Saccopteryx bilineata (Temminck, 1838)

Bonaccorso, Frank, 2019, Emballonuridae, Handbook of the Mammals of the World – Volume 9 Bats, Barcelona: Lynx Edicions, pp. 350-373 : 371-372

50 . Greater Sac-winged Bat

Saccopteryx bilineata

French: Saccoptère à deux bandes / German: Grosse Sackflügelfledermaus / Spanish: Sacóptero mayor

Other common names: Greater White-lined Bat

Taxonomy. Urocryptus bilineatus Temminck, 1838 ,

“ Surinam [= Suriname ].”

Saccopteryx bilineata was originally described in the genus Urocryptus but later recognized as monophyletic in the existing genus Saccopteryx . Bats from Mexico and Central America previously were referred to centralis and those from Trinidad to perspicillifer, but they were considered to be synonymous with S. bilineata byJ. K. Jones, Jr. and. S. Hood in 1993. Monotypic.

Distribution. From C Mexico (Jalisco and Veracruz) S throughout both Pacific and Atlantic slopes of Central America to Colombia, E to E & SE Brazil (S to Rio de Janeiro State), and S to Ecuador, E Peru, W Brazil, and N & NE Bolivia; also on Trinidad and Tobago Is.

Descriptive notes. Head-body 47-56 mm, tail 16-23 mm, ear 13-17 mm, hindfoot 10-12 mm, forearm 44-48 mm; weight 6-9-3 g. Female Greater Sac-winged Bats are larger than males. Dorsal fur is black, with two prominent, wavy bully stripes extending from neck to rump; venter is dark gray. Dorsal fur is black when pelage is “fresh,” but it grades to deep brown when it becomes worn. Although it is not known if multiple molts occur annually, five of nine individuals observed in Trinidad were molting in August. Ears extend slightly above crown of head. Eyes are large and conspicuous, with brown irises. Radio-metacarpal sacs open along forward edge of propatagium and are especially prominent in males. Flight membranes are black. Uropatagium is slightly hairy at its base and around tail. When fully extended, uropatagium is support by stiff ", long calcars and reaches almost to full extremity of claws on hindfeet. Dental formula of all species of Saccopteryx is 11/3, C 1/1, P 2/2, M 3/3 (x2) = 32.

Habitat. Lowland evergreen, semideciduous, dry forests, forest edges, villages, and urban areas generally below elevations of 500 m, with a few records up to 1000 m. Greater Sac-winged Bats often forage near streams and in moist areas. They prefer multi-strata evergreen forests and forages in natural and man-made forest clearings, edges, and corridors. In Mexico, it has also been reported in secondary forests, croplands, and grasslands.

Food and Feeding. The Greater Sac-winged Bat is an aerial insectivore that forages in cluttered spaces. Its diet includes flies, beetles, moths, and even butterflies that are active in late afternoon. Foraging habitats shift seasonally when Greater Sac-winged Bats cue on variation in insect phenology and abundance. They forage alone; individuals usually move from one feeding area to another after c.25-30 minutes.

Breeding. Gestation of Greater Sac-winged Bats across Mexico and Central America begins near end of dry season, and one young is bom annually at onset of rainy season. Timing of parturition varies with climate across the distribution. Females carry young or leave them at hidden night roosts when they forage. Young are able to fly at two weeks old but continue to suckle for 10-12 weeks. Yearling females disperse to other roosting groups, but young males remain with parental roost groups, waiting their chance to succeed older males.

Activity patterns. Greater Sac-winged Bats are crepuscular and can be seen in foraging areas in late afternoon, well before sunset, within shaded forest understories. This primary foraging activity occurs for c.3 hours into the night. A secondary foraging period occurs in early morning, and individuals return to day roosts soon after dawn. Mean flight speed is 5-8 m/s. Roost shelters include dimly lit cave entrances, trees hollows, boles and between plank buttresses, buildings, window screens of inhabited buildings, and undersides of bridges. The Greater Sac-winged Bat capably maintains appreciable temperature differentials with its environment. It usually remains normothermic and is alert and active in daytime roosts. It maintains a resting rate of metabolism that is high compared with small insectivorous bats in other families. It is likely that its diet of small, abundant insects provides enough energy year-round to permit a roosting strategy of alertness and vigilance in dimly lit shelters potentially vulnerable to predators. By maintaining individual distances from roost mates, groups of Greater Sac-winged Bats are able to simultaneously fly as an escape response, which would not be possible for bats that cluster tighdy because individuals on outer edges of a cluster must fly off first and those in the center of a cluster must wait for critical seconds before taking flight. Search-phase echolocation pulses of Greater Sac-winged Bats are relatively long (5-6 milliseconds) and paired. They are characterized by slight rise in frequency at onset of pulse, followed by a long F part, and terminated with slight decrease in frequency. Maximum energy in prey searching echolocation calls varies with geography at 42-50 kHz from populations in Belize, Costa Rica, and Panama. During approach or pursuit phase, calls become shorter, with more pronounced rise in frequency than in search phase. Terminal stage emissions, or feeding buzzes, are even shorter (c.1-1.7 milliseconds), with less pronounced rise in frequency.

