Bory’s White Bat

“Small white bats” seek shelter in palm leaves

The French naturalist and botanist Jean Baptiste Bory de Saint-Vincent explored the mouth of the Rivière du Mât in November 1801, in what is now the municipality of Saint-Joseph in the southern part of the island of Réunion. He was studying red latan palms (Latania lontaroides) growing there when he discovered something: “Small white bats (…) seek shelter during the day between the leaf stalks” in the palms. And when Bory walked along the sandy beach of the municipality of L’Étang-Salé a few days later, he noticed “a few latan palms, spindle-thin and tousled by the wind, the only trees I have seen here. (…) The small white bats come to seek shelter from the heat of the day in the torn leaves of these trees”.

Bory spent some time on the Mascarene island of La Réunion between 1801 and 1802. He recorded the encounter with the small white bats in the second volume of his travel account, Voyage dans les Quatre Principales Iles des Mers d’Afrique, published in 1804. This is the only historical evidence for this bat species, which did not receive the name Bory’s white bat until 2000.

Bory’s description of the white bat is sketchy, but the possibility that he confused it with another species native to Réunion can be ruled out. At least that was the view of the French geologist and paleontologist Pierre Brial in 2000, in an article about the bat described by Bory.

Other species found on the island are the black-brown Réunion free-tailed bat Mormopterus francoismoutoui, the lesser yellow bat (Scotophilus borbonicus), which is olive-brown on the upper side and whitish yellow on the underside, and the gray-brown Mauritian tomb bat (Taphozous mauritianus), which has a white belly. Bory described the Mauritian tomb bat in considerable detail in his travel account.

Bory’s white bat – fact sheet

scientific name	Boryptera alba
original distribution area	Réunion (Indian Ocean)
Time of extinction	1801 or later
Causes of extinction	Animals probably introduced to the island, loss of habitat

Why did the small white bat become extinct?

Why Bory’s white bat became extinct can only be guessed. Brial assumes that the decline of the red latan palm, which served the species as shelter, may have been one reason for the bat’s disappearance. He also considers it likely that rats introduced to the island of Réunion preyed on the white bats.

Bory’s white bat would not be the first animal species to become extinct because of mammals introduced to Réunion. Invasive rats and cats also contributed, among other factors, to the disappearance of the Réunion Ibis around 1710 and the Réunion Pigeon at the end of the 17th century.

In addition to Bory’s white bat, which was last and only sighted in 1801 or 1802, the small Mauritian flying fox, which was native to the islands of Réunion and Mauritius, has also been considered extinct since the mid-19th century. The lesser yellow bat was last seen on Réunion in the late 19th century. Experts therefore assume that the species also became extinct because of the loss of its natural habitat.

Bory’s white bat—A hypothetical species

About 200 years after its discovery, Brial gave Bory’s white bat its scientific name, Boryptera alba, in 2000. Bory’s travel account forms the basis for his scientific description. Bory’s description of the bat, however, is not detailed enough to determine the species’ systematic position.

Boryptera alba is an incertae sedis, because it is unclear which genus or family the bat species belongs to. Bory’s white bat is also described as a hypothetical species, since apart from Bory’s report, there is still no further evidence for its existence.

The biologist Anthony Cheke and the paleontologist Julian P. Hume consider it possible in Lost Land of the Dodo (2008) that Bory’s white bat belongs to the genus Myzopoda, which is endemic to Madagascar.

Bory’s white bat—Not the only one that sleeps in plant leaves

According to Brial, there are two bat species in Madagascar that show behavior similar to Bory’s white bat: the banana pipistrelle (Pipistrellus nanus), which occasionally hides in banana leaves, and the Malagasy sucker-footed bat (Myzopoda aurita), which sleeps in the rolled leaves of the traveler’s tree (Ravenala madagascariensis).

Bory’s white bat is not the only bat with white fur. In Central America, for example, the Honduran white bat (Ectophylla alba) lives and hides in the leaves of heliconias (Heliconia) to sleep. The Honduran white bat even cuts the side veins of the leaf along the midrib, so that the leaf folds downward like a tent. In this way, the sleeping animals remain hidden from predators during the day.

Brial suggests that the white fur color of Bory’s white bat served as camouflage during the day. When the animals stayed sheltered during the day in the leaves of the red latan palm lit by the sun, the green color of the leaves may have been reflected by the bats’ white fur.

Albinism in bats

Although albinism is documented in many groups of vertebrates, the congenital disorder of pigment biosynthesis is relatively rare in bats. According to a report (2014) by the biologist Beza Ramasindrazana on a free-tailed bat (Molossidae) with albinism from the southwestern Indian Ocean region, there are 43 bat species in 24 countries in which albino individuals have been documented.

Ramasindrazana now reports a free-tailed bat with albinism from the island of La Réunion. It was first observed in December 2012; in February 2013 the animal was captured. It had completely white, long fur and red or pink eyes. Since the white bat lived within a colony of Mormopterus francoismoutoui and is also morphologically identical to them except for its fur and eye color, Ramasindrazana assumes that it is an albino M. francoismoutoui and not a separate species.

Besides Ramasindrazana, only Bory reported white bats on Réunion. It is almost impossible that Bory’s white bat was merely M. francoismoutoui with albinism. Bory described a small colony of white bats, whereas M. francoismoutoui are more likely to be exceptions and occur only individually. Furthermore, M. francoismoutoui roosts mainly in rock caves and crevices, with colony sizes of up to 65,000 animals. It is also not known to use palm leaves as a roost.

Not every white bat is an albino bat

The little-studied genus of ghost bats (Diclidurus), which live in Central and South America, comprises four species, all of which have pale gray to white fur. Besides these, only one other species with white fur is known: the Honduran white bat (Ectophylla alba), which is endemic to South America. The eyes of American ghost bats and Honduran white bats are dark and not red, as was the case in M. francoismoutoui with albinism studied by Ramasindrazana.

Albinism is a congenital phenomenon in which melanin production is disrupted, which is reflected in lighter skin, hair and eye color. Eyes can sometimes appear almost red if the iris is nearly pigment-free, because the blood vessels show through. The defect mutation leucism also causes animals’ skin to be pink and their fur or feathers to be white. Leucistic animals do not have red eyes.

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