Dyacopterus spadiceus
Dyak fruit bat

Dayak fruit bats are endemic to the Sunda Shelf in southeast Asia, including peninsular Malaysia, Borneo, western Indonesia and the Philippines. (Kristofer M, et al., 2007)

Dayak fruit bats are found in tropical rainforests, specifically in old growth segments of the forest where fruit is plentiful. These bats have been observed in the sub canopy and above the canopy and are most commonly caught in mist nets while foraging above the canopy. Dayak fruit bats have been found roosting near limestone caves, rivers, and near fruiting trees. They have also been observed in hollow trees, likely in large Ficus trees, the fruit of which they eat. (Francis, 1994; Hodgkison, et al., 2004a; Kristofer M, et al., 2007)

Dayak fruit bats are the smallest of Dyacopterus species and are considered small to medium in size for a fruit bat. Fully mature Dayak fruit bats weigh 85 to 95 g. Their dorsal side has short dark fur that is brown-grey in color. Their ventral side is often lighter in color. Their wing membrane attaches to their second toe and their tail is small. They also have large eyes. Dayak fruit bats have a broad rostrum and a deep jaw. They have a dental formula of 2.1.1.2 on the dorsal side and 2.1.2.3 on the ventral jaw. Dayak fruit bats have very large cheek teeth specialized for eating fruit, although they are not as large as those of other species of Dyacopterus. The size of their teeth suggests that Dayak fruit bats eat large hard fruits. There is no sexual dimorphism in this species. Male Dayak fruit bats have enlarged mammary glands that can produce small amounts of milk. (Françis, 2008; Hodgkison, et al., 2003; Kristofer M, et al., 2007)

Little information is available regarding the mating systems of Dayak fruit bats, as the region where they live is not well studied. They are thought to be monogamous, though this is unconfirmed. (Kristofer M, et al., 2007)

Dayak fruit bats reach sexual maturity at approximately 70 g in mass. Mothers usually give birth to 1 or 2 offspring. Pregnant females have been found between June and September. This species is not well studied, and little information is otherwise available regarding its reproduction. (Kristofer M, et al., 2007)

Dayak fruit bats are much like other bats of the family Pteropodidae in the amount of time and care it invests in their young. Little information, however, has been compiled on the periods of gestation and lactation for this species. In September, neither male nor female captured individuals were lactating, but in July and August, captured individuals of both sexes were lactating. It is currently debated whether adult male bats nurse their young. If adult males in fact do nurse their young, then this species would be considered monogamous. Further study on the subject is necessary for a fuller understanding of parental investment. Some argue that Galactorrhoea is a better word to attribute to adult males rather than lactation, as it is currently unknown if males actually uses their milk to nurse their offspring. (Kristofer M, et al., 2007; Racey, et al., 2009)

The lifespan of Dayak fruit bats is currently unknown, however, members of old world bats, Pteropodidae, have reached 30 years of age in captivity. (Nowak, 1999; Nowak, 1999)

Unlike other types of bats, old world fruit bats of the family Pteropodidae, including Dayak fruit bats, do not use echolocation. Dayak fruit bats rely on their large eyes to see in the dark, and because they are nocturnal, their eyes are critical for navigation above and in the forest canopy at night. They do not migrate, however population size in certain areas can fluctuate greatly depending on the amount of food in the area. Dayak fruit bats are social, but little is known about their social structure. Notably, males of this species have functional mammary glands, and they are the only known male mammals to lactate in the wild. There are multiple hypotheses as to why lactation occurs in males. A malfunctioning liver can cause an imbalance of oestrogen causing the glands to lactate. Another theory is that bats eats vegetation high in phytoestrogens, which stimulate milk production. (Dearden and Mitchell, 2009; Francis, et al., 1994)

Little information is available regarding the home range of Dayak fruit bats.

Like most other bats in the family Pteropodidae, Dayak fruit bats have well developed senses of sight and smell. They do not use echolocation and thus rely on their eyes to navigate. (Dearden and Mitchell, 2009; Francis, et al., 1994)

Dayak fruit bats are frugivorous, meaning they eats fruits, which is common of old world bats. A staple in their diet is the fruit of the Ficus tree, including strangler fig trees. These bats likely use their large teeth to squeeze juices out of the fruits. Dayak fruit bats eat fruits of many different colors, though most are green and blend in with the vegetation. The odor of the fruit does not seem to be a major factor in finding fruit. Dayak fruit bats may eat certain leaves that are high in estrogen like hormones, which could throw off their hormonal balance. Large groupings of bats have been observed feeding on fruiting strangler fig trees. (Hodgkison, et al., 2003; Hodgkison, et al., 2004b)

Little information is available regarding predators of Dayak fruit bats.

As frugivores, Dayak fruit bats play a major role in seed dispersal. Many of the seeds that they excrete are scattered throughout the forest. Additionally, seeds that are too large to eat are dropped to the forest floor. These seeds are reported to have a high percentage of germination. Ladibocarpellus selangorensis, a species of mites, parasitize Dayak fruit bats. Additionally, a batfly Leptocyclopodia brachythrinax is speculated to use these bats as hosts. (Kristofer M, et al., 2007; Hodgkison, et al., 2003; Kristofer M, et al., 2007)

Dayak fruit bats are major seed dispersers and may also pollinate crops. (Hodgkison, et al., 2003)

There are no known adverse effects of Dayak fruit bats on humans.

Dayak fruit bats are listed as "near threatened" on the IUCN red list, and their population size is decreasing. This is most likely due to deforestation of its natural habitat. From the 1990s through 2005, Malaysia has lost approximatly 1,486,000 ha of natural land, including a large amount of old growth forest, in which Dayak fruit bats live. ("IUCN 2009", 2009; "IUCN 2009", 2009; "Malaysia Forest Information and Data", 2006)