Diadem Roundleaf Bat (Hipposideros diadema)
HB: 85-92; T: 50-60; FA: 80-96;
E: 30-32; HF: 16-20
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 nose leaf is pink and highly convoluted, but the ears are brown. 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 kilometres from the roost during the course of the night . During the day it roosts in small groups in caves, old mines and sheds, hollow trees and tree branches. There are 2 colour stages
1 Pale yellow or buff, with reddish tips with the underparts lighter.
2. Pale buff, with brown tips on the upper parts and the under parts paler brown with lighter tips. Both the phase have a the conspicuous buffy shoulder spot. The nose leaf is pinkish, the eras and wings brown. The ears are triangular, sharply pointed, and haired for 1/3 of the lenght; there is no antitragus. The posterior nose leaf is rounded and larger than the anterial leaf, which has a 3-4 supplementary lateral leaflets on each side, the other may be rudimentary. The posterior leaf is divided into 4 sections( only 2 in subspecies masoni). The skull is large and heavily built, with a broad facial portion. The upper first premolar is outside the tooth row, so the canine and upper second premolar are in contact or nearly so.
This widespread species ranges from the Nicobar Islands of
India through Southeast Asia to Australia. On the Nicobar Islands, the endemic
subspecies H. d. nicobarensis is present on the islands of Bompuka,
Katchal, Tillangchong, Tressa and Trinket (Aul and Vijaykumar 2003). In
Southeast Asia, it ranges from southern Myanmar, into Thailand, Cambodia, Vietnam and southern Lao PDR, to Peninsular Malaysia, and from here to much of
Indonesia (including the islands of Sumatra, Java, Bali and Sulawesi), East
Timor, the island of Borneo (Brunei, Indonesia and Malaysia), and the
Philippines. In the Philippines it is found in all regions (sea level to 900 m
asl) except the Batanes/Babuyan region. Specimens have been collected from the
Philippines islands of Bohol, Busuanga, Calauit, Catanduanes, Cebu (Lawrence,
1939), Dinagat, Guimaras, Leyte, Luzon [Benguet (Taylor, 1934), Bulacan,
Cagayan, Camarines Sur, Ilocos Norte, Isabela, Laguna, Nueva Vizcaya, Pampanga,
Quezon, Rizal (Taylor, 1934) provinces], Mindanao [Agusan del Norte, Bukidnon,
Davao Oriental, Lanao del Norte, Maguindanao, South Cotabato (Sanborn, 1952),
Zamboanga del Norte, Zamboanga del Sur (Taylor, 1934)], Mindoro (Lawrence,
1939), Negros, Palawan, Panay, Polillo, Samar, Siquijor (Heaney et al., 1998).
There are some records from the island of Tawi-tawi (K. Helgen pers. comm.). On
the island of New Guinea (Indonesia and Papua New Guinea) it is found in
scattered localities and it is present throughout much of the Bismarck
Archipelago (Papua New Guinea). The species has been recorded from the islands
of Bougainville and Buka (Papua New Guinea), and from many of the Solomon
Islands. It is present in Australia where it is largely restricted to the
rainforests of northern Queensland (Corbet and Hill 1992; Flannery 1995; Strahan
1995; Bonaccorso 1998). It is found from sea level to 1,300 m asl.
Australia; Cambodia; India; Indonesia (Irian Jaya, Jawa, Kalimantan, Lesser Sunda Is., Maluku, Sulawesi, Sumatera); Lao People's Democratic Republic; Malaysia (Peninsular Malaysia, Sabah, Sarawak); Myanmar; Papua New Guinea; Philippines; Solomon Islands; Thailand; Timor-Leste; Vietnam
The Nicobar subspecies, H.d. nicobarensis, is very
common and has been found to roost in large colonies of over 500 bats to small
colonies of over 30 bats on four islands of Nicobar Islands (Aul and Vijaykumar
2003). It was first recorded from a cave on Trinket Island, but it does not
occur on that island anymore (Aul and Vijaykumar 2003), the reason for this
disappearance is unknown. In the Philippines this species is considered to be
locally common (Heaney et al., 1998). There can be large roosts or thousands or
more individuals, though the species often roost in small numbers (K. Helgen and
L. Heaney pers. comm.). In New Guinea it is a relatively common species
Population Trend: Unknown
Biology and Ecology
Diadem Roundleaf bats are predominantly insectivorous, feeding mostly on large insects, favouring beetles, grasshoppers and locusts, and moths . This species is also carnivorous having been recorded feeding on birds at two sites in Australia. 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. This is amongst the largest of Roundleaf bats in Southeast Asia, and is easily identified by the presence of well-defined white or pale orange patches of fur on the sides of its body and shoulders. The rest of the upper body fur is a rich, dark brown colour, and the face and underparts pale. When hunting, this bat typically hangs from a perch waiting to ambush large insects, such as moths, as they fly past. Other insects consumed may include those with a thick exoskeleton such as beetles, weevils and katydids : the soft parts of such insects are consumed and the inedible parts, such as wings, carapace and legs are discarded below the perch.
The species makes use of a variety of roosts including tree holes, caves or the shelter of large-leaved palms. Large caves may shelter maternity roosts numbering in their thousands.
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