Tent-making bat

Appearance

"Uroderma bilobatum" is medium in size, weighing between 13–20 g with a body length of 59–69 mm. Typically, the females are slightly larger than the males. Their pelage ranges in color from dark gray to grayish brown, with their belly slightly lighter in color than their back.

The individual hairs of their coat are bicolor, being lighter in color at the base than at the top. A thin, white stripe runs down the middle of the back from behind the head to the rump. The face has two striking symmetrical pairs of white stripes. One pair goes over the head, between and to the back of the ears. The other pair lies just below the eye. This facemask may serve a camouflage purpose by making their eyes less obvious to would-be predators.

Their brown noseleaf and ears are rimmed with yellow or white. They have a U-shaped tail membrane that is practically hairless and measures 14–16 mm in length. A dorsal view of their skull reveals a depression between the frontal bone and their snout. Their dental formula is i 2/2, c 1/1, p 2/2, m 3/3, which gives them a total of 32 teeth. They also possess a calcar and a slightly pigmented, permanently open dactylopatagium minus.

Naming

Its common name comes from its curious behavior of constructing tents out of large, fan-shaped leaves. These roosts provide excellent protection from the tropical rains, and a single tent roost may house several bats at once.

Distribution

These bats are found in Central America from Oaxaca and Veracruz, Mexico to Peru, Bolivia, and southeastern Brazil. They also live on the island of Trinidad. Most specimens have been collected at elevations below 600 m, but some have been found as high as 1500 m above sea level.

Status

"Uroderma bilobatum" is a very common bat within its geographic range. While it has demonstrated some tolerance of man-made forest clearings, too much loss of lowland tropical forests could negatively impact its survival. Its conservation status is currently listed as Least Concern.

Behavior

As noted in their common name, "Uroderma bilobatum" exhibits a curious roosting behavior. They bite through the midrib or vein of a large leaf so that it folds in half to form an inverted-V-shaped shelter. This “tent” provides shelter from sun, wind, and rain. Eventually, the leaf dries up and breaks off from the plant, and they have to construct a new one, a feat that takes them several nights to accomplish. Amazingly, a single tent may be used for up to 60 days. "U. bilobatum" prefers the large, single leaves of banana trees and pinnate or palmate palms. They may roost in groups of 2–59 individuals, and are quite easily startled from their roosts during the day. They tend to choose tall trees, but not the tallest trees in the area. Taller trees may offer them greater protection from predators, but trees that are too tall would mostly likely expose them to greater winds. An additional preference has been demonstrated for younger fronds, which are also usually further from the ground.

Due to the nature of their roosts, foliage-roosting bats tend to be more nomadic than bats that roost in caves. Some suggest that this adaptation may enable them to track food sources throughout the seasons. The tents may also provide protection from predators that target typical bat roosts such as caves and hollow trees. However, the disadvantages of such a lifestyle include the energetic costs that the bats have to expend in the creation of new tents every few months and the decreased protection from the weather offered by such roosts.

Habitat

"Uroderma bilobatum" lives in low-elevation evergreen and deciduous forests, second-growth forests, and fruit groves. They are primarily frugivores and have been observed carrying small, unripe figs in their mouths. At times they may supplement their diet with insects, flower parts, or nectar.

Reproduction

Female tent-making bats may reproduce twice in one year. In Panama, pregnant females have been observed in February and in June. In Costa Rica, pregnant females move into coconut groves in July, just at the beginning of the wet season, and exhibit synchrony in parturition. Each litter consists of only one pup, which is born after a gestation period of 4–5 months. The nursing females form maternity colonies of 20–40 individuals in one tent roost. Roosting in groups may have thermoregulation benefits for the pups and lactating mothers. They do not carry their young with them on their nightly foraging flights; however, it appears that they may first move their pups to more protected roosts before beginning to forage. The pups become independent after one month.

Food

"Uroderma bilobatum" lives in low-elevation evergreen and deciduous forests, second-growth forests, and fruit groves. They are primarily frugivores and have been observed carrying small, unripe figs in their mouths. At times they may supplement their diet with insects, flower parts, or nectar.