Bioacoustics of Cormura brevirostris

Status and Conservation . Classified as Least Concern on 77/r IUCNRed List. The Chestnut Sac-winged Bat has a large distribution, and there is no evidence of rapid population decline. In general, deforestation is a threat; however, taken in context of its large area of endemism, that threat is not presently a serious concern, especially because it occurs in protected reserves throughout its distribution. Chestnut Sac-winged Bats are locally common in the Amazon Basin and uncommon in Central America lowland moist and wet forests, but it is not well studied because of limitations of early field investigations. As acoustic detection methodology is now becoming more common in Central America and South American, and such surveys likely will provide valuable insight on distribution and ecology of the Chestnut Sac-winged Bat Its distribution follows areas of moist lowland forests, but due to loss of these forests, it might no longer occur in southernmost parts of its distribution.

Habitat . Along streams and forest edges in moist lowland multi-strata tropical evergreen forests from sea level to elevations of c.1000 m. The Chestnut Sac-winged Bat forages in small open spaces including forest edges and tree fall gaps, flying in long, slow, beats between ground level and forest canopies. Food and Feeding . The Chestnut Sac-winged Bat is an aerial insectivore that capably forages in cluttered space. When foraging in areas with Greater Sac-winged Bats ( Saccopteryx bilineata ) or Lesser Sac-winged Bats ( S . lepturd ), Chestnut Sac-winged Bats partition space by foraging higher aboveground (5-10 m) or farther from vegetation in gaps and forest edges. It flies faster and in wider circles (20-30 m across) than the Saccopteryx species. Breeding . In Panama, female Chestnut Sac-winged Bats are pregnant in April-May but not in June—September. In French Guiana, females are pregnant in August- September. Litter size is not reported. Activity patterns. Chestnut Sac-winged Bats are crepuscular. Foraging activity begins at dusk and continues for 10-15 minutes, after which observers found individuals to fly above the canopy and disappear, perhaps moving to different foraging areas. Foraging in the middle of the night is rare, but a secondary foraging period occurs shortly before dawn. The Chestnut Sac-winged Bat roosts in tree hollows of living, rotting, and fallen trees and under concrete bridges. One group clung to underside of a large leaf of South American traveler’s palm { Phenakospermum guyannense , Strelitziaceae ). The Chestnut Sac-winged Bat emits search-phase echolocation calls in triplet pulses, with each subsequent sound pulse 2-3 kHz higher than the preceding pulse. First pulse has mean frequency of 25-4 kHz that rises to 28-7 kHz and 32-1 kHz on second and third pulses, respectively. Mean durations of these pulses are 5—10 milliseconds, and mean pulse intervals are 84-102 milliseconds. Chestnut Sac-winged Bats use search calls with components that are dominated by narrowband and small FM parts. These characteristics are well suited for detection of flying insects from relatively long-range detection distances, and similarly used by other members of the tribe Diclidurini . Movements, Home range and Social organization. Chestnut Sac-winged Bats roost in small groups. In French Guiana, roosting groups consisted of 2-5 individuals clustered in compact masses, with individuals touching each other back to belly in a stacked formation. Roosting groups in French Guinea sometimes consisted of more than one adult male but never more than one adult female. Females are able to locate young by contact calls emitted by young, which have been experimentally documented by a mother coming to a captive offspring held in a cloth bag.