Diadem roundleaf bat (Hipposideros diadema)
|Size||Head-body length: 7.5 – 9.6 cm (2) (3)|
Tail length: 3.2 – 5.5 cm (2) (3)
Forearm length: 7.8 – 8.9 cm (2) (3)
Wingspan: 50 cm (4)
|Weight||30 – 57 g (2) (3)|
Classified as Least Concern (LC) on the IUCN Red List (1).
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. 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 (3).
This species is widespread, occurring from Southeast Asia to North Queensland, Australia. It has many subspecies; Hipposideros diadema anderseni (Philippines), H. d. ceramensis (Moluccas), H. d. custos (Kei Islands), H. d. enganus (Sumatra) (5), H. d. inornatus (Northern Territory, Australia) (2), H. d. masoni (Borneo) (6), H. d. natuensis (Natuna Islands and Bunguran Island), H. d. reginae (North Queensland, Australia) (2), and H. d. speculator (Sulawesi) (5).
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 (7). Individuals are known to forage up to two and a half kilometres from the roost during the course of the night (7). During the day it roosts in small groups in caves, old mines and sheds, hollow trees and tree branches (8) (9).
Diadem roundleaf bats are predominantly insectivorous, feeding mostly on large insects, favouring beetles, grasshoppers and locusts, and moths (10) (11). This species is also carnivorous having been recorded feeding on birds at two sites in Australia (10). The main foraging method is perch hunting which is a low-energy strategy. Its prey commonly move with direct and predictable flight paths, making it possible for the bats to hang from a tree branch, up to ten metres above the ground, waiting for a suitable insect to fly past. Whilst at the perch, the bat scans the area using echolocation at a constant frequency of 58 to 60 kilohertz. Once it has detected an insect, it drops from its perch and flies fast and straight to snatch its quarry from the air.
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 (3).
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 (13). Disturbance of roost sites is also an issue (7), and despite the contribution of many bats in the control of insect crop pests, persecution of bats is also a threat (12).
Deforestation of primary forest, especially for oil palm plantations, and in particular within protected areas, is an issue of major concern and one that relies on both governmental and consumer action. Some large retailers have agreed, in collaboration with the World Wildlife Fund (WWF), to source products containing palm oil from plantations that are not on deforested land (12). 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 (14).
Authenticated (31/01/2008) by Dr. Chris Pavey, Senior Scientist – Threatened Species, Northern Territory Government, Australia.
- Carnivore: flesh-eating.
- Echolocation: detecting objects by reflected sound. Used for orientation and detecting and locating prey by bats and cetacea (whales and dolphins).
- Insectivorous: insect eating.
- 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)