Latin America is home to several species of sac-winged bats, which share similarities in appearance. They are
small bats, typical of the Emballonuridae family, in which they are classified. According to Wikipedia, the
family includes 47 species of bats, found worldwide in tropical and sub-tropical regions.
The sac-winged bat is fairly nondescript as bats go. Indeed, to the non-expert most bats look similar. But
closer inspection reveals how this type of bat gets its odd name. The name of this group comes from a sac
or pouch on each wing close to the forearm bone beyond the elbow. These structures are important for
breeding males to maintain harem structure (see below: "Breeding"). Their snouts are shrew-like,
lacking the "noseleaf" found in other bats. The white-lined sac-winged bat (Saccopteryx
bilineata, see photo) gets its name from a pair of wavy white-lines along its back. These may be to aid
individuals in seeing one another in the dark or to help species distinguish each other. Alternatively,
according to Maarten Vonhof (University of Alberta) the lines are an example of disruptive markings, an
adaptation to make the bats difficult for predators to pick out.
HABITAT AND DISTRIBUTION
The genus Saccopteryx is widespread from Central America (Mexico) to Peru and Bolivia east of the
Andes, found throughout lowland rainforest to the east coast of Brazil. S. bilineata is relatively
common in forest where its favored roost tree, kapok, is abundant. The bats roost in the cavities formed
between the plank-like buttress roots of mature kapok trees and are also found in tree-holes and under the
eaves of roofs.
FEEDING AND DIET
The sac-winged bats are specialist feeders on tiny insects. Like most insectivorous bats, they catch prey on
the wing via echolocation: sending out sound by calling and receiving it through highly sensitive hearing.
The mouth has a large gape, resulting from the long nose and upper lip which are highly mobile as the paired
bones forming the front of the upper jaw are not fused (as they are in most mammals). When the mouth is
opened the bones shift upward, thus allowing the bat to open its mouth much wider than would otherwise be
Due to their accessibility, the breeding biology of the white-lined sac-winged bat has been the subject
of several scientific studies. The species is polygynous,
forming large colonies of up to 80 individuals. Most of these will be female which belong to one or more
harems. The harems comprise 1 to 9 females, defended by a male. He uses strong smelling secretions from
the wing sacs to "mark" the females, claiming them as his own. The males also display and
vocalize to maintain the harem. Such groupings are relatively stable throughout the year so long as the
male can fend off rivals. (See tent-making bat for more
information on the harem breeding system.)
As with all bats, the main issue with conservation of this species is loss of habitat. Logging of kapok
trees where it prefers to roost may have a detrimental effect on the species' numbers but this may
be offset by its adaptability to roosting in human dwellings.