Diadem roundleaf bat
The Diadem roundleaf bat (Scientific name:Hipposideros diadema) is an impressive sight amongst the trees of the rainforest; this large bat is a formidable hunter with a wingspan of up to half a metre. Alternatively known as the Leaf-nosed bat, this chiefly cave-dwelling species is broadly distributed across Southeast Asia, including the archipelago encompassing Malaysia and Indonesia.
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Hipposideros diadema (E. Geoffroy, 1813)
Readily identifiable by its pig-like face, the Diadem roundleaf bat also possesses distinctive white flashes on the shoulders, contrasting with the reddish-brown back and light-brown underside. The colour varies quite strongly between individuals, and females are generally more orange. The noseleaf is pink and highly convoluted, but the ears are brown.
These bats are named for their complex anterior nose leaf, which is horseshoe-shaped and located on the slightly inflated nasal region. This nose shape evolved to assist in echolocation, adding the noseleaf and the associated intricate musculature to help the nose resonate more effectively. The transverse leaf is erect, and in contrast to the nose leaf of other rhinolopids, there is no median projection or sella.They have huge ears mainly because of the well-developed antitragus, while no tragus is present (DeBlase). Males have a sac located posterior to the nose which can secrete a waxy substance, thought to be used in attracting mates and status determination.
Body length ranges from six to ten centimeters when adult, with brown fur covering all but the limbs. The underbelly is paler in color, and white spots can be found in the shoulder region. Adults weigh between 34 and 50 grams, and the wingspan is approximately 15 to 22 cm. Hefty claws are found on the hind limbs, and a single claw on each of the forelimbs (Nowak, 1999). Each toe of the foot has two phalanges, and the short tail is usually enclosed within the small uropatagium (Feldhamer, 1999). The dental formula is 1/2 1/1 2/2 3/3, molars are dilambdodont, and hefty enamel tubules are present at dentin-enamel junctions (Lester, 1987). The oral region of the skull exhibits premaxillary palatal branches that are fused medially, and widely separated from the maxillae laterally (spatulate) (DeBlase).
The Diadem roundleaf bat is the most widespread of the subfamily Hipposiderinae. It ranges from northern Australia to New Guinea and southeastern Asia. This includes the Nicobar Islands, Indonesia, southern Burma and Thailand,Philippines, Timor, Solomon Islands, northeastern Queensland, Sunda Islands, Indochina, the Malay Peninsula, Sumatra, Java, and the Kangean Islands.
The Diadem roundleaf bat is common in both primary and secondary forest at at wide range of elevations, and is mainly a cave dweller. It often roosts in large groups in caves, but smaller colonies will use the crevices of large boulders. Occasionally, individuals will roost on their own under palms, or under leaves in the midstorey of the forest.
With a heavy body and long, narrow wings, the Diadem roundleaf bat is adept at fast flight but has relatively poor manoeuvring ability. It has adapted to foraging in gaps in forests, such as around tree falls or above rivers. This bat species is not restricted to rainforest and in outback Australia it forages within eucalypt woodland and open forest, deciduous vine thicket and within towns. Individuals are known to forage up to two and a half kilometers from the roost during the course of the night.
Hipposideros diadema is primarily an insectivorous bat. The diet varies depending on specific location, but they tend to prefer insects such as coleopterans (beetles),lepidoterans (butterflies and moths), and those within the orthopteroid (grasshoppers) orders. However, they will prey on small birds and spiders, albeit rarely. Thus, this bat is sometimes classified as an 'occasional carnivore'. It forages primarily by perch hunting in gaps in the midstorey or over trails, waiting for slow-flying insects to pass beneath, which it will then swoop out and catch before returning to its perch to eat them. In Australia, its diet is primarily beetles, moths, and orthopterans (grasshoppers, crickets, etc), and occasionally, birds. In Malaysia, its diet also includes termites during swarming periods.
These bats are nocturnal and gregarious. They congregate and live in groups that can be as large as two to three thousand individuals. Not on an individual level, but as a colony, there seems to be some territoriality exhibited.
One breeding season exists, and birthing and lactation coincide with the maximum quantity of insects in the spring. One young is born per litter. Male competition involves some physical skirmishes, but mainly the secretion and detection of a waxy material from behind the nose. Interestingly, females congregate in large groups during March and April, during which each one gives birth to a single offspring. The size of the pup relative to the mother in insectivorous bats is remarkable. This species can give birth to a single pup weighing 13 grams, a quarter of its mother's weight. The mother must carry the pup on foraging trips until it is developed enough to fly and feed alone. By one year the young diadem roundleaf bat will be ready to breed.
This large bat typically lives between four and seven years in the wild, but can live up to twelve years in captivity.
The Diadem roundleaf bat emits constant frequency call around 50 to 58 kilohertz (kHz), and maintained for 20 to 30 seconds at a time. Lepidopterans (eared moths) make up a significant portion of their diet, and these insects have an auditory range from 20 to 50 kHz. Research has shown that these insects can sense the echolocation pulses and have learned to evade or hide from the attacking bats.
These bats are probably preyed on by large, nocturnal birds of prey, such as owls and in roosts by snakes and small mammalian carnivores, such as Malayan civets (Viverra tangalunga).
These bats are vital in controlling insect populations within natural communities. Their feces are also very nutritive and help fertilize plant flora.
Habitat loss and degradation is the biggest problem facing the Diadem roundleaf bat. Deforestation continues at a steady rate for conversion to agricultural land and building communities. Of particular concern is the extensive loss of primary forest due to the rapid increase in land devoted to growing oil palm. Together, Malaysia and Indonesia export 88 percent of the world's palm oil, for use in products such as margarine, lipstick and detergent. Disturbance of roost sites is also an issue, and despite the contribution of many bats in the control of insect crop pests, persecution of bats is also a threat .
The Diadem roundleaf bat has been classified as Lower Risk / Least Concern (LR/lc) on the IUCN Red List 2007.
References and Further Reading
- A.F.DeBlase and R.E.Martin. 1974. A Manual of Mammalogy. Wm. C. Brown Co., Dubuque, Iowa.
- Encylopedia of Life. 2011. Hipposideros diadema (E. Geoffroy, 1813) EOL, accesssed October 6, 2009
- G.E.Dobson (1878) Catalogue of the Chiroptera in the collection of the British Museum. British Museum, London, xlii+567 pp, xxx pls.
- S.Van Dyke and R.Strahan (eds.) (2008) The Mammals of Australia, Third Edition, New Holland / Queensland Museum, Brisbane ISBN 9781877069253Chiroptera Specialist Group 1996. Hipposideros diadema. 2006 IUCN Red List of Threatened Species.
- Hipposideros diadema Malaysian Bat Education Adventure (includes video)