Caves have always fascinated people. In the past, especially during wartimes, caves were used as hiding places from enemies. People explore caves in search of buried treasures or to gather guano fertilizer. In the Philippines, vandals have invaded caves to collect stalactites and stalagmites for sale as decoration materials. Spelunkers have explored caves for recreation. In rare instances, people have used caves for worship. Presently, caves have been promoted as tourist attractions.
But the scientific study of caves, speleology, have attracted fewer academic people, and cave studies are not popular even among professional biologists in the Philippines. Among those studying caves are biologists interested in specific groups of vertebrates. Mammalogists, ornithologists and herpetologists have been studying cave fauna in the Philippines for some time. More recently, biology faculty members of some colleges and universities have explored caves for their vertebrate and invertebrate faunas under the Commission on Higher Education program on biodiversity. Initial results seem promising.
Scientists at the Philippine Museum have made diggings in some caves in Quezon, Palawan to study fossils and archaeological artifacts during the mid-1900s. Dr. Robert Fox and his colleagues traced the history of the early human populations that migrated to the Philippines from Borneo during the period of maximum regression of the sea 20,000 years ago. At least another American paleontologist studied the hard parts of animals used as food by these early human cave dwellers.
During the past 60 years, Silliman University biologists have been exploring the mammal, bird, reptile and amphibian faunas in caves in the Central Visayas. Thus far, one new species of fruit-eating bat (Dobsonia chapmani) has been found in caves in southern Negros. This species is no longer found in caves, its original habitat, in the 2000s, but a remnant population in southwestern Negros has been found living in trees with thick growths of a species of aerial ferns, probably as a result of the disturbance of their cave habitats by humans. This fruit bat is really an endangered species.
Among the herpetofauna, which includes snakes and lizards, are frogs mostly belonging to the genus Platymantis (Family Cerobatrachidae). Thus far, four species, all new species, have been described, and at least two more possibly new species have not yet been studied or described, and most probably more will turn out to be new from more caves as yet unexplored. Lizards of the genus Gekko include a couple of species, which need systematic reviews of their phylogenetic positions in evolution.
It is not yet clear whether these four described species of forest frogs and others still to be described, as well as the geckos, evolved in the caves they now inhabit or they evolved in forests around these caves but expanded their populations to cave habitats. From what we know about the Philippine environment, tropical rainforests used to occupy some 80-90% of the land area of the Philippines in the remote past before humans settled and cleared the forests. More studies are needed. But it is clear that the described frog and reptile species occupy only the first 10m or so from the cave openings, making it probable that the range expansion hypothesis is what actually happened. Further, all these cave species do not show reduction or lack of normal eyes, which are characteristic of cave species that evolved inside caves.
Whatever is the explanation, it is clear that some cave species, notably the insectivorous bats and swifts that live in caves are very useful to the ecology of cultivated species used by humans. These bats and birds feed on millions of insects, some of which are pests, and convert them to guano used for fertilizing the farms. This fact is lost to many of our people who persecute these lowly creatures by killing them directly, disturbing them, or destroying their cave habitats.
It is time to rethink and change human unkindness to our fellow creatures. I suggest that our environmental advocacy groups add cave animals to the list of creatures worthy of saving for the future.