Bats spend the majority of their lives in roosts, which provide shelter from the environment and predators, a secure place to mate, rear young and interact with other individuals. Caves are preferred roost sites for many species due to their size, permanency and stable microclimates. Many species are highly dependent upon caves for roosting and may form large aggregations. Free-tailed bats (Molossidae) roosting in the millions are known from caves throughout Southeast Asia, but species of Rhinolophidae, Hipposideridae and Miniopterinae (Vespertilionidae) also congregate within caves in numbers exceeding 100,000 individuals. Old World fruit bats (Pteropodidae) tend to make less use of caves than do other families, presumably because these species do not echolocate apart from the tongue-clicking Rousettus. However, several species are largely cave-dependent, most notably Rousettus spp., Dobsonia spp, Eonycteris spelaea and Penthetor lucasi.
Although even small caves are likely to support a few bat species, complex limestone karst systems support the greatest diversity and abundance of bats. These “Biodiversity Arks” cover >400,000 km2 in Southeast Asia, with particularly extensive systems in Indonesia, Thailand and Vietnam. Surveys of bats in karst areas clearly illustrate their significance to bat diversity.
The threats to cave bats are many-fold. Direct hunting affects several species, most notably large or abundant species such as Cheiromeles torquatus in Borneo. More generally, human activities at caves, such as tourism, disturb bats and, if sustained, can have severe consequences for the long-term viability of the bat populations. In Southeast Asia, collection of guano or cave swiftlet (Collocalia fuciphagus and C. maximus) nests are major causes of disturbance, and in several instances are compounded by visits by tourists. Regionally, quarrying of karst areas for limestone and basement minerals probably represents the greatest threats to cave-dependent species. Southeast Asia has the highest annual quarrying rates in the tropics (178 million metric tons per year) and the rate is increasing by 5.7% each year.
The significance of caves to bat diversity and the multitude of threats to cave populations prompted the Southeast Asian Bat Conservation Research Unit (SEABCRU) forum participants to identify cave bat conservation as the third priority for action. In this instance, it is the similarity of threats across Southeast Asia that supports a regional initiative. Foremost, there is a clear need for greater cave survey effort across Southeast Asia to identify and prioritize caves supporting the highest diversity of bats or populations performing key ecological functions in the local context.
The specific resolutions reflect the importance of caves to local economies and are:
- To develop cave management recommendations that recognize scientific, cultural/religious and economic values of caves AND provide for protection of bats.
- To instigate programs to monitor populations to assess effectiveness of management approaches.
