Hipposideros diadema
diadem roundleaf bat

The Malayan leaf-nosed 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 (Nowak, 1999; Kitchener, 1992).

These bats typically roost in large caves, hollow trees and buildings (Nowak, 1999). In Australia, they prefer tall limestone towers within which thousands of these bats congregate (Fenton, 1982). They typically forage along rivers in forested habitats.

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 (Gobbel, 2002). The transverse leaf is erect, and in contrast to the nose leaf of other rhinolopids, there is no median projection (sella)(Feldhamer, 1999). They have huge ears mainly because of the well-developed antitragus, while no tragus is present (DeBlase, 1991). 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, 1981).

The large Malayan leaf-nosed bat typically lives between four and seven years in the wild, but can live up to twelve in captivity (Nowak, 1999).

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 (Nowak, 1999).

These bats are usually insectivorous (Feldhamer, 1999). 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, H. diadema is sometimes classified as an 'occasional carnivore' (Pavey, 1997).

These bats are extremely adept predators. By using echolocation, intensified through their highly modified nose and nostrils, they achieve very high rates of success (Gobbel, 2002). A constant frequency call is emitted around 50 to 58 kilohertz, and maintained for 20 to 30 seconds at a time (Jen, 1982; Fenton, 1982). They are not continuous flight hunters; instead, they prefer to take short flights from their perches and intercept the prey in midair (Pavey, 1998). When hunting, they usually fly over a stream or creek that is covered in canopy. They very rarely venture out over open water (Fenton, 1982). 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 (Pavey, 1998).

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 (Nowak, 1999).

It is extremely rare, only when harassed or cornered, but these bats can have a painful bite, and they carry a myriad of parasites, most of which have no effect on humans (Uchikawa, 1983).

Insect populations are kept in check by these bats, and some locals use the dung for fertilizer (Nowak, 1999; Pavey, 1998).

The Malayan leaf-nosed bat is not currently endangered or threatened. It was listed as "lower risk - least concern" on the 1996 RedList, but has since been removed from that list.

There has been some controversy over the classification of the hipposiderid bats. Koopman (1993) and the majority of others have the subfamily Hipposiderinae listed under the family Rhinolophidae (Feldhamer, 1999). However, Hill and Smith (1984) and several others classify Hipposideridae as a separate family from the rhinolophid horseshoe bats (Eisentraut, 1975).