Most bat species are small in size, and flap rapidly in search of insects that they catch on the wing. Other species, fewer, feed on flesh or blood, like vampires, hence the bad reputation that has made them the subject of myths and legends.
But there is a very different group of bats, the megachiroptera, or flying foxes , and the largest species is Acerodon jubatus , the Philippine flying fox , also called the golden-diademed flying fox.
The biggest bat in the world
Talking about the “biggest” animal in a group is always debatable. It is necessary to clarify if reference is made to weight, to length, or in winged animals, to wingspan.
The adult Philippine flying fox weighs an average of 1.2 kilograms and has a wingspan of up to one and a half meters, with exceptional specimens reaching up to two meters. This makes it the heaviest known bat , exceeding the silver medal holder, the so-called giant flying fox , by more than 100 grams. However, both species are relatively equal in wingspan. Despite its scientific name, Pteropus vampyrus , the giant flying fox is also a frugivore and is completely unrelated to vampires.
It feeds on four different species of figs (genus Ficus ), and although farmers in the regions where it lives —especially those on the island of Mindanao— accuse them of stealing food from fruit crops, this behavior is not confirmed. In fact, it is unlikely, since they do not usually eat fruits other than figs, and they tend to avoid humans. The investigations seem to point to the same type of error as when the wolf is accused of attacking cattle in Spain: one species is blamed for the impacts of another. In the case of the Iberian wolves it is the feral dogs, and in the case of the Philippine flying fox that species is P. vampyrus .
Together but not mixed
Currently, all Philippine flying fox populations are part of mixed colonies , which also include individuals of P. vampyrus and other smaller flying foxes, such as the pygmy flying fox, Pteropus hyomelanus .
Neither flying foxes in general, nor the Philippine in particular, are cave-dwelling, as other smaller bats are, but rather forest dwellers . It usually rests hanging on the trees of the jungles or mangroves; when the different species have their roost in the same forest, it is observed that A. jubatus prefers the interior , while the rest of the species remain on the periphery. This behavior suggests that the Philippine flying fox is more sensitive to disturbance and therefore nests in much more stable areas.
A threatened endemism
The Philippine flying fox lives up to its name, it exclusively inhabits the Philippine archipelago, which makes it an endemic species . It lives between altitudes at sea level and 1,100 meters.
Currently, its population is estimated at about 10,000 individuals, and represents only between 1 and 2% of what it was two centuries ago. Among the main threats affecting the Philippine flying fox are habitat loss and hunting , reasons why the International Union for Conservation of Nature (IUCN) lists it as an endangered species .
Being a highly specialized animal —with very specific dietary and environmental requirements— any disturbance to the forests it inhabits can be fatal to Philippine flying fox populations. Today it is considered that about 90% of the original primary forest cover of the Philippine archipelago has been destroyed . Between 10 and 15% of this area has been replaced by secondary vegetation, where the Philippine flying fox cannot inhabit as effectively.
Although there is currently a moratorium on logging in the Philippines, for more than two decades, the removal of primary forest is ongoing, and, if the trend does not change, it is estimated that by 2030 there will be no primary forest left in the Philippines . Based on these deforestation rates, the future trend for this species will depend on the extent of secondary forest regeneration, and the ability of the species to successfully acclimatize to that environment.
On the other hand, hunting has been a historical problem for flying foxes. International trade data shows that thousands of individuals of all species, including A. jubatus , were exported each year from the Philippines.
Since the Convention on International Trade in Endangered Species of Wild Fauna and Flora ( CITES ) entered into force, the species has been included in its “Appendix I”, the highest level of trade restriction. This level of regulation prohibits all international trade in specimens, except when carried out for scientific research purposes, and always with prior import and export authorization.
The internal trade of these animals in the Philippines is also prohibited, as is hunting, except for the indigenous Aeta communities, and as long as they use traditional methods. However, poachers continue to operate, and their meat is sold illegally throughout the country as food, pets, and for its supposed —and non-existent— medicinal properties; ironically, these practices are a potential source of zoonotic diseases. As long as these illicit activities continue, Philippine flying fox populations will remain in peril.
CITES. 2015. Appendices I, II and III of CITES.
Hutson, A. M. et al. 1992. Old world fruit bats : an action plan for their conservation. IUCN. DOI: 10.2305/IUCN.CH.1992.SSC-AP.6.en
IUCN. 2022. The IUCN Red List of Threatened Species. Version 2021-3.
Mildenstein, T. L. et al. 2005. Habitat selection of endangered and endemic large flying-foxes in Subic Bay, Philippines. Biological Conservation, 126(1), 93-102. DOI: 10.1016/j.biocon.2005.05.001
Stier, S. C. et al. 2005. Dietary Habits of the World’s Largest Bats: the Philippine Flying Foxes, Acerodon Jubatus and Pteropus Vampyrus Lanensis. Journal of Mammalogy, 86(4), 719-728. DOI: 10.1644/1545-1542(2005)086[0719:DHOTWL]2.0.CO;2