Movements, Home range and Social organization. Roosting colonies of Greater Sacwinged Bats average 12 individuals but can range from five to 50 individuals. Larger roosting groups are composed of several male-dominated harems with 1-9 breeding females. Mating system is polygynous; males typically defend harems of 3-5 breeding females and 1-3 m2 of vertical roosting space. Most adult males roost alone or on peripheries of breeding colonies. Males obtain harems by splitting an existing harem or replacing a harem male that has been lost. Males have well-developed wing sacs in their ante-brachial membranes and emit scent while flapping their wings in ritualized mating displays called “salting” that are accompanied by singing. Males spend considerable time during the day cleaning their wing sacs with saliva and urine, which is followed by applying genital secretion to wing sacs with their chins. Natural selection favors smaller male Greater Sac-winged Bats due to energetic demands associated with aerial courtship and defense of harem females, and small breeding males sire more offspring than large males. Greater Sac-winged Bats use a variety of multisyllabic social calls in various contexts including sex-specific signatures and individual signatures in their calls. Isolation calls are used by young to call mothers and by young males to signify subordination to dominant males. Mothers respond to isolation calls of young with directive calls, especially to heel young bats when they begin to fly about the roost. Young vocalize in long bouts of “babbling” to practice social calls. Males produce territorial and courtship songs including whistling components, and males that sing often have greater reproductive success. Screeches are used in aggressive encounters by both sexes. Distress calls are produced during encounters with predators. Fur and skin of Greater Sac-winged Bats are often infested by ectoparasites that might influence condition and health, which include the mites Eutrombicula gpldii, Trombiculida vesperuginis, and. saccopteryx. The endoparasitic tapeworm, Hymenolepis mazanensis , has also been found in Greater Sac-winged Bats. Roosts of Greater Sac-winged Bats can be shared with a great many other species of bats including other species of sympatric emballonurids.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Greater Sac-winged Bat has a large distribution and presumably large and stable overall population, and it occupies a large variety of habitats. It occurs in many protected areas throughout its distribution.

Bibliography. Barclay (1983), Behr & von Helversen (2004), Behr et al. (2009), Bradbury & Emmons (1974), Bradbury & Vehrencamp (1977a, 1977b), Carter et al. (1981), Davidson & Wilkinson (2002, 2004), Genoud & Bonaccorso (1986), Goodwin & Greenhall (1961), Heckel & von Helversen (2002, 2003), Heckel, Achmann & Mayer (2000), Heckel, Voigt et al. (1999), Jones & Hood (1993), Knörnschild & von Helversen (2008), Knörnschild, Behr & von Helversen (2006), Knörnschild, Jung et al. (2012), Pye (1973), Simmons (2005), Tannenbaum (1975), Voigt & von Helversen (1999), Voigt, Heckel & von Helversen (2006), Voigt, Heckel & Mayer (2005), Yancey et al. (1998).

Figures

On following pages: 40. Lesser Ghost Bat (Diclidurus scutatus); 41. Isabelline Ghost Bat (Diclidurus isabella); 42. Lesser Dog-like Bat (Peropteryx macrotis); 43. Greater Dog-like Bat (Peropteryx kappleri); 44. Trinidad Dog-like Bat (Peropteryx trinitatis); 45. White-winged Dog-like Bat (Peropteryx leucoptera); 46. Pale-winged Dog-like Bat (Peropteryx pallidoptera); 47. Thomas's Shaggy Bat (Centronycteris centrali); 48. Common Shaggy Bat (Centronycteris maximiliani); 49. Proboscis Bat (Rhynchonycteris naso); 50. Greater Sac-winged Bat (Saccopteryx bilineata}; 51. Lesser Sac-winged Bat (Saccopteryx leptura); 52. rosted Sac-winged Bat (Saccopteryx canescens); 53. Antioquian Sac-winged Bat (Saccopteryx antioquensis); 54. Amazonian Sac-winged Bat (Saccopteryx gymnura).

Distribution. From C Mexico (Jalisco and Veracruz) S throughout both Pacific and Atlantic slopes of Central America to Colombia, E to E & SE Brazil (S to Rio de Janeiro State), and S to Ecuador, E Peru, W Brazil, and N & NE Bolivia; also on Trinidad and Tobago Is.