Eonycteris spelaea
lesser dawn bat

Long-tongued dawn fruit bats or lesser dawn fruit bats, Eonycteris spelaea, are found throughout much of south Asia, from southern China to the islands of Indonesia, and from southwestern India to throughout the Philippines. (Nowak, 1999; Wilson and Reeder, 2005)

Eonycteris spelaea is almost exclusively a cave roosting species. Eonycteris major, their closest relative, has also been known to use hollow tree cavities. Eonycteris spelaea is found in various habitats ranging from forested to mixed agricultural types. They are common in cultivated areas away from forests, within forests they mostly occur in openings. Secondary lowland, primary lowland, and transitional montane-mossy forests are most often used by these bats. (Findley, 1993; Hodgkison, et al., 2003; Kunz and Racey, 1998; Nowak, 1999)

Lesser dawn bats have large eyes, small, simple ears, and lack a tragus. The muzzle is narrow and the tongue long and extendable, with rasp-like papillae. Dorsal pelage is dark brown and the belly is paler. The necks of males are covered with long scent-dispersing "osmetrichia" hairs that are darker than the pelage of the head and body. The second finger is independent and lacks a claw. Molariform teeth are considerably reduced and barely extend past the gums. The dental formula in Eonycteris is i 2/2, c 1/1, pm 3/3, m 2/3 x 2 = 34. The type of tongue, a tail length between 12 and 33 mm, and absence of an index finger claw distiguishes Eonycteris. (Kunz and Fenton, 2003; Macdonald, 2001; McNab, 1989; Nowak, 1999)

Lesser dawn fruit bats are thought to be polygynous with single males mating with multiple females. Penis, baculum, and testes size are not a factor in male reproductive success, as sperm competition does not occur as in multi-male polyandrous and polygynandrous mating systems. However, residual baculum lengths are greater than in monogamous systems. It is reasonable that body size is a factor in mate selection in both sexes as it is generally an indicator of superior genes and fitness. (Hosken, et al., 2001; Hutchins, et al., 2003)

There is conflicting information on the cycle/pattern of estrus as well as birth in E. spelaea females. One study finds females exhibiting a pattern characterized by synchronous births and seasonal, bimodal polyestry, while other sources find no synchronicity between females and no seasonal synchronicity. Lesser dawn fruit bats are polyestrus and births occur in two seasonal peaks, which is consistent with females coming into estrus twice a year. The usual number of offspring per year is two. Gestation is reported to be 3 to 4 months; however, other reports suggest gestation periods possibly as long as 200 days (between 6 and 7 months). Weaning occurs at 3 months. Females mature between 6 months and 1 year. Males mature between 1 and 2 years. (Heideman and Utzurrum, 2003; Hutchins, et al., 2003; Nowak, 1999)

Reports suggest that females are the sole providers of pre-independence parental care. After birth, altricial young take hold of a nipple and stay attached for 4 to 6 weeks as the female flies around. After this time, young can make flights independently for short distances. Complete weaning occurs at 3 months. (Nowak, 1999)

There is little information available on the longevity of this species in the wild or in captivity. The highest lifespans in captivity of other Pteropodidae species include: straw-colored fruit bats (Eidolon helvum), 21.8 years; flying foxes (Pteropus), 31.4 years; and rousette fruit bats (Rousettus), 22.9 years. (Jones, 1982)

Lesser dawn fruit bats are gregarious, roosting during the day in the high ceilings of caves in colonies numbering from a dozen to over ten thousand individuals. The roosting colony is divided into sexually segregated clusters. Colonies of Rousettus leschenaulti and E. major share roost caves with E. spelaea. This species is nocturnal and will often travel 20 to 40 km from their day roosts to the night flowering trees where they feed. Lesser dawn fruit bats forage in flocks. Feeding occurs between 1900 and 0200 hours. A behavior unique to E. spelaea is the production of wing-clapping sounds during movement in dark situations. This is thought to be a primitive form of echolocation that aids orientation, or simply a product of slowed flight which may reduce the force with which bats collide with other objects in dark caves. (Gould, 1978; Gould, 1988; Hutchins, et al., 2003; Kunz and Fenton, 2003; Macdonald, 2001; Nowak, 1999)

