The Tent-making bat (Uroderma bilobatum)

Apr 20, 2014 Features / Columnists, Interesting Creatures in Guyana

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The tent-making bat (Uroderma bilobatum) is an American leaf-nosed bat found in lowland forests of Central and South America. This medium-sized bat has a grey coat with a pale white stripe running down the middle of the back. Its face is characterized by a fleshy nose leaf and four white stripes.
Primarily a frugivore, it may supplement its diet with insects, flower parts, pollen, and nectar. Its common name comes from its curious behaviour 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. This bat is quite common in its geographic range; hence, its conservation status is listed as Least Concern.
The bat is a member of the family Phyllostomidae, which contains 49 genera and a

greater variety in feeding habits than any other bat family. Carnivores, frugivores, and bats that specialize on blood or nectar and pollen are all represented in this family.
Commonly known as the American leaf-nosed bats, phyllostomids are characterized by a special structure consisting of a leaf-shaped projection extending up from a “horseshoe-shaped” base attached to their upper lip. These bats send their echolocation calls out their nostrils, and so the nose leaf may help direct the sounds that they emit. Because they emit calls at such low frequencies, standard bat detectors have trouble picking up their calls. Thus they are sometimes called “whispering bats”.
Within Phyllostomidae is the subfamily Stenodermatinae, members of which are sometimes called tailless bats. These 17 genera from Central America have broad shoulders and faces and narrow tail membranes, with a tail that is either greatly reduced or absent. The upward projection of their nose leaf has two creases and the lower part is at least partly free. The shape of their faces has been correlated to their frugivorous diet. They are known to pick fruit with their mouths and carry it to a night roost to consume it. Thus, they are important seed dispersers for certain plants.
Bats in the genus Uroderma are characterized by a pale, white stripe that runs down the back and two pairs of white stripes on the face. Their tail membrane is curved into the shape of a U and lacks hair along its edge.
Female tent-making bats may reproduce twice in one year. 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.
As noted in their common name, Uroderma bilobatum exhibits a curious roosting behaviour. 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.
These bats prefer 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 most 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.
While it has demonstrated some tolerance of man-made forest clearings, too much loss of lowland tropical forests could negatively impact its survival.
(Source: Wikipedia – The Free Online Encyclopedia)

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