly disappearing Atlantic forests.

Bibliography. Arroyo-Cabrales & Jones (1988b), Lim, Engstrom et al. (2004), Reid (2009), Thomas (1904b), Villa (1967).

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).

Distribution. Atlantic slope of Mexico and Central America from S Veracruz and Oaxaca to E Guatemala and Belize.