There is little available information on the home range of E. spelaea. However, this species travels considerable distances to feed, and may often fly 20 to 40 km from their day roosts to the night flowering trees where they feed. Long flights between roosting and feeding grounds is common in Pteropodidae. (Neuweiler, 2000; Nowak, 1999)

There is little available information on the way lesser dawn fruit bats communicate and perceive their environment. The presence of long scent-dispersing "osmetrichia" hairs on males indicates the use of olfaction and is probably used in reproductive state determination and mating. In many species of bats males have a much stronger odor than females. Pteropodidae species have large, well-developed eyes, and conspicious simple ears. The perception of their environment is mostly visual. However, E. spelaea is unique in the production of wing-clapping sounds during movement in dark situations, which may be a primitive form of echolocation that aids orientation. Most Pteropodidae species locate food by smell. (Kunz and Fenton, 2003; Macdonald, 2001; Nowak, 1999)

Diet consists primarily of the nectar and pollen of night flowering plant species. Two studies state that stomach and tongue contents contained pollen exclusively. Lesser dawn fruit bats are nectarivorous generalists that have been documented feeding on over 31 plant species. The nectar and pollen of Oroxylum indicum is described as their preferred and principle food source. Eonycteris spelaea and O. indicum are referred to as an example of coevolution because the flowers are adapted to the head morphology and feeding behavior of the this bat species. Durio zibethinus, Parkia speciosa, Musa acuminata, and Ficus species are also used. Lesser dawn fruit bats have shown a particular affinity for a specific species of Agave. They use durian fruit nectar and pollen, and it is suggested that they are the among the most important pollinators of this economically important fruit. It is also reported that Eonycteris are occasional flower eaters. In captivity, individuals have been fed coconut (Cocos) pulp and guava (Psidium). (Allen, 1939; Gould, 1978; Heideman and Utzurrum, 2003; Hutchins, et al., 2003; Neuweiler, 2000; Nowak, 1999; Peterson, 1964; Wilson, 1997)

There is very little information available on the predators of this species, nor the adaptations it uses to evade predation. Like most bats, their nocturnality, flight, and habit of roosting in inaccessible places protects them from most predation. They are likely to be vulnerable to predation by climbing snakes and nocturnal birds of prey, such as owls.

The primary ecological function of E. spelaea is pollination. A possible secondary role is seed dispersal, however, the use of fruit as a wild food item is not confirmed. (Allen, 1939; Hutchins, et al., 2003; Kunz and Fenton, 2003; Neuweiler, 2000; Nowak, 1999; Wilson, 1997)

The primary significance of E. spelaea to humans is the pollination of commercially important plant species, especially durian fruits (Durio spp.), which can add up to $120 million (U.S. dollars) to the Southeast Asian economy annually. Lesser dawn bats are also hunted for use as food. Bat guano from the Philippines is harvested for use as fertilizer. (Gould, 1978; Hutchins, et al., 2003; Neuweiler, 2000; Nowak, 1999; Wilson, 1997)

There are no known adverse effects of E. spelaea on humans. (Hutchins, et al., 2003)

Lesser dawn fruit bats are considered lower risk/least concern by the IUCN. The major threat to E. spelaea is loss and degradation of forest habitat through ongoing wood extraction and limestone quarrying. Conservation actions that are needed include monitoring and research of population numbers, range and trends. The subspecies E. spelaea glandifera of Indonesia and the Philippines and Sulawesi was reported as vulnerable 1992. Populations in Java and the Lesser Sundas Islands are considered endangered because of cave disturbance, hunting, and habitat destruction. Populations of E. spelaea glandifera in the Philippines seem more adaptable to habitat alterations but are at risk due to hunting and human disturbance. (Nowak, 1999; Wilson and Reeder, 2005)