Haplonycteris fischeri
Philippine pygmy fruit bat

Haplonycteris fischeri, also known as the pygmy fruit bat, or simply the pigmy bat, is found only in some of the Philippine Islands at altitudes ranging from below 100 meters to above 1,500 meters (Nowak, 1999).

Haplonycteris fischeri prefers primary forests and is rarely found elsewhere.

The pygmy fruit bat gets its name from its small size when compared to other megachiropterans. The average mass of an individual is between 16 and 20 grams and the average body length is between 68 and 80 millimeters. These bats lack tails, have thumbs measuring up to 25 millimeters in length, and are cinnamon brown with a darker brown head. The number of teeth appears to be reduced in favor of larger individual teeth. The teeth have strongly developed transverse ridges and cusps (Nowak, 1999).

Males reach sexual maturity within 11 months, while females reach sexual maturity within 3-5 months. Females usually become pregnant as soon as maturity is reached. Most parous females ovulate between late May and early July, while most young females ovulate between August and September. This means that mating takes place in at least 6 months of the year, and probably more. Upon fertilization, the embryo implants in the mother's uterus, but development then dramatically slows for a period of up to 8 months. After this delay, the rate of development increases and development completes in approximately 3 months, making pregnancy last over 11 months. This makes Haplonycteris fischeri the bat species with the longest known gestation period (Heidemann, 1989). Parturition is followed by 10 weeks of lactation (Nowak, 1999). While many hypotheses have attempted to explain this postimplantation deveolpmental delay, it has been difficult to find concrete answers. In a different species, the hypothesis that the delay coincides with food availability has been tested by providing food in excess and elevating temperatures. Embryonic growth rate was not affected. During this investigation, a temporarily lowered level of plasma thyroxine concentrations was observed in the bats during part of the delay. Further testing using injections of thyroxin daily for up to 40 days also failed to increase the rate of development (Burns & Wallace, 1975). It has also been suggested that environmental cues may trigger the end of the delay, but photoperiod is the most likely candidate, and since the maximum daily change in photoperiod is only 40 seconds in the Philippine Islands, it is unlikely that it is responsible (Heidemann, 1989). (Burns, J. M. & Wallace, W. E., 1975; Heidemann, P. D., 1989; Nowak, R. M., 1999)

Some individuals have been known to live over 10 years (Nowak, 1999).

As a frugivore, the pygmy fruit bat eats primarily fruits. It is known to feed on the fruit of Ficus, and most likely of plants of the genus Piper. In addition, it may depend on flowers during certain parts of the year (Heidemann, 1989).

The pygmy fruit bat, being a frugivore, functions as a seed disperser, and may also be a pollinator while feeding from flowers.

Since Haplonycteris fischeri lives exclusively in the forest, it has limited interaction with humans, and as it favors forest over agricultural fields, it has little or no negative economic effect on farmers (Nowak, 1999).

Like many species confined to one type of habitat in islands, the Haplonycteris fischeri population is rapidly thinning. The International Union for Conservation of Nature and Natural Resources (IUCN) states that deforestation is the reason for placing these bats on the vulnerable species (VU A1c) list. The IUCN defines VU A1c as having suffered a reduction of at least 20% over 10 years due to loss of habitat (Hilton-Taylor, 2000).