Hollow-faced bat (Nycteris tragata)
|Also known as:||Malayan slit-faced bat|
|Synonyms:||Nycteris javanicus tragata|
|Size||Head-and-body length: 50 - 65 mm (2)|
Tail length: 65 – 80 mm (2)
Forearm length: 47 - 63 mm (2)
|Weight||14 - 19 grams (2)|
The hollow-faced bat is classified as Near Threatened (NT) on the IUCN Red List (1).
This species is named after the deep slit running down the face, from a central point between the eyes down to the nostrils. This is, in fact, part of the noseleaf, which the hollow-faced bat needs for echolocation. Folds of skin extend from either side of the slit to direct echolocation calls with great accuracy, leaving little space for the minute eyes. The ears are brown and particularly long, with a short, rounded tragus (inner ear). The tail is commonly equal in length to the head and body, and is enclosed in a membrane that stretches between the hind legs (the interfemoral membrane). A tiny triangular cut in the membrane where the tail reaches the edge helps to identify the species. The hollow-faced bat is very furry, with a greyish-brown back, paler underside, and even brown fur on the forearms. The wings are very broad and short, with a large area of membrane above the forearm (known as the propatagium). This gives the bat great agility, but reduces its flight speed (2).
Found in Burma, Peninsular Malaysia, Sumatra and Borneo (3). Nycteris tragata was previously thought to be a subspecies of Nycteris javanica, which occurs on Java. However, size differences led to a genetic investigation, which confirmed that two species are present (4).
A tropical forest-dwelling bat, the hollow-faced bat has been found at all altitudes, and is known to roost in small groups in tree holes, rotten fallen trees, and rock crevices (2).
Although this insect-eating species is capable of complex echolocation calls involving a rapid, low intensity sweep of the frequency range, it is also thought to hunt simply by listening for sounds made by the insects themselves. Its large wing area and comparatively low body weight allows it to take off nearly vertically from the forest floor when hunting, possibly with heavy prey (2). It tends to hover over its prey before snatching it up into the air (5).
There are thought to be two breeding seasons per year, with females giving birth to a single pup (2). At first the pup is carried in foraging flights, which may well limit the diet of the hollow-faced bat, as it can only take lighter prey. The pup learns quickly to fly and forage alone, and at one year old will be sexually mature (2).
The rapid increase in land devoted to growing oil palm has resulted in extensive loss of primary forest. Together, Malaysia and Indonesia export 88% of the world’s palm oil, for use in products such as margarine, lipstick and detergent. Deforestation continues at a steady rate for conversion to agricultural land and building communities, and despite the contribution of many bats in the control of insect crop pests, persecution of bats is also a threat (6).
Deforestation of primary forest for oil palm plantations, including within protected areas, is an issue of major concern and one that relies on both governmental action and consumer concern. Some large retailers have agreed, in collaboration with the WWF, to source products containing palm oil from plantations that are not on deforested land (6). Many scientific and charitable groups contribute to bat monitoring and local education programmes that can help to reduce persecution and raise awareness of the natural assets of the land (7).
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- Echolocation: detecting objects by reflected sound. Used for orientation and detecting and locating prey by bats and cetacea (whales and dolphins).
- Primary forest: forest that has remained undisturbed for a long time and has reached a mature condition.
- Subspecies: A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
IUCN Red List (December, 2009)