Bat Caves in the Philippines: An endangered safe haven

Caves together with their often unique fauna and flora and delicate speleothems constitute one of the most fragile environments on Earth. Cave ecosystem holds a variety of species of unique and sensitive organisms, many of which are caves obligates, one of this are bats. Caves are used by bats for a variety of reasons, including courtship and mating, raising young, and hibernating. Bats seek shelter during the day and disperse from these sites to forage for food at night. In addition, many insectivorous species retreat to caves between feeding bouts, where they may cull the wings and heads of insects that were captured while foraging. Frugivorous species sometimes transport large fruits to caves where they cull soft pulp and where they can reduce the risks of predation (Kunz, 1982; Kunz and Fenton, 2003).

The Philippines contains a wide array of tropical karst landscapes. There are over 1,500 caves have been recorded by the Department of Environment and Natural Resources since the start of its implementation of the Caves Management and Conservation Program in 1994, with still a significant number of caves yet to be discovered and mapped. These caves are considered unique, natural and non-renewable resources with important scientific, economic, educational, cultural, historical and aesthetic values. They are also home to specialized mineral formations, as well as unique and diverse flora and fauna (PAWB-DENR, 2008).

Out of these numerous caves, a very small proportion are documented to house bat species. At present, only 221 caves throughout the islands are known occupied by bats. The most number is in Luzon with 109 locations, 73 in the Visayas and only 39 in Mindanao Island (The Philippine Caves and Bats, 2010). It is also important to take note that there are more than 30 species of Philippine bats are dependent to caves for various life histories (Ingle et al. 2011).

Throughout the archipelago, there are several significant bat surveys and studies conducted on various cave ecosystems. In Bohol, more than of 30 species across different caves in the Island were recorded (Pamaong-Jose et al. 2007; Phelps et al. 2015). In Siquijor Island, twenty large caves were surveyed with 19 species recorded (Sedlock et al. 2012). In these caves, four caves have relatively large (> 100 individuals) colonies and five caves had fruit bats (Rousettus sp. or Eonycteris spp.) present. In Negros, recent expedition resulted in the rediscovery of the Negros fruit bat (Dobsonia chapmani), a species previously thought to be extinct (Alcala et al. 2004).

In Polilio Island, ten cave bat species namely Eonycteris robusta, E. spalaea, Rousettus amplexicaudatus, Rhinolophus rufus, R. arcuatus, Hipposideros diadema, H. coronatus, H. pygmaeus, Miniopterus schreibersi and M. australis were recorded (Galvan 2011). In Marinduque Island, fourteen cave sites were assessed. Thirteen species of cave bats were recorded with single fruit bat Rousettus amplexicaudatus. Six cave bat species were new island records (Emballonura alecto, Hipposideros diadema, Megaderma spasma, Rhinolophus arcuatus, Rhinolophus philippinensis, and Rhinolophus virgo). Miniopterus schreibersi was found to be present in 77.78% of the caves containing bats suggesting that it thrives in varying cave environments (Macasaet et al. 2011). Additionally, Vinarao and Cabauatan (n.d.) surveyed selected caves in the Northern Sierra Madre Natural Park, Luzon, Philippines and recorded 24 species namely Miniopterus australis, M. schreibersii, M. tristi, Myotis, macrotarsus, Pippistrellus javanicus, Rhinolophus philippinensis, R. virgo, R. macrotis, R. arcuatus, R. acuminatus, R. inops, R. subrufus, R. rufus, Rhinolophus sp., Hipposideros pygmeus, H. diadema, H. ater, H. obscurus, H. coronatus, Ptenochiros jagori, Haplonycteris fischeri, Taphozous melanopogon, Emballonura alecto and Chaeropon plicata.

In Mindanao Island, Nuṅeza et al. (2010), conducted Mindanao wide survey of cave ecosystem covering the diversity of terrestrial vertebrate fauna including bats, a total of 28 caves were surveyed from different locations in Mindanao. Thirteen bat species were recorded namely Cynopterus brachyotis, Hipposideros pygmaeus, H. obscuros, H. diadema, Miniopterus schrebersi, Myotis macrotarsus, Pippistrellus javanicus, Philetor brachypterus, Ptenochirus jagori, Rhinolophus cf. arcuatus, Rhinolophus virgo, Rousettus amplexicaudatus and Taphozous melanopogon. In Samal Island, fifteen species of cave bat species were recorded after surveying 30 cave sites in the location (Quibod et al. 2013). In Southcentral region of Mindanao, five caves were assessed with total 14 species identified –higher diversity in terms of species over a number of caves assessed in Mindanao (Tanalgo and Tabora 2015).

Despite their diversity and significance, most of the country’s cave ecosystems and its inhabitants are in peril due to lack of specific statutory protection, increased demand for recreational sites, treasure hunting, mining, pollution, illegal collection of cave resources and rapid urbanization. Human activities and exploitation threaten many cave and karst ecosystems and the endemic species within these systems (Clements et al. 2006; Ball 2002; Niu et al. 2007). The proximity and accessibility of cave sites to human settlements are important factors in cave preservation. For instance, in Southcentral Mindanao, caves nearer to the settlement have shown high population declines in short periods of time due to susceptibility to illegal hunting, trade, and other activities (Tanalgo and Tabora 2015). Illegal hunting and trade of bats from caves have also become a concern in bat cave conservation, many caves species are exploited for food, bush meat, and trade. For example, some local communities the Philippines believed bat meat has special medicinal properties and may cure certain diseases (Mildenstein 2012; Tanalgo et al. 2017; Tanalgo and Baleva, in-review). One of the major problems that place bat populations at risk is that they have relatively low reproductive rates and are unable to recover quickly from population declines brought by various anthropogenic use (Kunz and Racey, 1998). Hence, the unprecedented anthropogenic activities and lack of regulations in caves will certainly severe many ecologically and economically important species and the ecosystem services they provide which are vital for the existence of present and future generations.

The protection of caves leading to the conservation of many dependent species particularly bats is probably the most important challenge in bat conservation globally. Identification of priority sites for conservation and research is urgent to respond to the Continuous research on the cave bat taxonomy, roosting preferences, determination of effects of anthropogenic activities, and ecosystem services, which are probably among the important priorities to consider. Increasing collaborative research and outreach programs to intensify awareness among locals especially those near high biodiversity areas is an urgent call to all.

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